A nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand, preparation method thereof, iridium complex and organic electroluminescent device

Abstract

The present invention discloses a dibromo-1,3-bis(1-butylimidazole-3-yl)benzene ligand modified with an nitrogen heteroaromatic ring and a preparation method thereof, an iridium complex and an organic electroluminescent device. The dibromo-1,3-bis(1-butylimidazole-3-yl)benzene ligand modified with an nitrogen heteroaromatic ring has the following structure: wherein R is an nitrogen heteroaromatic ring group or a derivative thereof. The present invention introduces an nitrogen heteroaromatic ring group or a derivative thereof at position 5 of dibromo-1,3-bis(1-butylimidazole-3-yl)benzene to obtain a dibromo-1,3-bis(1-butylimidazole-3-yl)benzene ligand modified with an nitrogen heteroaromatic ring, which can be used as a tridentate ligand of an iridium complex, increases the rigidity of the ligand and the complex, regulates the luminescent color and efficiency of the complex, increases steric hindrance, reduces molecular stacking, thereby suppressing the non-radiative transition process of the molecule and improving the luminous efficiency of an organic electroluminescent device using an iridium complex.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescent materials, and in particular to a nitrogen heteroaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand, a preparation method thereof, an iridium complex and an organic electroluminescent device. Background Art

[0002] In modern display and lighting technologies, organic electroluminescence (OLED) technology has attracted considerable attention due to its unique advantages. The core of OLED technology lies in organic light-emitting materials, which emit light under the influence of an electric field and possess characteristics such as self-luminescence, high contrast, fast response, low energy consumption, and flexibility. With the continuous advancement of OLED technology, the demand for high-performance organic light-emitting materials is growing, especially in the deep blue light region. Achieving high efficiency and high stability of light-emitting materials is key to the development of OLED technology.

[0003] Among the many organic light-emitting materials, metal complexes have become a hot topic of research due to their unique optoelectronic properties. Iridium (Ir) complexes, due to their stable triplet metal centers and strong spin-orbit coupling, exhibit high photoluminescence quantum yields and long luminescence lifetimes, and are considered ideal OLED light-emitting materials. However, traditional iridium complexes have certain limitations in terms of luminescence color control and efficiency improvement, especially in the deep blue region, where achieving high efficiency and high stability remains a challenge.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] In order to make up for the deficiencies of the prior art, the present invention provides a nitrogen heteroaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand and a preparation method thereof, an iridium complex and an organic electroluminescent device.

[0006] The present invention adopts the following technical solutions:

[0007] In the first aspect, a nitrogen heteroaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand is provided, which has the following structure:

[0008]

[0009] Wherein, R is an nitrogen heteroaromatic ring group or a derivative thereof.

[0010] In the second aspect, an iridium complex is provided, which has metal Ir as the central atom and is coordinated with a tridentate ligand, a bidentate ligand and a monodentate ligand, wherein the tridentate ligand is the nitrogen-aromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand described in the first aspect.

[0011] In the third aspect, a method for preparing the nitrogen-heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand described in the first aspect is provided, comprising the following steps: using 1,3-dibromo-5-fluorobenzene and R as starting materials, reacting under the action of alkali, and introducing a nitrogen-heteroaromatic ring derivative at the 5 position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain the nitrogen-heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand.

[0012] In a fourth aspect, an organic electroluminescent device is provided, comprising: an anode, a cathode, and an organic light-emitting layer arranged between the anode and the cathode, wherein the iridium complex described in the second aspect is used as a light-emitting material in the organic light-emitting layer.

[0013] The present invention has the following beneficial effects: the present invention introduces an azoaromatic ring group or its derivative at the 5-position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain an azoaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand, which can be used as a tridentate ligand of an iridium complex, thereby increasing the rigidity of the ligand and the complex, regulating the luminescent color and efficiency of the complex, increasing steric hindrance, reducing molecular stacking, thereby inhibiting the non-radiative transition process of the molecule, and improving the luminescent efficiency of an organic electroluminescent device using the iridium complex.

