Compound and luminescent material comprising the same

Abstract

To provide a compound in which a carbon-bridged p-phenylenevinylene backbone is two-dimensionally arranged in a regular manner.SOLUTION: A compound comprises a repeating unit represented by general formula (1) in the figure, where: M is a transition metal element; and A and B are phenylenevinylene backbones.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a compound and a light-emitting material comprising the same. [Background technology]

[0002] In recent years, organic light-emitting materials have been increasingly used as light-emitting elements in organic light-emitting diodes (OLEDs) that make up the displays of smart devices and in various imaging applications. These light-emitting materials are composed of molecules called fluorescent dyes, which become excited by the action of electric fields or ultraviolet light, and then emit light of specific wavelengths when they return to their ground state. Therefore, to accommodate various wavelengths of light, such as the three primary colors, molecular design of organic light-emitting materials, such as the length of the π-conjugated system and the selection and arrangement of electron-donating and electron-accepting groups, is important. Furthermore, these molecules must be chemically stable because they are exposed to highly oxidizing or reducing environments when an electric field is applied and, depending on the application, to high temperatures. Furthermore, these molecules must have high quantum yields to enhance their usefulness as light-emitting materials.

[0003] To solve these problems, the present inventors have proposed a carbon-bridged p-phenylene vinylene polymer in Non-Patent Document 1. In this polymer, the carbon-bridged p-phenylene vinylene unit, which is a repeating unit, functions as a donor equipped with a long conjugated system, and by bonding an acceptor group to this as necessary, visible light of various wavelengths is emitted. Furthermore, in this polymer, the carbon bridge in the p-phenylene vinylene unit suppresses intramolecular rotation, thereby contributing to an improvement in quantum yield, and the bulky substituents protruding above and below the π-conjugated system are believed to suppress attack by molecular species on the π-conjugated system, thereby improving the chemical stability and thermal stability of the dye molecule.

[0004] Furthermore, in Patent Document 1, the present inventors have shown that when a single or multiple-linked carbon-bridged phenylene vinylene is used as the donor moiety (D) and a substituent whose LUMO is 0 to −5 eV when the donor moiety exists independently as a single compound is used as the acceptor moiety (A), a compound to which a group of substituents is bonded, such as DAD or ADA, can emit fluorescence of various wavelengths in the visible light region with a good quantum yield, even without having a large π-conjugated system like the polymer described in Non-Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-016207 [Non-patent literature]

[0006] [Non-Patent Document 1] Xiaozhang Zhu, Hayato Tsuji, Juan T. Lopez Navarrete, Juan Casado, Eiichi Nakamura J. Am. Chem. Soc. 2012, 134, 46, 19254-19259 Summary of the Invention [Problem to be solved by the invention]

[0007] The compounds having a carbon-bridged p-phenylene vinylene skeleton described in Patent Document 1 and Non-Patent Document 1 have a rigid and linear π-conjugated system derived from the carbon-bridged p-phenylene vinylene skeleton, and this π-conjugated system brings about strong light absorption and fluorescence emission with a high quantum yield. Furthermore, by regularly aligning molecules having such a π-conjugated system, energy exchange occurs between the π-conjugated units, which may lead to fluorescence emission with a higher quantum yield.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a novel compound in which carbon-bridged p-phenylene vinylene skeletons are regularly arranged in a two-dimensional manner. Although the compound of the present invention exhibits good fluorescence, its main object is not to provide only fluorescence, but also to provide a novel compound that may have various functions related to energy transfer by two-dimensionally aligning carbon-bridged p-phenylene vinylene skeletons that have donor properties. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above problems, the present inventors have found that by bonding carboxy groups, which are bidentate ligands, to both ends of a compound molecule having a carbon-bridged p-phenylenevinylene skeleton and then coordinating this as a ligand to one of the transition metal ions from periods 4 to 6 of the periodic table, a compound having a repeating unit such as that shown in general formula (1) below and in which carbon-bridged p-phenylenevinylene skeletons are regularly arranged in two dimensions can be obtained. The present invention was made based on this finding and provides the following:

[0010] (1) The present invention is a compound having a repeating unit represented by the following general formula (1): [ka] (In general formula (1), M is any one of the transition metal elements of the fourth to sixth periods of the periodic table, and the A structure and the B structure are each independently represented by the following general formula (X). In addition, the compound having a repeating unit represented by the above general formula (1) contains a counter anion required according to the number of charges thereof.) [ka] (In the above general formula (X), each R is independently a carbon chain having 1 to 30 carbon atoms which may contain a heteroatom in the chain, a cycloalkyl group having 4 to 20 carbon atoms which may have a substituent, an aryl group having 5 to 30 carbon atoms which may have a substituent, a trialkylsilyl group, an arylalkyl group, or an alkylarylalkyl group, or two adjacent Rs are linked to each other to form a cyclic structure, and each R 1 each independently represents a carbazolyl group, -NR 2 2. An alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or a phenyl group which may have a substituent, 2 are each independently a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, p is an integer of 1 to 10, each m is independently an integer of 0 to 2, and each n is independently an integer of 0 to 2.

