Light-emitting element, electronic device and lighting device

Abstract

Light-emitting element comprising: a pair of electrodes; and a light-emitting layer between the pair of electrodes, the light-emitting layer comprising: a first organic compound; a second organic compound; and an organometallic complex represented by the general formula G1: wherein X represents a substituted or unsubstituted six-membered heteroaromatic ring containing two or more nitrogen atoms including one nitrogen atom which is a coordinating atom, where R 1 to R 4 each represent an alkyl group having 1 to 6 carbon atoms, wherein the first organic compound and the second organic compound are a combination forming an exciplex, where a T 1 -level of the first organic compound is higher than a T1 -level of the organometallic complex, where a T 1 -level of the second organic compound is higher than the T 1 -level of the organometallic complex, and where an emission spectrum of the exciplex overlaps with an absorption spectrum of the organometallic complex.

Description

Technical field

[0001] An embodiment of the present invention relates to a light-emitting element, an electronic device, and a lighting device each using an organometallic complex. State of the art

[0002] Organic compounds are brought into an excited state by the absorption of light. This excited state, in some cases, triggers various reactions (photochemical reactions) or, in some cases, produces luminescence. As a result, organic compounds have numerous applications.

[0003] A well-known example of a photochemical reaction is the reaction of singlet oxygen with an unsaturated organic molecule (oxygen addition). Since the ground state of an oxygen molecule is a triplet state, oxygen in a singlet state (singlet oxygen) is not generated by direct photoexcitation. However, in the presence of another excited triplet molecule, singlet oxygen is generated, causing an oxygen addition reaction. In this case, a compound capable of forming the excited triplet molecule is called a photosensitizer.

[0004] As described above, to generate singlet oxygen, a photosensitizer capable of forming an excited triplet molecule through photoexcitation is required. However, the ground state of an ordinary organic compound is a singlet state; thus, photoexcitation to an excited triplet state is a forbidden transition, and generating an excited triplet molecule is difficult. A compound that can easily effect intersystem crossing from the excited singlet state to the excited triplet state (or a compound that enables the forbidden transition, direct photoexcitation, to the excited triplet state) is therefore required as such a photosensitizer. In other words, such a compound can be used and is useful as a photosensitizer.

[0005] The above compound often emits phosphorescence. Phosphorescence means luminescence generated upon transition between different energies in multiplicity. For an ordinary organic compound, phosphorescence means luminescence generated upon decay from the triplet excited state to the singlet ground state (in contrast, fluorescence means luminescence generated upon decay from the singlet excited state to the singlet ground state). Fields in which a compound capable of emitting phosphorescence, that is, a compound capable of converting the triplet excited state into luminescence (hereinafter referred to as a phosphorescent compound), is applied include a light-emitting element containing an organic compound as a light-emitting substance.

[0006] This light-emitting element has a simple structure in which a light-emitting layer containing an organic compound, which is a light-emitting substance, is sandwiched between electrodes. This light-emitting element has attracted attention as a next-generation flat panel display element because of its features such as being thinner and lighter, fast response time, and low-voltage DC operation. A display device incorporating this light-emitting element also exhibits excellent contrast and image quality, as well as a wide viewing angle.

[0007] In the light-emitting element containing an organic compound as the light-emitting substance, the light-emitting mechanism is a carrier injection type: a voltage is applied between electrodes with a light-emitting layer interposed therebetween, electrons and holes injected from the electrodes recombine, so that the light-emitting substance is excited, and then light is emitted when the excited state returns to the ground state. As in the case of photoexcitation mentioned above, the types of excited states include a singlet excited state (S*) and a triplet excited state (T*). The statistical generation ratio of these in the light-emitting element is considered to be S* to T* = 1:3.

[0008] At room temperature, a compound capable of converting a singlet excited state into luminescence (hereinafter referred to as a fluorescent compound) exhibits only luminescence from the singlet excited state (fluorescence) without luminescence from the triplet excited state (phosphorescence). Therefore, the internal quantum efficiency (the ratio of the number of generated photons to the number of injected charge carriers) of a light-emitting element containing the fluorescent compound is theoretically limited to 25% due to S* to T* = 1:3.

[0009] In contrast, in the case of a light-emitting element containing the above-mentioned phosphorescent compound, the internal quantum efficiency can theoretically be increased to 75% to 100%. In other words, the emission efficiency can be three to four times higher than that of the light-emitting element containing a fluorescent compound. Consequently, the light-emitting element containing a phosphorescent compound has recently been actively developed to achieve a highly efficient light-emitting element. As a phosphorescent compound, an organometallic complex having iridium or the like as the central metal has attracted particular attention due to its high phosphorescence quantum efficiency (see Patent Document 1, Patent Document 2, and Patent Document 3).Patent Document 4 discloses a light-emitting element using an organometallic iridium complex in a light-emitting layer. [Reference][Patent document] [Patent document 1] JP 2007 - 137 872 A [Patent Document 2] JP 2008 - 069 221 A [Patent Document 3] WO 2008 / 035 664 A1 [Patent document 4] US 2010 / 0 123 127 A1 Disclosure of the invention

[0010] Phosphorescent materials emitting various colors have been developed as reported in Patent Documents 1 to 3, but not many red light emitting materials achieving high color purity have been reported.

[0011] In view of the above, according to an embodiment of the present invention, there is provided a light-emitting element, an electronic device or a lighting apparatus having a high emission efficiency.

[0012] One embodiment of the present invention is a light-emitting element comprising: a pair of electrodes; and a light-emitting layer between the pair of electrodes, wherein the light-emitting layer comprises: a first organic compound; a second organic compound; and an organometallic complex having a structure represented by the following general formula (G1), wherein the first organic compound and the second organic compound are a combination forming an exciplex, wherein a T1 level of the first organic compound is higher than a T1 level of the organometallic complex, wherein a T1 level of the second organic compound is higher than the T1 level of the organometallic complex, and wherein an emission spectrum of the exciplex overlaps with an absorption spectrum of the organometallic complex.

[0013] In the formula, X represents a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom. Examples of a substituent bonded to X include a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, and a phenyl group having a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. In addition, R 1 to R 4 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0014] In the general formula (G1), R 1 and R 2each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, whereby a dihedral angle formed by carbon atoms of the benzene ring bonded to iridium can be large. By increasing the dihedral angle, a secondary peak of an emission spectrum of the organometallic complex can be theoretically reduced as follows, whereby the half-width can be reduced. Note that it is particularly preferable that R 1 and R 2 each represent a methyl group.

[0015] In the above structure, preferably, the substituted or unsubstituted six-membered heteroaromatic ring having the two or more nitrogen atoms including the nitrogen atom which is the coordinating atom is represented by any one of the general formulas (X1) to (X4).

[0016] It should be noted that in the formulas R 5 to R15 separately represent hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. Examples of a substituent bonded to the phenyl group include a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0017] In a preferred embodiment of the light-emitting element of the present invention, the organometallic complex is represented by a general formula (G2).

[0018] In the formula, R 1 to R 4 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and R 5 to R 7 separately represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 5 and R 6can represent hydrogen.

[0019] In a preferred embodiment of the present invention, the organometallic complex is represented by a general formula (G3).

[0020] In the formula, R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 8 to R 10 separately a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. R 8 and R 10 can represent hydrogen.

[0021] In a preferred embodiment of the present invention, the organometallic complex is represented by a general formula (G4).

[0022] In the formula, R 1 to R 4each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 11 to R 13 separately hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. R 11 may represent hydrogen, and it is preferred that R 12 or R 13 represents hydrogen.

[0023] In a preferred embodiment of the present invention, the organometallic complex is represented by a general formula (G5).

[0024] In the formula, R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 14 and R 15separately represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 14 and R 15 can represent hydrogen. In a preferred embodiment of the present invention, the organometallic complex is represented by a structural formula (100).

[0025] Another embodiment of the present invention is an organometallic complex represented by a structural formula (107).

[0026] In a preferred embodiment of the present invention, the organometallic complex is represented by a structural formula (108). In a preferred embodiment of the present invention, the organometallic complex is represented by a structural formula (109).

[0027] In addition, the organometallic complex is very effective for the following reason: the organometallic complex can emit phosphorescence, that is, it can provide luminescence from a triplet excited state and can show emission, and therefore, higher efficiency is possible when the organometallic complex is applied to a light-emitting element.

[0028] In the above structure, the substituted or unsubstituted six-membered heteroaromatic ring having the two or more nitrogen atoms including the nitrogen atom which is the coordinating atom is preferably represented by one of the general formulas (X1) to (X4).

[0029] It should be noted that in the formulas R 5 to R 15separately represent hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. Examples of a substituent bonded to the phenyl group include a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0030] Further embodiments of the present invention are an electronic device and a lighting device, each including the light-emitting element.

[0031] An organometallic complex can be provided that exhibits high emission efficiency and achieves improved color purity by narrowing the half-width of an emission spectrum. Furthermore, a novel organometallic complex with excellent sublimation properties can be provided. Using the novel organometallic complex, a light-emitting element, an electronic device, or a lighting device with high emission efficiency can be provided. Alternatively, it is possible to provide a light-emitting element, an electronic device, or a lighting device with low power consumption. Short description of the drawings Fig. 1 shows a structure of a light-emitting element. Fig. 2 shows a structure of a light-emitting element. Fig. 3A and Fig. 3B show structures of light-emitting elements. Fig. 4 shows a light emitting device. Fig. 5A and Fig. 5B show a light emitting device. Fig. 6A to Fig. 6D show electronic devices. Fig. 7A to Fig. 7C show an electronic device. Fig. 8 shows lighting devices. Fig. 9 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (100). Fig. Figure 10 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (100). Fig. 11 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (107). Fig. Figure 12 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (107). Fig. 13 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (108). Fig. Figure 14 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (108). Fig. 15 shows a light emitting element. Fig. Figure 16 shows current density-luminance characteristics of a light-emitting element 1. Fig. Figure 17 shows voltage-luminance characteristics of a light-emitting element 1. Fig. Figure 18 shows luminance-current efficiency characteristics of a light-emitting element 1. Fig. Figure 19 shows voltage-current characteristics of a light-emitting element 1. Fig. 20 shows an emission spectrum of a light-emitting element 1. Fig. Figure 21 shows the reliability of a light-emitting element 1. Fig. Figure 22 shows the reliability of a light-emitting element 1. Fig. Figure 23 shows current density-luminance characteristics of a light-emitting element 2. Fig. 24 shows voltage-luminance characteristics of a light-emitting element 2. Fig. Figure 25 shows luminance-current efficiency characteristics of a light-emitting element 2. Fig. 26 shows voltage-current characteristics of a light-emitting element 2. Fig. 27 shows an emission spectrum of a light-emitting element 2. Fig. 28 shows the reliability of a light-emitting element 2. Fig. 29 shows the reliability of a light-emitting element 2. Fig. 30 shows current density-luminance characteristics of a light-emitting element 3. Fig. 31 shows voltage-luminance characteristics of a light-emitting element 3. Fig. 32 shows luminance-current efficiency characteristics of a light-emitting element 3. Fig. 33 shows voltage-current characteristics of a light-emitting element 3. Fig. 34 shows an emission spectrum of a light-emitting element 3. Fig. 35 shows the reliability of a light-emitting element 3. Fig. 36 shows the reliability of a light-emitting element 3. Fig. Figure 37 shows TG / DTA results of an organometallic complex represented by the structural formula (100). Fig. 38 shows phosphorescence spectra of [Ir(ppr) 2 (acac)] (abbreviation) and [Ir(dmppr) 2 (acac)] (abbreviation). Fig. Figure 39 shows results of a comparison of a dihedral angle formed by carbon atoms of a benzene ring between [Ir(ppr) 2 (acac)] (abbreviation) and [Ir(dmppr) 2 (acac)] (abbreviation) Fig. 40 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (121). Fig. Figure 41 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (121). Fig. Figure 42 shows TG / DTA results of an organometallic complex represented by the structural formula (121). Fig. 43 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (122). Fig. Figure 44 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (122). Fig. Figure 45 shows TG / DTA results of an organometallic complex represented by the structural formula (122). Fig. Figure 46 shows LC / MS measurement results of an organometallic complex represented by the structural formula (122). Fig. 47 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (123). Fig. Figure 48 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (123). Fig. Figure 49 shows LC / MS measurement results of an organometallic complex represented by the structural formula (123). Fig. 50 shows a 1H-NMR diagram of an organometallic complex represented by the structural formula (124). Fig. Figure 51 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (124). Fig. Figure 52 shows TG / DTA results of an organometallic complex represented by the structural formula (124). Fig. Figure 53 shows LC / MS measurement results of an organometallic complex represented by the structural formula (124). Fig. 54 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (125). Fig. Figure 55 shows a UV-VIS absorption spectrum and an emission spectrum of an organometallic complex represented by the structural formula (125). Fig. Figure 56 shows TG / DTA results of an organometallic complex represented by the structural formula (125). Fig. Figure 57 shows current density-luminance characteristics of light-emitting elements 4 to 7. Fig. 58 shows voltage-luminance characteristics of light-emitting elements 4 to 7. Fig. 59 shows luminance-current efficiency characteristics of light-emitting elements 4 to 7. Fig. 60 shows voltage-current characteristics of light-emitting elements 4 to 7. Fig. Figure 61 shows emission spectra of light-emitting elements 4 to 7. Fig. 62 shows the reliability of light-emitting elements 4 to 7. Fig. 63 shows the reliability of light-emitting elements 4 to 7. Fig. 64 shows a 1H-NMR diagram of an organometallic complex represented by the structural formula (126). Fig. 65 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (127). Fig. 66 shows a 1 H-NMR diagram of an organometallic complex represented by the structural formula (106). Best mode for carrying out the invention

[0032] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] (Embodiment 1)

[0033] In this embodiment, organometallic complexes are described that are used in embodiments of the present invention.

[0034] An organometallic complex for use in the present invention is an organometallic complex in which a β-diketone and a six-membered heteroaromatic ring are ligands, the six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom. Note that an embodiment of an organometallic complex described in this embodiment, in which a β-diketone and a six-membered heteroaromatic ring are ligands, the six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom, is an organometallic complex having the structure represented by the general formula (G1).

[0035] In the general formula (G1), X represents a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including one nitrogen atom that is a coordinating atom. In addition, R 1 to R 4 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0036] It should be noted that specific examples of the substituted or unsubstituted alkyl group having 1 to 6 carbon atoms in R 1 to R 4include: a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group and a 2,3-dimethylbutyl group.

[0037] It is preferred that the substituted or unsubstituted six-membered heteroaromatic ring X having the two or more nitrogen atoms including the nitrogen atom which is the coordinating atom is represented in particular by one of the general formulas (X1) to (X4).

[0038] It should be noted that in an organometallic complex according to one embodiment of the present invention, two substituted or unsubstituted alkyl groups each having 1 to 6 carbon atoms are bonded to the 2-position and the 4-position of a phenyl group bonded to both metallic iridium and a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom, resulting in a reduction in the half-width of an obtained emission spectrum, so that the organometallic complex has an advantage of achieving improved color purity. Furthermore, the ligand has a β-diketone structure, thereby increasing the solubility of the organometallic complex in an organic solvent and enhancing purification, which is preferable.The β-diketone structure is preferably included to achieve an organometallic complex with high emission efficiency. Incorporating the β-diketone structure has advantages such as higher sublimation properties and excellent vapor deposition properties.

[0039] In a preferred embodiment of the present invention, the organometallic complex is represented by the general formula (G2).

[0040] In the general formula (G2), R 1 to R 4 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and R 5 to R 7 separately represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 5 and R 6 can represent hydrogen. Concrete examples of R 1 to R 7include the concrete examples for R 1 to R 4 in the general formula (G1). Furthermore, the substituted or unsubstituted phenyl group in R 5 to R 7 have a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0041] In a preferred embodiment of the present invention, the organometallic complex is represented by the general formula (G3).

[0042] In the general formula (G3), R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 8 to R 10 separately represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 8 and R 10 can represent hydrogen. Concrete examples of R1 to R 4 and R 8 to R 10 include the concrete examples for R 1 to R 4 in the general formula (G1). Furthermore, the substituted or unsubstituted phenyl group in R 8 to R 10 have a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0043] In a preferred embodiment of the present invention, the organometallic complex is represented by the general formula (G4).

[0044] In the general formula (G4), R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 11 to R 13 separately represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 11can represent hydrogen, and it is preferred that R 12 or R 13 represents hydrogen. Concrete examples of R 1 to R 4 and R 11 to R 13 include the concrete examples for R 1 to R 4 in the general formula (G1). Furthermore, the substituted or unsubstituted phenyl group in R 11 to R 13 have a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. In a preferred embodiment of the present invention, the organometallic complex is represented by the general formula (G5).

[0045] In the general formula (G5), R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Furthermore, R 14 and R 15separately represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted phenyl group. It should be noted that R 14 and R 15 can represent hydrogen. Concrete examples of R 1 to R 4 and R 14 and R 15 include the concrete examples for R 1 to R 4 in the general formula (G1). Furthermore, the substituted or unsubstituted phenyl group in R 14 and R 15 have a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0046] The following are specific structural formulas of the previously described organometallic complexes (structural formulas (100) to (127)), each of which is an embodiment of the present invention.

[0047] It should be noted that organometallic complexes represented by structural formulas (100) to (127) are novel substances capable of emitting phosphorescence. It should be noted that these substances can exist in the form of geometric isomers and stereoisomers, depending on the nature of the ligand. The organometallic complex for use in one embodiment of the present invention includes all of these isomers.

[0048] The following describes an example of a method for producing an organometallic complex having the structure represented by the general formula (G1). ((Process for producing a six-membered heterocyclic derivative represented by a general formula (G0-X1)))

[0049] An example of a process for producing a six-membered heterocyclic derivative represented by the general formula (G0-X1) is described.

[0050] In the general formula (G0-X1) R 1 , R 2 and R 5 to R 7 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. R 5 and R 6 can represent hydrogen.

[0051] Four synthesis schemes (A1), (A2), (A3) and (A4) of a pyrazine derivative represented by the general formula (G0-X1), which is a six-membered heterocycle, are shown below.

[0052] In the synthesis scheme (A1), a halide of 3,5-disubstituted phenyl (a1-1) is lithiated with alkyllithium or the like and reacted with pyrazine (a2-1) to obtain the derivative (G0-X1).

[0053] In the synthesis scheme (A2), a boronic acid of 3,5-disubstituted phenyl (a1-2) and a halide of pyrazine (a2-2) are coupled to obtain the derivative (G0-X1).

[0054] In the synthesis scheme (A3), a diketone of 3,5-disubstituted phenyl (a1-3) is reacted with diamine (a2-3) to obtain the derivative (G0-X1).

[0055] In the synthesis scheme (A4), a pyrazine of 3,5-disubstituted phenyl (a1-4) and a lithium compound or a Grignard reagent (a2-4) are reacted to obtain the derivative (G0-X1). Note that in the formula, Y represents a halogen element.

[0056] In addition to the four methods described above, there are a variety of known methods for preparing the derivative (G0-X1). Thus, any of the methods can be used.

[0057] Since the compounds (a1-1), (a2-1), (a1-2), (a2-2), (a1-3), (a2-3), (a1-4), and (a2-4) in the above schemes have many commercially available variants or their synthesis is possible, a wide variety of pyrazine derivatives can be prepared as pyrazine derivatives represented by the general formula (G0-X1). Consequently, a feature of the organometallic complex is the abundance of ligand variants. ((Process for producing an organometallic complex represented by the general formula (G1)))

[0058] Next, a synthesis method of the organometallic complex represented by the general formula (G1) is described.

[0059] It should be noted that in the general formula (G1), X represents a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom. In addition, R 1 to R 4 each represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0060] Synthesis scheme (B) of the organometallic complex represented by the general formula (G1) is shown below.

[0061] It should be noted that in the synthesis scheme (B), X represents a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom. In addition, Y represents a halogen, and R 1 and R 2each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0062] As shown in the synthesis scheme (B), a six-membered heterocyclic derivative represented by a general formula (LG0) and an iridium compound containing a halogen (such as iridium chloride, iridium bromide, or iridium iodide) are heated in an inert gas atmosphere without using a solvent, solely using an alcohol-based solvent (e.g., glycerol, ethylene glycol, 2-methoxyethanol, or 2-ethoxyethanol), or using a mixed solvent of water and one or more of the alcohol-based solvents, whereby a binuclear complex (P), which is a type of organometallic complex including a halogen-bonded structure, can be obtained.

[0063] There are no specific restrictions regarding the heating medium, so an oil bath, a sand bath, or an aluminum block can be used. Alternatively, microwaves can be used as the heating medium.

[0064] Furthermore, as shown in a synthesis scheme (C), the dinuclear complex (P) obtained in the synthesis scheme (B) is reacted with a β-diketone derivative in an inert gas atmosphere, thereby removing a proton from the β-diketone derivative and coordinating a monoanionic β-diketone derivative to the central metal, iridium. In this way, the organometallic complex represented by the general formula (G1) can be obtained.

[0065] It should be noted that in the synthesis scheme (C), X represents a substituted or unsubstituted six-membered heteroaromatic ring having two or more nitrogen atoms including a nitrogen atom that is a coordinating atom. Furthermore, Y represents a halogen, and R 1 to R 4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0066] There are no specific restrictions regarding the heating medium, so an oil bath, a sand bath, or an aluminum block can be used. Alternatively, microwaves can be used as the heating medium.

[0067] The above is the description of the example of a method for producing the organometallic complex, however, the present invention is not limited to this example and other synthesis methods can also be applied.

[0068] The previously described organometallic complex can emit phosphorescence and can therefore be used as a light-emitting material or as a light-emitting substance for a light-emitting element.

[0069] Using the organometallic complex, a light-emitting element, a light-emitting device, an electronic device, or a lighting device with high emission efficiency can be obtained. Alternatively, it is possible to obtain a light-emitting element, a light-emitting device, an electronic device, or a lighting device with low power consumption.