[0014] Specifically, the iridium complex of the present invention has the following characteristics:

[0015] 1. High photoluminescence quantum yield: Due to the introduction of nitrogen heteroaromatic ring groups or their derivatives, the interaction between the ligand and the metal center is enhanced, thereby improving the luminescence efficiency.

[0016] 2. Short excited state lifetime: The complex has a short excited state lifetime, which is beneficial for fast-response OLED devices.

[0017] 3. Characteristics of anti-intersystem crossing: Iridium complexes can effectively utilize triplet excitons, improving the luminescence efficiency and stability of the device.

[0018] 4. Regulation of luminescence color and efficiency: By changing the type and amount of nitrogen heteroaromatic ring groups or their derivatives, the luminescence color and efficiency of the complex can be regulated, achieving regulation from blue light to deep blue light.

[0019] Therefore, the iridium complex of the present invention has potential application value in the field of 0LED display and lighting, provides a new direction for the development of OLED technology, and is expected to promote the progress of related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The single crystal structure of the iridium complex Ir-114 in Example 1 of the present invention;

[0021] Figure 2 The photoluminescence spectra of the iridium complexes Ir-1, Ir-22, Ir-53 and Ir-84 in Example 1 of the present invention are shown below:

[0022] Figure 3 The absorption spectra of the iridium complexes Ir-3, Ir-9, Ir-11 and Ir-20 in Example 1 of the present invention are shown in FIG.

[0023] Figure 4 The excited state spectra of the iridium complexes Ir-3, Ir-9, Ir-11 and Ir-20 in Example 1 of the present invention;

[0024] Figure 5 The emission spectrum of the OLED device using iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101 as light-emitting materials in Example 2 of the present invention;

[0025] Figure 6 The current density-voltage-brightness curves of the OLED device using iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101 as light-emitting materials in Example 2 of the present invention;

[0026] Figure 7 This is the external quantum efficiency-brightness curve of the OLED device using iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101 as light-emitting materials in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail. It should be emphasized that the following description is merely illustrative and is not intended to limit the scope of the present invention and its application. The embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. In the following examples, various processes and methods not described in detail are conventional methods known in the art.

[0028] The "nitrogen heteroaromatic ring" of the present invention contains a heteroaryl group, wherein "heteroaryl" refers to an aryl group containing 1 to 4 heteroatoms selected from N, O, S, and P as aromatic ring backbone atoms, and carbon atoms as the remaining aromatic ring backbone atoms. The heteroaryl group can be a 5-, 6-, 7-, or 8-membered monocyclic heteroaryl group or a polycyclic heteroaryl group fused to one or more benzene rings, which can be partially saturated. The polycyclic heteroaryl group can contain 6-40, preferably 6-20, and more preferably 9-13 ring atoms. Specific examples include monocyclic heteroaryl groups such as furyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, tetrazolyl, furazolyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl and the like; polycyclic heteroaryl groups such as benzofuranyl, benzothienyl, isobenzofuranyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, indazolyl, benzothiadiazolyl, quinolyl, isoquinolyl, quinazolinyl, quinolizinyl, quinoxalyl, carbazolyl, phenanthridinyl and benzodioxolyl, but are not limited thereto.

[0029] The term "substituted" in the present invention refers to optional substitution by at least one substituent, including but not limited to monosubstituted, disubstituted, trisubstituted, tetrasubstituted, pentasubstituted, etc.

[0030] The “solid line” connecting the metal iridium and the ligand used in the general structural formula of the present invention refers to a coordinate covalent bond, which includes but is not limited to a single bond, a double bond, and the like.

[0031] A specific embodiment of the present invention provides a nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand having the following structure:

[0032]

[0033] Wherein, R is an nitrogen heteroaromatic ring group or a derivative thereof.

