Aza aromatic ring modified dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene ligand and preparation method thereof, iridium complex and organic electroluminescent device

Abstract

The invention discloses an aza aromatic ring modified dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene ligand, a preparation method of the aza aromatic ring modified dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene ligand, an iridium complex and an organic electroluminescent device. The nitrogen heteroaromatic ring modified dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene ligand has the following structure: # imgabs0 #, and R is a nitrogen heteroaromatic ring group or a derivative thereof. According to the invention, an aza aromatic ring group or a derivative thereof is introduced to a No.5 site of dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene to obtain an aza aromatic ring modified dibromo-1, 3-bis (1-butylimidazole-3-yl) benzene ligand which can be used as a tridentate ligand of an iridium complex, so that the rigidity of the ligand and the complex is increased, the light emitting color and efficiency of the complex are regulated and controlled, and the luminous efficiency of the iridium complex is improved. The iridium complex can be used for preparing the organic electroluminescent device, the steric hindrance is increased, and the molecular accumulation is reduced, so that the non-radiative transition process of molecules is inhibited, and the luminous efficiency of the organic electroluminescent device adopting the iridium complex is improved.

Description

Technical Field

[0001] The 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 and 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 much attention due to its unique advantages. The core of OLED technology lies in organic light-emitting materials, which can emit light under the action of an electric field and have the characteristics of 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 light-emitting materials is the key to the development of OLED technology.

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

[0004] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the 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 solution:

[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 azo aromatic 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 a third aspect, a method for preparing the nitrogen-aromatic 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 to introduce a nitrogen-aromatic ring derivative at the 5th position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain the nitrogen-aromatic 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 derivatives at the 5th position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain a dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand modified with an azoaromatic ring, 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 the steric hindrance, reducing the 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 excited state lifetime of the complex is short, which is conducive to 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 luminescent color and efficiency: By changing the type and amount of nitrogen heteroaromatic ring groups or their derivatives, the luminescent 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 photoinduced spectra of the iridium complexes Ir-1, Ir-22, Ir-53 and Ir-84 in Example 1 of the present invention;

[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;

[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 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;

[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 is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention and its application. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. In the following embodiments, the 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 heteroaryl, wherein "heteroaryl" refers to an aryl group containing 1 to 4 heteroatoms selected from N, O, S, and P as aromatic ring skeleton atoms, and carbon atoms as the remaining aromatic ring skeleton atoms. The heteroaryl can be a 5-, 6-, 7- or 8-membered monocyclic heteroaryl or a polycyclic heteroaryl fused with one or more benzene rings, which can be partially saturated, and the polycyclic heteroaryl can contain 6-40, preferably 6-20, and more preferably 9-13 ring atoms. Specific examples include monocyclic heteroaryl groups such as furanyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, tetrazolyl, furazolyl, pyridyl, 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" of the present invention refers to optional substitution by at least one substituent, including but not limited to: monosubstitution, disubstitution, trisubstitution, tetrasubstitution, pentasubstitution and the like.

[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] The 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 azo aromatic 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-butylimidazole-3-yl)benzene ligand as described in any one of claims 1 to 2.

[0039] In some embodiments, the bidentate ligand includes: 2,6-difluoro-2-phenylpyridine or its derivatives, 2,6-difluoro-2,3-bipyridine 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)-diazolyl or its derivatives, 2-(2-pyridyl)-triazole or its derivatives, 8-(2-pyridyl)benzofuran[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, Si(CH3)3; 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 in the following 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 dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand modified by the nitrogen heteroaromatic ring, 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 dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand modified by the nitrogen heteroaromatic ring. Specifically, a 1,3-dibromo-5-fluorobenzene derivative is reacted with a nitrogen heterocyclic derivative to obtain a nitrogen heterocyclic modified 1,3-dibromobenzene derivative, and then the imidazole and nitrogen heterocyclic modified 1,3-dibromobenzene derivative are subjected to an Ullmann reaction, and then a branched derivatization reaction is performed to obtain a nitrogen heteroaromatic modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand.

[0055] In some embodiments, the synthesis of the iridium complex includes: reacting each synthesized ligand with an iridium source, and synthesizing the iridium complex by a coordination chemical method. 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 dried to obtain a precursor mixture: then the iridium precursor mixture and a bidentate ligand of a corresponding structure are directly refluxed in propionic acid for 12 hours to obtain a monodentate halogen iridium complex, and the monodentate halogen iridium complex is further subjected to a replacement reaction with sodium cyanide to obtain a crude product, and further column chromatography is performed to obtain a pure product, and further sublimation and purification under vacuum conditions are performed 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, which includes: an anode, a cathode, and an organic light-emitting layer arranged between the anode and the cathode, wherein the iridium complex is used as the 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 a further preferred 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 a specific wavelength band (from ultraviolet light to near infrared light) emitted by the iridium complex, for example, a blue-green light OLED device can be prepared using the iridium complex as a light-emitting material. The organic electroluminescent device can also be prepared through a device preparation process, such as stacking multiple light-emitting layers, doping with other light-emitting materials, wherein any light-emitting layer is prepared using the iridium complex, so that the organic electroluminescent device can emit mixed light.

