Metal complex and organic electroluminescent device

Abstract

The present invention relates to the technical field of electronic materials, and in particular to a metal complex and an organic electroluminescent device. The metal complex provided by the present invention has a structure as shown in Formula I: The metal complex provided by the present invention can reduce device roll-off, which is conducive to the preparation of a metal complex of a high-stability OLED device, and the metal complex is applied to an organic electroluminescent device, and the luminescent color can be adjusted and the luminescent efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of electronic materials, and in particular to a metal complex and an organic electroluminescent device. Background Art

[0002] Organic light-emitting diodes (OLEDs) are electroluminescent devices with a multilayer structure consisting of a cathode and cathode electrode layer and an intermediate single or multilayer organic functional material light-emitting layer. OLEDs have the characteristics of self-luminescence, short response time, wide operating temperature range, low driving voltage, low energy consumption, and flexibility. They have broad application prospects in the field of new generation display and lighting technology, especially small-sized OLEDs have entered the mobile phone and smart watch application market on a large scale. As one of the most important functional materials of OLED devices, luminescent materials have an important influence on the performance of OLED devices. OLED luminescent materials are divided into fluorescence, phosphorescence, and thermally activated delayed fluorescence (TADF) according to the luminescence mechanism. In terms of exciton utilization, fluorescent materials can only utilize about 25% of excitons, while phosphorescent and TADF materials can theoretically utilize 100% of excitons, which has the advantage of high efficiency. However, the luminescent materials used in blue light OLEDs are pure organic small molecules, while red and green light materials use phosphorescent complexes based on the precious metal iridium. The development of new, efficient and stable luminescent materials is the key to breakthroughs in the next generation of OLED technology.

[0003] Gold (I) complexes have a full d-shell electronic structure, which can avoid excited state quenching caused by dd states. Whether it is phosphorescence or TADF, it can easily obtain high luminescence efficiency, and has always been one of the focuses of luminescent material research. In particular, "carbene-metal-amine" complexes with linear coordination structures have made breakthrough progress in TADF materials and OLED device efficiency in recent years. However, the structure commonly used in existing gold (I) complexes is a linear di-coordination structure, and the metal-nitrogen bond is easy to rotate and break, which is not suitable for the manufacture of high-performance OLEDs using vapor deposition. If it is applied to devices, the device roll-off is serious. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to overcome the defect that the existing linear di-coordinated gold (I) complex is used in devices and has a serious device roll-off, and further provide a metal complex and an organic electroluminescent device.

[0005] The scheme adopted by the present invention is as follows:

[0006] A metal complex having the structure shown below:

[0007]

[0008] Among them, R 1 Selected from hydrogen, substituted or unsubstituted C1-C6 alkyl;

[0009] R 2 -R 3 Each of the following is independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C48 aryl, and substituted or unsubstituted C4-C48 heteroaryl;

[0010] R 4 -R 5 are independently selected from hydrogen, or R 4 -R 5 Connect to each other to form C 6 -C 30 Aryl, C 5 -C 30 Heteroaryl.

[0011] It can be understood that the complex shown in formula I has the following structure:

[0012]

[0013] The two hydrogen atoms in Formula I will form a tetracoordinate configuration similar to that of metallic gold. The "hydrogen atoms (H a )-Carbon (C a )-Hydrogen (H b )” The three atoms coordinate with the metal atoms respectively to form a chelate ligand structure, which improves the thermal stability of the complex and reduces the device roll-off.

[0014] Preferably, R 1 Selected from hydrogen, C1-C4 alkyl;

[0015] R 2 -R 3 Each of the following is independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C18 aryl;

[0016] R 4 -R 5 are independently selected from hydrogen, or R 4 -R 5 Connect to each other to form C 6 -C 18 Aryl, C 5 -C 20 Heteroaryl.

[0017] Preferably, R 1 is selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl;

[0018] R 2 -R 3are independently selected from C1-C4 alkyl, substituted or unsubstituted C6-C18 aryl, wherein the substituted C6-C18 aryl is optionally substituted by 1-4 substituents R a Replace; each R a independently selected from C1-C6 alkyl; preferably, the substituted C6-C18 aryl is optionally substituted by 1-2 substituents R a Replace; each R a Independently selected from C1-C4 alkyl;

[0019] R 4 -R 5 are independently selected from hydrogen, or R 4 -R 5 They are connected to each other to form the following structure: The connection site.

[0020] Preferably, R 1 is selected from hydrogen, tert-butyl;

[0021] R 2 -R 3 are independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, 3,5-dimethylphenyl, 2,6-diisopropylphenyl, naphthyl, anthracenyl, preferably, R 2 -R 3 Each of the following is independently selected from methyl, phenyl, 3,5-dimethylphenyl and 2,6-diisopropylphenyl.

[0022] Preferably,

[0023] The carbene ligand in the metal complex Has the following structure:

[0024]

[0025] Preferably, the metal complex has the structure shown below:

[0026]

[0027]

[0028] The metal complex of the present invention is a phosphorescent or thermally activated delayed fluorescent material.

[0029] The present invention also provides a method for preparing the above-mentioned metal complex, comprising the following steps:

[0030] First, compound 3 is obtained by a nucleophilic substitution reaction between compound 1 and 2, and then compound 4 is obtained by a CC coupling reaction of 3. Compound 4 undergoes a bromination reaction with NBS to generate a monobrominate 5. Monobrominate 5 and boric acid pinacol ester undergo a Suzuki coupling reaction to obtain a compound aryl borate ester 6. Ligand 6 undergoes a coordination reaction with carbene metal chloride 7 to obtain a complex shown in formula I.