[0011] (2) The present invention also relates to the compound according to item (1), wherein the general formula (X) is represented by the following general formula (X1): [ka] (In the above general formula (X1), each R is independently a carbon chain having 1 to 30 carbon atoms which may contain a heteroatom in the chain, a cycloalkyl group having 4 to 20 carbon atoms which may have a substituent, an aryl group having 5 to 30 carbon atoms which may have a substituent, a trialkylsilyl group, an arylalkyl group, or an alkylarylalkyl group, or two adjacent Rs are linked to each other to form a cyclic structure.)

[0012] (3) The present invention also relates to the compound according to item (1), wherein the general formula (X) is represented by the following general formula (X2): [ka] (In the above general formula (X2), each R is independently an alkyl group having 1 to 20 carbon atoms.)

[0013] (4) The present invention also provides a light-emitting material comprising the compound according to any one of (1) to (3). [Effects of the Invention]

[0014] According to the present invention, there is provided a novel compound in which carbon-bridged p-phenylenevinylene skeletons are regularly arranged two-dimensionally. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, one embodiment of the compound and light-emitting material of the present invention will be described. Note that the present invention is not limited to the following embodiment, and can be practiced by making appropriate modifications within the scope of the present invention.

[0016] <Compound> First, the compound of the present invention will be described. The compound of the present invention is a compound having a repeating unit represented by the following general formula (1), and the A structure and B structure in the following general formula (1) are each independently represented by the following general formula (X). The structure represented by the following general formula (X) is a carbon-bridged p-phenylenevinylene skeleton, and this carbon-bridged p-phenylenevinylene skeleton is repeated as the A structure and B structure of the general formula (1), resulting in a two-dimensional mesh-like structure.

[0017] The carbon-bridged p-phenylene vinylene skeleton is bridged by carbon atoms to form a fused five-membered ring structure in the vinylene moiety, and this bridge restricts the free rotation of the vinylene moiety, suppressing twisting of the π-conjugated system and facilitating smooth electron transfer in the π-conjugated system. Furthermore, the carbon-bridged p-phenylene vinylene skeleton possesses donor properties. By arranging such carbon-bridged p-phenylene vinylene skeletons in a two-dimensional network, the compound of the present invention is expected to exhibit fluorescence emission with a high quantum yield and various functions related to electron exchange and energy transfer. Hereinafter, carbon-bridged p-phenylene vinylene is also referred to as COPV (Carbon-bridged Oligo(Phenylene Vinylene)s).

[0018] [ka]

[0019] [ka]

[0020] In the general formula (1), M represents any of the transition metal elements from the fourth to sixth periods of the periodic table, and this transition metal element is considered to form an ion in the molecule. As shown in general formula (1), one of the two Ms in the formula is coordinated with one oxygen atom from each of four carboxylate groups, and the other is coordinated with one oxygen atom from each of the same four carboxylate groups. A complex with this structure is called a paddlewheel complex. Any of the transition metal elements from the fourth to sixth periods of the periodic table can have a planar tetracoordinate structure, a square pyramidal pentagonal pentagonal octahedral hexagonal pentagonal structure, or a hexagonal octahedral pentagonal ... In this case, examples of the ligand include water molecules (aqua ligands), solvent molecules, and dissolved ions.

[0021] As described above, M may be any transition metal element from the fourth to sixth periods of the periodic table. Among these, Zn, Rh, Cu, Ni, Co, Cr, Ru, Pd, etc. are preferred, with Zn, Rh, Cu, etc. being more preferred. These transition metal elements are known to form paddlewheel complexes with two carboxylate anions, as described in a known paper (Chem. Mater. 2012, 24, 3153-3167). In many cases, the coordination structure represented by general formula (1) takes the form of a cation or anion. In this case, the compound of the present invention having a repeating unit represented by general formula (1) will contain a counter anion required according to the charge number.

[0022] The A structure and the B structure in the general formula (1) are each independently represented by the general formula (X). That is, the A structure and the B structure present in plural may be different from each other, or some or all of them may be the same. It is preferable that all the A structures and the B structures are the same structure.