[0070] The structure in this embodiment can be appropriately combined with any of the structures of the other embodiments. (Embodiment 2)

[0071] In Embodiment 2, which is a comparative embodiment and is not covered by the present invention, a light-emitting element in which the organometallic complex described in Embodiment 1 is used for a light-emitting layer is prepared by Fig. 1 described.

[0072] In a light-emitting element that is Fig. 1, an EL layer 102 including a light-emitting layer 113 is disposed between a pair of electrodes (a first electrode (anode) 101 and a second electrode (cathode) 103), and the EL layer 102 includes a hole-injection layer 111, a hole-transport layer 112, an electron-transport layer 114, an electron-injection layer 115, a charge-generation layer (E) 116, and the like, in addition to the light-emitting layer 113.

[0073] When a voltage is applied to such a light-emitting element, holes injected from the first electrode 101 side and electrons injected from the second electrode 103 side recombine in the light-emitting layer 113, causing the organometallic complex to enter an excited state. When the organometallic complex returns from the excited state to the ground state, light is emitted. In this way, the organometallic complex serves as a light-emitting substance in the light-emitting element.

[0074] The hole-injection layer 111, included in the EL layer 102, is a layer containing a substance with a high hole-transport property and an acceptor substance. When electrons are extracted from the substance with a high hole-transport property by the acceptor substance, holes are generated. In this way, holes are injected from the hole-injection layer 111 via the hole-transport layer 112 into the light-emitting layer 113.

[0075] The charge generation layer (E) 116 is a layer containing a substance with a high hole-transport property and an acceptor substance. The acceptor substance extracts electrons from the substance with a high hole-transport property, and the extracted electrons are injected into the light-emitting layer 113 by the electron injection layer 115 with an electron-injection property via the electron transport layer 114.

[0076] A specific example in which the light-emitting element is manufactured will be described.

[0077] For the first electrode (anode) 101 and the second electrode (cathode) 103, a metal, an alloy, an electrically conductive compound, a mixture thereof, and the like can be used. Specifically, indium oxide-tin oxide (indium tin oxide; indium tin oxide (ITO)), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide (indium zinc oxide), indium oxide containing tungsten oxide and zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ti) can be used. Furthermore, an element belonging to Group 1 or Group 2 of the periodic table, for example, an alkali metal such as lithium (Li) or cesium (Cs), an alkaline earth metal such as Ni, Cu, or Ni, can be used. B. Calcium (Ca) or Strontium (Sr), Magnesium (Mg), an alloy containing such an element (MgAg, AlLi), a rare earth metal such asEuropium (Eu) or ytterbium (Yb), an alloy containing such an element, graphene, and the like can be used. The first electrode (anode) 101 and the second electrode (cathode) 103 can be formed using, for example, a sputtering method, a vapor deposition method (including a vacuum vapor deposition method), or the like.

[0078] As a substance having a high hole transport property used for the hole injection layer 111, the hole transport layer 112 and the charge generation layer (E) 116, for example, the following can be given: aromatic amine compounds such as4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA) and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB); 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1); 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2); 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1); and the like. Furthermore, the following carbazole derivatives and the like can be used: 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB) and 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).The substances mentioned here are mainly those with a hole mobility of 10. -6 cm 2 / Vs or higher. Note that any substance other than the above substances can be used as long as the hole-transport property is higher than the electron-transport property.

[0079] A high molecular weight compound such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) or poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD) can also be used.

[0080] As examples of the acceptor substance used for the hole injection layer 111 and the charge generation layer (E) 116, an oxide of a transition metal or an oxide of a metal belonging to any of Group 4 to Group 8 of the Periodic Table can be cited. Specifically, molybdenum oxide is particularly preferred.

[0081] The light-emitting layer 113 contains the organometallic complex described in Embodiment 1 as a guest material serving as a light-emitting substance and a substance having a higher triplet excitation energy than this organometallic complex as a host material.

[0082] Preferred examples of the substance (i.e., host material) used for dispersing each of the aforementioned organometallic complexes include: any of the compounds having an arylamine skeleton such as 2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn) and NPB, carbazole derivatives such as CBP and 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), and metal complexes such as bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp 2 ), Bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX) 2 ), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium (abbreviation: BAlq), and tris(8-quinolinolato)aluminium (abbreviation: Alq 3 ). Alternatively, a high-molecular compound such as PVC can be used.

[0083] It should be noted that when the light-emitting layer 113 contains the above-described organometallic complex (guest material) and the host material, phosphorescence can be emitted with high efficiency from the light-emitting layer 113.

[0084] The electron transport layer 114 is a layer containing a substance with a high electron transport property. Metal complexes such as Alq can be used for the electron transport layer 114. 3 , Tris(4-methyl-8-quinolinolato)aluminium (abbreviation: Almq 3 ), Bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq 2 ), BAlq, Zn(BOX) 2 or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ) 2), can be used. Alternatively, a heteroaromatic compound such as B. 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP) or 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can be used. Alternatively, a high-molecular compound such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can be used. The substances mentioned here are mainly those with an electron mobility of 10 -6 cm 2 / Vs or higher. Note that any substance other than the above substances can be used for the electron-transport layer 114 as long as the electron-transport property is higher than the hole-transport property.

[0085] Furthermore, the electron transport layer 114 is not limited to a single layer, and a stacked layer in which two or more layers containing one of the substances described above are stacked may be used.

[0086] The electron injection layer 115 is a layer containing a substance with a high electron injection property. For the electron injection layer 115, an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF 2 ) or lithium oxide (LiOx). Alternatively, a rare earth metal compound, such as erbium fluoride (ErF3 ). Alternatively, the above substances can be used to form the electron transport layer 114.

[0087] Alternatively, a composite material in which an organic compound and an electron donor (donor) are mixed can be used for the electron-injection layer 115. Such a composite material has excellent electron injection properties and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that can transport the generated electrons well. For example, in particular, the above substances for forming the electron-transport layer 114 (such as a metal complex and a heteroaromatic compound) can be used. As the electron donor, a substance that has an electron-donating property with respect to the organic compound can be used.In particular, an alkali metal, an alkaline earth metal, and a rare earth metal are preferred, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be cited. Furthermore, an alkali metal oxide or an alkaline earth metal oxide such as lithium oxide, calcium oxide, barium oxide, and the like can be cited. A Lewis base such as magnesium oxide can be used alternatively. An organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used alternatively.

[0088] It should be noted that the above-described hole injection layer 111, hole transport layer 112, light-emitting layer 113, electron transport layer 114, electron injection layer 115, and charge generation layer (E) 116 can each be formed by a method such as a vapor deposition method (e.g., a vacuum vapor deposition method), an inkjet method, or a coating method.

[0089] In the light-emitting element described above, a current flows due to a potential difference between the first electrode 101 and the second electrode 103, and holes and electrons recombine in the EL layer 102, thereby emitting light. The emitted light is then extracted to the outside through the first electrode 101 and / or the second electrode 103. Therefore, the first electrode 101 and / or the second electrode 103 must be a light-transmitting electrode.

[0090] The light-emitting element described above can emit phosphorescence derived from the organometallic complex and thus can have higher efficiency than a light-emitting element containing a fluorescent compound.

[0091] Note that the light-emitting element is an example of a light-emitting element manufactured using the above-described organometallic complex. Furthermore, as a light-emitting device including the above-described light-emitting element, a passive matrix light-emitting device and an active matrix light-emitting device can be manufactured. It is also possible to manufacture a light-emitting device having a microcavity structure including a light-emitting element different from the above-described light-emitting elements, which will be described in another embodiment. Each of the above-described light-emitting devices is included in the present invention.

[0092] Note that when manufacturing the active matrix light-emitting device, there is no particular limitation on the structure of the TFT. For example, a staggered TFT or an inverted staggered TFT can be appropriately used. Furthermore, a driving circuit formed over a TFT substrate can be formed using an n-type TFT and / or a p-type TFT. Furthermore, there is no particular limitation on the crystallinity of a semiconductor film used for the TFT. For example, an amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

[0093] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. (Embodiment 3)

[0094] In this embodiment, which is an embodiment of the present invention, a light-emitting element in which two or more kinds of organic compounds and an organometallic complex are used for a light-emitting layer is described.

[0095] A light-emitting element described in this embodiment includes an EL layer 203 between a pair of electrodes (an anode 201 and a cathode 202) as shown in Fig. 2. Note that the EL layer 203 includes at least one light-emitting layer 204 and may include a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer (E), and the like. Note that the substances described in Embodiment 2 can be used for the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer, and the charge generation layer (E).

[0096] The light-emitting layer 204 described in this embodiment includes a phosphorescent compound 205 using the organometallic complex described in Embodiment 1, a first organic compound 206, and a second organic compound 207. Note that the phosphorescent compound 205 is a guest material in the light-emitting layer 204. One of the first organic compound 206 and the second organic compound 207, whose content is higher than that of the other in the light-emitting layer 204, is also a host material in the light-emitting layer 204.

[0097] When the light-emitting layer 204 has a structure in which the guest material is dispersed in the host material, crystallization of the light-emitting layer can be suppressed. It is also possible to suppress concentration quenching due to a high concentration of the guest material, so that the light-emitting element can have higher emission efficiency.

[0098] It should be noted that a triplet excitation energy level (T 1 -level) of both the first organic compound 206 and the second organic compound 207 is higher than that of the phosphorescent compound 205. The reason for this is that when the T 1-level of the first organic compound 206 (or the second organic compound 207) is lower than that of the phosphorescent compound 205, the triplet excitation energy of the phosphorescent compound 205, which contributes to the light emission, is quenched by the first organic compound 206 (or the second organic compound 207), thereby reducing the emission efficiency.

[0099] To improve the efficiency of energy transfer from a host material to a guest material, the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction), which are known as mechanisms of energy transfer between molecules, are considered here. According to these mechanisms, it is preferable that an emission spectrum of a host material (a fluorescence spectrum in the case of energy transfer from an excited singlet state, and a phosphorescence spectrum in the case of energy transfer from a triplet excited state) widely overlaps an absorption spectrum of a guest material (more precisely, the spectrum of an absorption band on the longest wavelength (lowest energy) side).However, it is generally difficult to obtain an overlap between the fluorescence spectrum of a host material and the absorption spectrum of the absorption band on the longest wavelength (lowest energy) side of a guest material. The reason for this is the following: when the fluorescence spectrum of the host material overlaps the absorption spectrum of the absorption band on the longest wavelength (lowest energy) side of the guest material, the T becomes larger. 1 -Level of host material lower than the T 1 -level of the phosphorescent compound and the previously described problem of quenching occurs because the phosphorescence spectrum of the host material lies on the side of a longer wavelength (lower energy) than the fluorescence spectrum. If the host material is designed in such a way that the T 1 -level of the host material is higher than the T 1However, to circumvent the quenching problem, the fluorescence spectrum of the host material shifts to the shorter wavelength (higher energy) side, so that the fluorescence spectrum does not overlap the absorption spectrum of the absorption band on the longest wavelength (lowest energy) side of the guest material. For this reason, it is generally difficult to obtain an overlap between a fluorescence spectrum of a host material and an absorption spectrum in an absorption band on the longest wavelength (lowest energy) side of a guest material in order to maximize the energy transfer from an excited singlet state of a host material.

[0100] Therefore, in this embodiment, a combination of the first organic compound 206 and the second organic compound 207 forms an exciplex (also referred to as an excited complex). In this case, the first organic compound 206 and the second organic compound 207 form an exciplex at the time of recombination of charge carriers (electrons and holes) in the light-emitting layer 204. In this way, the fluorescence spectrum of the first organic compound 206 and that of the second organic compound 207 in the light-emitting layer 204 are converted into an emission spectrum of the exciplex that is in the longer wavelength range. Furthermore, if the first organic compound 206 and the second organic compound 207 are selected so that the emission spectrum of the exciplex largely overlaps with the absorption spectrum of the guest material, energy transfer from an excited singlet state can be maximized.It should be noted that even in the case of an excited triplet state, energy transfer occurs from the exciplex, not from the host material.

[0101] For the phosphorescent compound 205, the organometallic complex described in Embodiment 1 is used. The combination of the first organic compound 206 and the second organic compound 207 can be selected to form an exciplex, but a combination of a compound that tends to accept electrons (a compound having an electron-trapping property) and a compound that tends to accept holes (a compound having a hole-trapping property) is preferably used.

[0102] As examples of a compound that tends to accept electrons, the following are given: 2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II) and 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II).

[0103] Examples of compounds that tend to accept holes include: 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene (abbreviation: DPA2SF), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N-(9,9-Dimethyl-2-N',N'-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), N,N',N''-Triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2-[N-(4-Diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), N,N'-Bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4'-Bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD), 4,4'-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N-(9,9-Dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), 3-[N-(9-Phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3-[N-(4-Diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 4,4'-Bis(N-{4-[N-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 3,6-Bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2) and 3,6-Bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2).

[0104] With respect to the above-described first and second organic compounds 206 and 207, the present invention is not limited to the above examples. The combination is determined such that an exciplex can be formed, wherein the emission spectrum of the exciplex overlaps the absorption spectrum of the phosphorescent compound 205, and the peak of the emission spectrum of the exciplex has a longer wavelength than the peak of the absorption spectrum of the phosphorescent compound 205.

[0105] Note that when a compound with a tendency to accept electrons and a compound with a tendency to accept holes are used for the first organic compound 206 and the second organic compound 207, the carrier balance can be controlled by the mixing ratio of the compounds. Specifically, the ratio of the first organic compound to the second organic compound is preferably 1:9 to 9:1.

[0106] In the light-emitting element described in this embodiment, the energy transfer efficiency can be improved thanks to energy transfer utilizing an overlap between the emission spectrum of the exciplex and the absorption spectrum of a phosphorescent compound; thus, a high external quantum efficiency of the light-emitting element can be obtained.

[0107] It should be noted that in another structure of the present invention, the light-emitting layer 204 may be formed by using, apart from the phosphorescent compound 205 (guest material), a host molecule having a hole-trapping property and a host molecule having an electron-trapping property as two kinds of organic compounds (the first organic compound 206 and the second organic compound 207), such that a phenomenon (guest coupled with complementary hosts, GCCH) occurs in which holes and electrons are introduced into guest molecules existing in the two kinds of host molecules and the guest molecules are brought into an excited state.

[0108] At this time, the host molecule having a hole-trapping property and the host molecule having an electron-trapping property can be selected from the above-mentioned compounds tending to accept holes and the above-mentioned compounds tending to accept electrons, respectively.

[0109] Note that the light-emitting element described in this embodiment is a structural example of a light-emitting element; it is possible to apply a light-emitting element having another structure described in another embodiment to a light-emitting device. Further, as a light-emitting device including the above-described light-emitting element, a passive matrix light-emitting device and an active matrix light-emitting device can be manufactured. A light-emitting device having a microcavity structure including a light-emitting element different from the above-described light-emitting elements described in another embodiment can also be manufactured. Any of the above-described light-emitting devices is included in the present invention.

[0110] Note that when manufacturing the active matrix light-emitting device, there is no particular limitation on the structure of the TFT. For example, a staggered TFT or an inverted staggered TFT can be appropriately used. Furthermore, a driving circuit formed over a TFT substrate can be formed using an n-type TFT and / or a p-type TFT. Furthermore, there is no particular limitation on the crystallinity of a semiconductor film used for the TFT. For example, an amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

[0111] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. (Embodiment 4)

[0112] In this embodiment, as one embodiment of the present invention, a light-emitting element (hereinafter referred to as a tandem light-emitting element) in which a charge generation layer is provided between a plurality of EL layers will be described.

[0113] A light-emitting element described in this embodiment is a tandem light-emitting element including a plurality of EL layers (a first EL layer 302(1) and a second EL layer 302(2)) between a pair of electrodes (a first electrode 301 and a second electrode 304) as shown in Fig. 3A shown.

[0114] In this embodiment, the first electrode 301 serves as an anode, and the second electrode 304 serves as a cathode. Note that the first electrode 301 and the second electrode 304 may have structures similar to those in Embodiment 2. Although the plurality of EL layers (the first EL layer 302(1) and the second EL layer 302(2)) may have a structure similar to that of the EL layer described in Embodiment 2 or 3, one of the EL layers may have a structure similar to that of the EL layer described in Embodiment 2 or 3. In other words, the structures of the first EL layer 302(1) and the second EL layer 302(2) may be the same as or different from each other, and may be similar to that of the EL layer described in Embodiment 2 or 3.

[0115] Furthermore, a charge generation layer (I) 305 is provided between the plurality of EL layers (the first EL layer 302(1) and the second EL layer 302(2)). The charge generation layer (I) 305 has a function of injecting electrons into one of the EL layers and injecting holes into the other of the EL layers when a voltage is applied between the first electrode 301 and the second electrode 304. In this embodiment, when a voltage is applied such that the potential of the first electrode 301 is higher than that of the second electrode 304, the charge generation layer (I) 305 injects electrons into the first EL layer 302(1) and holes into the second EL layer 302(2).

[0116] Note that, in terms of light extraction efficiency, the charge generation layer (I) 305 preferably has a visible light transmittance (specifically, the charge generation layer (I) 305 has a visible light transmittance of 40% or more). Furthermore, the charge generation layer (I) 305 functions even if it has a lower conductivity than the first electrode 301 or the second electrode 304.

[0117] The charge generation layer (I) 305 may have a structure in which an electron acceptor (Acceptor) is added to an organic compound with a high hole-transport property, or a structure in which an electron donor (Donor) is added to an organic compound with a high electron-transport property. Alternatively, both of these structures may be stacked.

[0118] In the case of the structure in which an electron acceptor is added to an organic compound with a high hole-transport property, an aromatic amine compound such as NPB, TPD, TDATA, MTDATA, or 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), or the like, can be used as the organic compound with a high hole-transport property. The substances indicated here are mainly substances that have a hole mobility of 10 -6 cm 2 / Vs or higher. It should be noted that a substance other than those described above can be used as long as they are organic compounds with a higher hole-transport property than an electron-transport property.

[0119] As electron acceptor, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F 4-TCNQ), chloranil, or the like may be used. Alternatively, a transition metal oxide may be used. An oxide of metals belonging to Group 4 to Group 8 of the Periodic Table may also be used. Vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, or rhenium oxide are particularly preferably used because their electron-accepting property is high. Among these oxides, molybdenum oxide is particularly preferred because it is stable in air, has low hygroscopicity, and can be easily handled.

[0120] In contrast, in the case of the structure in which an electron donor is added to an organic compound with a high electron transport property, the organic compound with a high electron transport property can be, for example, a metal complex having a quinoline skeleton or a benzoquinoline skeleton, such as Alq, Almq 3 , BeBq 2or BAlq, or the like. Alternatively, it is possible to use a metal complex with an oxazole-based ligand or a thiazole-based ligand such as Zn(BOX) 2 or Zn(BTZ) 2 Instead of such a metal complex, PBD, OXD-7, TAZ, BPhen, BCP, or the like can also be used. The substances mentioned here are mainly those with an electron mobility of 10 -6 cm 2 / Vs or higher. It should be noted that substances other than those described above can be used, as long as they are organic compounds with a higher electron-transport property than a hole-transport property.

[0121] An alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Group 2 or 13 of the Periodic Table, or an oxide or carbonate thereof can be used as the electron donor. In particular, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or the like is preferably used. An organic compound such as tetrathianaphthacene can alternatively be used as the electron donor.

[0122] Note that forming the charge generation layer (I) 305 using any of the above materials can suppress an increase in operating voltage caused by the stacking of the EL layers.

[0123] In this embodiment, the light-emitting element having two EL layers is described, but the present invention can similarly be applied to a light-emitting element in which n EL layers (302(1) to 302(n)) (n is three or more) are stacked as shown in Fig. 3B. When a plurality of EL layers are arranged between a pair of electrodes as in the light-emitting element according to this embodiment, light emission with high luminance can be obtained by providing the charge generation layers (I) (305(1) to 305(n-1)) between the EL layers, while keeping the current density low. Since the current density can be kept low, the element can have a long lifetime. When the light-emitting element is used for lighting devices, a voltage drop due to the resistance of an electrode material can be reduced, so that uniform light emission can be obtained in a large area. In addition, it is possible to obtain a light-emitting device that can be operated at a low voltage and has low power consumption.

[0124] By fabricating the EL layers to emit light of different colors from each other, the light-emitting element can emit light of the desired overall color. For example, if a light-emitting element is fabricated with two EL layers so that the emission color of the first EL layer and the emission color of the second EL layer are complementary colors, the light-emitting element can emit overall white light. Note that the word "complementary" refers to a color ratio in which an achromatic color is achieved when colors are mixed. In other words, when light obtained from a light-emitting substance and light of a complementary color are mixed, white light emission can be achieved.

[0125] The same can be further applied to a light-emitting element with three EL layers. For example, the light-emitting element as a whole can emit white light if the emission color of the first EL layer is red, the emission color of the second EL layer is green, and the emission color of the third EL layer is blue.

[0126] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. (Embodiment 5)

[0127] In this embodiment, a light-emitting device is described.

[0128] A light-emitting device described in this embodiment has a structure of an optical microresonator (a microcavity) that utilizes a light resonance effect between a pair of electrodes. The light-emitting device includes a plurality of light-emitting elements, each having at least one EL layer 405 between a pair of electrodes (a reflective electrode 401 and a semi-transparent and semi-reflective electrode 402), as shown in Fig. 4. Furthermore, the EL layer 405 includes at least light-emitting layers 404 (404R, 404G, and 404B), each serving as a light-emitting region, and may further include a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, a charge-generation layer (E), and the like. Note that the light-emitting layer 404 contains the organometallic complex.

[0129] In this embodiment, a light-emitting device is described that includes light-emitting elements (a first light-emitting element (R) 410R, a second light-emitting element (G) 410G, and a third light-emitting element (B) 410B) having different structures as shown in Fig. 4 shown.