[0034] In some embodiments, R represents one of the following structures substituted at any position by one or more H, methyl, methoxy, tert-butyl, trifluoromethyl, trimethylsilyl, or triphenylsilyl:

[0035]

[0036] In some embodiments, the ligand is selected from one of the following 16 structures:

[0037]

[0038] A specific embodiment of the present invention also provides an iridium complex having metal Ir as the central atom and coordinated with a tridentate ligand, a bidentate ligand and a monodentate ligand, wherein the tridentate ligand is the nitrogen-aromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand according to any one of claims 1-2.

[0039] In some embodiments, the bidentate ligand includes: 2,6-difluoro-2-phenylpyridine or its derivatives, 2,6-difluoro-2,3-dipyridine or its derivatives, tetraphenylphosphimide or its derivatives, thiotetraphenylphosphimide or its derivatives, thiopicolinic acid or its derivatives, amidine derivatives, 2-(5-phenyl-1,3,4-oxadiazole-2-)phenol or its derivatives, 2-(2-pyridyl)-diazole or its derivatives, 2-(2-pyridyl)-triazole or its derivatives, 8-(2-pyridyl)benzofurano[2,3-b]pyridine or its derivatives; the monodentate ligand is selected from one of fluorine, chlorine, bromine, iodine, cyano, and cyanate.

[0040] In some embodiments, the iridium complex has the following general structural formula:

[0041] Wherein, the structure of the bidentate ligand is:

[0042] X is carbon or nitrogen, R1-R4 are the same or different and are independently selected from one of hydrogen, halogen, CF3, C(CH3)3, and Si(CH3)3; and Y is the monodentate ligand.

[0043] In some embodiments, the bidentate ligand is selected from one of the following 24 structures:

[0044]

[0045] In some embodiments, the iridium complex is selected from one of the structures shown below: Ir-1 to Ir-128:

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] The specific embodiment of the present invention also provides a method for preparing the nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand, which comprises the following steps: using 1,3-dibromo-5-fluorobenzene and R (i.e., a nitrogen heterocyclic derivative) as starting materials, reacting under the action of alkali to introduce a nitrogen heteroaromatic ring derivative at the 5th position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain the nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand. Specifically, a 1,3-dibromo-5-fluorobenzene derivative is reacted with a nitrogen heterocyclic derivative to obtain a nitrogen heterocyclic ring modified 1,3-dibromobenzene derivative, and then the imidazole and nitrogen heterocyclic ring modified 1,3-dibromobenzene derivative are subjected to an Ullmann reaction, and then a branched derivatization reaction is performed to obtain a nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand.

[0055] In some embodiments, the synthesis of the iridium complex includes reacting the synthesized ligands with an iridium source to synthesize the iridium complex via coordination chemistry. For example, a tridentate ligand and [Ir(COD)Cl]2 are refluxed in an acetonitrile solution at a ratio of 2:1 for 12 hours, cooled, and then dried by spin drying to obtain a precursor mixture. The iridium precursor mixture and a bidentate ligand of the corresponding structure are then directly refluxed in propionic acid for 12 hours to obtain a monodentate halogen iridium complex. The monodentate halogen iridium complex is then subjected to a displacement reaction with sodium cyanide to obtain a crude product, which is then purified by column chromatography to obtain a pure product. The product is then further purified by sublimation under vacuum conditions to obtain an iridium complex that meets the requirements for preparing OLED device light-emitting materials.

[0056] A specific embodiment of the present invention further provides an organic electroluminescent device, comprising: an anode, a cathode, and an organic light-emitting layer disposed between the anode and the cathode, wherein the iridium complex serves as a light-emitting material in the organic light-emitting layer.

[0057] In some embodiments, the organic light-emitting layer further includes a host material, and the doping concentration of the iridium complex in the organic light-emitting layer is 5-20 wt %, and more preferably the doping concentration is 10 wt %.

[0058] In some embodiments, the organic electroluminescent device is an OLED device, which includes, from bottom to top, a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, the organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode.

[0059] In some embodiments, a display device is also provided, which includes the organic electroluminescent device.

[0060] In some embodiments, a lighting device is also provided, which includes the organic electroluminescent device.