[0023] In general formula (X), each R is independently a carbon chain having 1 to 30 carbon atoms, which may contain a heteroatom in the chain; a cycloalkyl group having 4 to 20 carbon atoms, which may have a substituent; an aryl group having 5 to 30 carbon atoms, which may have a substituent; a trialkylsilyl group, an arylalkyl group, or an alkylarylalkyl group; or two adjacent Rs are bonded to each other to form a cyclic structure. As can be seen from general formula (X), these Rs are bonded to the carbon atoms forming the above-mentioned crosslink and are bulky substituents. These bulky substituents, R, protrude above and below the π-conjugated system of the compound, covering it and suppressing attack by chemical species on the π-conjugated system. As a result, the skeleton portion represented by general formula (X) of the present invention exhibits high thermal stability and chemical stability. Note that "each R is independently determined" means that multiple Rs included in general formula (X) are independently determined, and they may be the same or different from each other. The expression "independently" is frequently used in this specification, and is interpreted in the same way in all cases.

[0024] The carbon chain having 1 to 30 carbon atoms which may contain heteroatoms in the chain is a chain group which may be linear or branched and contains 1 to 30 carbon atoms, and the chain group is a monovalent group which may or may not contain heteroatoms along the chain. Examples of heteroatoms include oxygen atoms, sulfur atoms, and nitrogen atoms. One or more of these heteroatoms may be contained, and the group may be, for example, a polyoxyethylene group containing multiple oxygen atoms.

[0025] The cycloalkyl group having 4 to 20 carbon atoms and optionally having a substituent is a cycloalkyl group having or not having a substituent, and when having a substituent, a hydrogen atom of the cycloalkyl group is replaced by the substituent. Examples of such a substituent include an alkyl group, an arylalkyl group, an alkylarylalkyl group, etc. having 1 to 12 carbon atoms.

[0026] The aryl group having 5 to 30 carbon atoms, which may have a substituent, is an aryl group which may or may not have a substituent, and when it has a substituent, a hydrogen atom of the aryl group is replaced by the substituent. Examples of such a substituent include an alkyl group having 1 to 12 carbon atoms. Examples of the aryl group which may have a substituent include a phenyl group, an alkylphenyl group, an arylalkyl group, and an alkylarylalkyl group, and among the alkylphenyl groups, a 4-octylphenyl group is preferred.

[0027] An arylalkyl group is a group having an aromatic ring at the end of an alkyl chain, such as a benzyl group. In this case, the alkyl chain may have about 1 to 20 carbon atoms. In addition, examples of the aromatic ring include a phenyl group, a naphthyl group, a fluorenyl group, and a carbazolyl group. An alkylarylalkyl group is a group having a structure in which an aromatic ring is sandwiched between two alkyl chains. In this case, examples of the alkyl chain may include about 1 to 20 carbon atoms. In addition, examples of the aromatic ring include a phenyl group, a naphthyl group, a fluorenyl group, and a carbazolyl group.

[0028] When two adjacent Rs are linked to form a cyclic structure, the cyclic structure will form a spiro structure together with the five-membered ring contained in the general formula (X). The cyclic structure may be a non-aromatic ring (i.e., an alicyclic ring) or an aromatic ring, may contain a heteroatom such as nitrogen, sulfur, or oxygen, or may form a fused ring. Examples of such cyclic structures include a fluorene ring and a cycloalkane ring having 4 to 20 carbon atoms. For example, when the cyclic structure is a fluorene ring, two adjacent Rs will form a spirofluorenyl group, and when the cyclic structure is a cycloalkane ring such as a cyclopentane ring or a cyclohexane ring, two adjacent Rs will form a spirocycloalkyl group such as a spirocyclopentyl group or a spirocyclohexyl group. When the cyclic structure is a fluorene ring, the fused five-membered ring and the five-membered ring in the general formula (X) will form a spiro structure. Furthermore, "two adjacent Rs" means that two Rs are bonded to the same carbon atom.

[0029] In the above general formula (X), each R 1 each independently represents a carbazolyl group, -NR 2 2. An alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or a phenyl group which may have a substituent. These alkyl groups and alkyloxy groups may be linear or branched. The phenyl group which may have a substituent may be a phenyl group which has a substituent, or may be a phenyl group which has no substituent. Examples of the substituent include an alkyl group, an arylalkyl group, and an alkylarylalkyl group which have 1 to 12 carbon atoms. -NR 2 R in 2 2 are each independently a hydrogen atom or an alkyl group having 1 to 30 carbon atoms.