[0130] The first light-emitting element (R) 410R has a structure in which a first transparent conductive layer 403a; an EL layer 405 including a first light-emitting layer (B) 404B, a second light-emitting layer (G) 404G, and a third light-emitting layer (R) 404R as parts; and a semi-transparent and semi-reflective electrode 402 are sequentially stacked over a reflective electrode 401. The second light-emitting element (G) 410G has a structure in which a second transparent conductive layer 403b, the EL layer 405, and the semi-transparent and semi-reflective electrode 402 are sequentially stacked over the reflective electrode 401. The third light-emitting element (B) 410B has a structure in which the EL layer 405 and the semi-transparent and semi-reflective electrode 402 are sequentially stacked over the reflective electrode 401.

[0131] It should be noted that the reflective electrode 401, the EL layer 405, and the semi-transparent and semi-reflective electrode 402 are common to the light-emitting elements (the first light-emitting element (R) 410R, the second light-emitting element (G) 410G, and the third light-emitting element (B) 410B). The first light-emitting layer (B) 404B emits light (λ B ) with a peak in a wavelength range of 420 nm to 480 nm. The second light-emitting layer (G) 404G emits light (λ G ) with a peak in a wavelength range of 500 nm to 550 nm. The third light-emitting layer (R) 404R emits light (λ R) with a peak in a wavelength range of 600 nm to 760 nm. Therefore, in each of the light-emitting elements (the first light-emitting element (R) 410R, the second light-emitting element (G) 410G, and the third light-emitting element (B) 410B), light emitted from the first light-emitting layer (B) 404B, light emitted from the second light-emitting layer (G) 404G, and light emitted from the third light-emitting layer (R) 404R overlap with each other. Accordingly, light having a broad emission spectrum including a visible light range can be emitted. Note that the above wavelengths satisfy the relationship of λ B < λ G < λ R fulfill.

[0132] Each of the light-emitting elements described in this embodiment has a structure in which the EL layer 405 is provided between the reflective electrode 401 and the semi-transparent and semi-reflective electrode 402. Light emitted from the light-emitting layers in the EL layer 405 in all directions resonates with the reflective electrode 401 and the semi-transparent and semi-reflective electrode 402, which serve as an optical micro-resonator (micro-cavity). Note that the reflective electrode 401 is formed using a conductive material having reflectivity, and a film whose visible light reflectivity is 40% to 100%, preferably 70% to 100%, and whose specific resistance is 1 × 10 -2Ωcm or lower. In addition, the semi-transparent and semi-reflective electrode 402 is formed using a conductive material having reflectivity and a conductive material having light transmittance, and a film is used whose visible light reflectivity is 20% to 80%, preferably 40% to 70%, and whose specific resistance is 1 × 10 -2 Ωcm or lower.

[0133] In this embodiment, the thicknesses of the transparent conductive layers (the first transparent conductive layer 403a and the second transparent conductive layer 403b) provided in the first light-emitting element (R) 410R and the second light-emitting element (G) 410G, respectively, differ between the light-emitting elements, whereby the light-emitting elements differ from each other in the optical path length from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402.In other words, in the light with a broad emission spectrum emitted from the light-emitting layers of each of the light-emitting elements, light with a wavelength that resonates between the reflective electrode 401 and the semi-transparent and semi-reflective electrode 402 can be amplified, while light with a wavelength that does not resonate between them can be attenuated. Therefore, when the elements differ in the optical path length from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402, light with different wavelengths can be extracted.

[0134] Note that the optical path length (also referred to as optical distance) is represented as a product of an actual distance and a refractive index, and in this embodiment, it is a product of an actual thickness and n (refractive index). That is, an optical path length = actual thickness × n.

[0135] Furthermore, the total thickness from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402 is set to mλ R / 2 (m is a natural number) at the first light-emitting element (R) 410R. The total thickness from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402 is set to mλ G / 2 (m is a natural number) at the second light-emitting element (G) 410G. The total thickness from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402 is set to mλ B / 2 (m is a natural number) at the third light-emitting element (B) 410B.

[0136] In this way, the light (λ R ) emitted from the third light-emitting layer (R) 404R in the EL layer 405 is mainly taken from the first light-emitting element (R) 410R, which emits light (λ G ) emitted from the second light-emitting layer (G) 404G in the EL layer 405 is mainly taken from the second light-emitting element (G) 410G, and the light (λ B ) emitted from the first light-emitting layer (B) 404B in the EL layer 405 is mainly taken out from the third light-emitting element (B) 410B. Note that the light taken out from each of the light-emitting elements is emitted from the side of the semi-transparent and semi-reflective electrode 402.

[0137] Furthermore, strictly speaking, the total thickness from the reflective electrode 401 to the semi-transparent and semi-reflective electrode 402 may be the total thickness from a reflection region in the reflective electrode 401 to a reflection region in the semi-transparent and semi-reflective electrode 402. However, it is difficult to determine precise positions of the reflection regions in the reflective electrode 401 and the semi-transparent and semi-reflective electrode 402. Therefore, it is believed that the above effect can be sufficiently obtained wherever the reflection regions in the reflective electrode 401 and the semi-transparent and semi-reflective electrode 402 are located.

[0138] Next, in the first light-emitting element (R) 410R, the optical path length from the reflective electrode 401 to the third light-emitting layer (R) 404R is set to a desired thickness ((2m'+1)λ R / 4, where m' is a natural number). Thus, light emitted from the third light-emitting layer (R) 404R can be amplified. Light (first reflected light) reflected by the reflective electrode 401 from the light emitted by the third light-emitting layer (R) 404R interferes with light (first incident light) directly entering the semi-transparent and semi-reflective electrode 402 from the third light-emitting layer (R) 404R. Therefore, by setting the optical path length from the reflective electrode 401 to the third light-emitting layer (R) 404R to the desired value ((2m'+1)λ R / 4, where m' is a natural number), the phases of the first reflected light and the first incident light can be adjusted to each other, and the light emitted from the third light-emitting layer (R) 404R can be amplified.

[0139] Note that, strictly speaking, the optical path length from the reflective electrode 401 to the third light-emitting layer (R) 404R may be the optical path length from a reflection region in the reflective electrode 401 to a light-emitting region in the third light-emitting layer (R) 404R. However, it is difficult to determine precise positions of the reflection region in the reflective electrode 401 and the light-emitting region in the third light-emitting layer (R) 404R. Therefore, it is considered that the above effect can be sufficiently obtained wherever the reflection region and the light-emitting region are located in the reflective electrode 401 and the third light-emitting layer (R) 404R, respectively.

[0140] Next, in the second light-emitting element (G) 410G, the optical path length from the reflective electrode 401 to the second light-emitting layer (G) 404G is set to a desired thickness ((2m''+1)λ G / 4, where m'' is a natural number). Thus, light emitted from the second light-emitting layer (G) 404G can be amplified. Light (second reflected light) reflected by the reflective electrode 401 from the light emitted from the second light-emitting layer (G) 404G interferes with light (second incident light) directly entering the semi-transparent and semi-reflective electrode 402 from the second light-emitting layer (G) 404G. Therefore, by setting the optical path length from the reflective electrode 401 to the second light-emitting layer (G) 404G to the desired value ((2m''+1)λ G / 4, where m'' is a natural number), the phases of the second reflected light and the second incident light can be adjusted to each other, and the light emitted from the second light-emitting layer (G) 404G can be amplified.

[0141] Note that, strictly speaking, the optical path length from the reflective electrode 401 to the second light-emitting layer (G) 404G may be the optical path length from a reflection region in the reflective electrode 401 to a light-emitting region in the second light-emitting layer (G) 404G. However, it is difficult to determine precise positions of the reflection region in the reflective electrode 401 and the light-emitting region in the second light-emitting layer (G) 404G. Therefore, it is believed that the above effect can be sufficiently obtained wherever the reflection region and the light-emitting region are located in the reflective electrode 401 and the second light-emitting layer (G) 404G, respectively.

[0142] Next, in the third light-emitting element (B) 410B, the optical path length from the reflective electrode 401 to the first light-emitting layer (B) 404B is set to a desired thickness ((2m'''+1)λ B / 4, where m''' is a natural number). Thus, light emitted from the first light-emitting layer (B) 404B can be amplified. Light (third reflected light) reflected by the reflective electrode 401 from the light emitted from the first light-emitting layer (B) 404B interferes with light (third incident light) directly entering the semi-transparent and semi-reflective electrode 402 from the first light-emitting layer (B) 404B. Therefore, by setting the optical path length from the reflective electrode 401 to the first light-emitting layer (B) 404B to the desired value ((2m'''+1)λ B / 4, where m''' is a natural number), the phases of the third reflected light and the third incident light can be adjusted to each other, and the light emitted from the first light-emitting layer (B) 404B can be amplified.

[0143] Note that, strictly speaking, the optical path length from the reflective electrode 401 to the first light-emitting layer (B) 404B in the third light-emitting element may be the optical path length from a reflection region in the reflective electrode 401 to a light-emitting region in the first light-emitting layer (B) 404B. However, it is difficult to determine precise positions of the reflection region in the reflective electrode 401 and the light-emitting region in the first light-emitting layer (B) 404B. Therefore, it is believed that the above effect can be sufficiently obtained wherever the reflection region and the light-emitting region are located in the reflective electrode 401 and the first light-emitting layer (B) 404B, respectively.

[0144] Note that although each of the light-emitting elements in the above-described structure includes a plurality of light-emitting layers in the EL layer, the present invention is not limited thereto. For example, the structure of the tandem light-emitting element described in Embodiment 4 may be combined, in which case a plurality of EL layers and an intermediate charge generation layer are provided in one light-emitting element, and one or more light-emitting layers are formed in each of the EL layers.

[0145] The light-emitting device described in this embodiment has a microcavity structure from which light with wavelengths different depending on the light-emitting elements can be taken out even if they include the same EL layers. This makes it unnecessary to manufacture light-emitting elements for colors of R, G, and B. The above structure is therefore advantageous for a color display due to the ease with which a higher-resolution display or the like can be achieved. In addition, the intensity of emission with a predetermined wavelength can be increased in the forward direction, thereby reducing power consumption. The above structure is particularly useful in the case where it is applied to a color display (image display device) including pixels of three or more colors, but it can also be applied to illumination or the like. (Embodiment 6)

[0146] In this embodiment, a light-emitting device including a light-emitting element in which the above-described organometallic complex is used for a light-emitting layer is described.

[0147] The light-emitting device may be either a passive matrix light-emitting device or an active matrix light-emitting device. Note that any of the light-emitting elements described in the other embodiments may be applied to the light-emitting device described in this embodiment.

[0148] In this embodiment, an active matrix light-emitting device is manufactured using Fig. 5A and Fig. 5B.

[0149] It should be noted that Fig. 5A is a plan view showing a light-emitting device, and Fig. 5B is a cross-sectional view along the dotted line AA' in Fig. 5A. The active matrix light-emitting device according to this embodiment includes a pixel portion 502 provided above an element substrate 501, a driving circuit portion (a source line driving circuit) 503, and driving circuit portions (gate line driving circuits) 504 (504a and 504b). The pixel portion 502, the driving circuit portion 503, and the driving circuit portions 504 are sealed with a sealant 505 between the element substrate 501 and the sealing substrate 506.

[0150] A lead wiring 507 is additionally arranged above the element substrate 501. The lead wiring 507 is provided to connect an external input terminal, through which a signal (for example, a video signal, a clock signal, a start signal, and a reset signal) or a potential is transmitted from the outside, to the drive circuit section 503 and the drive circuit sections 504. Here, an example is shown in which a flexible printed circuit (FPC) 508 is provided as the external input terminal. Although only the FPC 508 is shown, this FPC may be provided with a printed wiring board (PWB). The light-emitting device in this specification includes within its category not only the light-emitting device itself but also the light-emitting device provided with the FPC or the PWB.

[0151] Next, a cross-sectional structure is created using Fig. 5B. The driver circuit section and the pixel section are formed over the element substrate 501. Shown here are the driver circuit section 503, which is the source line driver circuit, and the pixel section 502.

[0152] The driver circuit section 503 is an example in which a CMOS circuit is formed, which is a combination of an n-channel TFT 509 and a p-channel TFT 510. Note that a circuit included in the driver circuit section can be formed using various CMOS circuits, PMOS circuits, or NMOS circuits. In this embodiment, a driver-integrated type in which the driver circuit is formed above the substrate is described; the driver circuit is not necessarily formed above the substrate and may also be formed outside the substrate.

[0153] The pixel section 502 includes a plurality of pixels, each including a TFT 511 for switching, a TFT 512 for current control, and a first electrode (anode) 513 electrically connected to a line (a source electrode or a drain electrode) of the TFT 512 for current control. Note that an insulator 514 is formed to cover end portions of the first electrode (anode) 513. In this embodiment, the insulator 514 is formed using a positive photosensitive acrylic resin.

[0154] The insulator 514 preferably has a curved surface with a curvature in its upper end portion or its lower end portion to obtain good coverage with a film that is subsequently stacked over the insulator 514. For example, in the case of using a positive photosensitive acrylic resin as the material for the insulator 514, the insulator 514 preferably has a curved surface with a radius of curvature (0.2 μm to 3 μm) in the upper end portion. Note that the insulator 514 can be formed using a negative photosensitive resin or a positive photosensitive resin. The material for the insulator 514 is not limited to an organic compound, and an inorganic compound such as silicon oxide or silicon oxynitride can also be used.

[0155] An EL layer 515 and a second electrode (cathode) 516 are stacked over the first electrode (anode) 513. The EL layer 515 includes at least one light-emitting layer containing the organometallic complex. The EL layer 515 may appropriately further include, in addition to the light-emitting layer, a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, a charge-generation layer, and the like.

[0156] A light-emitting element 517 has a stacked structure of the first electrode (anode) 513, the EL layer 515, and the second electrode (cathode) 516. For the first electrode (anode) 513, the EL layer 515, and the second electrode (cathode) 516, the materials described in Embodiment 2 can be used. Although not shown, the second electrode (cathode) 516 is electrically connected to the FPC 508, which is an external input terminal.

[0157] Although the cross-sectional view of Fig. While FIG. 5B shows only the single light-emitting element 517, a plurality of light-emitting elements are arranged in a matrix form in the pixel section 502. Light-emitting elements that emit three types of light (R, G, and B) are selectively formed in the pixel section 502, whereby a light-emitting device capable of full-color display can be manufactured. Alternatively, a light-emitting device capable of full-color display can be manufactured by combining it with color filters.

[0158] The sealing substrate 506 is further attached to the element substrate 501 with the sealant 505, so that the light-emitting element 517 is provided in a space 518 enclosed by the element substrate 501, the sealing substrate 506, and the sealant 505. The space 518 can be filled with an inert gas (such as nitrogen or argon) or with the sealant 505.

[0159] An epoxy-based resin is preferably used for the sealant 505. It is preferable that such a material permits as little moisture or oxygen permeation as possible. A glass substrate, a quartz substrate, or a plastic substrate made of fiberglass reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like can be used as the sealant substrate 506.

[0160] In the manner described above, an active matrix light-emitting device can be manufactured.

[0161] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. (Embodiment 7)

[0162] In this embodiment, Fig. 6A to Fig. 6D and Fig. 7A to Fig. 7C describes examples of various electronic devices fabricated using a light-emitting device. The organometallic complex is applied to the light-emitting device.

[0163] Examples of the electronic devices to which the light-emitting device is applied include a television set (also referred to as a television or television receiver), a monitor of a computer or the like, a camera such as a digital camera or a digital video camera, a digital photo frame, a mobile phone (also referred to as a cellular phone or mobile phone device), a portable game console, a portable information terminal, an audio playback device, and a large-scale gaming device such as a pachinko machine. Specific examples of these electronic devices are described in Fig. 6A to Fig. 6D shown.

[0164] Fig. 6A shows an example of a television set. In a television set 7100, a display section 7103 is installed in a housing 7101. Images can be displayed on the display section 7103, and the light-emitting device can be used for the display section 7103. In addition, the housing 7101 is supported by a stand 7105.

[0165] The television set 7100 can be operated using an operation switch of the housing 7101 or a separate remote control 7110. Operation buttons 7109 of the remote control 7110 can control the TV channels and volume, and images displayed on the display section 7103. Furthermore, the remote control 7110 can include a display section 7107 for displaying data output from the remote control 7110.

[0166] Note that the television set 7100 is equipped with a receiver, a modem, and the like. The receiver can receive a general television broadcast. Furthermore, when the television set 7100 is connected to a communication network via a wired connection or wirelessly via the modem, unidirectional (from a transmitter to a receiver) or bidirectional (between a transmitter and a receiver, between receivers, or the like) data communication can be performed.

[0167] Fig. 6B shows a computer including a main body 7201, a casing 7202, a display section 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured using the light-emitting device for the display section 7203.

[0168] Fig. Figure 6C shows a portable game console with two housings, a housing 7301 and a housing 7302, which are connected to each other via a hinge section 7303 so that the portable game console can be opened or closed. A display section 7304 is installed in the housing 7301, and a display section 7305 is installed in the housing 7302. In addition, the portable game console includes Fig. 6C, a speaker section 7306, a recording medium insertion section 7307, an LED lamp 7308, input means (an operation button 7309, a connection terminal 7310, a sensor 7311 (a sensor with a function for measuring force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), and a microphone 7312), and the like. Of course, the structure of the portable game console is not limited to the above structure, as long as the light-emitting device is used for at least one of the display section 7304 and the display section 7305, and the portable game console may appropriately include other accessories. The portable game console in Fig. 6C has a function for reading a program or data stored in a storage medium to display it on the display section, and a function for sharing information with another portable game console via wireless communication. The functions of the portable game console in Fig. 6C are not limited to these examples, and the portable game console can have various functions.

[0169] Fig. 6D shows an example of a mobile phone. A mobile phone 7400 includes a display section 7402 installed in a housing 7401, operation buttons 7403, an external connection terminal 7404, a speaker 7405, a microphone 7406, and the like. Note that the mobile phone 7400 is manufactured using the light-emitting device for the display section 7402.

[0170] When the display section 7402 of the mobile phone 7400 is in Fig. 6D is touched with a finger or the like, data can be input into the mobile phone 7400. Furthermore, operations such as calling and writing an email can be performed by touching the display section 7402 with a finger or the like.

[0171] There are mainly three screen modes for the display section 7402. The first mode is a display mode, which mainly displays images. The second mode is an input mode, which mainly inputs data such as text. The third mode is a display-input mode, which combines two modes: display mode and input mode.

[0172] For example, in the case of making a call or writing an email, a text input mode that primarily inputs text is selected for the display section 7402 so that text displayed on the screen can be input. In this case, it is preferable to display a keyboard or number buttons on almost the entire screen of the display section 7402.

[0173] When a detection device having a sensor for detecting inclination, such as a gyroscope or an acceleration sensor, is provided within the mobile phone 7400, the display on the screen of the display section 7402 can be automatically switched by determining the orientation of the mobile phone 7400 (whether the mobile phone is placed horizontally or vertically for a landscape or portrait orientation).

[0174] The screen modes are switched by touching the display section 7402 or operating the operation buttons 7403 of the body 7401. The screen modes can also be switched depending on the type of image displayed on the display section 7402. For example, if a signal for an image displayed on the display section is a signal for moving image data, the screen mode is switched to the display mode. If the signal is a signal for text data, the screen mode is switched to the input mode.

[0175] In addition, in the input mode, when input by touching the display section 7402 is not performed for a certain period of time while a signal detected by an optical sensor in the display section 7402 is detected, the screen mode can be controlled to be switched from the input mode to the display mode.

[0176] The display section 7402 can serve as an image sensor. For example, a palm print, a fingerprint, or the like is photographed when the display section 7402 is touched with the palm or finger, thereby performing personal authentication. Furthermore, if a backlight or a scanning light source that emits near-infrared light is provided in the display section, an image of a finger vein, a palm vein, or the like can be captured.

[0177] Fig. 7A and Fig. 7B show a tablet computer that can be folded. In Fig. 7A, the tablet computer is opened. The tablet computer includes a case 9630, a display section 9631a, a display section 9631b, a button 9034 for switching display modes, a power switch 9035, a button 9036 for switching to a power saving mode, a bracket 9033, and an operation button 9038. The tablet computer is manufactured using the light-emitting device for the display section 9631a and / or the display section 9631b.

[0178] A part of the display section 9631a may be a touchscreen area 9632a, and data can be input when a displayed operation button 9637 is touched. Although a structure is shown as an example in which one half of the display section 9631a has only a display function and the other half also has a touchscreen function, the display section 9631a is not limited to this structure. The entire area of ​​the display section 9631a may have a touchscreen function. For example, the display section 9631a may display keyboard buttons in the entire area intended to be a touchscreen, and the display section 9631b may be used as a display screen.

[0179] As with the display section 9631a, a part of the display section 9631b may be a touchscreen area 9632b. When a button 9639 for switching a keyboard display displayed on the touchscreen is touched with a finger, a stylus, or the like, a keyboard may be displayed on the display section 9631b.

[0180] Touch-sensitive input can be performed on the touchscreen area 9632a and the touchscreen area 9632b at the same time.

[0181] The display mode switching switch 9034 can, for example, switch the display between portrait mode, landscape mode, and the like, and between monochrome display and color display. The power saving mode switching button 9036 can control the display luminance according to the amount of external light detected by an optical sensor in the tablet when using the tablet computer. In addition to the optical sensor, another detection device such as a sensor for detecting inclination, such as a gyroscope or an acceleration sensor, can be installed in the tablet computer.

[0182] It should be noted that Fig. 7A shows an example in which the display section 9631a and the display section 9631b have the same display area. However, without limitation, one of the display sections may be different from the other in terms of size and display quality. For example, higher-resolution images may be displayed on one of the display sections 9631a and 9631b.

[0183] The tablet computer is in Fig. 7B closed. The tablet computer includes the housing 9630, a solar cell 9633, a charge and discharge control circuit 9634, a battery 9635 and a DC-DC converter 9636. In Fig. 7B is a structure including the battery 9635 and the DC-DC converter 9636 as an example of the charge and discharge control circuit 9634.

