Boron-nitrogen compound, preparation method thereof and organic electroluminescent device prepared from boron-nitrogen compound

Abstract

The invention discloses a boron-nitrogen compound, a preparation method thereof and an organic electroluminescent device prepared from the boron-nitrogen compound. The structural formula of the boron-nitrogen compound is # imgabs0, R1 to R8 are independently one of H, alkyl of C1 to C16, naphthenic base of C3 to C20, aryl of C6 to C30, aryl of C6 to C18 substituted by single or multiple Ra, heteroaryl of 5 to 18 membered and heteroaryl of 5 to 18 membered substituted by single or multiple Ra, and Ra is one of deuterium, fluorine, alkyl of C1 to C12, alkoxy of C1 to C12, naphthenic base of C3 to C12 and aryl of C6 to C14. The electroluminescent device made of the boron-nitrogen compound as a luminescent layer material can realize narrow spectrum emission, the electroluminescent external quantum efficiency of the device exceeds 10%, the service life of the device exceeds 300 h, the luminous efficiency and the stability are greatly improved, and the boron-nitrogen compound is suitable for an OLED (Organic Light Emitting Diode) display.

Description

Technical Field

[0001] The present invention relates to the technical field of electroluminescence, and in particular to a boron nitrogen compound, a preparation method thereof, and an organic electroluminescent device prepared therefrom. Background Art

[0002] Organic optoelectronic materials are a class of organic materials that possess properties such as the generation, conversion, and transmission of photons and electrons. They are used in devices such as organic light-emitting diodes (OLEDs), organic solar cells (OPVs), organic field-effect transistors (OFETs), and organic lasers. OLED displays are a very popular type of flat-panel display product, boasting advantages such as self-luminescence, wide viewing angles, fast response times, high luminous efficiency, a wide color gamut, low operating voltage, thin panels, the ability to manufacture large, flexible panels, and low cost.

[0003] Thermally activated delayed fluorescence (TADF) materials are a type of material that can break through the exciton utilization limit of traditional fluorescent molecular materials. They can achieve 100% exciton utilization, which can greatly improve the quantum efficiency of OLED devices. For example, in 2012, the Adachi research group at Kyushu University reported a high-efficiency all-fluorescent OLED device based on the thermally activated delayed fluorescence mechanism (Uoyama H, Goushi K, Shizu K, et al. Highly efficient organic light-emitting diodes from delayed fluorescence, Nature, 2012, 492(7428):234-238.). When the difference between the S1 and T1 energy levels of the molecule is small enough, the triplet excitons can absorb thermal energy, return to the singlet state through the RISC process, and then emit fluorescence. The internal quantum efficiency (IQE) of the device can theoretically reach 100%, and the external quantum efficiency (EQE) can even reach as high as 30%, comparable to the level of phosphorescent devices.

[0004] At present, TADF molecules are mainly doped as guest materials in wide bandgap host materials to achieve high-efficiency thermally activated delayed fluorescence (Q. Zhang, J. Li, K. Shizu, et al. Design of Efficient Thermally Activated Delayed Fluorescence Materials for Pure Blue Organic Light Emitting Diodes, J. Am. Chem. Soc. 2012, 134, 14706; H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Highly efficient organic light-emitting diodes from delayed fluorescence, Nature, 2012, 492, 234; T. Nishimoto, T. Yasuda, et al., A six-carbazole-decorated cyclophosphazene as a host with high triplet energy to realize efficient delayed-fluorescence OLEDs, Mater. Horiz., 2014, 1, 264). However, TADF emission mainly originates from the transition of ICT state, which is different from the localized (LE) state luminescence of traditional fluorescent molecules. It is easily affected by the vibrational and rotational motion between donor and acceptor, resulting in low electroluminescence efficiency and poor stability.

[0005] Therefore, it is of great significance to develop a high-efficiency and high-stability TADF material. Summary of the Invention

[0006] The object of the present invention is to provide a boron nitrogen compound, a preparation method thereof and an organic electroluminescent device prepared therefrom.

[0007] The technical solution adopted by the present invention is:

[0008] A boron-nitrogen compound, characterized in that it has the structural formula:

[0009] In the formula, R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, C1-C 16 Alkyl, C3~C 20 Cycloalkyl, C6~C 30 Aryl, single or multiple R a Substituted C6~C 18aryl, 5- to 18-membered heteroaryl, single or multiple R a One of the substituted 5- to 18-membered heteroaryl groups, R a For deuterium, fluorine, C1~C 12 Alkyl, C1~C 12 Alkoxy, C3~C 12 Cycloalkyl, C6~C 14 One of the aromatic groups.