[0061] The organic electroluminescent device emits light in the unique wavelength band (from ultraviolet light to near-infrared light) emitted by the iridium complex. For example, a blue-green OLED device can be produced using the iridium complex as the luminescent material. The organic electroluminescent device can also emit mixed light through device preparation processes, such as stacking multiple luminescent layers or doping with other luminescent materials, where any luminescent layer is produced using the iridium complex.

[0062] Specific embodiments of the present invention are further described below.

[0063] Example 1: Preparation of Iridium Complex

[0064]

[0065] Specifically, the synthesis route of the nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand and the iridium complex is as follows:

[0066] 1: Synthesis of 3,6-di-tert-butyl-9-(3,5-dibromophenyl)-9H-carbazole:

[0067]

[0068] Under nitrogen protection, 1,3-dibromo-5-fluorobenzene (4.0 g, 15.8 mmol, 1.0 eq), 3,6-di-tert-butyl-9H-carbazole (5.33 g, 19.1 mmol, 1.2 eq), cesium carbonate (7.7 g, 31.6 mmol, 1.5 eq) and 100 ml of DMF were refluxed at 150 ° C for 48 hours. After the mixture was filtered, the organic layer was washed with water and extracted with dichloromethane. It was then dried over anhydrous magnesium sulfate and concentrated to dryness under reduced pressure. The crude product was purified by silica gel column chromatography and eluted with petroleum ether to obtain the desired product 3,6-di-tert-butyl-9-(3,5-dibromophenyl)-9H-carbazole as a white powder (6.46 g, yield 80%). Its nuclear magnetic spectrum data are as follows:

[0069] 1 HNMR (400MHz, DMSO-d6) δ8.29(d,J=2.0Hz,2H),7.97(t,J=1.7Hz,1H),7.88(d,J=1.7Hz,2 H),7.51(d,J=2.0Hz,1H),7.49(d,J=2.0Hz,1H),7.35(s,1H),7.33(s,1H),1.41(s,18H).

[0070] 2: Synthesis of 3,6-di-tert-butyl-9-(3,5-di(1H-imidazol-1-yl)phenyl)-9H-carbazole:

[0071]

[0072] 3,6-di-tert-butyl-9-(3,5-dibromophenyl)-9H-carbazole (3.20 g, 6.27 mmol, 1.0 eq), imidazole (1.07 g, 15.68 mmol, 2.5 eq), potassium carbonate (2.17 g, 15.68 mmol, 2.5 eq), and copper oxide (0.5 g, 20%) were dissolved in 50 ml of DMSO and then refluxed at 150°C under nitrogen for 48 hours. After cooling to room temperature (e.g., 300K), the mixture was filtered, the filtrate was washed with water, and extracted with dichloromethane. The organic phase was collected and dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure, petroleum ether was added, and the mixture was filtered to obtain 3,6-di-tert-butyl-9-(3,5-di(1H-imidazol-1-yl)phenyl)-9H-carbazole as a white solid (1.68 g, 55% yield). Its NMR spectrum data are as follows:

[0073] 1 HNMR(400MHz,DMSO-d6)δ8.55(s,2H),8.32(s,2H),8.12(t,J=2.0Hz,1H),8.04(t, J=1.4Hz,2H),7.97(d,J=2.0Hz,2H),7.54–7.46(m,4H),7.16(s,2H),1.43(s,18H).

[0074] 3: Synthesis of 1,1'-(5-(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,3-phenyl)bis(3-butyl-1H-imidazol-3-ium) dibromide:

[0075]

[0076] 3,6-di-tert-butyl-9-(3,5-di(1H-imidazol-1-yl)phenyl)-9H-carbazole (1.68 g, 3.45 mmol, 1.0 eq) and 1-bromobutane (2.36 g, 17.2 mmol, 5.0 eq) were dissolved in 50 ml of acetonitrile and refluxed at 100°C for 24 hours under nitrogen. After cooling to room temperature, volatile substances were removed under reduced pressure, and then diethyl ether was added and filtered to obtain a colorless product (1.89 g, 91% yield). Its NMR spectrum data are as follows:

[0077] 1HNMR(400MHz,DMSO-d6)δ10.13(s,2H),8.59(s,2H),8.51(s,1H),8.39(d,J=2 .0Hz,2H),8.36(d,J=1.9Hz,2H),8.15(t,J=1.9Hz,2H),7.63(s,1H),7.61(s,1 H),7.54(d,J=2.0Hz,1H),7.51(d,J=2.0Hz,1H),4.31(t,J=7.3Hz,4H),1.97–1 .86(m,4H),1.44(s,18H),1.36(dt,J=14.7,7.4Hz,4H),0.95(t,J=7.4Hz,6H).

[0078] Four: Preparation method of 2-(2',4'-difluorophenyl)-4-trifluoromethylpyridine:

[0079]

[0080] 2,4-Difluorophenylboronic acid (1.91 g, 12 mmol), potassium carbonate (6.8 g, 50 mmol) and Pd(PPh3)4 (0.578 g, 0.5 mmol) were placed in a 250 ml two-necked round-bottom flask equipped with a condenser. The reaction flask was evacuated and filled with nitrogen three times. Tetrahydrofuran (THF, 70 ml), water (30 ml) and 2-bromo-4-trifluoromethylpyridine (2.26 g, 10 mmol) were then added. The mixture was refluxed under a nitrogen atmosphere for 24 hours. After cooling to room temperature, THF was removed by evaporation and the residue was dissolved in dichloromethane (150 ml). The precipitate was filtered and the filtrate was washed with 1N sodium hydroxide (2×50 ml) and saturated sodium chloride aqueous solution (50 ml), then dried over sodium persulfate and filtered. After evaporation of the solvent, the reaction mixture was purified by silica gel column chromatography (ethyl acetate / n-hexane = 1 / 15) to give 2-(2',4'-difluorophenyl)-4-trifluoromethylpyridine (2.15 g, 83.00% yield) as a colorless solid. Its NMR spectrum data are as follows:

[0081] 1 HNMR(400MHz,chloroform-d)δ8.90(d,J=5.1Hz,1H),8.75(dt,J=9.6,8.0Hz,1H),8.16–8.05(m,1H),7.61–7.51(m,1H),7.02(ddd,J=8.3,3.1,0.9Hz,1H).

[0082] 19FNMR(376MHz,chloroform-d)δ-64.96,-66.35(d,J=9.9Hz),-68.63(d,J=10.1Hz).

[0083] 5: Synthesis of 2-(2',4'-difluorophenyl)-5-trifluoromethylpyridine

[0084] The difference from the fourth method mentioned above is that 2-bromo-4-trifluoromethylpyridine is replaced with 2-bromo-5-trifluoromethylpyridine. The other methods are the same as 2-(2',4'-difluorophenyl)-4-trifluoromethylpyridine. The synthetic route is as follows:

[0085]

[0086] 2.22 g of 2-(2',4'-difluorophenyl)-5-trifluoromethylpyridine was obtained with a yield of 85.70%. Its NMR spectrum data are as follows:

[0087] 1 HNMR(400MHz,chloroform-d)δ9.00(dd,J=2.2,1.1Hz,1H),8.87–8.75(m,1H),8.12–8.00(m,2H),7.05(ddd,J=8.3,3.0,0.9Hz,1H).

[0088] 19 FNMR(376MHz,chloroform-d)δ-62.46,-65.89(d,J=10.2Hz),-68.15(d,J=10.0Hz).