[0184] Since the tablet computer can be folded, the casing 9630 can be closed when not in use. Thus, the display section 9631a and the display section 9631b can be protected. Therefore, a tablet computer with high durability and high reliability for long-term use can be provided.

[0185] The tablet computer in Fig. 7A and Fig. 7B may additionally have a function of displaying various types of data (e.g., a still image, a moving image, and a text image), a function of displaying a calendar, a date, a time, or the like on the display section, a touch input function of operating or editing the data displayed on the display section by touch input, a function of controlling processing by various types of software (programs), and the like.

[0186] The solar cell 9633 on a surface of the tablet computer can supply power to the touchscreen, the display section, an image signal processing section, or the like. Note that the solar cell 9633 can be arranged on one or both surfaces of the case 9630 to charge the battery 9635 that supplies power, which is preferable. Using a lithium-ion battery as the battery 9635 is advantageous because of the size reduction and so on.

[0187] The structure and operation of the charge and discharge control circuit 9634 shown in Fig. 7B are shown with reference to a block diagram in Fig. 7C. The solar cell 9633, the battery 9635, the DC-DC converter 9636, a converter 9638, switches SW1 to SW3 and the display section 9631 are shown in Fig. 7C, and the battery 9635, the DC-DC converter 9636, the converter 9638 and the switches SW1 to SW3 correspond to the charge and discharge control circuit 9634 shown in Fig. 7B is shown.

[0188] First, an example of operation in the case where power is generated from the solar cell 9633 using external light will be described. The voltage of the power generated by the solar cell 9633 is increased or decreased by the DC-DC converter 9636 so that the power has a voltage required for charging the battery 9635. When the power from the solar cell 9633 is used to drive the display section 9631, the switch SW1 is turned on, and the voltage of the power is increased or decreased by the converter 9638 so that it becomes a voltage required for the display section 9631. Further, when no display is being performed on the display section 9631, the switch SW1 is turned off, and the switch SW2 is turned on so that charging of the battery 9635 can be performed.

[0189] Note that the solar cell 9633 has been described as an example of a power generation means; however, the battery 9635 may also be charged using other power generation means, such as a piezoelectric element or a thermoelectric conversion element (Peltier element), without limitation. The battery 9635 may be charged, for example, using a non-contact power transmission module that can charge the battery by wirelessly (contactlessly) transmitting and receiving power, or using other charging means in combination.

[0190] It is needless to say that an embodiment of the present invention is not limited to the electronic device in Fig. 7A to Fig. 7C as long as the display section described in this embodiment is included.

[0191] As described above, electronic devices can be obtained by using the light-emitting device. The light-emitting device has a very wide range of applications and can be applied to electronic devices in various fields.

[0192] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. (Embodiment 8)

[0193] In this embodiment, Fig. 8 Examples of a lighting device to which a light-emitting device containing the organometallic complex according to an embodiment of the present invention is applied are described.

[0194] Fig. 8 shows an example in which the light-emitting device is used as a room lighting device 8001. Since the light-emitting device can have a large area, it can be used for a lighting device with a large area. In addition, a lighting device 8002 in which a light-emitting region has a curved surface can also be obtained by using a housing with a curved surface. A light-emitting element in the light-emitting device described in this embodiment is in the form of a thin film, which allows the housing to be designed more freely. Consequently, the lighting device can be artistically designed in various ways. Furthermore, a wall of the room can be provided with a large lighting device 8003.

[0195] Furthermore, when the light-emitting device is used for a table, by using it as a surface of the table, a lighting device 8004 having a function as a table can be obtained. When the light-emitting device is used as part of other furniture, a lighting device having a function as the furniture is obtained.

[0196] In this way, various lighting devices to which the light-emitting device is applied can be obtained. It should be noted that such lighting devices are also embodiments of the present invention.

[0197] It should be noted that the structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. [Example 1]((Synthesis Example 1))

[0198] In this example, a synthesis procedure of Bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}( 2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P) 2 (dibm)]), which is represented by structural formula (100) in Embodiment 1. The structure of [Ir(dmdppr-P) 2 (dibm)] (abbreviation) is shown below. (Step 1: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr)〉

[0199] First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of 3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2), 20 ml of water, and 20 ml of acetonitrile were added to a round-bottom flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2 , 5 ml of water and 5 ml of acetonitrile were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes, so that heating was carried out.

[0200] Water was then added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium bicarbonate, water, and a saturated saline solution, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1. The solvent was distilled off, and the obtained solid was purified by flash column chromatography using dichloromethane and ethyl acetate as the eluent in a volume ratio of 10:1, so that Hdmdppr (abbreviation), which was the pyrazine derivative to be prepared, was obtained as a white powder in a yield of 44%.Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (a-1). 〈Step 2: Preparation of 2,3-bis(3,5-dimethylphenyl)-5-phenylpyrazine (abbreviation: Hdmdppr-P)〉

[0201] First, 4.28 g of Hdmdppr (abbreviation) obtained in step 1 and 80 ml of dry THF were added to a three-necked flask, and the air in the flask was replaced with nitrogen. After the flask was cooled with ice, 9.5 ml of phenyllithium (1.9M solution of phenyllithium in butyl ether) was added dropwise, and the mixture was stirred at room temperature for 23.5 hours. The reaction solution was poured into water, and the solution was extracted with chloroform. The obtained organic layer was washed with water and a saturated saline solution and dried with magnesium sulfate. Manganese oxide was added to the obtained mixture, and the mixture was stirred for 30 minutes. Then, the solution was filtered, and the solvent was distilled off.The resulting residue was purified by silica gel column chromatography using dichloromethane as the eluent, yielding Hdmdppr-P (abbreviation), the pyrazine derivative to be prepared, as an orange oil in 26% yield. A synthesis scheme of step 2 is shown in (a-2). (Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppr-P) 2 Cl] 2 )〉

[0202] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 1.40 g of Hdmdppr-P (abbreviation), which had been obtained in step 2, and 0.51 g of iridium chloride hydrate (IrCl 3 ·H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a round-bottom flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and the obtained residue was then subjected to suction filtration and washed with ethanol to obtain [Ir(dmdppr-P)]. 2 Cl] 2 (abbreviation), which was a dinuclear complex, as a reddish-brown powder in a yield of 58%. A synthesis scheme of step 3 is shown in (a-3). (Step 4: Preparation of Bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}( 2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P) 2 (dibm)])〉

[0203] In addition, 30 ml of 2-ethoxyethanol, 0.94 g of [Ir(dmdppr-P) 2 Cl]2 , which is the dinuclear complex obtained in step 3, 0.23 g of diisobutyrylmethane (abbreviation: Hdibm) and 0.52 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol, and recrystallization was carried out with a mixed solvent of dichloromethane and ethanol to obtain [Ir(dmdppr-P)]. 2 (dibm)] (abbreviation) was obtained as a dark red powder in 75% yield. A synthesis scheme of step 4 is shown in (a-4).

[0204] An analysis result by nuclear magnetic resonance spectroscopy ( 1H-NMR) on the dark red powder obtained by the synthesis procedure described above is described below. Fig. 9 shows the 1 H-NMR diagram. These results show that [Ir(dmdppr-P) 2 (dibm)] (abbreviation), which is represented by the structural formula (100), was obtained in Synthesis Example 1.

[0205] 1 H-NMR. δ(CDCl 3 ): 0.79 (d, 6H), 0.96 (d, 6H), 1.41 (s, 6H), 1.96 (s, 6H), 2.24-2.28 (m, 2H), 2.41 (s, 12H), 5.08 (s, 1H), 6.46 (s, 2H), 6.82 (s, 2H), 7.18 (s, 2H), 7.39-7.50 (m, 10H), 8.03 (d, 4H), 8.76 (s, 2H).

[0206] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppr-P) 2(dibm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.062 mmol / L) was placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.010 mmol / L) was placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 10, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig. 10, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 10 is the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.062 mmol / l) in a quartz cell.

[0207] As in Fig. 10, [Ir(dmdppr-P) 2 (dibm)] (abbreviation) exhibited an emission peak at approximately 640 nm, and reddish-orange light emission was observed from the dichloromethane solution.

[0208] In addition, the weight loss percentage of [Ir(dmdppr-P) 2(dibm)] (abbreviation) was measured by a high vacuum differential type differential thermal balance (TG / DTA 2410SA, manufactured by Bruker AXS KK). The temperature was measured at a rate of 10 °C / min under a vacuum degree of 1 × 10 -3 Pa. As a result, it was found that the percentage of weight loss of [Ir(dmdppr-P) 2 (dibm)] (abbreviation) was 100%, as in Fig. 37, indicating an advantageous sublimation property of the organometallic complex. For comparison, the percentage weight loss of Compound A, in which methyl groups are not bonded to the 3- and 5-positions, is shown. A comparison with a 78% weight loss percentage of Compound A showed that the organometallic complex has an improved sublimation property due to the presence of the methyl groups in the 3- and 5-positions. [Example 2]〈〈Synthesis Example 2〉〉

[0209] In this example, a synthesis method of bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-di methyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dibm)]), which is represented by structural formula (107) in Embodiment 1. The structure of [Ir(dmdppm) 2 (dibm)] (abbreviation) is shown below. (Step 1: Preparation of 4,6-bis(3,5-dimethylphenyl)pyrimidine (abbreviation: Hdmdppm)〉

[0210] First, 5.97 g of 4,6-dichloropyrimidine, 12.04 g of 3,5-dimethylphenylboronic acid, 8.48 g of sodium carbonate, 0.34 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2), 20 ml of water, and 20 ml of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (abbreviation: DMPU) were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.58 g of 3,5-dimethylphenylboronic acid, 1.78 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2 , 5 ml of water and 5 ml of DMPU were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes, so that heating was carried out.

[0211] The obtained residue was then subjected to suction filtration with water and washed with water and ethanol. The obtained residue was dissolved in dichloromethane, filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order, and then washed with ethanol, so that Hdmdppm, which was the pyrimidine derivative to be prepared, was obtained as a white powder in a yield of 56%. Note that microwave irradiation was carried out using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (b-1). 〈Step 2: Preparation of di-µ-chloro-tetrakis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppm) 2 Cl] 2 )〉

[0212] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 2.10 g of Hdmdppm (abbreviation), which had been obtained in step 1, and 1.07 g of iridium chloride hydrate (IrCl 3 ·H 2 O) (manufactured by Sigma-Aldrich Corporation) was placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with ethanol to obtain [Ir(dmdppm)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in a yield of 74%. A synthesis scheme of step 2 is shown in (b-2). 〈Step 3: Preparation of bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-di methyl-3,5-heptanedionato-κ2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dibm)])〉

[0213] In addition, 30 ml of 2-ethoxyethanol, 1.09 g of [Ir(dmdppm) 2 Cl] 2 (abbreviation), which is the dinuclear complex obtained in step 2, 0.32 g of diisobutyrylmethane (abbreviation: Hdibm) and 0.72 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol, and recrystallization was carried out with a mixed solvent of dichloromethane and ethanol to obtain [Ir(dmdppm)]. 2(dibm)] (abbreviation) was obtained as a red powder in a yield of 62%. A synthesis scheme of step 3 is shown in (b-3).

[0214] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the red powder obtained by the synthesis procedure described above is described below. Fig. 11 shows the 1 H-NMR diagram. These results showed that [Ir(dmdppm) 2 (dibm)] (abbreviation), which is represented by the structural formula (107), was obtained in Synthesis Example 2.

[0215] 1 H-NMR. δ(CDCl 3 ): 0.69 (d, 6H), 0.82 (d, 6H), 1.51 (s, 6H), 2.17-2.23 (m, 2H), 2.31 (s, 6H), 2.45 (s, 12H), 5.19 (s, 1H), 6.61 (s, 2H), 7.17 (s, 2H), 7.56 (s, 2H), 7.82 (s, 4H), 8.11 (d, 2H), 8.88 (d, 2H).

[0216] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppm) 2 (dibm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.072 mmol / L) placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.072 mmol / L) placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 12, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig. 12, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 12 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.072 mmol / l) in a quartz cell.

[0217] As in Fig. 12, [Ir(dmdppm) 2 (dibm)] (abbreviation) exhibited an emission peak at approximately 609 nm, and reddish-orange light emission was observed from the dichloromethane solution. [Example 3]〈〈Synthesis Example 3〉〉

[0218] In this example, a synthesis method of bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2',6, 6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dpm)]), which is represented by structural formula (108) in Embodiment 1. The structure of [Ir(dmdppm) 2 (dpm)] (abbreviation) is shown below. 〈Step 1: Preparation of 4,6-bis(3,5-dimethylphenyl)pyrimidine (abbreviation: Hdmdppm)〉

[0219] First, 5.97 g of 4,6-dichloropyrimidine, 12.04 g of 3,5-dimethylphenylboronic acid, 8.48 g of sodium carbonate, 0.34 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2), 20 ml of water, and 20 ml of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (abbreviation: DMPU) were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.58 g of 3,5-dimethylphenylboronic acid, 1.78 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2 , 5 ml of water and 5 ml of DMPU were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes, so that heating was carried out.

[0220] Subsequently, the obtained residue was subjected to suction filtration with water and washed with water and ethanol. The obtained solid was dissolved in dichloromethane, filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order, and then washed with ethanol, so that Hdmdppm (abbreviation), which was the pyrimidine derivative to be prepared, was obtained as a white powder in a yield of 56%. Note that microwave irradiation was carried out using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (c-1). 〈Step 2: Preparation of di-µ-chloro-tetrakis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppm) 2 Cl] 2 )〉

[0221] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 2.10 g of Hdmdppm (abbreviation), which had been obtained in step 1, and 1.07 g of iridium chloride hydrate (IrCl 3 ·H 2 O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with ethanol to obtain [Ir(dmdppm)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in a yield of 74%. A synthesis scheme of step 2 is shown in (c-2). 〈Step 3: Preparation of bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2',6, 6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dpm)])〉

[0222] In addition, 30 ml of 2-ethoxyethanol, 1.08 g of [Ir(dmdppm) 2 Cl] 2(abbreviation), which is the dinuclear complex obtained in step 2, 0.37 g of dipivaloylmethane (abbreviation: HDPM) and 0.71 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol. The obtained solid was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order. Recrystallization was then carried out with a mixed solvent of dichloromethane and ethanol; thus, [Ir(dmdppm)] was obtained. 2(dpm)] (abbreviation) was obtained as a red powder in a yield of 21%. A synthesis scheme of step 3 is shown in (c-3).

[0223] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the red powder obtained by the synthesis procedure described above is described below. Fig. 13 shows the 1 H-NMR diagram. These results showed that [Ir(dmdppm) 2 (dpm)] (abbreviation), which is represented by the structural formula (108), was obtained in Synthesis Example 3.

[0224] 1 H-NMR. δ(CDCl 3 ): 0.84 (s, 18H), 1.51 (s, 6H), 2.31 (s, 6H), 2.45 (s, 12H), 5.52 (s, 1H), 6.60 (s, 2H), 7.17 (s, 2H), 7.55 (s, 2H), 7.81 (s, 4H), 8.10 (s, 2H), 8.84 (d, 2H).

[0225] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppm) 2(dpm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.070 mmol / L) placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.070 mmol / L) placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 14, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig. 14, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 14 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.070 mmol / l) in a quartz cell.

[0226] As in Fig. 14, [Ir(dmdppm) 2 (dpm)] (abbreviation) exhibited an emission peak at approximately 615 nm, and reddish-orange light emission was observed from the dichloromethane solution. [Example 4]

[0227] In this example, a light-emitting element 1 is identified by Fig. 15, in which [Ir(dmdppr-P) 2(dibm)] (abbreviation), represented by the structural formula (100), is used for a light-emitting layer. Chemical formulas of materials in this example are shown below. 〈〈Manufacture of the light-emitting element 1〉〉

[0228] First, indium tin oxide containing silicon oxide (ITSO) was deposited over a glass substrate 1100 by a sputtering method, forming a first electrode 1101 serving as an anode. The thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

[0229] Subsequently, as a pretreatment for forming the light-emitting element over the substrate 1100, a UV-ozone treatment was performed for 370 seconds after a surface of the substrate was washed with water and the substrate was heated at 200 °C for 1 hour.

[0230] The substrate was then transferred to a vacuum deposition device, where the pressure was increased to approximately 10 -4 Pa, and heated in a heating chamber of the vacuum evaporation device at 170 °C for 30 minutes in vacuum, and then the substrate 1100 was cooled for about 30 minutes.

[0231] Then, the substrate 1100 was fixed to a holder in the vacuum evaporation apparatus such that a surface of the substrate 1100 over which the first electrode 1101 was formed was provided facing downward. In this example, a case will be described in which a hole injection layer 1111, a hole transport layer 1112, a light-emitting layer 1113, an electron transport layer 1114, and an electron injection layer 1115 included in an EL layer 1102 are sequentially formed by a vacuum evaporation method.

[0232] After the pressure of the vacuum evaporation device has been increased to 10 -4Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were co-evaporated, with the mass ratio of DBT3P-II (abbreviation) to molybdenum oxide being 4:2, thereby forming the hole-injection layer 1111 over the first electrode 1101. The thickness of the hole-injection layer 1111 was 40 nm. It should be noted that co-evaporation is a deposition method in which several different substances are simultaneously deposited from respective different deposition sources.

[0233] Thereafter, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) was deposited to a thickness of 20 nm by vapor deposition, so that the hole transport layer 1112 was formed.

[0234] Then, the light-emitting layer 1113 was formed over the hole-transporting layer 1112 in the following manner. 2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), and bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P) 2 (dibm)]) were co-evaporated, whereby the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmdppr-P) 2 (dibm)] (abbreviation) was 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.

[0235] Then, 2mDBTPDBq-II (abbreviation) was evaporated to a thickness of 10 nm over the light-emitting layer 1113, and bathophenanthroline (abbreviation: BPhen) was then evaporated to a thickness of 20 nm, thereby forming the electron-transport layer 1114 with a stacked structure. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm over the electron-transport layer 1114, thereby forming the electron-injection layer 1115.

[0236] Finally, aluminum was evaporated to a thickness of 200 nm over the electron injection layer 1115 to form a second electrode 1103 serving as a cathode; thus, the light-emitting element 1 was obtained. Note that in all the above deposition steps, the deposition was performed by a resistance heating method.

[0237] An element structure of the light-emitting element 1 obtained in the above-described manner is shown in Table 1. [Table 1] Erste Elektrode Lochinjektions schicht Lochtransport schicht Licht emittierende Schicht Elekt tran sch ronen sport icht Elektronen injektions schicht Zweite Elektrode Licht emittierendes Element 1 ITSO (110nm) DBT3P-II:MoOx (4:2 40nm) BPAFLP (20nm) * ** BPhen (20nm) LiF (1nm) Al (200nm) * 2mDBTPDBq-II:NPB: [Ir(dmdppr-P) 2 (dibm)] (0.8:0.2:0.05 40nm) ** 2mDBTPDBq-II(10nm)

[0238] Furthermore, the fabricated light-emitting element 1 was sealed in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (specifically, a sealant was applied to an outer edge of the element, and a heat treatment was performed at 80 °C for 1 hour at the time of sealing). 〈〈Operating characteristics of the light-emitting element 1〉〉

[0239] The operating characteristics of the fabricated light-emitting element 1 were measured. Note that the measurement was conducted at room temperature (in an atmosphere maintained at 25 °C).

[0240] Fig. 16 shows current density-luminance characteristics of the light-emitting element 1. In Fig. 16 the vertical axis represents the luminance (cd / m 2 ), and the horizontal axis represents the current density (mA / cm 2 ). Fig. 17 shows voltage-luminance characteristics of the light-emitting element 1. In Fig. 17 the vertical axis represents the luminance (cd / m 2 ) and the horizontal axis represents the voltage (V). Fig. 18 also shows luminance-current efficiency characteristics of the light-emitting element 1. In Fig. 18, the vertical axis represents the current efficiency (cd / A), and the horizontal axis represents the luminance (cd / m 2 ). Fig. 19 shows voltage-current characteristics of the light-emitting element 1. In Fig. 19, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).

[0241] Fig. 18 demonstrates a high efficiency of the light-emitting element 1, in which a part of the light-emitting layer [Ir(dmdppr-P) 2 (dibm)] (abbreviation). Table 2 shows the initial values ​​of the main properties of the light-emitting element 1 at a luminance of approximately 1000 cd / m 2 . [Table 2] Spannu ng (V) Strom (mA) Current density (mA / cm 2 ) Farbart (x;y) Luminance e (cd / m 2 ) Stromeffizie nz (cd / A) Leistungseffiz ienz (Im / W) Quanteneffiz ienz (%) Licht emittierendes Element 1 3,3 0,22 5,6 (0,69;0,31) 920 16,0 16,0 26,0

[0242] The above results show that the light-emitting element 1 fabricated in this example is a light-emitting element with high luminance and high current efficiency. Regarding color purity, it can be further found that the light-emitting element emits red light with excellent color purity.

[0243] Fig. Figure 20 shows an emission spectrum at the time of applying a current with a current density of 2.5 mA / cm 2to the light-emitting element 1. The emission spectrum of the light-emitting element 1 has, as shown in Fig. 20, a peak at approximately 640 nm, and it is suggested that the peak is due to emission from the organometallic complex [Ir(dmdppr-P) 2 (dibm)] (abbreviation). It should be noted that Fig. 20 also shows an emission spectrum of a comparative light-emitting element 1 as a comparative example. The comparative light-emitting element 1 was prepared using an organometallic complex [Ir(tppr) 2 (dpm)] (abbreviation) instead of the organometallic complex [Ir(dmdppr-P) 2(dibm)] (abbreviation), which was used in the light-emitting element 1. Therefore, it was considered that the half-width of the emission spectrum of the light-emitting element 1 is smaller than that of the emission spectrum of the comparison light-emitting element 1. It can be assumed that this is an effect caused by the structure of the organometallic complex [Ir(dmdppr-P) 2 (dibm)] (abbreviation), in which methyl groups are bonded to the 2- and 4-positions of the phenyl group bonded to iridium. Thus, it can be said that the light-emitting element 1 has high emission efficiency and achieves high color purity.