[0010] Preferably, R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, C1-C 10 Alkyl, C3~C 10 Cycloalkyl, C6~C 14 Aryl, single or multiple R a Substituted C6~C 18 aryl, 5- to 18-membered heteroaryl, single or multiple R a One of substituted 5- to 18-membered heteroaryl groups.

[0011] More preferably, R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, methyl, tert-butyl, adamantyl, cyclohexyl, phenyl, One of the following, * indicates the connection site.

[0012] More preferably, the boron nitrogen compound is any one of compounds BN-1 to BN-28:

[0013] Compounds BN-1 to BN-4:

[0014]

[0015] Compounds BN-5 to BN-8:

[0016]

[0017] Compounds BN-9 to BN-12:

[0018]

[0019] Compounds BN-13 to BN-16:

[0020]

[0021] Compounds BN-17 to BN-20:

[0022]

[0023] Compounds BN-21 to BN-24:

[0024]

[0025] Compounds BN-25 to BN-28:

[0026]

[0027] A method for preparing the boron nitrogen compound as described above comprises the following steps: 1) preparation of intermediate 1 and intermediate 2:

[0028] Preparation of intermediate 1: Di-tert-butyl dicarbonate and 4-dimethylaminopyridine are dispersed in an organic solvent to carry out amino protection reaction to obtain It is recorded as intermediate 1;

[0029] Preparation of intermediate 2: Palladium catalyst, phosphine ligand and alkali metal compound are dispersed in organic solvent to carry out carbon-nitrogen coupling reaction to obtain It is recorded as intermediate 2;

[0030] 2) Dispersing intermediate 1, intermediate 2 and palladium catalyst in an organic solvent to carry out carbon-nitrogen coupling reaction to obtain It is recorded as intermediate 3;

[0031] 3) The intermediate 3 is added to an acidic solvent for deprotection to obtain It is recorded as intermediate 4;

[0032] 4) Preparation of asymmetric boron-nitrogen compounds and symmetric boron-nitrogen compounds:

[0033] Preparation of asymmetric boron-nitrogen compounds:

[0034] a) 1,3-Difluoro-4,6-dibromobenzene and an alkali metal compound are dispersed in an organic solvent to undergo a nucleophilic substitution reaction to obtain It is recorded as intermediate 5;

[0035] b) Intermediate 5 and an alkali metal compound are dispersed in an organic solvent to undergo a nucleophilic substitution reaction. Different, get It is recorded as intermediate 6;

[0036] c) dispersing the intermediate 6, a lithiation reagent, a boration reagent, and a cyclization reagent in an organic solvent to carry out lithiation reaction, boration reaction, and cyclization reaction to obtain an asymmetric boron nitrogen compound;

[0037] Preparation of symmetrical boron-nitrogen compounds:

[0038] i) will 1,3-Difluoro-4,6-dibromobenzene and alkali metal compounds are dispersed in an organic solvent to undergo a nucleophilic substitution reaction. Same, get It is designated as intermediate 7;

[0039] ii) The intermediate 7, a lithiation agent, a boration agent and a cyclization agent are dispersed in an organic solvent to carry out lithiation reaction, boration reaction and cyclization reaction to obtain a boron nitrogen compound with a symmetrical structure.

[0040] Preferably, step 1) The molar ratio of di-tert-butyl dicarbonate is 1:1-10.

[0041] Preferably, step 1) The molar ratio of 4-dimethylaminopyridine is 1:0.1-10.

[0042] Preferably, in step 1) the The organic solvent of di-tert-butyl dicarbonate and 4-dimethylaminopyridine is at least one of dichloromethane, tetrahydrofuran and acetone.

[0043] Preferably, the amino protection reaction in step 1) is carried out under reflux of an organic solvent, and the reaction time is 4 h to 24 h.

[0044] Preferably, step 1) The molar ratio is 1:0.5~10.

[0045] Preferably, step 1) The molar ratio of the palladium catalyst is 1:0.005-1.

[0046] Preferably, the palladium catalyst in step 1) is at least one of palladium acetate, tris(dibenzylideneacetone)dipalladium, bis(dibenzylideneacetone)palladium, and [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium.

[0047] Preferably, step 1) The molar ratio of the phosphine ligand is 1:0.005-2.

[0048] Preferably, the phosphine ligand in step 1) is at least one of tri-tert-butylphosphine and tricyclohexylphosphine.