[0031] The synthesis route of the metal complex of the present invention is as follows:

[0032]

[0033] The present invention also provides an organic electroluminescent device, which comprises a first electrode, a second electrode and an organic layer located between the first electrode and the second electrode, wherein the organic layer comprises any one or a combination of at least two of the above-mentioned metal complexes.

[0034] Preferably, the organic layer includes a light-emitting layer, and the light-emitting layer includes any one or a combination of at least two of the above-mentioned metal complexes.

[0035] Preferably, the light-emitting layer comprises the metal complex and the organic functional material mentioned above, and in terms of mass percentage, the metal complex accounts for 0.01%-100%, and the organic functional material accounts for 0-99.9%.

[0036] Preferably, the organic layer further comprises an electron functional layer and a hole functional layer;

[0037] The electronic functional layer includes at least one of an electron injection layer, an electron transport layer and a hole blocking layer;

[0038] The hole functional layer includes at least one of a hole injection layer, a hole transport layer and an electron blocking layer.

[0039] It should be noted that the application of the metal complex of the present invention is not limited to the device composition, and the film thickness or constituent materials of each layer can be appropriately changed according to the basic physical properties of the specific compound structure of the present invention.

[0040] The method for preparing the organic device described in the present invention is a conventional method in the art. Optionally, the preparation of the organic electroluminescent device includes the following steps: using a glass substrate with ITO evaporated as a transparent supporting substrate; and sequentially evaporating each organic layer and an aluminum electrode on the ITO film of the transparent supporting substrate.

[0041] Beneficial effects of the present invention:

[0042] The metal complex provided by the present invention contains a linear structure of carbene-metal-aryl derivatives, wherein the aryl derivatives serve as electron donors and the carbene serves as electron acceptors or auxiliary ligands, forming ligand-ligand charge transfer or localized excited states of the aryl ligands, inducing TADF luminescence or phosphorescence, wherein the heavy atom effect of the metal center can enhance the spin-orbit coupling effect, increase the intersystem crossing rate, reduce the delayed fluorescence lifetime or promote phosphorescence emission, and provide a new direction for preparing high-efficiency new OLED device materials. At the same time, in the metal complex provided by the present invention, the two hydrogen atoms adjacent to gold in the aryl ligands can form gold-hydrogen bonds with the gold center, so that the complex is transformed from a two-coordinate structure with low stability to a four-coordinate configuration with high stability, wherein the "hydrogen (H a )-Carbon (C a )-Hydrogen (H b )" three atoms are respectively coordinated with the metal atoms to form a chelate ligand structure, which is beneficial to reduce the device roll-off, improve the thermal stability of the complex, and is beneficial to prepare a metal complex of a high-stability OLED device. At the same time, the complex of the present invention also has high light stability and can effectively reduce the delayed fluorescence lifetime.

[0043] At the same time, the carbene used in the metal complex provided by the present invention is a traditional carbene structure, which can be prepared with high yield through simple organic synthesis and has low raw material cost. When applied to an organic electroluminescent device, the luminescent color can be adjusted and the luminescent efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 Schematic diagram of the structure of the organic electroluminescent device in device embodiments 1-3 of the present invention.

[0046] Figure 2 This is the electroluminescence spectrum diagram based on compound C-12 in device examples 1-3 of the present invention.

[0047] Figure 3 This is a graph showing the electroluminescent quantum yield-brightness curve based on compound C-12 in device embodiments 1-3 of the present invention.

[0048] Figure 4 This is a current density-voltage curve diagram based on compound C-12 in device embodiments 1-3 of the present invention.

[0049] Figure 5 This is a brightness-voltage curve diagram based on compound C-12 in device embodiments 1-3 of the present invention.

[0050] Figure 6 This is a diagram of the device life based on compound C-12 in device embodiment 1 of the present invention.

[0051] Figure 7 The emission spectra of the complexes C-7 (ImtIDCz) and C-12 (IPztIDCz) of the present invention in di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0052] Figure 8 This is the emission spectrum of the complex C-3 (MePhIDCz) of the present invention in di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0053] Fig. 9 This is the emission spectrum of the complex C-5 (MePzIDCz) of the present invention in di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0054] Fig.10 The graph is a transient decay curve of the luminescence of the complex C-12 (IPztIDCz) of the present invention in a di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0055] Fig.11 The graph is a transient decay curve of the luminescence of the complex C-7 (ImtIDCz) of the present invention in a di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0056] Fig.12 The figure is a temperature-dependent lifetime decay curve of the complex C-12 (IPztIDCz) of the present invention in a di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0057] Fig.13 This is the lifetime decay curve of the complex C-3 (MePhIDCz) of the present invention in toluene solution.

[0058] Fig.14 This is the lifetime decay curve of the complex C-5 (MePzIDCz) of the present invention in toluene solution.

[0059] Description of reference numerals:

[0060] 1- anode layer, 2- hole injection layer, 3- hole transport layer, 4- electron blocking layer, 5- electron blocking layer, 6- light emitting layer, 7- electron transport layer, 8- electron injection layer, 9- electron injection layer, 10- cathode layer. DETAILED DESCRIPTION

[0061] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0062] The chemicals used in the following examples of the present invention were obtained from regular channels without further purification, and all reactions were carried out in an argon atmosphere.

[0063] Example 1

[0064] This embodiment provides a method for preparing an intermediate compound, which is specifically as follows:

[0065] 1) Preparation of intermediate 1

[0066] The synthesis path is as follows:

[0067]

[0068] The preparation method specifically comprises the following steps:

[0069] Carbazole (1.67 g, 10 mmol) and cesium carbonate (6.5 g, 20 mmol) were dissolved in 20 mL DMF solution and placed in a 250 mL reaction bottle and stirred at room temperature for half an hour. Subsequently, 1,5-dibromo-2,4-difluorobenzene (1.08 g, 4 mmol) was dissolved in 10 ml of ultra-dry DMF solvent and slowly added dropwise to the reaction bottle, and then reacted at 60 ° C overnight. After the reaction was completed, water was added to dissolve the excess cesium carbonate, and the crude product was filtered to obtain a white solid intermediate 1 (yield 75%), which was then recrystallized from dichloromethane and methanol.