[0030] In the above general formula (X), p is an integer of 1 to 10, preferably an integer of 1 to 5, more preferably an integer of 1 to 3, and particularly preferably 1 or 2. Each m is independently an integer of 0 to 2, and each n is independently an integer of 0 to 2.

[0031] A preferred example of the structure represented by the above general formula (X) is one represented by the following general formula (X1).

[0032] [ka]

[0033] In the general formula (X1), each R is independently a carbon chain having 1 to 30 carbon atoms which may contain a heteroatom in the chain, a cycloalkyl group having 4 to 20 carbon atoms which may have a substituent, an aryl group having 5 to 30 carbon atoms which may have a substituent, a trialkylsilyl group, an arylalkyl group, an alkylarylalkyl group, or two adjacent Rs are linked to each other to form a cyclic structure. This is the same as R in the general formula (X), so further explanation will be omitted here.

[0034] In the structure represented by the general formula (X1) above, p is specified to be 2, and m and n are specified to be 0 in the general formula (X) above.

[0035] More preferred examples of the structures represented by the above general formulas (X) and (X1) include those represented by the following general formula (X2).

[0036] [ka]

[0037] In the general formula (X2), each R is independently an alkyl group having 1 to 20 carbon atoms. Ph in the general formula (X2) represents a phenyl group. The structure represented by the general formula (X2) is such that four R in the general formula (X1) are specified as phenyl groups, and the remaining four R are specified as 4-alkylphenyl groups. A preferred example of the 4-alkylphenyl group is, but is not limited to, a 4-octylphenyl group.

[0038] Next, an example of a method for synthesizing the compound of the present invention will be described. For ease of explanation, the following example will be used: in which M in the above general formula (1) is Zn, all Structures A and B are structures represented by general formula (X2), and Ar is a 4-octylphenyl group. However, the present invention is not limited to this example, and the compound of the present invention may be synthesized by another synthetic route. Compound 10, the starting material for the synthetic route described below, can be synthesized according to the method described in JP 2011-32197 A. In the synthetic route described below, Ph represents an unsubstituted phenyl group, Ar represents a 4-octylphenyl group, Zn(OAc)2·2H2O represents zinc acetate dihydrate, and BuLi represents butyllithium. In the synthetic route described below, the compound obtained by reacting Compound 12 with Zn(OAc)2·2H2O (i.e., the final product) is depicted in a schematic diagram; however, Ph and Ar are omitted from this diagram for simplicity and ease of understanding.

[0039] [ka]

[0040] As shown in the above synthesis scheme, starting with compound 10 synthesized according to the description of JP 2011-32197 A, compound 11 is brominated at both ends, and compound 12 is obtained by converting the bromo group to a carboxy group. A dimethylformamide solution of compound 12 and a dimethylformamide solution of zinc acetate dihydrate are prepared and gently mixed. The mixture is then heated from room temperature to 90°C at a rate of 2°C per minute and maintained at that temperature for approximately 24 hours. The mixture is then cooled to room temperature at a rate of 0.1°C per minute and allowed to stand at room temperature for approximately one and a half days. Crystals of the target compound can then be obtained by allowing the solution to stand at approximately -20°C for approximately one month.

[0041] <Light-emitting materials> The present invention also relates to a light-emitting material containing the compound of the present invention. The compound of the present invention can emit fluorescence with a high quantum yield and can be preferably used, for example, as an optical waveguide or a laser medium. [Example]

[0042] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples in any way.

[0043] Synthesis of compound 11 [ka]

[0044] Compound 10 (0.282 g, 0.203 mmol), synthesized according to the method described in JP 2011-32197 A, and a carbon tetrachloride mixture (14 mL) of CuBr / Al2O3 (0.82 g, 1.22 mmol) were heated at 85 °C for 12 hours. The mixture was cooled to room temperature, quenched by the addition of an aqueous solution of sodium hydrogen sulfate, and passed through a short-path silica gel column using dichloromethane. The solvent was evaporated, and the residue was washed with methanol and n-hexane to give compound 11 as a yellow solid (yield: 0.281 g, 90%).