[0062] The 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 NMR 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 for 48 hours under nitrogen protection. After cooling to room temperature (such as 300K), the mixture was filtered, the filtrate was washed with water in layers, and extracted with dichloromethane. The organic phase was collected and dried over anhydrous magnesium sulfate. After the solution was concentrated under reduced pressure, petroleum ether was added and 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, yield 55%). 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-carbazole-9-yl)-1,3-phenyl)bis(3-butyl-1H-imidazole-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 protection. After cooling to room temperature, the volatile substances were removed under reduced pressure, and then ether was added and filtered to obtain a colorless product (1.89 g, yield 91%). 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 obtain 2-(2',4'-difluorophenyl)-4-trifluoromethylpyridine (2.15 g, yield 83.00%) 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 is that 2-bromo-4-trifluoromethylpyridine is changed to 2-bromo-5-trifluoromethylpyridine. The other methods are the same as 2-(2',4'-difluorophenyl)-4-trifluoromethylpyridine. The synthesis 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 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, 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. 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 in dichloromethane / ether.

[0092] VII: Synthesis of Iridium Complex Ir-2

[0093]

[0094] Under nitrogen protection, the intermediate product 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 by decompression 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 an 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] The 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 photoinduced spectra of iridium complexes Ir-1, Ir-22, Ir-53 and Ir-84; Figure 3 Absorption spectra of iridium complexes Ir-3, Ir-9, Ir-11 and Ir-20; Figure 4 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: Synthesis Example Product Data Summary

[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 device prepared with iridium complexes Ir-27, Ir-38, Ir-62 and Ir-101 as the luminescent materials has the following emission spectra: 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 OLED, and the purpose of regulating the efficiency and life of the device is achieved by designing and optimizing the structure of the compound. It can be seen from the results in Table 2 above that the iridium complex of the present invention has excellent performance in device performance.

[0128] The present invention introduces carbazole, phenoxazine, phenothiazine, 9,9-dimethyl-9,10-dihydroacridinyl or other nitrogen heteroaromatic ring groups or their derivatives at 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, wherein 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 groups or their derivatives can enhance the electron donor ability of the ligand, thereby improving the luminescence efficiency of the complex; and as an electron donor group, the luminescence 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-butylimidazole-3-yl)benzene of the present invention is used 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 realizes the increase of steric hindrance, reduces molecular accumulation, and inhibits the non-radiative transition process of the molecule. The iridium complex in the present invention has a high photoluminescence quantum yield and a short excited state lifetime, and has the characteristics of anti-system crossing. The present invention also discloses an organic electroluminescent device, wherein the organic light-emitting layer contains the above-mentioned iridium complex, and the above-mentioned iridium complex is used as the luminescent material of the light-emitting layer to prepare a deep blue light OLED device, and the device prepared by 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, and has the characteristics of 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 content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. 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 can be made herein without departing from the scope of protection of the patent application.

Claims

1. A nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand, characterized in that: It has the following structure: Wherein, R is an azo aromatic ring group or a derivative thereof.

2. The nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand according to claim 1, characterized in that: R represents one of the following structures substituted at any position by one or more H, methyl, methoxy, tert-butyl, trifluoromethyl, trimethylsilyl or triphenylsilyl: Preferably, the ligand is selected from one of the following 16 structures:

3. An iridium complex, characterized in that The metal Ir is used 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 heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand as described in any one of claims 1-2.

4. The iridium complex according to claim 3, characterized in that The bidentate ligand includes: 2,6-difluoro-2-phenylpyridine or its derivatives, 2,6-difluoro-2,3-bipyridine 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)-diazolyl or its derivatives, 2-(2-pyridyl)-triazole or its derivatives, 8-(2-pyridyl)benzofuran[2,3-b]pyridine or its derivatives; The monodentate ligand is selected from one of fluorine, chlorine, bromine, iodine, cyano and cyanate.

5. The iridium complex according to claim 4, characterized in that The general structural formula of the iridium complex is as follows: Wherein, 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 the monodentate ligand.

6. The iridium complex according to claim 5, characterized in that The bidentate ligand is selected from one of the following 24 structures:

7. The iridium complex according to claim 3, characterized in that The iridium complex is selected from one of the structures shown in the following Ir-1 to Ir-128:

8. A method for preparing the nitrogen heteroaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand according to any one of claims 1 to 2, characterized in that: The steps include: 1,3-Dibromo-5-fluorobenzene and R are used as starting materials and reacted under the action of alkali to introduce an azaaromatic ring derivative at the 5th position of dibromo-1,3-di(1-butylimidazol-3-yl)benzene to obtain the azaaromatic ring modified dibromo-1,3-di(1-butylimidazol-3-yl)benzene ligand.

9. 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 described in any one of claims 3 to 7 is used as the light-emitting material in the organic light-emitting layer.

10. The electroluminescent device according to claim 9, characterized in that The organic light-emitting layer also includes a host material, and the doping concentration of the iridium complex in the organic light-emitting layer is 5-20wt%.

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