[0070] 2) Preparation of Intermediate 2

[0071] The synthesis path is as follows:

[0072]

[0073] The preparation method specifically comprises the following steps:

[0074] Take 3,6-di-tert-butylcarbazole (2.79g, 10mmol) and cesium carbonate (6.5g, 20mmol) and dissolve them in 20mL DMF solution, place them in a 250mL reaction bottle, and stir them at room temperature for half an hour. Subsequently, 1,5-dibromo-2,4-difluorobenzene (1.08g, 4mmol) was dissolved in 10mL ultra-dry DMF solvent and slowly added dropwise to the reaction bottle, and then reacted at 60°C overnight. After the reaction, water was added to dissolve the excess cesium carbonate, and the crude product was filtered to obtain a white solid intermediate 2 (yield 79%), which was then recrystallized from dichloromethane and methanol.

[0075] 3) Preparation of Intermediate 3

[0076] The synthesis path is as follows:

[0077]

[0078] The preparation method specifically comprises the following steps:

[0079] Intermediate 1 (2.26 g, 4 mmol), triphenylphosphine (1.05 g, 4 mmol), benzyltriethyl chloride (1.82 g, 8 mmol), potassium carbonate (5.53 g, 40 mmol) and palladium acetate (180 mg, 0.8 mmol) were placed in a 500 mL reaction bottle, and the air was removed by double-row pipe evacuation three times, and 50 mL of ultra-dry dimethylacetamide solvent was added and refluxed for 12 hours. After the reaction was completed, deionized water was added and the crude product was filtered, and then recrystallized from dichloromethane and methanol to obtain a white solid intermediate 3 (yield 80%).

[0080] 4) Preparation of intermediate 4

[0081] The synthesis path is as follows:

[0082]

[0083] The preparation method specifically comprises the following steps:

[0084] Intermediate 2 (3.16 g, 4 mmol), triphenylphosphine (1.05 g, 4 mmol), benzyltriethyl chloride (1.82 g, 8 mmol), potassium carbonate (5.53 g, 40 mmol) and palladium acetate (180 mg, 0.8 mmol) were placed in a 500 mL reaction bottle, and the air was removed by double-row pipe evacuation three times, and 50 mL of ultra-dry dimethylacetamide solvent was added and refluxed for 12 hours. After the reaction was completed, deionized water was added and the crude product was filtered, and then recrystallized from dichloromethane and methanol to obtain white solid intermediate 4 (yield 88%). 1 H NMR (400 MHz, CDCl 3)δ8.84(s,1H),8.23-8.17(m,5H),8.13(s,2H),7.97(d,J=8.4Hz,2H),7.66(dd,J=8.4,1.6Hz,2H),1.60(s,18H),1.51(s,18H).

[0085] 5) Preparation of Intermediate 5

[0086] The synthesis path is as follows:

[0087]

[0088] The preparation method specifically comprises the following steps:

[0089] Take intermediate 3 (4.04 g, 10 mmol) and add 100 ml of DMF solution. Cool the mixture to 0°C in an ice bath and stir. Add 10 ml of DMF solution of NBS (N-bromosuccinimide, 1.18 g, 10 mmol) dropwise. Wrap with aluminum foil and react overnight. Remove the solvent by vacuum distillation and purify by dichloromethane / petroleum ether column chromatography to obtain white solid intermediate 5 (yield 90%).

[0090] 6) Preparation of Intermediate 6

[0091] The synthesis path is as follows:

[0092]

[0093] The preparation method specifically comprises the following steps:

[0094] Take intermediate 4 (6.28 g, 10 mmol) and add 100 ml of DMF solution. Cool the mixture to 0°C in an ice bath and stir. Add 10 ml of DMF solution containing NBS (1.18 g, 10 mmol) dropwise. Wrap with aluminum foil and react overnight. Remove the solvent by distillation under reduced pressure and purify by dichloromethane / petroleum ether column chromatography to obtain white solid intermediate 6 (yield 88%). 1 H NMR (400 MHz, CDCl 3 )δ9.01(d,J=7.5Hz,2H),8.78(s,1H),8.17-8.11(m,6H),7.58-7.60(dd,J=7.5,J=2.0Hz,2H),1.60(s,18H),1.51(s,18H).

[0095] 7) Preparation of Intermediate 7

[0096] The synthesis path is as follows:

[0097]

[0098] The preparation method specifically comprises the following steps:

[0099] Intermediate 5 (4.83 g, 10 mmol), pinacol borane (8 mL, 50 mmol), [bis(triphenylphosphino)]palladium dichloride (140 mg, 0.2 mmol), and triethylamine (3 mL) were dissolved in 30 ml of ultra-dry 1,4-dioxane solvent, refluxed at 108 ° C overnight, the reaction solution was filtered through diatomaceous earth, and the filtrate was distilled under reduced pressure and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1) to obtain a white solid intermediate 7 (yield 95%).