[0089] VI: Synthesis of Iridium(III) Complexes

[0090]

[0091] Under nitrogen protection, [Ir(COD)Cl]2 (300 mg, 0.447 mmol, 1.0 eq) and a tridentate ligand (0.894 mmol, 2.0 eq) were added to a mixed solvent of triethylamine (1 ml) and acetonitrile (15 ml) in a dry Schlenk tube. The suspension was heated to 90 ° C for 12 hours. After cooling to room temperature, the solvent was removed by rotary evaporation to obtain a yellow solid intermediate. The yellow solid was then dissolved in propionic acid (15 ml). A bidentate ligand, a 2-(2,4-difluorophenyl)pyridine derivative (170 mg, 0.894 mmol, 2.0 eq) and triethylamine (1 ml) were added to the solution and heated to 150 ° C for 24 hours under a nitrogen atmosphere. It was then cooled to room temperature and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography to give intermediate 4, which was then further purified by recrystallization from dichloromethane / ether.

[0092] 7: Synthesis of iridium complex Ir-2

[0093]

[0094] Under nitrogen, intermediate 4 and sodium cyanide (2 equivalents) were dissolved in 20 ml of DMF and heated to 100°C for 1 hour. The solvent was then removed under reduced pressure to obtain a crude product, which was then purified by column chromatography to obtain the final product. The final product was then recrystallized from dichloromethane / ether to obtain the iridium complex Ir-2, whose NMR spectrum data are as follows:

[0095] 1 HNMR(400MHz,chloroform-d)δ10.51(d,J=5.9Hz,1H),8.64(d,J=4.5Hz,1H),8.20(d,J=1.9Hz,2H), 7.53(dt,J=9.7,4.8Hz,3H),7.47–7.41(m,4H),7.35(s,2H),6.82(d,J=2.1Hz,2H),6.39(ddd,J=13. 2,8.8,2.5Hz,1H),5.68(dd,J=8.5,2.5Hz,1H),3.36–3.26(m,2H),3.26–3.16(m,2H),1.51(s,18H), 1.46–1.38(m,2H),1.17–1.08(m,2H),0.91(dt,J=13.3,7.0Hz,2H),0.79(s,2H),0.76–0.71(m,6H).

[0096] 19FNMR(376MHz,chloroform-d)δ-64.82,-106.72(d,J=10.9Hz),-109.42(d,J=10.5Hz).

[0097] ESI-MScalcdforC 53 H 54 F5IrN7:[M+1] + 1076.3985,found1076.3969([M+1] + ).

[0098] 8: Synthesis of Iridium Complex Ir-34

[0099] The method is the same as that of iridium complex Ir-2. The NMR spectrum data of iridium complex Ir-34 are as follows:

[0100] 1 HNMR(400MHz,chloroform-d)δ10.55(s,1H),8.56(dd,J=8.7,3.7Hz,1H),8.20(d,J=1.8Hz,2H),8.17–8 .11(m,1H),7.54(dd,J=8.6,1.9Hz,2H),7.48–7.42(m,4H),7.34(s,2H),6.82(d,J=2.1Hz,2H),6.37(dd d,J=13.3,8.7,2.5Hz,1H),5.67(dd,J=8.4,2.4Hz,1H),3.30(ddd,J=13.5,9.7,6.1Hz,2H),3.21–3.12( m,2H),1.51(s,18H),1.46(d,J=5.6Hz,2H),1.31–1.23(m,2H),0.98–0.85(m,4H),0.78(t,J=7.1Hz,6H).

[0101] 19 FNMR(376MHz,chloroform-d)δ-61.94,-106.28,-108.66.

[0102] ESI-MScalcdforC 53 H 54 F5IrN7:[M+1] + 1076.3985,found1076.3970([M+1] + ).

[0103] 9: Synthesis of Iridium Complex Ir-66

[0104] The method is the same as that of iridium complex Ir-2. The NMR spectrum data of iridium complex Ir-66 are as follows:

[0105] 1 HNMR(400MHz,Chloroform-d)δ10.25(d,J=5.5Hz,1H),8.55(d,J=3.1Hz,1H),8.20(d,J=1.9Hz,2H),7.53( dd,J=8.6,1.9Hz,2H),7.48–7.36(m,5H),7.31(s,2H),6.79(d,J=2.1Hz,2H),6.32(ddd,J=13.3,8.8,2.5Hz ,1H),5.63(dd,J=8.5,2.5Hz,1H),3.37–3.28(m,2H),3.23(ddd,J=13.4,10.6,5.7Hz,2H),1.51(s,18H),1. 47–1.39(m,2H),1.14–1.02(m,2H),0.86(td,J=10.5,10.1,4.8Hz,2H),0.73(t,J=4.6Hz,8H),0.43(s,9H).