[0244] The light-emitting element 1 was subjected to reliability tests. The results of the reliability tests are shown in Fig. 21 and Fig. 22. In Fig.21, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. It should be noted that in one of the reliability tests, the light-emitting element 1 was operated under the conditions where the initial luminance was set to 5000 cd / m 2 was set and the current density was constant. The light-emitting element 1 retained about 68% of the initial luminance after 100 hours. In Fig. Furthermore, in Figure 22, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. Note that in the other reliability test, light-emitting element 1 was operated at a current value of 0.3 mA. Light-emitting element 1 retained approximately 90% of the initial luminance after 100 hours.

[0245] Consequently, both reliability tests conducted under different conditions showed that the light-emitting element 1 is highly reliable. Furthermore, it was confirmed that a light-emitting element with a long lifetime can be obtained using the above-described organometallic complex. [Example 5]

[0246] In this example, a light-emitting element 2 is described in which [Ir(dmdppm) 2 (dibm)] (abbreviation), which is represented by a structural formula (107), is used for a light-emitting layer. It should be noted that in the description of the light-emitting element 2 in this example, Fig. 15, which was used in the description of the light-emitting element 1 in Example 4. Chemical formulas of materials in this example are shown below. 〈〈Manufacture of the light-emitting element 2〉〉

[0247] First, indium tin oxide containing silicon oxide (ITSO) was deposited over the glass substrate 1100 by a sputtering method, forming the first electrode 1101, which served as the anode. The thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

[0248] Then, as a pretreatment for forming the light-emitting element over the substrate 1100, UV ozone treatment was performed for 370 seconds after a surface of the substrate was washed with water and the substrate was heated at 200 °C for 1 hour.

[0249] The substrate was then transferred to a vacuum deposition device, where the pressure was increased to approximately 10 -4Pa, and heated in a heating chamber of the vacuum evaporation device at 170 °C for 30 minutes in vacuum, and then the substrate 1100 was cooled for about 30 minutes.

[0250] The substrate 1100 was then fixed to a holder in the vacuum evaporation apparatus such that a surface of the substrate 1100 over which the first electrode 1101 was formed faced downward. In this example, a case will be described in which the hole-injection layer 1111, the hole-transport layer 1112, the light-emitting layer 1113, the electron-transport layer 1114, and the electron-injection layer 1115 included in the EL layer 1102 were sequentially formed by a vacuum evaporation method.

[0251] After the pressure of the vacuum evaporation device has been increased to 10 -4Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were co-evaporated, with the mass ratio of DBT3P-II (abbreviation) to molybdenum oxide being 4:2, thereby forming the hole-injection layer 1111 over the first electrode 1101. The thickness of the hole-injection layer 1111 was 40 nm. It should be noted that co-evaporation is a deposition method in which several different substances are simultaneously deposited from respective different deposition sources.

[0252] Then, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) was deposited to a thickness of 20 nm by vapor deposition, so that the hole transport layer 1112 was formed.

[0253] Then, the light-emitting layer 1113 was formed over the hole-transporting layer 1112 in the following manner. 2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), and bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dibm)]) were co-evaporated, whereby the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmdppm) 2 (dibm)] (abbreviation) was 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.

[0254] Then, 2mDBTPDBq-II (abbreviation) was evaporated to a thickness of 10 nm over the light-emitting layer 1113, and bathophenanthroline (abbreviation: BPhen) was then evaporated to a thickness of 20 nm, thereby forming the electron-transport layer 1114 with a stacked structure. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm over the electron-transport layer 1114, thereby forming the electron-injection layer 1115.

[0255] Finally, aluminum was evaporated to a thickness of 200 nm over the electron injection layer 1115 to form the second electrode 1103 serving as a cathode; thus, the light-emitting element 2 was obtained. Note that in all the above deposition steps, the deposition was performed by a resistance heating method.

[0256] An element structure of the light-emitting element 2 obtained in the above-described manner is shown in Table 3. [Table 3] First electrode Hole injection layer Perforated transparent layer Light-emitting layer Electron transport layer Electron injection layer Second electrode Light-emitting element 2 ITSO (110nm) DBT3P-II :MoOx (4:2 40nm) BPAFLP (20nm) * ** BPhen (20nm) LiF (1nm) Al (200nm) * 2mDBTPD Bq-II:NPB: [Ir(dmdppn) 2 (dibm)] ( 0.8:0.2:0.05 40nm) ** 2mDBTP DBq-II (10 nm)

[0257] Furthermore, the fabricated light-emitting element 2 was sealed in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (specifically, a sealant was applied to an outer edge of the element, and a heat treatment was performed at 80 °C for 1 hour at the time of sealing). 〈〈Operating characteristics of the light-emitting element 2〉〉

[0258] The operating characteristics of the fabricated light-emitting element 2 were measured. Note that the measurement was conducted at room temperature (in an atmosphere maintained at 25 °C).

[0259] Fig.23 shows current density-luminance characteristics of the light-emitting element 2. In Fig. 23 the vertical axis represents the luminance (cd / m 2 ), and the horizontal axis represents the current density (mA / cm 2 ). Fig. 24 shows voltage-luminance characteristics of the light-emitting element 2. In Fig. 24 the vertical axis represents the luminance (cd / m 2 ) and the horizontal axis represents the voltage (V). Fig. 25 further shows luminance-current efficiency characteristics of the light-emitting element 2.

[0260] In Fig. 25, the vertical axis represents the current efficiency (cd / A), and the horizontal axis represents the luminance (cd / m 2 ). Fig. 26 shows voltage-current characteristics of the light-emitting element 2. In Fig. 26, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).

[0261] Fig. 25 demonstrates a high efficiency of the light-emitting element 2, in which a part of the light-emitting layer [Ir(dmdppm) 2 (dibm)] (abbreviation). Table 4 shows the initial values ​​of the main characteristics of the light-emitting element 2 at a luminance of about 1000 cd / m 2 . [Table 4] Voltage (V) Current (mA) Current density [mA / cm 2 ) Chromaticity (x;y) Luminance e (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) Quantum efficiency (%) Light-emitting element 2 2,9 0,062 1,6 (0,62;0,38) 870 56 60 31

[0262] The above results show that the light-emitting element 2 fabricated in this example is a light-emitting element with high luminance and high power efficiency. Regarding color purity, it can be further found that the light-emitting element emits reddish-orange light with excellent color purity.

[0263] Fig. Figure 27 shows an emission spectrum at the time of applying a current with a current density of 2.5 mA / cm 2to the light-emitting element 2. The emission spectrum of the light-emitting element 2 has, as shown in Fig. 27, a peak at approximately 610 nm, and it is suggested that the peak is due to emission from the organometallic complex [Ir(dmdppm) 2 (dibm)] (abbreviation). It should be noted that Fig. 27 also shows an emission spectrum of a comparative light-emitting element 2 as a comparative example. The comparative light-emitting element 2 was prepared using an organometallic complex [Ir(dppm) 2 (acac)] (abbreviation) instead of the organometallic complex [Ir(dmdppm) 2(dibm)] (abbreviation), which was used in the light-emitting element 2. Therefore, it was considered that the half-width of the emission spectrum of the light-emitting element 2 is smaller than that of the emission spectrum of the comparison light-emitting element 2. It can be assumed that this is an effect caused by the structure of the organometallic complex [Ir(dmdppm) 2 (dibm)] (abbreviation), in which methyl groups are bonded to the 2- and 4-positions of the phenyl group bonded to iridium. Thus, it can be said that the light-emitting element 2 has high emission efficiency and achieves high color purity.

[0264] The light-emitting element 2 has been subjected to reliability tests. The results of the reliability tests are shown in Fig. 28 and Fig. 29. In Fig.28, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. It should be noted that in one of the reliability tests, the light-emitting element 2 was operated under the conditions with the initial luminance set to 5000 cd / m 2 was set and the current density was constant. The light-emitting element 2 retained about 86% of the initial luminance after 100 hours. In Fig. Furthermore, in Figure 29, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. Note that in the other reliability test, the light-emitting element 2 was operated at a current value of 0.3 mA. The light-emitting element 2 retained approximately 90% of the initial luminance after 100 hours.

[0265] Consequently, both reliability tests conducted under different conditions showed that the light-emitting element 2 is highly reliable. Furthermore, it was confirmed that a light-emitting element with a long lifetime can be obtained using the above-described organometallic complex. [Example 6]

[0266] In this example, a light-emitting element 3 is described in which [Ir(dmdppm) 2 (dpm)] (abbreviation), which is represented by the structural formula (108), is used for a light-emitting layer. It should be noted that in the description of the light-emitting element 3 in this example, Fig. 15, which was used in the description of the light-emitting element 1 in Example 4. Chemical formulas of materials in this example are shown below. 〈〈Production of the light-emitting element 3〉〉

[0267] First, indium tin oxide containing silicon oxide (ITSO) was deposited over the glass substrate 1100 by a sputtering method, forming the first electrode 1101, which served as the anode. The thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

[0268] Then, as a pretreatment for forming the light-emitting element over the substrate 1100, UV ozone treatment was performed for 370 seconds after a surface of the substrate was washed with water and the substrate was heated at 200 °C for 1 hour.

[0269] The substrate was then transferred to a vacuum deposition device, where the pressure was increased to approximately 10 -4 Pa, and heated in a heating chamber of the vacuum evaporation device at 170 °C for 30 minutes in vacuum, and then the substrate 1100 was cooled for about 30 minutes.

[0270] The substrate 1100 was then fixed to a holder in the vacuum evaporation apparatus such that a surface of the substrate 1100 over which the first electrode 1101 was formed faced downward. In this example, a case will be described in which the hole-injection layer 1111, the hole-transport layer 1112, the light-emitting layer 1113, the electron-transport layer 1114, and the electron-injection layer 1115 included in the EL layer 1102 were sequentially formed by a vacuum evaporation method.

[0271] After the pressure of the vacuum evaporation device has been increased to 10 -4Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were co-evaporated, with the mass ratio of DBT3P-II (abbreviation) to molybdenum oxide being 4:2, thereby forming the hole-injection layer 1111 over the first electrode 1101. The thickness of the hole-injection layer 1111 was 40 nm. It should be noted that co-evaporation is a deposition method in which several different substances are simultaneously deposited from respective different deposition sources.

[0272] Then, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) was deposited to a thickness of 20 nm by vapor deposition, so that the hole transport layer 1112 was formed.

[0273] Then, the light-emitting layer 1113 was formed over the hole-transporting layer 1112 in the following manner. 2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), and bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2',6,6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppm) 2 (dpm)]) were co-evaporated, whereby the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmdppm) 2 (dpm)] (abbreviation) was 0.8:0.2:0.025. The thickness of the light-emitting layer 1113 was 40 nm.

[0274] Then, 2mDBTPDBq-II (abbreviation) was evaporated to a thickness of 10 nm over the light-emitting layer 1113, and bathophenanthroline (abbreviation: BPhen) was then evaporated to a thickness of 20 nm, thereby forming the electron-transport layer 1114 with a stacked structure. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm over the electron-transport layer 1114, thereby forming the electron-injection layer 1115.

[0275] Finally, aluminum was evaporated to a thickness of 200 nm over the electron injection layer 1115 to form the second electrode 1103 serving as a cathode; thus, the light-emitting element 3 was obtained. Note that in all the above deposition steps, the deposition was performed by a resistance heating method.

[0276] An element structure of the light-emitting element 3 obtained in the above-described manner is shown in Table 5. [Table 5] First electrode Hole injection layer Hole transport layer Light-emitting layer Electron transport layer Electron injection layer Second electrode Light-emitting element 3 ITSO (110nm) DBT3P-II :moOx (4:2 40nm) BPAFLP (20nm) * ** BPhen (20nm) LiF (1nm) Al (200nm) * 2mDBTPDBq-II:NPB: [lr(dmdppm) 2 (dpm)] (0,8:0,2:0,05 40nm) ** 2mDBTPDBq-II (10 nm)

[0277] Furthermore, the fabricated light-emitting element 3 was sealed in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (specifically, a sealant was applied to an outer edge of the element, and a heat treatment was performed at 80 °C for 1 hour at the time of sealing). 〈〈Operating characteristics of the light-emitting element 3〉〉

[0278] The operating characteristics of the fabricated light-emitting element 3 were measured. Note that the measurement was conducted at room temperature (in an atmosphere maintained at 25 °C).

[0279] Fig.30 shows current density-luminance characteristics of the light-emitting element 3. In Fig. 30 the vertical axis represents the luminance (cd / m 2 ), and the horizontal axis represents the current density (mA / cm 2 ). Fig. 31 shows voltage-luminance characteristics of the light-emitting element 3. In Fig. 31 the vertical axis represents the luminance (cd / m 2 ) and the horizontal axis represents the voltage (V). Fig. 32 further shows luminance-current efficiency characteristics of the light-emitting element 3. In Fig. 32, the vertical axis represents the current efficiency (cd / A), and the horizontal axis represents the luminance (cd / m 2 ). Fig. 33 shows voltage-current characteristics of the light-emitting element 3. In Fig. 33 the vertical axis represents current (mA) and the horizontal axis represents voltage (V).

[0280] Fig.32 proves a high efficiency of the light-emitting element 3, in which a part of the light-emitting layer [lr(dmdppm) 2 (dpm)] (abbreviation). Table 6 shows the initial values ​​of the main characteristics of the light-emitting element 3 at a luminance of about 1000 cd / m 2 . [Table 6] Voltage (V) Current (mA) Current density (mA / cm 2 ) Chromaticity (x;y) Luminance e (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) Quantum efficiency (%) Light-emitting element 3 3 0,091 2,3 0,62;0,38 1200 52 55 30,3

[0281] The above results show that the light-emitting element 3 manufactured in this example is a light-emitting element with high luminance and high power efficiency. Regarding color purity, it can be further found that the light-emitting element emits reddish-orange light with excellent color purity.

[0282] Fig. 34 shows an emission spectrum at the time of applying a current with a current density of 2.5 mA / cm 2to the light-emitting element 3. The emission spectrum of the light-emitting element 3 has, as shown in Fig. 34, a peak at approximately 610 nm, and it is suggested that the peak is due to emission from the organometallic complex [lr(dmdppm) 2 (dpm)] (abbreviation). It should be noted that Fig. 34 also shows the emission spectrum of a comparative light-emitting element 3 as a comparative example. The comparative light-emitting element 3 was prepared using an organometallic complex [Ir(dppm) 2 (acac)] (abbreviation) instead of the organometallic complex [Ir(dmdppm) 2(dpm)] (abbreviation), which was used in the light-emitting element 3. Therefore, it was considered that the half-width of the emission spectrum of the light-emitting element 3 is smaller than that of the emission spectrum of the comparison light-emitting element 3. It can be assumed that this is an effect caused by the structure of the organometallic complex [Ir(dmdppm) 2 (dpm)] (abbreviation), in which methyl groups are bonded to the 2- and 4-positions of the phenyl group bonded to iridium. Thus, it can be said that the light-emitting element 3 has high emission efficiency and achieves high color purity.

[0283] The light-emitting element 3 has been subjected to reliability tests. The results of the reliability tests are shown in Fig. 35 and Fig. 36. In Fig.35, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. It should be noted that in one of the reliability tests, the light-emitting element 3 was operated under the conditions with the initial luminance set to 5000 cd / m 2 was set and the current density was constant. The light-emitting element 3 retained about 85% of the initial luminance after 100 hours. In Fig. Furthermore, in Figure 36, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. Note that in the other reliability test, the light-emitting element 3 was operated at a current value of 0.3 mA. The light-emitting element 3 retained approximately 90% of the initial luminance after 100 hours.

[0284] Consequently, both reliability tests conducted under different conditions showed that the light-emitting element 3 is highly reliable. Furthermore, it was confirmed that a light-emitting element with a long lifetime can be obtained using the above-described organometallic complex. [Example 7]

[0285] In this example, phosphorescence spectra obtained by calculation are described. Note that the chemical formulas of organometallic complexes in this example are shown below. «Calculation example»

[0286] The most stable structures of [Ir(ppr) 2 (acac)] (abbreviation) in a singlet ground state (S 0 ) and the lowest excited triplet state (T 1 ) and the most stable structures of [Ir(dmppr) 2(acac)] (abbreviation), which is an analogous model of the organometallic complex, in a singlet ground state (S 0 ) and the lowest excited triplet state (T 1 ) were calculated using density functional theory (DFT). Furthermore, a vibration analysis was performed on each of the most stable structures, and a probability of transition between vibrational states in the S 0 - and T 1-states were determined, so the phosphorescence spectra were calculated. In DFT, the total energy is represented as the sum of potential energy, electrostatic energy between electrons, electronic kinetic energy, and exchange-correlation energy, including all complex interactions between electrons. In DFT, an exchange-correlation interaction is approximated by a functional (a function of another function) of a one-electron potential, represented as an electron density, to enable fast calculations. B3PW91, which is a hybrid functional, was used to determine the weight of each parameter with respect to exchange-correlation energy.

[0287] Additionally, 6-311G (a triple-split valence basis set basis function using three contraction functions for a valence orbital) was used as a basis function for each of H, C, N, and O atoms, and LanL2DZ was used for an Ir atom. According to the above basis function, for example, in the case of hydrogen atoms, 1s to 3s orbitals are considered, while in the case of carbon atoms, 1s to 4s and 2p to 4p orbitals are considered. Furthermore, the p-function and the d-function were added as polarization basis sets to hydrogen atoms and atoms other than hydrogen, respectively, to improve computational accuracy. Note that Gaussian 09 was used as the quantum chemistry computing program. A high-performance computer (Altix 4700, manufactured by SGI Japan, Ltd.) was used for the calculations.

[0288] It should be noted that the phosphorescence spectra of [Ir(ppr) 2 (acac)] (abbreviation) and [Ir(dmppr) 2 (acac)] (abbreviation), which is an analog model of the organometallic complex in Fig. 38. The calculations were carried out using the half-width of 135 cm -1 and the Franck-Condon factor was taken into account.

[0289] As in Fig. 38, the intensity of the secondary peak at approximately 640 nm in the phosphorescence spectrum of [Ir(ppr) 2 (acac)] (abbreviation) is high, while the intensity of the secondary peak at about 690 nm in the phosphorescence spectrum of [lr(dmppr) 2 (acac)] (abbreviation) is low. The secondary peaks are attributed to stretching vibrations of a CC bond or a CN bond in the ligand. In [lr(dmppr) 2(acac)] (abbreviation), the probability of transition between vibrational states of such stretching vibration is low. Consequently, one can understand that the spectrum of [lr(dmppr) 2 (acac)] (abbreviation), which is the analogous model of the organometallic complex, is narrower than that of [Ir(ppr) 2 (acac)] (abbreviation).

[0290] The dihedral angle formed by carbon atoms of the benzene ring was determined to be between [lr(ppr) 2 (acac)] (abbreviation) and [Ir(dmppr) 2 (acac)] (abbreviation), which is the analog model of the organometallic complex, obtained by the above calculation method. The results of the comparison are shown in Table 7. The positions of the dihedral angles formed by carbon atoms of the benzene ring, which were compared with each other, are shown in Fig. 39 shown. [Table 7] [Ir(ppr) 2 (acac)] [Ir(dmppr) 2 (acac)] S 0 1,2° 3,8° T 1 -1,7° 6,1°

[0291] The values ​​of the dihedral angles in [lr(ppr) 2 (acac)] (abbreviation) in the S 0 - and T 1 -states are small, as shown in Table 7, indicating that its benzene ring is very flat and that the probability of transition between vibrational states due to the stretching vibration of the CC bond or the CN bond in the ligand is high. In contrast, the values ​​of the dihedral angles in [lr(dmppr) 2 (acac)] (abbreviation) in the S 0 - and T 1-states is large, indicating that its benzene ring is less flat and that the probability of transitioning between vibrational states due to the stretching vibration of the C–C bond or C–N bond in the ligand is low. This can be attributed to the two methyl groups bonded to the phenyl group. In other words, it was found that when two alkyl groups are bonded to the 2- and 4-positions of a phenyl group bonded to iridium, the half-width of a phosphorescence spectrum is small and the color purity of emitted light is high. [Example 8]〈〈Synthesis Example 4〉〉

[0292] In Synthesis Example 4, a synthesis method of bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}( 2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P) 2(acac)]), which is represented by structural formula (121) in Embodiment 1. The structure of [Ir(dmdppr-P) 2 (acac)] (abbreviation) is shown below.

[0293] 〈Step 1: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppr-P) 2 Cl] 2 )〉 First, 30 ml of 2-ethoxyethanol, 10 ml of water, 3.18 g of Hdmdppr-P (abbreviation) and 1.27 g of iridium chloride hydrate (IrCl 3 -H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a round-bottom flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with ethanol to obtain [Ir(dmdppr-P)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in a yield of 67%. A synthesis scheme of step 1 is shown in (d-1). 〈Step 2: Preparation of bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}( 2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P) 2 (acac)])〉

[0294] Furthermore, 40 ml of 2-ethoxyethanol, 2.8 g of [Ir(dmdppr-P) 2 Cl] 2(abbreviation), which is the dinuclear complex obtained in step 1, 0.46 g of acetylacetone (abbreviation: Hacac), and 1.6 g of sodium carbonate were added to a round-bottomed flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 1 hour. The solvent was distilled off, and the residue obtained was subjected to suction filtration with ethanol and washed with water and ethanol. The obtained solid was purified by flash column chromatography using ethyl acetate and hexane as the eluent in a ratio of 1:10, and recrystallization was carried out with a mixed solvent of dichloromethane and ethanol to give [Ir(dmdppr-P)]. 2 (acac)] (abbreviation) was obtained as a dark red powder in a yield of 24%. A synthesis scheme of step 2 is shown in (d-2).

[0295] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the dark red powder obtained in step 2 is described below. Fig. 40 shows the 1 H-NMR diagram. These results showed that [Ir(dmdppr-P) 2 (acac)] (abbreviation), which is represented by the structural formula (121), was obtained in Synthesis Example 4.