[0100] 8) Preparation of Intermediate 8

[0101] The synthesis path is as follows:

[0102]

[0103] The preparation method specifically comprises the following steps:

[0104] Intermediate 6 (7.07 g, 10 mmol), pinacol borane (8 mL, 50 mmol), [bis(triphenylphosphino)]palladium dichloride (140 mg, 0.2 mmol), and triethylamine (3 mL) were dissolved in 30 ml of ultra-dry 1,4-dioxane solvent, refluxed at 108 ° C overnight, the reaction solution was filtered through diatomaceous earth, and the filtrate was distilled under reduced pressure and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1) to obtain a white solid intermediate 8 (yield 90%). 1 H NMR (500 MHz, CDCl 3 )δ8.93(s,1H),8.47-8.49(d,J=8.5Hz,2H),8.15(d,J=1.5Hz,2H),8.13(d,J=2.0Hz,2H),8.10( d, J=1.0Hz, 2H), 7.53-7.55 (dd, J=8.5, J=2.0Hz, 2H), 1.59 (s, 18H), 1.50 (s, 18H), 1.42 (s, 12H).

[0105] 9) Preparation of Intermediate 9

[0106] The synthesis path is as follows:

[0107]

[0108] The preparation method specifically comprises the following steps:

[0109] 1) To a stirred solution of aniline (4.3 g, 38.7 mmol) in toluene (17 mL) was added paraformaldehyde (0.58 g, 19.3 mmol), the resulting mixture was then heated to 100°C, cooled to 40°C, glyoxal (2.20 mL of a 40% aqueous solution, 19.3 mmol) was added, and the mixture was stirred for 5 minutes. HCl (6.45 mL, 3 M) was then added dropwise, and the mixture was heated to 100°C for 12 hours. After cooling to room temperature, the solvent was removed by a vacuum rotary evaporator. Subsequently, the resulting mixture was dissolved in water (20 mL), and HBF tetrafluoroborate was added. 4 (1.2 mL, 40 wt% aqueous solution, 19.3 mmol). The mixture was stirred for one hour and transferred to a separatory funnel. The aqueous phase was extracted three times with dichloromethane (3×50 mL), and the combined organic phases were washed with MgSO 4 After drying for 1 hour, all volatiles were removed in vacuo. Repeated recrystallization from dichloromethane / ether gave the tetrafluoroborate salt of the product as a white solid (70% yield), which was then used on an ion exchange resin to give NHC-1 (85% yield).

[0110] 2) Intermediate NHC-1 (348 mg, 1 mmol), Au(THT)Cl (tetrahydrothiophene gold chloride, 321 mg, 1 mmol) and K 2 CO 3 (0.3 g, 2 mmol) was dissolved in 30 mL of dichloromethane solution and stirred overnight. After the reaction was completed, potassium carbonate was filtered out, vacuum distilled, and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1) to obtain a white solid intermediate 9 (yield 80%).

[0111] 10) Preparation of intermediate 10

[0112] The synthesis path is as follows:

[0113]

[0114] The preparation method specifically comprises the following steps:

[0115] The intermediate NHC-2 (425 mg, 1 mmol), Au(THT)Cl (tetrahydrothiophene gold chloride, 321 mg, 1 mmol) and K 2 CO 3 (0.3 g, 2 mmol) was dissolved in 30 mL of dichloromethane solution and stirred overnight. After the reaction was completed, potassium carbonate was filtered off, vacuum distilled, and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1) to obtain a white solid intermediate 10 (yield 85%).

[0116] 11) Preparation of intermediate 11

[0117] The synthesis path is as follows:

[0118]

[0119] The preparation method specifically comprises the following steps:

[0120] 1) 2-Chloro-3-nitropyridine (5g, 31.54mmol) and aniline (3.5g, 37.84mmol) were dissolved in 60mL isopropanol solution and heated to 83℃ for reflux reaction for 24h. After the reaction was completed, the mixture was cooled to room temperature, and then distilled under reduced pressure and purified by column chromatography (eluent was petroleum ether: dichloromethane = 3:1) to obtain a red solid intermediate (yield: 70%). Then the above-synthesized compound (2g, 9.30mmol), reduced iron powder (5.6g, 98.58mmol) and ammonium chloride (5.3g, 98.58mmol) were added to a branch-mouth bottle for deoxygenation, and then formic acid (47mL, 1.2mol) and 80mL isopropanol mixed solution were added and stirred at 83℃ for 48h. After the reaction was completed, the mixture was cooled to room temperature, and then distilled under reduced pressure and purified by column chromatography (eluent was pure dichloromethane) to obtain a brown solid intermediate (yield: 70%).

[0121] 2) The above-synthesized brown solid intermediate (1.3 g, 6.6 mmol) and iodomethane (41 mL, 660 mmol) were dissolved in 60 mL of tetrahydrofuran solution, stirred for 3 days, and filtered to obtain a white solid intermediate NHC-3 (yield 75%).

[0122] 3) Intermediate NHC-3 (337 mg, 1 mmol), Ag 2 O (0.3 g, 2 mmol) was dissolved in a mixed solution of 30 mL of dichloromethane and 20 mL of ethanol, and the residue was filtered off after stirring for 6 hours. Au(THT)Cl (tetrahydrothiophene gold chloride, 321 mg, 1 mmol) was added to the filtrate and stirred overnight. After the reaction was completed, it was distilled under reduced pressure and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1) to obtain a white solid intermediate 11 (yield 75%).

[0123] 12) Preparation of intermediate 12

[0124] The synthesis path is as follows:

[0125]

[0126] The preparation method specifically comprises the following steps:

[0127] 1) 2,3-Dichloropyrazine (4mL, 0.38mol) and 3,5-dimethylaniline (12mL, 0.962mol) were refluxed at 140°C for 6h. After the reaction was completed, the temperature was cooled to room temperature and solids were generated. The solid product was filtered out and 50mL of dichloromethane and 50mL of distilled water were added thereto and stirred for 2h. Then, the mixture was extracted three times with 3×20mL of dichloromethane, the organic phases were combined, dried with anhydrous sodium sulfate for 30min, sodium sulfate was removed by filtration, and the organic phase was dried with a rotary evaporator to obtain an oily product. White solids were precipitated by adding n-hexane (yield: 7g, yield: 70%, 1 H NMR (400 MHz, CDCl 3 , δ)2.28(s,12H),6.13(s,2H),6.69(s,2H),6.87(s,4H),7.77(s,2H).).