[0049] Preferably, step 1) The molar ratio of the alkali metal compound is 1:0.5-10.

[0050] Preferably, the alkali metal compound in step 1) is at least one of sodium tert-butoxide, potassium tert-butoxide, cesium carbonate, potassium carbonate, sodium hydride, and sodium hydroxide.

[0051] Preferably, in step 1) the The organic solvent of the palladium catalyst, the phosphine ligand and the alkali metal compound is at least one of toluene, dimethylbenzene, chlorobenzene and dichlorobenzene.

[0052] Preferably, the carbon-nitrogen coupling reaction in step 1) is carried out at a temperature of 80° C. to 150° C., and the reaction time is 4 h to 48 h.

[0053] Preferably, in step 2), the molar ratio of intermediate 1 to intermediate 2 is 1:0.2-4.

[0054] Preferably, in step 2), the molar ratio of the intermediate 1 to the palladium catalyst is 1:0.005-2.

[0055] Preferably, the palladium catalyst in step 2) is at least one of palladium acetate, tris(dibenzylideneacetone)dipalladium, bis(dibenzylideneacetone)palladium, and [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium.

[0056] Preferably, the organic solvent in step 2) is at least one of toluene, xylene, chlorobenzene and dichlorobenzene.

[0057] Preferably, the carbon-nitrogen coupling reaction in step 2) is carried out at a temperature of 60° C. to 150° C., and the reaction time is 4 h to 48 h.

[0058] Preferably, the acidic solvent in step 3) is at least one of hydrochloric acid, trifluoromethanesulfonic acid, and trifluoroacetic acid.

[0059] Preferably, in step 4) step a) The molar ratio of 1,3-difluoro-4,6-dibromobenzene is 1:0.8-2.

[0060] Preferably, in step 4) step a) The molar ratio of the alkali metal compound is 1:0.5-10.

[0061] Preferably, the alkali metal compound in step a) in step 4) is at least one of sodium hydride, cesium carbonate, potassium tert-butoxide, sodium tert-butoxide, and potassium carbonate.

[0062] Preferably, the organic solvent in step a) in step 4) is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, chlorobenzene, and dichlorobenzene.

[0063] Preferably, the nucleophilic substitution reaction in step a) of step 4) is carried out at a temperature of 60° C. to 180° C., and the reaction time is 4 h to 48 h.

[0064] Preferably, in step b) of step 4) The molar ratio of intermediate 5 is 1:0.5-1.

[0065] Preferably, in step b) of step 4) The molar ratio of the alkali metal compound is 1:0.5-10.

[0066] Preferably, the alkali metal compound in step b) of step 4) is at least one of sodium hydride, cesium carbonate, potassium tert-butoxide, sodium tert-butoxide, and potassium carbonate.

[0067] Preferably, the organic solvent in step b) in step 4) is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, chlorobenzene, and dichlorobenzene.

[0068] Preferably, the nucleophilic substitution reaction in step b) of step 4) is carried out at a temperature of 60° C. to 180° C., and the reaction time is 4 h to 48 h.

[0069] Preferably, the molar ratio of the intermediate 6 to the lithiation reagent in step c) of step 4) is 1:1-5.

[0070] Preferably, the lithiation reagent in step c) of step 4) is at least one of n-butyllithium and tert-butyllithium.

[0071] Preferably, the lithiation reaction in step c) of step 4) is carried out at a temperature of -78°C to 80°C, and the reaction time is 0.5h to 12h.

[0072] Preferably, the molar ratio of the intermediate 6 to the boronation reagent in step c) of step 4) is 1:1-10.

[0073] Preferably, the boronation reagent in step c) of step 4) is at least one of boron tribromide and boron triiodide.

[0074] Preferably, the borylation reaction in step c) of step 4) is carried out at a temperature of -60°C to 50°C, and the reaction time is 0.5h to 24h.

[0075] Preferably, the molar ratio of the intermediate 6 to the cyclization reagent in step c) of step 4) is 1:1-20.

[0076] Preferably, the cyclization reagent in step c) of step 4) is N,N-diisopropylethylamine.

[0077] Preferably, the organic solvent in step c) in step 4) is at least one of toluene, tert-butylbenzene, xylene, chlorobenzene, dichlorobenzene, and trichlorobenzene.

[0078] Preferably, the ring-closing reaction in step c) of step 4) is carried out at a temperature of -30°C to 180°C, and the reaction time is 8h to 24h.