[0296] 1 H-NMR. δ(CDCl 3 ): 1.41 (s, 6H), 1.81 (s, 6H), 1.95 (s, 6H), 2.42 (s, 12H), 5.06 (s, 1H), 6.46 (s, 2H), 6.81 (s, 2H), 7.19 (s, 2H), 7.41-7.49 (m, 10H), 8.05 (d, 4H), 8.83 (s, 2H).

[0297] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppr-P) 2(acac)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.085 mmol / L) placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.085 mmol / L) placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 41, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig.41, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 41 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.085 mmol / l) in a quartz cell.

[0298] As in Fig. 41, [Ir(dmdppr-P) 2 (acac)] (abbreviation) exhibited an emission peak at approximately 633 nm, and red light emission from the dichloromethane solution was observed.

[0299] In addition, the weight loss percentage of [Ir(dmdppr-P) 2(acac)] (abbreviation) was measured by a high vacuum differential type differential thermal balance (TG / DTA 2410SA, manufactured by Bruker AXS KK). The temperature was measured at a rate of 10 °C / min under a vacuum degree of 8 × 10 -4 Pa. As a result, it was found that the percentage of weight loss of [Ir(dmdppr-P) 2 (acac)] (abbreviation) was 100%, as in Fig. 42, which indicated a favorable sublimation property of the organometallic complex. [Example 9]〈〈Synthesis Example 5〉〉

[0300] In Synthesis Example 5, a synthesis method of bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ N]phenyl-κ C}(2,4-pentanedionato-κ 2 0,0')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2(acac)], which is represented by structural formula (122) in Embodiment 1, is described. The structure of [Ir(dmdppr-dmp) 2 (acac)] (abbreviation) is shown below. (Step 1: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr))

[0301] First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of 3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 20 ml of water, and 20 ml of acetonitrile were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2, 5 ml of water and 5 ml of acetonitrile were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes to conduct heating. Then, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium bicarbonate, water and a saturated saline solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1.The solvent was distilled off, and the obtained solid was purified by flash column chromatography using dichloromethane and ethyl acetate as the eluent in a ratio of 10:1, to obtain Hdmdppr (abbreviation), the pyrazine derivative to be prepared, as a white powder with a yield of 44%. Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (e-1). 〈Step 2: Preparation of 5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr-dmp)〉

[0302] Then, 2.81 g of 2-bromo-m-xylene and 30 ml of dry THF were added to a 200 ml three-necked flask, and the air in the flask was replaced with nitrogen. After the flask was cooled to -78 °C, 9.4 ml of n-butyllithium (1.6M solution of n-butyllithium in hexane) was added dropwise, and the mixture was stirred at -78 °C for 1 hour. Here, 4.01 g of Hdmdppr (abbreviation), which was obtained in step 1, and 40 ml of dry THF were added, and the mixture was stirred at room temperature for 16.5 hours. The reaction solution was poured into water, and the solution was subjected to extraction with chloroform. The obtained organic layer was washed with water and a saturated saline solution and dried with magnesium sulfate. Manganese oxide was added to the obtained mixture, and the mixture was stirred for 30 minutes. Then the solution was filtered and the solvent was distilled off.The obtained residue was purified by silica gel column chromatography using dichloromethane and hexane as the eluent in a 1:1 ratio, to obtain Hdmdppr-dmp (abbreviation), the pyrazine derivative to be prepared, as a yellowish-white powder in a yield of 10%. A synthesis scheme of step 2 is shown in (e-2). (Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC} diiridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 Cl] 2 ))

[0303] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 1.12 g of Hdmdppr-dmp (abbreviation), which had been obtained in step 2, and 0.39 g of iridium chloride hydrate (IrCl 3 ·H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with hexane to obtain [Ir(dmdppr-dmp)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in 98% yield. A synthesis scheme of step 3 is shown in (e-3). 〈Step 4: Preparation of Bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ N]phenyl-κC} (2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 (acac)])〉

[0304] Furthermore, 30 ml of 2-ethoxyethanol, 1.28 g of [Ir(dmdppr-dmp) 2Cl] 2 (abbreviation), which is the dinuclear complex obtained in step 3, 0.19 g of acetylacetone (abbreviation: Hacac), and 0.68 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol. The obtained solid was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in that order. Recrystallization was then carried out with a mixed solvent of dichloromethane and ethanol; thus, [Ir(dmdppr-dmp)] was obtained. 2(acac)] (abbreviation) was obtained as a red powder in a yield of 51%. A synthesis scheme of step 4 is shown in (e-4).

[0305] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the red powder obtained in step 4 is described below. Fig. 43 shows the 1 H-NMR diagram. These results showed that [Ir(dmdppr-dmp) 2 (acac)] (abbreviation), which is represented by the structural formula (122), was obtained in Synthesis Example 5.

[0306] 1 H-NMR. δ(CDCl 3 ): 1.48 (s, 6H), 1.75 (s, 6H), 1.94 (s, 6H), 2.12 (s, 12H), 2.35 (s, 12H), 5.17 (s, 1H), 6.47 (s, 2H), 6.81 (s, 2H), 7.08 (d, 4H), 7.12 (s, 2H), 7.18 (t, 2H), 7.40 (s, 4H), 8.36 (s, 2H).

[0307] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppr-dmp)2 (acac)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.062 mmol / L) placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.062 mmol / L) placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 44, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig.44, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 44 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.062 mmol / l) in a quartz cell.

[0308] As in Fig. 44, [Ir(dmdppr-dmp) 2 (acac)] (abbreviation) exhibited an emission peak at approximately 610 nm, and reddish-orange light emission was observed from the dichloromethane solution.

[0309] In addition, the weight loss percentage of [Ir(dmdppr-dmp) 2(acac)] (abbreviation) was measured by a high vacuum differential type differential thermal balance (TG / DTA 2410SA, manufactured by Bruker AXS KK). The temperature was measured at a rate of 10 °C / min under a vacuum degree of 8 × 10 -4 Pa. As a result, it was found that the percentage of weight loss of [Ir(dmdppr-dmp) 2 (acac)] (abbreviation) was 100%, as in Fig. 45, which indicated a favorable sublimation property of the organometallic complex.

[0310] Then [Ir(dmdppr-dmp) 2 (acac)] (abbreviation), which was obtained in this example, was analyzed by liquid chromatography with mass spectrometry (LC / MS).

[0311] For LC / MS analysis, liquid chromatography (LC) separation was performed using ACQUITY UPLC (manufactured by Waters Corporation), and mass spectrometry (MS) analysis was performed using Xevo G2 Tof MS (manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1 × 100 mm, 1.7 µm) was used as the column for LC separation, and the column temperature was 40 °C. Acetonitrile was used as mobile phase A, and a 0.1% aqueous formic acid solution was used as mobile phase B. Furthermore, a sample was prepared in such a way that [Ir(dmdppr-dmp)] 2 (acac)] (abbreviation) was dissolved in chloroform at a given concentration and the mixture was diluted with acetonitrile. The injection volume was 5.0 µl.

[0312] A gradient method was used for the LC separation, in which the composition of the mobile phases was varied. The ratio of mobile phase A to mobile phase B was 85:15 for 0 to 1 minute after the start of the measurement, and then the composition was changed so that the ratio of mobile phase A to mobile phase B was 95:5 at the 10th minute. The composition was changed linearly.

[0313] In the MS analysis, ionization was performed using an electrospray ionization (ESI) method. The capillary voltage and sample cone voltage were 3.0 kV and 30 V, respectively. Detection was performed in positive mode. The mass range for the measurement was m / z = 100 to 1200.

[0314] A component with m / z 1075.45, which underwent separation and ionization under the conditions described above, was collided with argon gas in a collision cell, causing it to dissociate into product ions. The collision energy for collision with argon was 70 eV. The results of the detection of the dissociated product ions by time-of-flight (TOF) MS are presented in Fig. 46 shown.

[0315] The results in Fig. 46 show that the product ions of [Ir(dmdppr-dmp) 2 (acac)] (abbreviation), which is represented by the structural formula (122), were mainly detected at approximately m / z 973.38, m / z 957.35, m / z 679.18, m / z 577.13 and m / z 477.10. It should be noted that the results in Fig. 46 properties derived from [Ir(dmdppr-dmp) 2 (acac)] (abbreviation) and are therefore considered important data for identifying [Ir(dmdppr-dmp) 2(acac)] (abbreviation) which is contained in the mixture.

[0316] The product ion at approximately m / z 973.38 is believed to be a cation in a state where acetylacetone and a proton have been eliminated from the compound with structural formula (122), and this is characteristic of the organometallic complex. The product ion at approximately m / z 957.35 is believed to have resulted from the elimination of a methyl group from the product ion at approximately m / z 973.38, suggesting that [Ir(dmdppr-dmp)] 2 (acac)] (abbreviation) contains a methyl group. [Example 10]〈〈Synthesis Example 6〉〉

[0317] In Synthesis Example 6, a synthesis method of bis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmtppr) 2(dibm)]), which is represented by structural formula (123) in Embodiment 1. The structure of [Ir(dmtppr) 2 (dibm)] (abbreviation) is shown below. (Step 1: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr))

[0318] First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of 3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 20 ml of water, and 20 ml of acetonitrile were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2, 5 ml of water and 5 ml of acetonitrile were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes to conduct heating. Then, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium bicarbonate, water and a saturated saline solution, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1.The solvent was distilled off, and the obtained solid was purified by flash column chromatography using dichloromethane and ethyl acetate as the eluent in a ratio of 10:1, to obtain Hdmdppr (abbreviation), the pyrazine derivative to be prepared, as a white powder with a yield of 44%. Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (f-1). 〈Step 2: Preparation of 2,3,5-tris(3,5-dimethylphenyl)pyrazine (abbreviation: Hamtppr)〉

[0319] First, 2.81 g of 5-bromo-m-xylene and 30 mL of dry THF were added to a 200 mL three-necked flask, and the air in the flask was replaced with nitrogen. After the flask was cooled to -78 °C, 9.4 mL of n-butyllithium (1.6M solution of n-butyllithium in hexane) was added dropwise, and the mixture was stirred at -78 °C for 1 hour. Here, 4.02 g of Hdmdppr (abbreviation), which was obtained in step 1, and 40 mL of dry THF were added, and the mixture was stirred at room temperature for 18 hours. The reaction solution was poured into water, and the solution was subjected to extraction with chloroform. The obtained organic layer was washed with water and a saturated saline solution, and dried with magnesium sulfate. Manganese oxide was added to the obtained mixture, and the mixture was stirred for 30 minutes. Then the solution was filtered and the solvent was distilled off.The resulting residue was purified by silica gel column chromatography using dichloromethane and hexane as the eluent in a 1:1 ratio, yielding Hdmtppr (abbreviation), the pyrazine derivative to be prepared, as an orange oil in 37% yield. A synthesis scheme of step 2 is shown in (f-2). 〈Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]p henyl-κC}diiridium(III) (abbreviation: [Ir(dmtppr) 2 Cl] 2 )〉

[0320] Subsequently, 30 ml of 2-ethoxyethanol, 10 ml of water, 1.95 g of Hdmtppr (abbreviation), which had been obtained in step 2, and 0.72 g of iridium chloride hydrate (IrCl 3 -H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with ethanol to obtain [Ir(dmtppr)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in a yield of 78%. A synthesis scheme of step 3 is shown in (f-3). 〈Step 4: Preparation of bis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmtppr) 2 (dibm)])〉

[0321] In addition, 30 ml of 2-ethoxyethanol, 0.89 g of [Ir(dmtppr) 2 Cl] 2(abbreviation), which is the dinuclear complex obtained in step 3, 0.20 g of diisobutyrylmethane (abbreviation: Hdibm) and 0.47 g of sodium carbonate were added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 200 W) was carried out for 60 minutes. Here, 0.20 g of Hdibm was added, and microwave irradiation (2.45 GHz, 200 W) was carried out again for 60 minutes. The solvent was distilled off, and 0.20 g of Hdibm, 0.47 g of sodium carbonate, and 30 ml of 2-ethoxyethanol were added. The air in the flask was replaced with argon. After that, heating was carried out by microwave irradiation (2.45 GHz, 200 W) for 2 hours. The solvent was distilled off, and the residue was subjected to suction filtration with ethanol. The resulting solid was washed with water and ethanol.The obtained solid was dissolved in dichloromethane and filtered through a filter aid stacked with Celite, alumina, and Celite in that order. Recrystallization was then performed using a mixed solvent of dichloromethane and ethanol to yield [Ir(dmtppr). 2 (dibm)] (abbreviation) was obtained as a dark red powder in a yield of 73%. A synthesis scheme of step 4 is shown in (f-4).

[0322] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the dark red powder obtained in step 4 is described below. Fig. 47 shows the 1 H-NMR diagram. These results showed that [Ir(dmtppr) 2 (dibm)] (abbreviation), which is represented by the structural formula (123), was obtained in Synthesis Example 6.

[0323] 1 H-NMR. δ(CDCl 3): 0.78 (d, 6H), 0.99 (d, 6H), 1.41 (s, 6H), 1.96 (s, 6H), 2.24-2.30 (m, 2H), 2.35 (s, 12H), 2.42 (s, 12H), 5.07 (s, 1H), 6.46 (s, 2H), 6.78 (s, 2H), 7.04 (s, 2H), 7.18 (s, 2H), 7.47 (s, 2H), 7.49 (s, 2H), 7.67 (s, 4H), 8.77 (s, 2H).

[0324] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmtppr) 2(dibm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.068 mmol / L) was placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.31 µmol / L) was placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 48, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig.48, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 48 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.068 mmol / l) in a quartz cell.

[0325] As in Fig. 48, [Ir(dmtppr) 2 (dibm)] (abbreviation) exhibited an emission peak at approximately 629 nm, and reddish-orange light emission was observed from the dichloromethane solution.

[0326] Next, [Ir(dmtppr) 2 (dibm)] (abbreviation), which was obtained in this example, was analyzed by liquid chromatography with mass spectrometry (LC / MS).

[0327] For LC / MS analysis, liquid chromatography (LC) separation was performed using ACQUITY UPLC (manufactured by Waters Corporation), and mass spectrometry (MS) analysis was performed using Xevo G2 Tof MS (manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1 × 100 mm, 1.7 µm) was used as the column for LC separation, and the column temperature was 40 °C. Acetonitrile was used as mobile phase A, and a 0.1% aqueous formic acid solution was used as mobile phase B. Furthermore, a sample was prepared in such a way that [Ir(dmtppr)] 2 (dibm)] (abbreviation) was dissolved in chloroform at a given concentration and the mixture was diluted with acetonitrile. The injection volume was 5.0 µl.

[0328] The LC separation used a gradient method in which the composition of the mobile phases was changed. The ratio of mobile phase A to mobile phase B was 90:10 for 0 to 1 minute after the start of the measurement. Subsequently, the composition was changed so that the ratio of mobile phase A to mobile phase B was 95:5 after 2 minutes, and the ratio was maintained for 10 minutes. The composition changed linearly.

[0329] In the MS analysis, ionization was performed using an electrospray ionization (ESI) method. The capillary voltage and sample cone voltage were 3.01075 kV and 30 V, respectively. Detection was performed in positive mode. The mass range for the measurement was m / z = 100 to 1200.

[0330] A component with m / z 1131.52, which underwent separation and ionization under the conditions described above, was collided with argon gas in a collision cell, causing it to dissociate into product ions. The collision energy for the collision with argon was 70 eV. The results of the detection of the dissociated product ions by time-of-flight (TOF)-MS are shown in Fig. 49 shown.

[0331] The results in Fig. 49 show that the product ions of [Ir(dmtppr) 2 (dibm)] (abbreviation), which is represented by the structural formula (123), were mainly detected at approximately m / z 973.38 and m / z 583.13. It should be noted that the results in Fig. 49 properties derived from [Ir(dmtppr) 2 (dibm)] (abbreviation) and are therefore considered important data for identifying [Ir(dmtppr) 2 (dibm)] (abbreviation) which is contained in the mixture.

[0332] The product ion at approximately m / z 973.38 is assumed to be a cation in a state where acetylacetone and a proton have been eliminated from the compound with structural formula (123), which is characteristic of the organometallic complex. Furthermore, the product ion at approximately m / z 583.17 is assumed to be a cation in a state where Hdmtppr-dmp (abbreviation), which is the ligand, and acetylacetone have been eliminated from the compound with structural formula (123), which is characteristic of the organometallic complex. [Example 11]〈〈Synthesis Example 7〉〉

[0333] In Synthesis Example 7, a synthesis method of bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ, N]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2(dibm)]), which is represented by structural formula (124) in Embodiment 1. The structure of [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation) is shown below. (Step 1: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr))

[0334] First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of 3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 20 ml of water, and 20 ml of acetonitrile were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2, 5 ml of water and 5 ml of acetonitrile were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes to conduct heating. Then, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium bicarbonate, water and a saturated saline solution, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1.The solvent was distilled off, and the obtained solid was purified by flash column chromatography using dichloromethane and ethyl acetate as the eluent in a ratio of 10:1, to obtain Hdmdppr (abbreviation), the pyrazine derivative to be prepared, as a white powder with a yield of 44%. Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (g-1). 〈Step 2: Preparation of 5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr-dmp)〉

[0335] First, 2.81 g of 2-bromo-m-xylene and 30 ml of dry THF were added to a 200 ml three-necked flask, and the air in the flask was replaced with nitrogen. After the flask was cooled to -78 °C, 9.4 ml of n-butyllithium (1.6M solution of n-butyllithium in hexane) was added dropwise, and the mixture was stirred at -78 °C for 1 hour. Here, 4.01 g of Hdmdppr (abbreviation) obtained in Step 1 and 40 ml of dry THF were added, and the mixture was stirred at room temperature for 16.5 hours. The reaction solution was poured into water, and the solution was subjected to extraction with chloroform. The obtained organic layer was washed with water and a saturated saline solution and dried with magnesium sulfate. Manganese oxide was added to the obtained mixture, and the mixture was stirred for 30 minutes. Then the solution was filtered and the solvent was distilled off.The residue was purified by silica gel column chromatography using dichloromethane and hexane as the eluent in a 1:1 ratio, to obtain Hdmdppr-dmp (abbreviation), the pyrazine derivative to be prepared, as a yellowish-white powder in a yield of 10%. A synthesis scheme of step 2 is shown in (g-2). (Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 Cl] 2 ))

[0336] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 1.12 g of Hdmdppr-dmp (abbreviation), which had been obtained in step 2, and 0.39 g of iridium chloride hydrate (IrCl 3 ·H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with hexane to obtain [Ir(dmdppr-dmp)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in 98% yield. A synthesis scheme of step 3 is shown in (g-3). 〈Step 4: Preparation of Bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ N]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 (dibm)])〉

[0337] In addition, 30 ml of 2-ethoxyethanol, 0.80 g of [Ir(dmdppr-dmp)2 Cl] 2 (abbreviation), which is the dinuclear complex obtained in step 3, 0.19 g of diisobutyrylmethane (abbreviation: Hdibm) and 0.42 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order. Recrystallization was then carried out using a mixed solvent of dichloromethane and methanol; thus, [Ir(dmdppr-dmp)] was obtained. 2 (dibm)] (abbreviation) was obtained as a red powder in a yield of 48%. A synthesis scheme of step 4 is shown in (g-4).

[0338] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the red powder obtained in step 4 is described below. Fig. 50 shows that 1 H-NMR diagram. These results showed that [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which is represented by the structural formula (124), was obtained in Synthesis Example 7.

[0339] 1 H-NMR. δ(CDCl 3 ): 0.80 (d, 6H), 0.81 (d, 6H), 1.47 (s, 6H), 1.95 (s, 6H), 2.10 (s, 12H), 2.23-2.28 (m, 2H), 2.34 (s, 12H), 5.19 (s, 1H), 6.48 (s, 2H), 6.81 (s, 2H), 7.06 (d, 4H), 7.11 (s, 2H), 7.16 (t, 2H), 7.40 (s, 4H), 8.22 (s, 2H).

[0340] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppr-dmp) 2(dibm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.059 mmol / L) was placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.059 mmol / L) was placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 51, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig.51, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 51 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.059 mmol / l) in a quartz cell.

[0341] As in Fig. 51, [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation) exhibited an emission peak at approximately 616 nm, and reddish-orange light emission was observed from the dichloromethane solution.

[0342] In addition, the weight loss percentage of [Ir(dmdppr-dmp) 2(dibm)] (abbreviation) was measured by a high vacuum differential type differential thermal balance (TG / DTA 2410SA, manufactured by Bruker AXS KK). The temperature was measured at a rate of 10 °C / min under a vacuum degree of 1 × 10 -3 Pa. As a result, it was found that the percentage of weight loss of [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation) was 100%, as in Fig. 52, which indicated a favorable sublimation property of the organometallic complex.

[0343] Next, [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which was obtained in this example, was analyzed by liquid chromatography with mass spectrometry (LC / MS).

[0344] For LC / MS analysis, liquid chromatography (LC) separation was performed using ACQUITY UPLC (manufactured by Waters Corporation), and mass spectrometry (MS) analysis was performed using Xevo G2 Tof MS (manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1 × 100 mm, 1.7 µm) was used as the column for LC separation, and the column temperature was 40 °C. Acetonitrile was used as mobile phase A, and a 0.1% aqueous formic acid solution was used as mobile phase B. Furthermore, a sample was prepared in such a way that [Ir(dmdppr-dmp)] 2 (dibm) (abbreviation) was dissolved in chloroform at a given concentration and the mixture was diluted with acetonitrile. The injection volume was 5.0 µl.

[0345] A gradient method was used for the LC separation, in which the composition of the mobile phases was changed. The ratio of mobile phase A to mobile phase B was 90:10 for 0 to 1 minute after the start of the measurement, and then the composition was changed so that the ratio of mobile phase A to mobile phase B was 95:5 at the 10th minute. The composition changed linearly.