[0128] 2) After the above synthesized white solid compound (750 mg, 2.35 mmol) and triethyl orthoformate (10 mL) were mixed evenly, 37% concentrated hydrochloric acid was added under stirring. With the addition of hydrochloric acid, the solution immediately became turbid, and refluxed at 110°C until the solid dissolved to obtain a brown-yellow solution, and the reaction was continued for 6 hours. After the reaction was completed, the temperature was cooled to room temperature, 20 mL of n-hexane was added, and the product was precipitated. The solid was collected by filtration to obtain a light yellow product NHC-4 (yield: 510 mg, yield: 50%).

[0129] 3) The intermediate NHC-4 (373 mg, 1 mmol) and cuprous chloride (99 mg, 1 mmol) were placed in a 50 mL reaction bottle and purged to replace nitrogen three times, followed by the addition of 30 mL of ultra-dry tetrahydrofuran solution and reflux overnight. After the reaction was completed, the solid was filtered off and washed three times with tetrahydrofuran and dried. Subsequently, the obtained solid was dissolved in 30 mL of dichloromethane solution with Au(THT)Cl (tetrahydrothiophene gold chloride, 321 mg, 1 mmol) and stirred overnight. After the reaction was completed, the insoluble matter was filtered off, the mixture was distilled under reduced pressure, and the white solid intermediate 12 (yield 72%) was obtained by recrystallization with dichloromethane and petroleum ether.

[0130] 13) Preparation of intermediate 13

[0131] The synthesis path is as follows:

[0132]

[0133] The preparation method specifically comprises the following steps:

[0134] N,N'-dimethylbenzimidazole iodide was treated with ion exchange resin to obtain intermediate NHC-5 (yield 80%). Intermediate NHC-5 (182 mg, 1 mmol) and silver oxide (116 mg, 0.5 mmol) were dissolved in 30 mL of dichloromethane and 20 mL of ethanol solution and stirred overnight. Subsequently, the filtrate was filtered and Au(THT)Cl (tetrahydrothiophene gold chloride) (321 mg, 1 mmol) was added and stirred for 24 hours. After the reaction was completed, the insoluble matter was filtered off, distilled under reduced pressure, and recrystallized from dichloromethane and ether to obtain white solid intermediate 13 (yield 78%).

[0135] 14) Preparation of Intermediate 14

[0136] The synthesis path is as follows:

[0137]

[0138] The preparation method specifically comprises the following steps:

[0139] 1) In a 25mL reactor, 2,3-dichloropyrazine (2.08mL, 20.02mmol), methylamine (33% aqueous solution, 14mL), and copper powder (0.26g, 4.10mmol) were stirred and mixed with a glass rod, and then the reactor was placed in an oven at 140℃ for ten hours. After cooling to room temperature, the reactor was removed, and the brown-red supernatant was quickly filtered to remove insoluble impurities. The solution was then placed in a -20℃ refrigerator to cool, and yellow-green needle-shaped solid 2,3-dimethylaminopyrazine (2.51g, yield: 80%) was precipitated overnight. After the obtained 2,3-dimethylaminopyrazine (2.51g, 18mmol), triethyl orthoformate (10mL) and 37% concentrated hydrochloric acid (1mL) were mixed, the mixture quickly became turbid. The mixture was refluxed at 120℃ with magnetic stirring for 6h. After the reaction is completed, the mixture is cooled and 50 mL of ether is added, and the product is precipitated. The solid is collected by filtration, 20 mL of ethanol and an appropriate amount of activated carbon are added, and the mixture is heated for recrystallization. The activated carbon is filtered through diatomaceous earth, the filtrate is dried by rotary evaporation, and the obtained solid is recrystallized in a methanol / ether solution to obtain a light yellow solid 1,3-dimethylpyrazine imidazole chloride NHC-6 (1.56 g, yield: 55%).

[0140] 2) The intermediate NHC-6 (184 mg, 1 mmol) and silver oxide (116 mg, 0.5 mmol) were dissolved in 30 mL of dichloromethane and 20 mL of ethanol solution and stirred overnight. Subsequently, the filtrate was filtered and Au(THT)Cl (tetrahydrothiophene gold chloride) (321 mg, 1 mmol) was added and stirred for 24 hours. After the reaction was completed, the insoluble matter was filtered off, the mixture was distilled under reduced pressure, and the white solid intermediate 14 was obtained by recrystallization with dichloromethane and ether (yield 69%).

[0141] Example 2

[0142] This embodiment provides a metal complex C-1 (ImIDCz), and its synthesis path is as follows:

[0143]

[0144] The preparation method specifically comprises the following steps:

[0145] Intermediate 7 (530 mg, 1 mmol), intermediate 9 (452 ​​mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-1 (ImIDCz) (yield 60%).

[0146] Example 3

[0147] This embodiment provides a metal complex C-7 (ImtIDCz), and its synthesis path is as follows:

[0148]

[0149] The preparation method specifically comprises the following steps:

[0150] Intermediate 8 (754 mg, 1 mmol), intermediate 9 (452 ​​mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-7 (ImtIDCz) (yield 65%). 1 H NMR (500 MHz, CDCl 3)δ9.33-9.34(d,J=8.6Hz,2H),8.59(s,1H),8.09(s,2H),8.05(d,J=1.7Hz,2H),8.01-7.99(m,6H),7.57(s,2H),7.3 2-7.35(t,J=7.7Hz,4H),7.28(s,1H),7.27(s,1H),6.92-6.94(dd,J=8.7,J=1.8Hz,2H),1.58(s,18H),1.44(s,18H). 13 C NMR (126 MHz, CDCl 3 )δ150.03,145.45,144.27,142.64,139.30,138.60,132.81,130.18,129.59,129.10,124.68,123.88, 122.33,122.21,119.32,118.44,117.12,115.31,114.70,113.80,113.32,35.82,34.63,32.89,31.98.