[0106] 19 FNMR(376MHz,Chloroform-d)δ-109.52(d,J=9.6Hz),-110.33(d,J=9.7Hz).

[0107] 10: Synthesis of Iridium Complex Ir-98

[0108] The method is the same as that of iridium complex Ir-2. The NMR spectrum data of iridium complex Ir-98 are as follows:

[0109] 1HNMR(400MHz,Chloroform-d)δ10.28(s,1H),8.39(dd,J=8.2,2.5Hz,1H),8.26–8.16(m,2H),8.02(d,J=7.8Hz,1H),7. 54(dd,J=8.6,1.9Hz,2H),7.45(dd,J=16.5,5.4Hz,4H),7.34(s,2H),6.81(d,J=2.1Hz,2H),6.36–6.26(m,1H),5.55(d d,J=8.6,2.5Hz,1H),3.34(ddd,J=15.4,9.2,6.3Hz,2H),3.23(ddd,J=13.9,9.2,5.9Hz,2H),1.51(s,18H),1.42(dd,J =8.8,4.7Hz,2H),1.22(q,J=8.5,7.4Hz,2H),1.02–0.93(m,2H),0.91–0.82(m,2H),0.76(t,J=7.2Hz,6H),0.47(s,9H).

[0110] Other complexes were synthesized in the same way.

[0111] like Figure 1 As shown, it is the single crystal structure of the prepared compound Ir-114. Figure 2 The photoluminescence spectra of iridium complexes Ir-1, Ir-22, Ir-53 and Ir-84 are shown; Figure 3 Absorption spectra of iridium complexes Ir-3, Ir-9, Ir-11 and Ir-20; Figure 4 These are the excited state spectra of iridium complexes Ir-3, Ir-9, Ir-11 and Ir-20.

[0112] The product data of Ir-1 to Ir-128 of the above structure synthesized in the embodiment of the present invention are summarized in the following Table 1:

[0113] Table 1: Summary of product data of synthesis examples

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] Example 2: Preparation of organic electroluminescent device OLED

[0121] The structure of an OLED device includes: a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode. The substrate is glass, the anode is indium tin oxide (ITO), the hole injection layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), the hole transport layer is N-biphenyl-4-yl-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluorene-2-amine (BCFN), the electron blocking layer is 9-[3-(triphenylsilyl)phenyl]-3,9'-BI-9H-carbazole (SiCzCz), the hole blocking layer is 2-phenyl-4,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazine (mSiTrz), and the electron transport layer is 2-phenyl-4 ,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazine and 8-hydroxyquinoline lithium (1:1), the electron injection layer is 8-hydroxyquinoline lithium, the cathode is metal aluminum, the organic light-emitting layer includes a main material and a light-emitting material, the main material is a mixture of 9-[3-(triphenylsilyl)phenyl]-3,9'-bis-9H-carbazole (SiCzCz) and 9,9'-[6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl]bis-9H-carbazole (SiTrzCz2), the light-emitting materials are iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101, respectively, in the organic light-emitting layer, the mass fraction of the iridium complex is 10wt%.

[0122] The structures of the materials of the above functional layers are as follows:

[0123]

[0124] The OLED devices prepared with iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101 as the luminescent materials are: their emission spectra are as follows Figure 5 As shown, its current density-voltage-brightness curve is as follows Figure 6 As shown, its external quantum efficiency-brightness curve is as follows Figure 7 Its performance parameters are shown in Table 2 below:

[0125] Table 2:

[0126]

[0127] The iridium complex provided by the present invention can be used as a luminescent material in the organic light-emitting layer of OLEDs. By designing and optimizing the compound structure, the efficiency and lifespan of the device can be controlled. As can be seen from the results in Table 2 above, the iridium complex described in the present invention exhibits excellent device performance.