[0346] In the MS analysis, ionization was performed using an electrospray ionization (ESI) method. The capillary voltage and sample cone voltage were 3.0 kV and 30 V, respectively. Detection was performed in positive mode. The mass range for the measurement was m / z = 100 to 1200.

[0347] A component with m / z 1131.52, which underwent separation and ionization under the conditions described above, was collided with argon gas in a collision cell, causing it to dissociate into product ions. The collision energy for the collision with argon was 70 eV. The results of the detection of the dissociated product ions by time-of-flight (TOF) MS are presented in Fig. 53 shown.

[0348] The results in Fig. 53 show that the product ions of [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which is represented by the structural formula (124), were mainly detected at approximately m / z 973.38, m / z 959.36, m / z 581.16, m / z 555.15 and m / z 393.23. It should be noted that the results in Fig. 53 properties derived from [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation) and are therefore considered important data for identifying [Ir(dmdppr-dmp) 2(dibm)] (abbreviation) which is contained in the mixture.

[0349] The product ion at approximately m / z 973.38 is believed to be a cation in a state where acetylacetone and a proton have been eliminated from the compound with structural formula (124), and this is characteristic of the organometallic complex. The product ion at approximately m / z 959.36 is believed to have resulted from the elimination of a methyl group from the product ion at approximately m / z 973.38, suggesting that [Ir(dmdppr-dmp)] 2 (dibm)] (abbreviation) contains a methyl group. [Example 12]〈〈Synthesis Example 8〉〉

[0350] In Synthesis Example 8, a synthesis method of bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ N]phenyl-κC} (2,2',6,6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2(dpm)]), which is represented by structural formula (125) in Embodiment 1. The structure of [Ir(dmdppr-dmp) 2 (dpm)] (abbreviation) is shown below. (Step 1: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr))

[0351] First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of 3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 20 ml of water, and 20 ml of acetonitrile were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. Further, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodium carbonate, and 0.070 g of Pd(PPh 3 ) 2 Cl 2, 5 ml of water and 5 ml of acetonitrile were added to the flask, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes to conduct heating. Then, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium bicarbonate, water and a saturated saline solution, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1.The solvent was distilled off, and the obtained solid was purified by flash column chromatography using dichloromethane and ethyl acetate as the eluent in a ratio of 10:1, to obtain Hdmdppr (abbreviation), the pyrazine derivative to be prepared, as a white powder with a yield of 44%. Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (h-1). (Step 2: Preparation of 2,3-bis(3,5-dimethylphenyl)pyrazine 1-oxide)

[0352] Next, 6.6 g of Hdmdppr (abbreviation) obtained in step 1, 7.8 g of 3-chloroperbenzoic acid, and 90 mL of dichloromethane were added to a 300 mL three-necked flask, and the air in the flask was replaced with nitrogen. The mixture was stirred at room temperature for 24 hours, then the reaction solution was poured into water, and the solution was subjected to extraction with dichloromethane. The obtained organic layer was washed with a saturated aqueous solution of sodium hydrogen carbonate and then dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, whereby the pyrazine derivative to be prepared was obtained as a yellow powder in a yield of 100%. A synthesis scheme of step 2 is shown in (h-2). (Step 3: Preparation of 5-chloro-2,3-bis(3,5-dimethylphenyl)pyrazine)

[0353] Subsequently, 7.0 g of 2,3-bis(3,5-dimethylphenyl)pyrazine 1-oxide obtained in step 2 was placed in a 100 mL three-necked flask, and the air in the flask was replaced with nitrogen. 20 mL of phosphorus oxychloride was added, and the mixture was stirred at 100 °C for 1 hour. The reaction solution was poured into water, and the solution was subjected to extraction with chloroform. The obtained organic layer was washed with a saturated aqueous solution of sodium hydrogen carbonate, water, and a saturated saline solution, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, thereby obtaining the pyrazine derivative to be prepared as a gray powder in a yield of 90%. A synthesis scheme of step 3 is shown in (h-3). Step 4: Preparation of 5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdppr-dmp)

[0354] Then, 1.21 g of 5-chloro-2,3-bis(3,5-dimethylphenyl)pyrazine, which had been obtained in step 3, 1.10 g of 2,6-dimethylphenylboronic acid, 0.78 g of sodium carbonate, 15 mg of Pd(PPh 3 ) 2 CI 2 , 14 ml of water, and 14 ml of acetonitrile were placed in a receiving flask equipped with a reflux tube, and the mixture was bubbling with argon for 15 minutes. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 3 hours. 0.55 g of 2,6-dimethylphenylboronic acid, 0.39 g of sodium carbonate, and 7 mg of Pd(PPh 3 ) 2 Cl 2was added to the flask, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was again subjected to microwave irradiation (2.45 GHz, 100 W) for 3 hours to be heated. The mixture was subjected to suction filtration, and the obtained solid was washed with ethanol. The obtained solid was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order, so that Hdmdppr-dmp (abbreviation), which was the pyrazine derivative to be prepared, was obtained as a white powder in a yield of 89%. A synthesis scheme of step 4 is shown in (h-4). (Step 5: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 Cl] 2 ))

[0355] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 1.12 g of Hdmdppr-dmp (abbreviation), which had been obtained in step 4, and 0.39 g of iridium chloride hydrate (IrCl 3 -H 2 O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with hexane to obtain [Ir(dmdppr-dmp)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a reddish-brown powder in 98% yield. A synthesis scheme of step 3 is shown in (h-5). (Step 6: Preparation of Bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κ N]phenyl-κC}(2,2',6,6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III)(abbreviation: [Ir(dmdppr-dmp) 2 (dpm)]))

[0356] In addition, 30 ml of 2-ethoxyethanol, 1.38 g of [Ir(dmdppr-dmp) 2 Cl] 2(abbreviation), which is the dinuclear complex obtained in step 5, 0.39 g of dipivaloylmethane (abbreviation: HDPM) and 0.73 g of sodium carbonate were placed in a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 60 minutes. The solvent was distilled off, and the obtained residue was subjected to suction filtration with methanol. The obtained solid was washed with water and methanol. The obtained solid was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in this order. Recrystallization was then carried out with a mixed solvent of dichloromethane and methanol; thus, [Ir(dmdppr-dmp)] was obtained. 2(dpm)] (abbreviation) was obtained as a dark red powder in a yield of 59%. A synthesis scheme of step 6 is shown in (h-6).

[0357] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the dark red powder obtained in step 6 is described below. Fig. 54 shows the 1 H-NMR diagram. These results showed that [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which is represented by the structural formula (125), was obtained in Synthesis Example 8.

[0358] 1 H-NMR. δ(CDCl 3 ): 0.90 (s, 18H), 1.46 (s, 6H), 1.95 (s, 6H), 2.10 (s, 12H), 2.34 (s, 12H), 5.57 (s, 1H), 6.47 (s, 2H), 6.81 (s, 2H), 7.06 (d, 4H), 7.11 (s, 2H), 7.16 (t, 2H), 7.38 (s, 4H), 8.19 (s, 2H).

[0359] Then, a UV-VIS absorption spectrum (hereinafter referred to as “absorption spectrum” for simplicity) of a dichloromethane solution of [Ir(dmdppr-dmp)2 (dpm)] (abbreviation) and an emission spectrum thereof were measured. The absorption spectrum was measured at room temperature using a UV-VIS spectrophotometer (V550, manufactured by Japan Spectroscopy Corporation) and the dichloromethane solution (0.058 mmol / L) was placed in a quartz cell. In addition, the emission spectrum was measured at room temperature using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics KK) and the degassed dichloromethane solution (0.058 mmol / L) was placed in a quartz cell. Measurement results of the obtained absorption and emission spectra are shown in Fig. 55, where the horizontal axis corresponds to the wavelength and the vertical axes correspond to the absorption intensity and the emission intensity. In Fig.55, two solid lines are shown; the thin line corresponds to the absorption spectrum and the thick line corresponds to the emission spectrum. It should be noted that the absorption spectrum in Fig. 55 are the results obtained by subtracting the absorption spectrum of dichloromethane alone in a quartz cell from the absorption spectrum of the dichloromethane solution (0.058 mmol / l) in a quartz cell.

[0360] As in Fig. 55, [Ir(dmdppr-dmp) 2 (dpm)] (abbreviation) exhibited an emission peak at approximately 618 nm, and reddish-orange light emission was observed from the dichloromethane solution.

[0361] In addition, the weight loss percentage of [Ir(dmdppr-dmp) 2(dpm) (abbreviation) was measured by a high vacuum differential type differential thermal balance (TG / DTA 2410SA, manufactured by Bruker AXS KK). The temperature was measured at a rate of 10 °C / min under a vacuum degree of 1 × 10 -3 Pa. As a result, it was found that the percentage of weight loss of [Ir(dmdppr-dmp) 2 (dpm)] (abbreviation) was 97%, as in Fig. 56, which indicated a favorable sublimation property of the organometallic complex. [Example 13]

[0362] In this example, the following light-emitting elements are described, each of which uses an organometallic complex for a light-emitting layer: a light-emitting element 4 in which [Ir(dmdppr-P) 2(acac)] (abbreviation), which is represented by the structural formula (121), is used; a light-emitting element 5 in which [Ir(dmdppr-dmp) 2 (acac)] (abbreviation), which is represented by the structural formula (122), is used; a light-emitting element 6 in which [Ir(dmtppr) 2 (dibm)] (abbreviation), which is represented by the structural formula (123), is used; and a light-emitting element 7 in which [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which is represented by the structural formula (124), is used. It should be noted that in the description of the light-emitting elements 4 to 7 in this example, Fig. 15, which was used in the description of the light-emitting element 1 in Example 4. Chemical formulas of materials in this example are shown below. ((Production of light-emitting elements 4 to 7))

[0363] First, indium tin oxide containing silicon oxide (ITSO) was deposited over the glass substrate 1100 by a sputtering method, forming the first electrode 1101, which served as the anode. The thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

[0364] Then, as a pretreatment for forming the light-emitting element over the substrate 1100, UV ozone treatment was performed for 370 seconds after a surface of the substrate was washed with water and the substrate was heated at 200°C for 1 hour.

[0365] The substrate was then transferred to a vacuum deposition device, where the pressure was increased to approximately 10 -4 Pa, and heated in a heating chamber of the vacuum evaporation device at 170 °C for 30 minutes in vacuum, and then the substrate 1100 was cooled for about 30 minutes.

[0366] The substrate 1100 was then fixed to a holder in the vacuum evaporation apparatus such that a surface of the substrate 1100 over which the first electrode 1101 was formed faced downward. In this example, a case will be described in which the hole-injection layer 1111, the hole-transport layer 1112, the light-emitting layer 1113, the electron-transport layer 1114, and the electron-injection layer 1115 included in the EL layer 1102 were sequentially formed by a vacuum evaporation method.

[0367] After the pressure of the vacuum evaporation device has been increased to 10 -4Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were co-evaporated, with the mass ratio of DBT3P-II (abbreviation) to molybdenum oxide being 4:2, whereby the hole-injection layer 1111 was formed over the first electrode 1101. The thickness of the hole-injection layer 1111 was 20 nm. It should be noted that co-evaporation is a vapor deposition method in which several different substances are simultaneously vapor-deposited from respective different vapor deposition sources.

[0368] Then, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) was deposited to a thickness of 20 nm by vapor deposition, so that the hole transport layer 1112 was formed.

[0369] Next, the light-emitting layer 1113 was formed over the hole-transport layer 1112 in the following manner. In the case of the light-emitting element 4, 2mDBTPDBq-II (abbreviation), NPB (abbreviation), and [Ir(dmdppr-P) 2 (acac)] (abbreviation) was co-evaporated, whereby the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmdppr-P) 2(acac)] (abbreviation) was 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm. In the case of the light-emitting element 5, 2mDBTPDBq-II (abbreviation), NPB (abbreviation), and [Ir(dmdppr-dmp)2(acac)] (abbreviation) were co-evaporated, with the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmdppr-dmp)2(acac)] (abbreviation) being 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm. In the case of the light-emitting element 6, 2mDBTPDBq-II (abbreviation), NPB (abbreviation), and [Ir(dmtppr)2(dibm)] (abbreviation) were co-evaporated, with the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmtppr)2(dibm)] (abbreviation) being 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.In the case of the light-emitting element 7, 2mDBTPDBq-II (abbreviation), NPB (abbreviation), and [Ir(dmdppr-dmp)2(dibm)] (abbreviation) were co-evaporated, with the mass ratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and [Ir(dmppr-dmp)2(dibm)] (abbreviation) being 0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.

[0370] Then, 2mDBTPDBq-II (abbreviation) was evaporated to a thickness of 20 nm over the light-emitting layer 1113, and bathophenanthroline (abbreviation: BPhen) was then evaporated to a thickness of 20 nm, thereby forming the electron-transport layer 1114 with a stacked structure. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm over the electron-transport layer 1114, thereby forming the electron-injection layer 1115.

[0371] Finally, aluminum was evaporated to a thickness of 200 nm over the electron injection layer 1115 to form the second electrode 1103 serving as the cathode; thus, the light-emitting elements 4 to 7 were obtained. Note that in all deposition steps, the deposition was performed by a resistance heating method.

[0372] Element structures of the light-emitting elements 4 to 7 obtained in the manner described above are shown in Table 8. [Table 8] First electrode Hole injection layer Hole transport layer Light-emitting layer Electron transport layer Electron injection layer Second electrode Light-emitting element 4 ITSO (110nm) DBT3P-II :MoOx (4:2 20nm) BPAFLP (20nm) * 2mDBTPDBq-II (20nm) BPhen (20nm) LiF (1nm) Al (200nm) Light-emitting element 5 ** Light-emitting element 6 *** Light-emitting element 7 **** * 2mDBTPDBq-II:NPB: [Ir(dmdppr-P) 2 (acac)] (0.8:0.2:0.05 40nm) <h2 style=";text-align:left;direction:ltr">** 2mDBTPDBq-[I:NPB: [Ir(dmdppr-dmp)<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> (acac)] (0.8:0,2:0.05 40nm) *** 2mDBTPDBq-II:NPB: [Ir(dmtppr) 2 (dibm)] (0.8:0.2:0.05 40nm) **** 2mDBTPDBq-I[:NPB: [Ir(dmdppr-dmp) 2 (dibm)] (0.8:0.2:0.05 40nm)

[0373] Furthermore, the fabricated light-emitting elements 4 to 7 were sealed in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealant was applied specifically to an outer edge of the element, and a heat treatment was performed at 80 °C for 1 hour at the time of sealing). 〈〈Operating characteristics of light-emitting elements 4 to 7〉〉

[0374] The operating characteristics of the fabricated light-emitting elements 4 to 7 were measured. Note that the measurement was conducted at room temperature (in an atmosphere maintained at 25 °C).

[0375] Fig. 57 shows current density-luminance characteristics of the light-emitting elements 4 to 7. In Fig. 57 the vertical axis represents the luminance (cd / m 2 ), and the horizontal axis represents the current density (mA / cm 2 ). Fig.58 shows voltage-luminance characteristics of the light-emitting elements 4 to 7. In Fig. 58 the vertical axis represents the luminance (cd / m 2 ) and the horizontal axis represents the voltage (V). Fig. 59 further shows luminance-current efficiency characteristics of the light-emitting elements 4 to 7. In Fig. 59, the vertical axis represents the current efficiency (cd / A), and the horizontal axis represents the luminance (cd / m 2 ). Fig. 60 shows voltage-current characteristics of the light-emitting elements 4 to 7. In Fig. 60 the vertical axis represents current (mA) and the horizontal axis represents voltage (V).

[0376] Fig. 59 demonstrates a high efficiency of the light-emitting elements 4 to 7, which contain the following in part of their light-emitting layers: [Ir(dmdppr-P) 2(acac)] (abbreviation), which is represented by the structural formula (121), [Ir(dmdppr-dmp)2(acac)] (abbreviation), which is represented by the structural formula (122), [Ir(dmtppr) 2 (dibm)] (abbreviation), which is represented by the structural formula (123), or [Ir(dmdppr-dmp) 2 (dibm)] (abbreviation), which is represented by the structural formula (124). Table 9 shows the initial values ​​of the main properties of the light-emitting elements 4 to 7 at a luminance of approximately 1000 cd / m 2 . [Table 9] Voltage (V) Current (mA) Current density (mA / cm 2 ) Chromaticity (x;y) Luminance e (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) Quantum efficiency (%) Light-emitting element 4 3,9 0,22 5,5 (0,68;0,32) 1100 20 16 25 Light-emitting element 5 3,3 0,1 2,5 (0,66;0,34) 1000 40 38 29 Light-emitting element 6 3,3 0,19 4,8 (0,68;0,32) 920 19 18 23 Light-emitting element 7 3,3 0,088 2,2 (0,66;0,34) 850 38 37 27

[0377] The above results show that the light-emitting elements 4 to 7 fabricated in this example are light-emitting elements with high luminance and high current efficiency. Regarding color purity, it can be further found that the light-emitting elements emit reddish-orange light with excellent color purity.

[0378] Fig. Figure 61 shows emission spectra at the time of applying a current with a current density of 2.5 mA / cm 2 to the light-emitting elements 4 to 7. The emission spectra of the light-emitting elements 5 and 7 have, as shown in Fig.61, each has a peak at approximately 617 nm, and the emission spectra of light-emitting elements 4 and 6 each have a peak at approximately 630 nm. It is therefore suggested that the peaks originate from emission of the organometallic complexes contained in the respective light-emitting elements. In addition, the half-widths of the emission spectra of light-emitting elements 4 to 7 were observed to be small. It can be assumed that this is an effect brought about by the structure of each of the organometallic complexes in this example, in which methyl groups are bonded to the 2-position and the 4-position of the phenyl group bonded to iridium. Thus, it can be said that light-emitting elements 4 to 7 have high emission efficiency and achieve high color purity.

[0379] Light-emitting elements 4 to 7 were subjected to reliability tests. The results of the reliability tests are shown in Fig. 62 and Fig. 63. In Fig. 62, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. It should be noted that in one of the reliability tests, the light-emitting elements 4 to 7 were operated under the conditions with the initial luminance set to 5000 cd / m 2was set and the current density was constant. Consequently, the light-emitting element 4 retained about 60% of the initial luminance after 100 hours; the light-emitting element 5 retained about 88% of the initial luminance after 38 hours; the light-emitting element 6 retained about 80% of the initial luminance after 40 hours; and the light-emitting element 7 retained about 86% of the initial luminance after 39 hours. Fig.63, the vertical axis represents the normalized luminance (%) at an initial luminance of 100%, and the horizontal axis represents the operating time (h) of the element. Note that in the other reliability test, the light-emitting elements 4 to 7 were driven at a current value of 0.3 mA. Consequently, the light-emitting element 4 retained about 86% of the initial luminance after 100 hours; the light-emitting element 5 retained about 91% of the initial luminance after 100 hours; the light-emitting element 6 retained about 90% of the initial luminance after 100 hours; and the light-emitting element 7 retained about 86% of the initial luminance after 100 hours.

[0380] Consequently, both reliability tests conducted under different conditions showed that the light-emitting elements 4 to 7 are highly reliable. Furthermore, it was confirmed that a light-emitting element with a long lifetime can be obtained using the above-described organometallic complex. [Example 14]((Synthesis Example 9))

[0381] In Synthesis Example 9, a synthesis method of bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phenyl-κC}(2,4-pen tandionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmppm2-dmp) 2 (acac)]), which is represented by structural formula (126) in Embodiment 1. The structure of [Ir(dmppm2-dmp) 2 (acac)] (abbreviation) is shown below. (Step 1: Preparation of 5-Bromo-2-(3,5-dimethylphenyl)pyrimidine)

[0382] First, 2.97 g of 5-bromo-2-iodopyrimidine, 1.62 g of 3,5-dimethylphenylboronic acid, 1.21 g of sodium carbonate, 0.093 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 20 ml of water, and 20 ml of acetonitrile were added to a receiving flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 1 hour to heat it. 0.40 g of 3,5-dimethylphenylboronic acid, 0.30 g of sodium carbonate, and 0.024 g of Pd(PPh 3 ) 2 Cl 2 was added to the flask, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was again subjected to microwave irradiation (2.45 GHz, 100 W) for 1 hour to heat it.

[0383] Water was then added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with water and a saturated saline solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the residue obtained was purified by flash column chromatography using hexane and ethyl acetate as the eluent in a ratio of 5:1. The solid obtained by concentrating a fraction was purified by flash column chromatography using dichloromethane and hexane as the eluent in a ratio of 1:1, so that the pyrimidine derivative to be prepared was obtained as a white powder in a yield of 33%. Note that the microwave irradiation was carried out using a microwave synthesis system (Discover, manufactured by CEM Corporation).A synthesis scheme of step 1 is shown in (i-1). (Step 2: Preparation of 5-(2,6-Dimethylphenyl)-2-(3,5-dimethylphenyl)pyrimidine (abbreviation: Hdmppm2-dmp))

[0384] Then, 0.91 g of 5-bromo-2-(3,5-dimethylphenyl)pyrimidine, 1.05 g of 2,6-dimethylphenylboronic acid, 0.74 g of sodium carbonate, 0.029 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 13 ml of water, and 13 ml of acetonitrile were added to a receiving flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 4 hours to heat it. 1.07 g of 2,6-dimethylphenylboronic acid, 0.73 g of sodium carbonate, and 0.029 g of Pd(PPh 3 ) 2 Cl 2was added to the flask, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was again subjected to microwave irradiation (2.45 GHz, 100 W) for 3 hours to heat it. Thereafter, the obtained mixture was subjected to suction filtration with water. The obtained solid was purified by flash column chromatography using toluene and hexane as the eluent in a ratio of 1:1, so that Hdmppm2-dmp (abbreviation), which was the pyrimidine derivative to be prepared, was obtained as a white powder in a yield of 83%. A synthesis scheme of step 2 is shown in (i-2). 〈Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phen yl-κC}diiridium(III) (abbreviation: [Ir(dmppm2-dmp) 2 Cl] 2 )〉

[0385] Subsequently, 15 ml of 2-ethoxyethanol, 5 ml of water, 0.83 g of Hdmppm2-dmp (abbreviation), which had been obtained in step 2, and 0.39 g of iridium chloride hydrate (IrCl 3 ·H 2 O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with hexane to obtain [Ir(dmppm2-dmp)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a brown powder in a yield of 91%. A synthesis scheme of step 3 is shown in (i-3). 〈Step 4: Preparation of bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phenyl-κC}(2,4-pen tandionato-κ 2O,O')iridium(III) (abbreviation: [Ir(dmppm2-dmp) 2 (acac)])〉

[0386] Then, 30 ml of 2-ethoxyethanol, 0.95 g of [Ir(dmppm2-dmp) 2 CI] 2(abbreviation), which is the binuclear complex obtained in step 3, 0.18 g of acetylacetone (abbreviation: Hacac), and 0.63 g of sodium carbonate were added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 120 W) was carried out for 60 minutes. Here, 0.18 g of Hacac was added, and microwave irradiation (2.45 GHz, 200 W) was carried out again for 60 minutes, so that heating was carried out. The solvent was distilled off, and the obtained residue was subjected to suction filtration with methanol. The obtained solid was washed with water and methanol.After the obtained solid was purified by flash column chromatography using hexane and ethyl acetate as eluent in a ratio of 5:1, recrystallization was carried out using a mixed solution of dichloromethane and methanol; thus, [Ir(dmppm2-dmp)] was obtained. 2 (acac)] (abbreviation) was obtained as a yellow-orange powder in a yield of 14%. A synthesis scheme of step 4 is shown in (i-4).