[0045] 1 H-NMR(500MHz, CDCl3):δ(ppm) 7.50(d,J=1.8Hz,2H),7.25(s,2H),7.23-7.15(m,22H),7.06(d,J=8.6Hz,8H),6.99(d,J=8.0Hz,2H),6. 95(d,J=8.0Hz,8H),2.49(t,J=8.0Hz,8H),1.55-1.50(m,8H),1.30-1.27(m,40H),0.88(t,J=6.3Hz,12H) MS(APCI + ):1542.9

[0046] Synthesis of compound 12 [ka]

[0047] To a solution of compound 11 (508 mg, 0.328 mmol) in tetrahydrofuran (10 mL), tert-butyllithium (1.56 M pentane solution, 890 μL, 1.38 mmol) was added at −78°C and stirred at that temperature for 1 hour. An excess of carbon dioxide was then bubbled into the reaction solution at room temperature, and the mixture was stirred at room temperature for an additional 18 hours. Dilute hydrochloric acid was added to the reaction solution, followed by extraction with chloroform. The organic phase was dried over anhydrous magnesium sulfate, and the solvent was then evaporated under reduced pressure. This was purified by column chromatography (ethyl acetate:n-hexane = 2:5) to give compound 12 as a yellow solid (yield 297 mg, 61%).

[0048] 1 H-NMR(600MHz,THF-d8):δ(ppm) 8.07(s,2H),7.81(d,J=8.3Hz,2H),7.45(s,2H),7.25-7.23(m,12H),7.20-7.14(m,18H),6.99(d, J=8.3Hz,8H),2.51(t,J=7.9Hz,8H),1.58-1.53(m,8H),1.34-1.29(m,40H),0.89(t,J=7.2Hz,12H) HRMS(APCI + ):1475.8792

[0049] Preparation of complexes [ka]

[0050] A solution of zinc acetate dihydrate (15.49 mg, 0.070 mmol) in dimethylformamide (1 mL) was added dropwise to a solution of compound 12 (20.71 mg, 0.014 mmol) in dimethylformamide (2 mL) at room temperature, and the mixture was gently stirred. Upon mixing, a very fine solid rapidly formed, and the mixture became opaque. The mixture was heated from room temperature to 90 °C at a rate of 2 °C per minute and then allowed to stand at that temperature for 24 hours. The temperature was then cooled to room temperature at a rate of 0.1 °C per minute and allowed to stand at room temperature for another 1.5 days. The mixture was then placed in a -20 °C freezer and allowed to stand at -20 °C for approximately one month. The resulting crystals were recovered and subjected to crystal structure analysis, revealing that compound 12 and zinc formed a complex with a two-dimensional network structure. In the above chemical reaction formula, the products are expressed in a schematic diagram, and for simplification and to facilitate understanding, Ph and Ar are omitted from this diagram.

[0051] The solid-state fluorescence quantum yields of both compound 12 and the complex obtained by the above procedure were measured. The fluorescence quantum yield of compound 12 was 0.17-0.20, while the fluorescence quantum yield of the complex was improved to 0.27. This indicates that the COPV skeleton exhibits superior properties as a light-emitting material by forming a two-dimensional network structure through complex formation.

Claims

1. A compound having a repeating unit represented by the following general formula (1): 【Chemical 1】 (In general formula (1), M is any one of the transition metal elements of the fourth to sixth periods of the periodic table, and the A structure and the B structure are each independently represented by the following general formula (X). In addition, the compound having a repeating unit represented by the general formula (1) contains a counter anion required according to the number of charges thereof.) 【Chemistry 2】 (In the general formula (X), each R is independently a carbon chain having 1 to 30 carbon atoms which may contain a heteroatom in the chain, a cycloalkyl group having 4 to 20 carbon atoms which may have a substituent, an aryl group having 5 to 30 carbon atoms which may have a substituent, a trialkylsilyl group, an arylalkyl group, an alkylarylalkyl group, or two adjacent Rs are bonded to each other to form a cyclic structure, and each R １ are each independently a carbazolyl group, —NR ２ ２ , an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or a phenyl group which may have a substituent, ２ are each independently a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, p is an integer of 1 to 10, each m is independently an integer of 0 to 2, and each n is independently an integer of 0 to 2.

2. The compound according to claim 1, wherein the general formula (X) is represented by the following general formula (X1): 【Chemistry 3】 (In the above general formula (X1), each R is independently a carbon chain having 1 to 30 carbon atoms which may contain a heteroatom in the chain, a cycloalkyl group having 4 to 20 carbon atoms which may have a substituent, an aryl group having 5 to 30 carbon atoms which may have a substituent, a trialkylsilyl group, an arylalkyl group, or an alkylarylalkyl group, or two adjacent Rs are linked to each other to form a cyclic structure.)

3. The compound according to claim 1, wherein the general formula (X) is represented by the following general formula (X2): 【Chemistry 4】 (In the general formula (X2) above, each R is independently an alkyl group having 1 to 20 carbon atoms.)

4. A light-emitting material comprising the compound according to any one of claims 1 to 3.

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