[0151] Example 4

[0152] This embodiment provides a metal complex C-2 (IPrIDCz), and its synthesis path is as follows:

[0153]

[0154] The preparation method specifically comprises the following steps:

[0155] Intermediate 7 (530 mg, 1 mmol), intermediate 10 (620 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-2 (IPrIDCz) (yield 62%).

[0156] Example 5

[0157] This embodiment provides a metal complex C-8 (IPrtIDCz), and its synthesis path is as follows:

[0158]

[0159] The preparation method specifically comprises the following steps:

[0160] Intermediate 8 (754 mg, 1 mmol), intermediate 10 (620 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-8 (IPrtIDCz) (yield 65%).

[0161] Example 6

[0162] This embodiment provides a metal complex C-4 (IPyIDCz), and its synthesis path is as follows:

[0163]

[0164] The preparation method specifically comprises the following steps:

[0165] Intermediate 7 (530 mg, 1 mmol), intermediate 11 (440 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-4 (IPyIDCz) (yield 60%).

[0166] Example 7

[0167] This embodiment provides a metal complex C-10 (IPytIDCz), and its synthesis path is as follows:

[0168]

[0169] The preparation method specifically comprises the following steps:

[0170] Intermediate 8 (754 mg, 1 mmol), intermediate 11 (440 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex IPytIDCz (yield 75%).

[0171] Example 8

[0172] This embodiment provides a metal complex C-6 (IPzIDCz), and its synthesis path is as follows:

[0173]

[0174] The preparation method specifically comprises the following steps:

[0175] Intermediate 7 (530 mg, 1 mmol), intermediate 12 (560 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a yellow powder complex C-6 (IPzIDCz) (yield 62%).

[0176] Example 9

[0177] This embodiment provides a metal complex C-12 (IPztIDCz), and its synthesis path is as follows:

[0178]

[0179] The preparation method specifically comprises the following steps:

[0180] Intermediate 8 (754 mg, 1 mmol), intermediate 12 (560 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a yellow powder complex C-12 (IPztIDCz) (yield 70%). 1 H NMR (500 MHz, CDCl 3 )δ9.39-9.40(d,J=8.5Hz,2H),8.65(s,2H),8.59(s,1H),8.10(t,J=1.5Hz,4H),8.03(d,J=1.0Hz,2H),7 .68(s,4H),7.16-7.18(dd,J=8.5,J=2.0Hz,2H),7.00(s,2H),2.16(s,12H),1.58(s,18H),1.45(s,18H). 13 CNMR (126MHz, CDCl 3)δ149.86,145.57,144.27,142.97,140.97,140.05,139.60,138.67,134.91,131.81,130.45,124.35,123 .88,122.07,119.26,118.72,117.06,115.21,114.82,113.93,113.46,35.83,34.68,32.88,32.01,21.21.

[0181] In dichloromethane and n-hexane solutions, the crystals of the metal complex C-12 (IPztIDCz) were obtained by layered diffusion. The analytical results are shown below (the distances between gold and the two hydrogen atoms are 2.564 and ):

[0182]

[0183] Example 10

[0184] This embodiment provides a metal complex C-3 (MePhIDCz), and its synthesis path is as follows:

[0185]

[0186] The preparation method specifically comprises the following steps:

[0187] Intermediate 7 (530 mg, 1 mmol), intermediate 13 (380 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 mL of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-3 (MePhIDCz) (yield 60%).

[0188] Embodiment 11

[0189] This embodiment provides a metal complex C-9 (MePhtIDCz), and its synthesis path is as follows:

[0190]

[0191] The preparation method specifically comprises the following steps:

[0192] Intermediate 8 (754 mg, 1 mmol), intermediate 13 (380 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a white powder complex C-9 (MePhtIDCz) (yield 77%). 1 H NMR (500 MHz, CDCl 3 )δ(ppm):9.80(d,J=8.5Hz,2H),8.73(s,1H),8.18(d,J=1.0Hz,2H),8.15(d,J=2.0Hz,2H),8.08(d ,J=1.0Hz,2H),7.59(m,4H),7.28(dd,J=8.5,2.0Hz,2H),4.32(s,6H),1.62(s,18H),1.44(s,18H). 13 C NMR (126 MHz, CDCl 3 )δ(ppm):δ197.39,149.85,145.69,144.38,143.17,138.66,134.46,130.55,124.49,124.12,121.94, 119.28,118.90,117.04,115.38,114.91,114.00,113.85,111.25,35.87,35.11,34.66,32.91,31.94.

[0193] Example 12

[0194] This embodiment provides a metal complex C-5 (MePzIDCz), and its synthesis path is as follows:

[0195]

[0196] The preparation method specifically comprises the following steps:

[0197] Intermediate 7 (530 mg, 1 mmol), intermediate 14 (380 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 mL of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a yellow powder complex C-5 (MePzIDCz) (yield 66%).