[0128] The present invention introduces a nitrogen heteroaromatic ring group such as carbazole, phenoxazine, phenothiazine, 9,9-dimethyl-9,10-dihydroacridinyl or its derivatives into the 5th position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene or its derivatives to obtain nitrogen heteroaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene. The introduction of these nitrogen heteroaromatic ring groups or their derivatives not only enriches the chemical diversity of the ligand, but also provides more degrees of freedom for regulating the photoelectric properties of the iridium complex by changing the electronic structure and spatial configuration of the ligand. The introduction of the nitrogen heteroaromatic ring group or its derivatives can enhance the electron donor ability of the ligand, thereby improving the luminous efficiency of the complex. Moreover, as an electron donor group, the luminous color of the complex can be adjusted to achieve regulation from blue light to green light.

[0129] The nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene of the present invention serves as the main ligand structure (tridentate ligand) of the iridium complex, which increases the rigidity of the ligand and the complex, regulates the luminescent color and efficiency of the complex, and achieves increased steric hindrance, reduced molecular stacking, and inhibition of the non-radiative transition process of the molecule. The iridium complex of the present invention has a high photoluminescence quantum yield and a short excited state lifetime, and has the characteristic of anti-intersystem crossing. The present invention also discloses an organic electroluminescent device, the organic light-emitting layer of which contains the above-mentioned iridium complex, and the iridium complex is used as the luminescent material of the light-emitting layer to prepare a deep blue light OLED device. The device prepared using the iridium complex of the present invention has excellent performance, high external quantum efficiency and low efficiency roll-off characteristics, and has potential application value in the field of 0LED display and lighting.

[0130] In summary, the nitrogen heteroaromatic ring-modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene provided by the present invention is used as a tridentate ligand to form an iridium complex, which has the effect of regulating the luminescent color, efficiency and electron transport performance of the material, increasing the stability of the material, improving the efficiency of the device, and reducing the efficiency roll-off. The iridium complex of the present invention has the characteristics of high photoluminescence quantum yield, short excited state lifetime and long device life. The device prepared using the iridium complex of the present invention has excellent performance, low starting voltage, high external quantum efficiency, low efficiency roll-off and long device life. It has potential application value in the field of OLED lighting and display, especially in the fields of high-resolution display, flexible display and solid-state lighting.

[0131] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. An iridium complex, characterized in that The metal Ir is used as the central atom and coordinated with a tridentate ligand, a bidentate ligand and a monodentate ligand, wherein the tridentate ligand is selected from one of the following 16 structures: The bidentate ligand is selected from one of the following 24 structures: The monodentate ligand is selected from one of fluorine, chlorine, bromine, iodine, cyano, and cyanate.

2. An iridium complex, characterized in that The general structural formula of the iridium complex is as follows: Among them, the structure of the bidentate ligand is: X is carbon or nitrogen, R1-R4 are the same or different and are independently selected from one of hydrogen, halogen, CF3, C(CH3)3, Si(CH3)3; Y is selected from one of fluorine, chlorine, bromine, iodine, cyano, and cyanate; the ligand having R is selected from one of the following 16 structures:

3. The iridium complex according to claim 2, wherein The bidentate ligand is selected from one of the following 24 structures:

4. An iridium complex, characterized in that The iridium complex is selected from one of the structures shown in the following Ir-1 to Ir-128:

5. An organic electroluminescent device, characterized in that: include: An anode, a cathode, and an organic light-emitting layer arranged between the anode and the cathode, wherein the iridium complex according to any one of claims 1 to 4 is used as the light-emitting material in the organic light-emitting layer.

6. The organic electroluminescent device according to claim 5, wherein The organic light-emitting layer further comprises a host material, and the doping concentration of the iridium complex in the organic light-emitting layer is 5-20 wt %.

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