[0387] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the yellow-orange powder obtained in step 4 is described below. Fig. 64 shows the 1 H-NMR diagram. These results showed that [Ir(dmppm2-dmp) 2 (acac)] (abbreviation), which is represented by the structural formula (126), was obtained in Synthesis Example 9.

[0388] 1 H-NMR. δ(CDCl 3): 1.58 (s, 6H), 1.62 (s, 6H), 2.03 (s, 6H), 2.15 (s, 6H), 2.28 (s, 6H), 5.17 (s, 1H), 6.63 (d, 2H), 7.15 (t, 4H), 7.24 (t, 2H), 7.81 (d, 2H), 8.39 (d, 2H), 8.53 (d, 2H). [Example 15]〈〈Synthesis Example 10〉〉

[0389] In Synthesis Example 10, a synthesis method of bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmppm-dmp) 2 (acac)]), which is represented by structural formula (127) in Embodiment 1. The structure of [Ir(dmppm-dmp) 2 (acac)] (abbreviation) is shown below. 〈Step 1: Preparation of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine〉

[0390] First, 5.05 g of 4,6-dichloropyrimidine, 5.08 g of 3,5-dimethylphenylboronic acid, 3.57 g of sodium carbonate, 0.14 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2), 20 ml of acetonitrile, and 20 ml of water were added to a round-bottom flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. Heating was then carried out by microwave irradiation (2.45 GHz, 100 W) for 1 hour. After heating, 2.54 g of 3,5-dimethylphenylboronic acid, 1.79 g of sodium carbonate, and 0.066 g of Pd(PPh 3 ) 2 Cl 2 was added and the mixture was bubbled with argon for 15 minutes.

[0391] Subsequently, heating was carried out for 1 hour by irradiation with microwaves (2.45 GHz, 100 W). After heating, 1.27 g of 3,5-dimethylphenylboronic acid and 0.091 g of Pd(PPh 3 ) 2 Cl 2was added, and the mixture was bubbled with argon for 15 minutes. Further, heating was carried out by microwave irradiation (2.45 GHz, 100 W) for 1 hour. An organic layer was extracted with dichloromethane, and the extract solution was washed with water and a saturated salt solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and then the obtained residue was purified by silica gel column chromatography using dichloromethane as the eluent, so that the pyrimidine derivative to be prepared was obtained as a yellow crystal in a yield of 31%. Note that the microwave irradiation was carried out using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 1 is shown in (j-1). 〈Step 2: Preparation of 6-(2,6-Dimethylphenyl)-4-(3,5-dimethylphenyl)pyrimidine (abbreviation: Hdmppm-dmp)〉

[0392] Subsequently, 1.18 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine, which had been obtained in step 1, 0.754 g of 2,6-dimethylphenylboronic acid, 0.535 g of sodium carbonate, 0.036 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh 3 ) 2 Cl 2 ), 10 ml of acetonitrile, and 10 ml of water were added to a round-bottom flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. Heating was carried out for 1 hour by microwave irradiation (2.45 GHz, 100 W). Furthermore, 0.380 g of 2,6-dimethylphenylboronic acid, 0.268 g of sodium carbonate, and 0.020 g of Pd(PPh 3 ) 2 Cl 2 was added and the mixture was bubbled with argon for 15 minutes.

[0393] Subsequently, heating was carried out for 3 hours by microwave irradiation (2.45 GHz, 100 W). Then, 0.404 g of 2,6-dimethylphenylboronic acid, 0.277 g of sodium carbonate, and 0.019 g of Pd(PPh 3 ) 2 Cl 2 was added, and the mixture was bubbled with argon for 15 minutes. Heating was carried out for 3 hours by microwave irradiation (2.45 GHz, 100 W). Furthermore, 10 ml of acetonitrile and 10 ml of water were added, and heating was carried out for 3 hours by microwave irradiation (2.45 GHz, 100 W). An organic layer was extracted with dichloromethane, and the extract solution was washed with water and a saturated saline solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off to obtain a residue.

[0394] Similarly, 1.13 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine obtained in step 1, 0.802 g of 2,6-dimethylphenylboronic acid, 0.548 g of sodium carbonate, 0.040 g of Pd(PPh 3 ) 2 Cl 2 , 20 ml of acetonitrile and 20 ml of water were added to a round-bottom flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. Heating was then carried out for 2 hours by microwave irradiation (2.45 GHz, 100 W). Furthermore, 0.408 g of 2,6-dimethylphenylboronic acid, 0.288 g of sodium carbonate and 0.021 g of Pd(PPh 3 ) 2 Cl 2 was added and the mixture was bubbled with argon for 15 minutes.

[0395] Then, heating was carried out for 4 hours by microwave irradiation (2.45 GHz, 100 W). Furthermore, 7 ml of acetonitrile, 0.214 g of 2,6-dimethylphenylboronic acid, 0.273 g of sodium carbonate, and 0.020 g of Pd(PPh 3 ) 2 Cl 2 was added, and the mixture was bubbled with argon for 15 minutes. Heating was carried out by microwave irradiation (2.45 GHz, 100 W) for 2.5 hours. An organic layer was extracted with dichloromethane, and the extract solution was washed with water and a saturated saline solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off to obtain a residue.

[0396] The two residues obtained were purified by silica gel column chromatography using dichloromethane as the eluent. The solid obtained by concentrating a fraction was dissolved in dichloromethane and filtered through a filter aid stacked with Celite, alumina, and Celite in that order to obtain a 0.3 g coarse crystal (yellow).

[0397] Then, 1.10 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine, which had been obtained by the above silica gel column chromatography, 0.753 g of 2,6-dimethylphenylboronic acid, 0.534 g of sodium carbonate, 0.038 g of Pd(PPh 3 ) 2 Cl 2, 20 ml of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (abbreviation: DMPU) and 20 ml of water were added to a round-bottom flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. Heating was then carried out for 1 hour by microwave irradiation (2.45 GHz, 100 W). Furthermore, 0.376 g of 2,6-dimethylphenylboronic acid, 0.269 g of sodium carbonate, and 0.011 g of Pd(PPh 3 ) 2 Cl 2 was added and the mixture was bubbled with argon for 15 minutes.

[0398] Next, heating was carried out for 2 hours by microwave irradiation (2.45 GHz, 100 W). An organic layer was extracted with dichloromethane, and the extract solution was washed with water and a saturated saline solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off to obtain a residue. This residue and the yellow coarse crystal were combined and purified by silica gel column chromatography using dichloromethane and ethyl acetate as eluents to obtain Hdmppm-dmp (abbreviation), which was the precursor derivative to be prepared, as a yellow oily substance in a yield of 34%. A synthesis scheme of step 2 is shown in (j-2). 〈Step 3: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phe nyl-κC}diiridium(III) (abbreviation: [Ir(dmppm-dmp) 2 Cl] 2 )〉

[0399] Subsequently, 30 ml of 2-ethoxyethanol, 10 ml of water, 1.00 g of Hdmppm-dmp (abbreviation), which was obtained in step 2, and 0.568 g of iridium chloride hydrate (IrCl 3 ·H 2 O) (manufactured by Sigma-Aldrich Corporation) was added to a round-bottom flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with hexane to obtain [Ir(dmppm-dmp)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a black solid in 79% yield. A synthesis scheme of step 3 is shown in (j-3). 〈Step 4: Preparation of bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-xC}(2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmppm-dmp) 2 (acac)])〉

[0400] Then, 30 ml of 2-ethoxyethanol, 0.606 g of [Ir(dmppm-dmp) 2 Cl] 2(abbreviation), which is the dinuclear complex obtained in step 3, 0.138 g of acetylacetone (abbreviation: Hacac), and 0.489 g of sodium carbonate were added to a round-bottomed flask equipped with a reflux tube, and the air in the flask was replaced with argon. Heating was then carried out by microwave irradiation (2.45 GHz, 120 W) for 1 hour. The solvent was distilled off, and the obtained solid was purified by flash column chromatography using ethyl acetate and hexane as the eluent in a ratio of 1:2. Recrystallization was then carried out using a mixed solvent of dichloromethane and hexane; thus, [Ir(dmppm-dmp)] 2 (acac)] (abbreviation) was obtained as a dark red powder in 50% yield. A synthesis scheme of step 4 is shown in (j-4).

[0401] An analysis result by nuclear magnetic resonance spectroscopy ( 1H-NMR) on the dark red powder obtained in step 4 is described below. Fig. 65 shows the 1 H-NMR diagram. These results showed that [Ir(dmppm-dmp) 2 (acac)] (abbreviation), which is represented by the structural formula (127), was obtained in Synthesis Example 10.

[0402] 1 H NMR. δ(DMSO-d6): 1.43 (s, 6H), 1.70 (s, 6H), 2.19 (s, 12H), 2.18 (s, 6H), 5.34 (s, 1H), 6.54 (s, 2H), 7.23 (d, 4H), 7.30-7.33 (m, 2H), 7.79 (s, 2H), 8.23 ​​(s, 2H), 8.95 (ds, 2H). [Example 16]〈〈Synthesis Example 11〉〉

[0403] In Synthesis Example 11, a synthesis method of bis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato -κ 2 O,O')iridium(III) (Abbreviation: [Ir(tBudmppm) 2 (acac)]), which is represented by structural formula (106) in Embodiment 1. The structure of [Ir(tBudmppm) 2(acac)] (abbreviation) is shown below. 〈Step 1: Preparation of 4-tert-butyl-6-hydroxypyrimidine〉

[0404] First, 7.2 g of formamidine hydrochloride, 7.5 g of sodium methoxide, and 70 ml of methanol were added to a 100 ml three-necked flask. Then, 10 g of methyl 4,4-dimethyl-3-oxovalerate was added to this mixed solution. The mixture was stirred at room temperature for 24 hours. After that, a mixed solution of 17 ml of water and 7.2 ml of acetic acid was added to the reaction solution, and the mixture was stirred at room temperature. This mixture was concentrated, and the resulting residue was dissolved in water. The solution was extracted with ethyl acetate. The obtained extract solution was washed with a saturated saline solution, and magnesium sulfate was added for drying. After drying, the solution was filtered. After the solvent of this solution was distilled off, the obtained solid was washed with ethyl acetate, so that the pyrimidine derivative to be prepared was obtained as a white solid in a yield of 49%.A synthesis scheme of step 1 is shown in (k-1). 〈Step 2: Preparation of 4-tert-butyl-6-chloropyrimidine〉

[0405] Subsequently, 4.7 g of 4-tert-butyl-6-hydroxypyrimidine obtained in step 1 and 14 ml of phosphoryl chloride were added to a 50 ml three-necked flask, and the mixture was heated and refluxed for 1.5 hours. After reflux, phosphoryl chloride was distilled off under reduced pressure. The residue obtained was dissolved in dichloromethane, washed with water and a saturated aqueous solution of sodium hydrogen carbonate, and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and then the residue obtained was purified by silica gel column chromatography using hexane and ethyl acetate as the eluent in a ratio of 10:1, to obtain the pyrimidine derivative to be prepared as a white solid in a yield of 78%. A synthesis scheme of step 2 is shown in (k-2). 〈Step 3: Preparation of 4-tert-butyl-6-(3,5-dimethylphenyl)pyrimidine (abbreviation: HtBudmppm)〉

[0406] Then, 2.01 g of 4-tert-butyl-6-chloropyrimidine, which had been obtained in step 2, 3.63 g of 3,5-dimethylphenylboronic acid, 2.48 g of sodium carbonate, 0.10 g of bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh a ) 2 Cl 2 ), 20 ml of water, and 20 ml of DMF were added to a receiving flask equipped with a reflux tube, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 60 minutes to heat it. 0.90 g of 3,5-dimethylphenylboronic acid, 0.64 g of sodium carbonate, and 0.025 g of Pd(PPh 3 ) 2 Cl 2was added to the flask, and the mixture was bubbled with argon for 15 minutes. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) again for 60 minutes to heat it. Then, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with water and a saturated salt solution and dried with magnesium sulfate. After drying, the solution was filtered. The solvent of this solution was distilled off, and the obtained residue was purified by silica gel column chromatography using dichloromethane and ethyl acetate as the eluent in a ratio of 10:1, so that HtBudmppm (abbreviation), which was the pyrimidine derivative to be prepared, was obtained as a light yellow oil in a yield of 96%.Note that microwave irradiation was performed using a microwave synthesis system (Discover, manufactured by CEM Corporation). A synthesis scheme of step 3 is shown in (k-3). 〈Step 4: Preparation of di-µ-chloro-tetrakis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}diiridium(III) (abbreviation: [Ir(tBudmppm) 2 Cl] 2 )〉

[0407] Subsequently, 30 ml of 2-ethoxyethanol, 10 ml of water, 2.69 g of HtBudmppm (abbreviation), which had been obtained in step 3, and 1.48 g of iridium chloride hydrate (IrCl 3 ·H 2O) (manufactured by Sigma-Aldrich Corporation) was added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 100 W) was carried out for 1 hour to initiate a reaction. The solvent was distilled off, and then the obtained residue was subjected to suction filtration and washed with ethanol to obtain [Ir(tBudmppm)]. 2 Cl] 2 (abbreviation), which is a dinuclear complex, as a green powder in a yield of 62%. A synthesis scheme of step 4 is shown in (k-4). 〈Step 5: Preparation of bis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato -κ 2 O,O')iridium(III) (Abbreviation: [Ir(tBudmppm) 2 (acac)])〉

[0408] Then, 30 ml of 2-ethoxyethanol, 0.98 g of [Ir(tBudmppm) 2 Cl] 2(abbreviation), which is the binuclear complex obtained in step 4, 0.21 g of acetylacetone (abbreviation: Hacac), and 0.73 g of sodium carbonate were added to a receiving flask equipped with a reflux tube, and the air in the flask was replaced with argon. Subsequently, microwave irradiation (2.45 GHz, 200 W) was carried out for 60 minutes. Here, 0.21 g of Hacac (abbreviation) was added, and microwave irradiation (2.45 GHz, 100 W) was carried out again for 60 minutes, so that heating was carried out. The solvent was distilled off, and the obtained residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol. The obtained solid was dissolved in dichloromethane and filtered through a filter aid in which Celite, alumina, and Celite were stacked in that order.Then, recrystallization was carried out using a solvent mixture of dichloromethane and ethanol; thus, [Ir(tBudmppm). 2 (acac)] (abbreviation) was obtained as a yellow-orange powder in 61% yield. A synthesis scheme of step 5 is shown in (k-5).

[0409] An analysis result by nuclear magnetic resonance spectroscopy ( 1 H-NMR) on the yellow-orange powder obtained in step 5 is described below. Fig. 66 shows the 1 H-NMR diagram. These results showed that [Ir(tBudmppm) 2 (acac)] (abbreviation), which is represented by the structural formula (106), was obtained in Synthesis Example 11.

[0410] 1 H-NMR. δ(CDCl 3 ): 1.38 (s, 6H), 1.46 (s, 18H), 1.69 (s, 6H), 2.26 (s, 6H), 5.17 (s, 1H), 6.55 (s, 2H), 7.43 (s, 2H), 7.71 (s, 2H), 8.87 (s, 2H). Explanation of reference symbols

[0411] 101: first electrode, 102: EL layer, 103: second electrode, 111: hole injection layer, 112: hole transport layer, 113: light-emitting layer, 114: electron transport layer, 115: electron injection layer, 116: charge generation layer, 201: anode, 202: cathode, 203: EL layer, 204: light-emitting layer, 205: phosphorescent compound, 206: first organic compound, 207: second organic compound, 301: first electrode, 302(1): first EL layer, 302(2): second EL layer, 302(n-1): (n-1)th EL layer, 302(n): (n)th EL layer, 304: second electrode, 305: charge generation layer (I), 305(1): first charge generation layer (I), 305(2): second charge generation layer (I), 305(n-2): (n-2)th charge generation layer (I), 305(n-1): (n-1)th charge generation layer (I), 401: reflective electrode, 402: semi-transparent and semi-reflective electrode, 403a: first transparent conductive layer, 403b: second transparent conductive layer,404B: first light-emitting layer (B), 404G: second light-emitting layer (G), 404R: third light-emitting layer (R), 405: EL layer, 410R: first light-emitting element (R), 410G: second light-emitting element (G), 410B: third light-emitting element (B), 501: element substrate, 502: pixel portion, 503: driver circuit portion (source line driver circuit), 504a and 504b: driver circuit portion (gate line driver circuit), 505: sealant, 506: seal substrate, 507: lead, 508: flexible printed circuit (FPC), 509: n-channel TFT, 510: p-channel TFT, 511: TFT for Switching, 512: TFT for current control, 513: first electrode (anode), 514: insulator, 515: EL layer, 516: second electrode (cathode), 517: light-emitting element, 518: space, 1100: substrate, 1101: first electrode, 1102: EL layer, 1103: second electrode, 1111: hole injection layer, 1112: hole transport layer,1113: Light-emitting layer, 1114: Electron transport layer, 1115: Electron injection layer, 7100: TV, 7101: Housing, 7103: Display section, 7105: Base, 7107: Display section, 7109: Operation button, 7110: Remote control, 7201: Main body, 7202: Housing, 7203: Display section, 7204: Keyboard, 7205: External connection port, 7206: Pointing device, 7301: Housing, 7302: Housing, 7303: Hinge section, 7304: Display section, 7305: Display section, 7306: Speaker section, 7307: Recording media insertion section, 7308: LED lamp, 7309: Operation button, 7310: Connection port, 7311: Sensor, 7312: Microphone, 7400: Mobile phone, 7401: Housing, 7402: Display section, 7403: Operation button, 7404: External connection port, 7405: Speaker, 7406: Microphone, 8001: Lighting device, 8002: Lighting device, 8003: Lighting device, 8004: Lighting device, 9033: Bracket, 9034: Switch for switching display modes,9035: Power switch, 9036: Button for switching to a power saving mode, 9038: Operation button, 9630: Housing, 9631: Display section, 9631a: Display section, 9631b: Display section, 9632a: Touch screen area, 9632b: Touch screen area, 9633: Solar cell, 9634: Charge and discharge control circuit, 9635: Battery, 9636: DC-DC converter, 9637: Operation button, 9638: Converter and 9639: Button.

Claims

[1] Light-emitting element comprising: a pair of electrodes; and a light-emitting layer between the pair of electrodes, the light-emitting layer comprising: a first organic compound; a second organic compound; and an organometallic complex represented by the general formula G1: wherein X represents a substituted or unsubstituted six-membered heteroaromatic ring containing two or more nitrogen atoms including one nitrogen atom which is a coordinating atom, where R 1 to R 4 each represent an alkyl group having 1 to 6 carbon atoms, wherein the first organic compound and the second organic compound are a combination forming an exciplex, where a T 1 -level of the first organic compound is higher than a T 1-level of the organometallic complex, where a T 1 -level of the second organic compound is higher than the T 1 -level of the organometallic complex, and where an emission spectrum of the exciplex overlaps with an absorption spectrum of the organometallic complex. [2] Light-emitting element according to claim 1, where X represents one of the formulas X1 to X3: and where R 5 to R 13 each represents hydrogen, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group. [3] Light-emitting element according to claim 1, where the organometallic complex is represented by the formula G2: where R 5 and R 6 each represents hydrogen, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group, and where R7 an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group. [4] Light-emitting element according to claim 1, where the organometallic complex is represented by the formula G3: where R 8 and R 10 each represents hydrogen, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group, and where R 9 an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group. [5] Light-emitting element according to claim 1, where the organometallic complex is represented by the formula G4:and where R 11 to R 13 each represents hydrogen, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group, and where one of R 12and R 13 an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group. [6] Light-emitting element according to claim 1, where R 1 and R 2 are each a methyl group. [7] Light-emitting element according to claim 1, wherein the organometallic complex is represented by one of the formulas 100 to 105 and 121 to 125: [8] Light-emitting element according to claim 1, where the organometallic complex is represented by one of the formulas 106 to 111 and 127: [9] The light-emitting element according to claim 1, wherein the organometallic complex is represented by any one of formulas 112 to 117 and 126: [10] Electronic device comprising: a display section comprising the light-emitting element according to claim 1, wherein the electronic device is selected from a television, a monitor, a camera, a photo frame, a portable information terminal, an audio playback device, and a game device. [11] A lighting device comprising the light-emitting element according to claim 1.

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