[0198] Example 13

[0199] This embodiment provides a metal complex C-11 (MePztIDCz), and its synthesis path is as follows:

[0200]

[0201] The preparation method specifically comprises the following steps:

[0202] Intermediate 8 (754 mg, 1 mmol), intermediate 14 (380 mg, 1 mmol) and potassium carbonate (46 mg, 3 mmol) were placed in a 50 mL reaction bottle, and 20 ml of ethanol solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, it was directly distilled under reduced pressure, and dichloromethane was added to dissolve the residue and filter out the potassium carbonate. The filtrate was then distilled under reduced pressure again and recrystallized from ethanol to obtain a yellow powder complex C-11 (MePztIDCz) (yield 79%). 1 H NMR (500 CDCl 3 )δ(ppm):9.70(d,J=8.5Hz,2H),8.72(s,1H),8.63(s,2H),8.16(dd,J=12.0,0.5Hz,4H ),8.07(s,2H),7.30(dd,J=9.0,2.5Hz,2H),4.39(s,6H),1.61(s,18H),1.44(s,18H). 13 C NMR (125 MHz, CDCl 3 )δ(ppm):146.84,144.86,143.66,140.10,138.51,137.05,130.36,125.14,123.92,121.90, 119.75,118.41,117.24,115.94,115.75,115.00,111.55,96.01,32.87,32.85,31.94,31.92.

[0203] Device Example 1

[0204] This embodiment provides an organic electroluminescent device, such as Figure 1 As shown, it includes an anode layer 1, a hole injection layer 2, a hole transport layer 3, an electron blocking layer 4, an electron blocking layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, an electron injection layer 9 and a cathode layer 10 which are sequentially arranged on a glass substrate from bottom to top;

[0205] The device structure is ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / DMIC-TRZ:C-12 (45nm) / POT2T (20nm) / ANT-BIZ (30nm) / Liq (2nm) / Al (100nm).

[0206] The anode layer 1 is made of ITO material, i.e. indium tin oxide material;

[0207] The hole injection layer 2 material is 1,2-hexaazatriphenylene (HAT-CN), and the structure is as follows:

[0208]

[0209] The hole transport layer 3 material is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), and the structure is as follows:

[0210]

[0211] The electron blocking layer 4 material is tris(4-carbazolyl-9-phenyl)amine (TCTA), and the structure is as follows:

[0212]

[0213] The electron blocking layer 5 material is 3,3'-di(9H-carbazole-9-yl)-1,1'-biphenyl; 3,3'-bis(9H-carbazole-9-yl)-1,1'-biphenyl (mCBP), and the structure is as follows:

[0214]

[0215] The light-emitting layer 6 is formed by co-doping a host material and a guest material, wherein the host material is the compound DMIC-TRZ, and the guest material is the metal complex C-12 (IPztIDCz) of the present invention, and the doping amount of the guest material accounts for 1% of the total mass of the host material and the guest material; wherein the host material is 5-(3-(4,6-diphenyl-1,3,5-triazine-2-yl)phenyl)-7,7-dimethyl-5,7-dihydroindeno[2,1-b]carbazole (DMIC-TRZ), and the structure is as follows:

[0216]

[0217] The material of the electron transport layer 7 is: 2,4,6-tris[3-(diphenylphosphinoyl)phenyl]-1,3,5-triazole (POT2T), the structure of which is as follows:

[0218]

[0219] The material of the electron injection layer 8 is (1-(4-(10-([1,1'-biphenyl]-4-yl) anthracene-9-yl) phenyl)-2-ethyl-1H-benzo[d]-imidazole) (ANT-BIZ), and the structure is as follows:

[0220]

[0221] The material of the electron injection layer 9 is Liq (8-hydroxyquinoline lithium), and the structure is as follows:

[0222]

[0223] The cathode layer 10 is made of metal Al.

[0224] Device Example 2

[0225] This embodiment provides an organic electroluminescent device, which is different from the organic electroluminescent device provided in device embodiment 1 in that the doping amount of the guest material in the light-emitting layer accounts for 3% of the total mass of the host material and the guest material.

[0226] Device Example 3

[0227] This embodiment provides an organic electroluminescent device, which is different from the organic electroluminescent device provided in device embodiment 1 in that the doping amount of the guest material in the light-emitting layer accounts for 6% of the total mass of the host material and the guest material.

[0228] As an alternative embodiment, the guest material of the light-emitting layer may also be selected from any other compound having the chemical structure shown in Formula I.

[0229] Test Example 1

[0230] The organic electroluminescent devices provided in device embodiments 1-3 were tested, and the current-brightness-voltage characteristics of the devices were measured by a Keithley source measurement system (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter) with a calibrated silicon photodiode. All tests were completed in room temperature atmosphere. The test results are shown in Table 1.

[0231] Table 1 Device performance test results

[0232]

[0233] [a] Starting voltage (brightness 1cd m -2 ).

[0234] [b] At maximum brightness, 1000cd m -2 and 10000cd m -2Current efficiency CE, lumen efficiency PE, external quantum efficiency EQE.

[0235] [c] CIE coordinates (brightness 1000cd m -2 ).

[0236] like Figure 2-Figure 5 The present invention uses C-12 (IPztIDCz) as the guest material and prepares the doped luminescent OLED with a doping concentration of 1%. The emission peak is located at 531nm and the maximum brightness is 165047cd m -2 , the maximum current efficiency is 75.7cd A -1 , the maximum lumen efficiency is 63.2lm W -1 The maximum external quantum efficiency is as high as 23.9% at a brightness of 1000cd m -2 The lower CIE coordinates are (0.37, 0.57).

[0237] Test Example 2

[0238] The device stability life test was performed on the organic electroluminescent device provided in device embodiment 1. All tests were completed in the atmosphere at room temperature. The test results are shown in Table 2.

[0239] Table 2 Device life test results

[0240]

[0241]

[0242] like Figure 6 The initial brightness of the doped luminescent OLED prepared by the present invention with C-12 (IPztIDCz) as the guest material and a doping concentration of 1% is 3000 cd m -2 Under this condition, LT 95 (brightness drops by 5%): 4.9 hours, LT 50 (Brightness drops by 50%) is 334 hours. Initial brightness is 1000 cd m -2 , under this condition LT 95 (Brightness decreases by 5%) is 27.4 hours. Based on an initial brightness of 3000 cd m -2 The test data is roughly assumed to be a moderate acceleration factor of 1.6 and a brightness of 100 cd m -2 Under these conditions, LT 95 (brightness decreases by 5%) is 1131 hours, LT 50 (brightness drops by 50%) is 77115 hours; brightness is 1000cd m -2 Under these conditions, LT 50 (brightness drops by 50%) is 1868 hours.

[0243] Test Example 3

[0244] The photoluminescence test of the complexes C-7 (ImtIDCz) and C-12 (IPztIDCz) doped di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film was carried out. The emission spectrum results are shown in Figure 7 As shown, it shows the fluorescence emission change of the complex from blue light to green light. Figure 8 This is the emission spectrum of the complex C-3 (MePhIDCz) of the present invention in di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film. Fig. 9 This is the emission spectrum of the complex C-5 (MePzIDCz) of the present invention in di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film.

[0245] The transient spectrum test of the complex C-7 (ImtIDCz) and C-12 (IPztIDCz) doped di[2-((oxy)diphenylphosphino)phenyl]ether (DPEPO) film was carried out, and the lifetime decay data are shown in Figure 10-11 As shown, it shows that the IPztIDCz complex has a short decay lifetime with good TADF effect.

[0246] The temperature-dependent transient spectrum test of the C-12 (IPztIDCz) doped film was carried out, and the lifetime decay data are as follows: Fig.12 As shown, from top (low temperature) to bottom (high temperature), these are the lifetime decay data at 77K, 120K, 200K, and 300K, respectively, which show that the IPztIDCz complex has typical TADF properties, and the lifetime decreases by 10 orders of magnitude as the temperature increases.

[0247] Fig.13 This is a lifetime decay curve of the complex C-3 (MePhIDCz) of the present invention in a toluene solution. The existence of triplet excitons can be obtained through the lifetime results under oxygen and argon atmospheres. The triplet excitons are quenched under oxygen conditions.

[0248] Fig.14 This is a lifetime decay curve of the complex C-5 (MePzIDCz) of the present invention in a toluene solution. The existence of triplet excitons can be obtained through the lifetime results under oxygen and argon atmospheres. The triplet excitons are quenched under oxygen conditions.

[0249] In summary, the carbene-metal-aryl derivative structure in the present invention has good TADF performance. Through the unique molecular structure and transition mode, the two hydrogen atoms in the aromatic derivative can form a "gold-hydrogen bond" similar to the hydrogen bond with the metal center, so that the complex is transformed from a two-coordinate structure with low stability to a four-coordinate configuration with high stability, wherein the three "hydrogen-carbon-hydrogen" atoms of the aromatic derivative are coordinated with the metal atoms respectively to form a chelate ligand structure, thereby improving the light stability and thermal stability of the molecule, reducing the device roll-off, and being conducive to the preparation of metal complexes for high-stability OLED devices.

[0250] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A metal complex, characterized in that Has the following structure: Wherein, R1 is selected from hydrogen, unsubstituted C1-C6 alkyl; R2-R3 are independently selected from C1-C4 alkyl, substituted or unsubstituted C6-C18 aryl, wherein the substituted C6-C18 aryl is optionally substituted by 1-4 substituents R a Replace; each R a Independently selected from C1-C6 alkyl; R4-R5 are independently selected from hydrogen, or R4-R5 are connected to form C6-C 18 Aryl, C5-C 20 Heteroaryl.

2. The metal complex according to claim 1, characterized in that R1 is selected from hydrogen, C1-C4 alkyl.

3. The metal complex according to claim 1 or 2, characterized in that R1 is selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl; R4-R5 are independently selected from hydrogen, or R4-R5 are connected to each other to form the following structure: The connection site.

4. The metal complex according to claim 1, characterized in that R2-R3 are independently selected from C1-C4 alkyl, substituted or unsubstituted C6-C18 aryl, wherein the substituted C6-C18 aryl is optionally substituted by 1-2 substituents R a Replace; each R a Independently selected from C1-C4 alkyl.

5. The metal complex according to claim 1, characterized in that R1 is selected from hydrogen, tert-butyl; R2-R3 are independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, 3,5-dimethylphenyl, 2,6-diisopropylphenyl, naphthyl, and anthracenyl.

6. The metal complex according to claim 1, characterized in that R2-R3 are independently selected from methyl, phenyl, 3,5-dimethylphenyl, and 2,6-diisopropylphenyl.

7. The metal complex according to claim 1, characterized in that The carbene ligand in the metal complex Has the following structure:

8. The metal complex according to claim 1, characterized in that The metal complex has the structure shown below:

9. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises a first electrode, a second electrode and an organic layer located between the first electrode and the second electrode, and the organic layer comprises any one or a combination of at least two of the metal complexes according to any one of claims 1 to 8.

10. The organic electroluminescent device according to claim 9, characterized in that: The organic layer comprises a light-emitting layer, and the light-emitting layer comprises any one or a combination of at least two of the metal complexes according to any one of claims 1 to 8.

11. The organic electroluminescent device according to claim 9 or 10, characterized in that: The light-emitting layer comprises the metal complex according to any one of claims 1 to 8 and an organic functional material, wherein, by mass percentage, the metal complex accounts for 0.01% to 100%, and the organic functional material accounts for 0 to 99.9%.

12. The organic electroluminescent device according to claim 9, characterized in that: The organic layer also includes an electron functional layer and a hole functional layer; The electronic functional layer includes at least one of an electron injection layer, an electron transport layer and a hole blocking layer; The hole functional layer includes at least one of a hole injection layer, a hole transport layer and an electron blocking layer.

Images