[0079] Preferably, in step 4) step i) The molar ratio of 1,3-difluoro-4,6-dibromobenzene is 1:0.8~1.2:1.8~2.4.

[0080] Preferably, in step 4) step i) The molar ratio of the alkali metal compound is 1:0.5-10.

[0081] Preferably, the alkali metal compound in step i) in step 4) is at least one of sodium hydride, cesium carbonate, potassium tert-butoxide, sodium tert-butoxide, and potassium carbonate.

[0082] Preferably, the organic solvent in step i) in step 4) is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, chlorobenzene, and dichlorobenzene.

[0083] Preferably, the nucleophilic substitution reaction in step i) of step 4) is carried out at a temperature of 60° C. to 180° C., and the reaction time is 4 h to 48 h.

[0084] Preferably, the molar ratio of the intermediate 7 to the lithiation reagent in step ii) of step 4) is 1:1-5.

[0085] Preferably, the lithiating agent in step ii) of step 4) is at least one of n-butyllithium and tert-butyllithium.

[0086] Preferably, the lithiation reaction in step ii) of step 4) is carried out at a temperature of -78°C to 80°C, and the reaction time is 0.5h to 12h.

[0087] Preferably, the molar ratio of the intermediate 7 to the boronation reagent in step ii) of step 4) is 1:1-10.

[0088] Preferably, the boronation reagent in step ii) of step 4) is at least one of boron tribromide and boron triiodide.

[0089] Preferably, the borylation reaction in step ii) of step 4) is carried out at a temperature of -60°C to 50°C, and the reaction time is 0.5h to 24h.

[0090] Preferably, the molar ratio of the intermediate 7 and the cyclization reagent in step ii) in step 4) is 1:1-20.

[0091] Preferably, the cyclization reagent in step ii) of step 4) is N,N-diisopropylethylamine.

[0092] Preferably, the organic solvent in step ii) in step 4) is at least one of toluene, tert-butylbenzene, xylene, chlorobenzene, dichlorobenzene and trichlorobenzene.

[0093] Preferably, the ring-closing reaction in step ii) of step 4) is carried out at a temperature of -30°C to 180°C, and the reaction time is 8h to 24h.

[0094] An organic electroluminescent composition, comprising a host material and the above-mentioned boron-nitrogen compound; the host material is at least one of compounds H-1 to H-25 and compounds H-1 to H-25 substituted with single or multiple deuterium atoms:

[0095] Compounds H-1 to H-5:

[0096]

[0097] Compounds H-6 to H-10:

[0098]

[0099] Compounds H-11 to H-15:

[0100]

[0101] Compounds H-16 to H-20:

[0102]

[0103] Compounds H-21 to H-25:

[0104]

[0105] Preferably, the mass percentage of the boron nitrogen compound in the organic electroluminescent composition is 0.5% to 30%.

[0106] An organic electroluminescent device comprises the organic electroluminescent composition.

[0107] Preferably, the organic electroluminescent device comprises a substrate, an anode layer, an organic light-emitting functional layer and a cathode layer stacked in sequence; the organic light-emitting functional layer comprises a light-emitting layer; and the light-emitting layer comprises an organic electroluminescent composition.

[0108] Preferably, the organic light-emitting functional layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

[0109] An application of the organic electroluminescent device as described above in the preparation of a display or a lighting source.

[0110] The beneficial effects of the present invention are as follows: the boron nitrogen compound of the present invention has a double boron structure, which greatly reduces the energy level difference between singlet and triplet states, enhances the TADF performance, and reduces the lifetime of triplet excitons. The electroluminescent device made of it as a light-emitting layer material can not only achieve narrow spectrum emission, but also the electroluminescent external quantum efficiency of the device exceeds 10%, the device lifetime exceeds 300 hours, the luminous efficiency and stability are greatly improved, and it is suitable for use in OLED displays.

[0111] Note:

[0112] The "alkyl" in the present invention refers to a branched / straight chain saturated aliphatic hydrocarbon group with a specified number of carbon atoms, for example: C1~C 12 The alkyl group refers to a linear / branched alkyl group having 1 to 12 carbon atoms.

[0113] The "alkoxy group" in the present invention refers to an alkyl group connected via an oxygen bond (-O-).

[0114] The term "cycloalkyl" in the present invention refers to a cyclic aliphatic hydrocarbon group having a specified number of carbon atoms, for example: C3 to C 12 The cycloalkyl group refers to a cycloalkyl group having 3 to 12 carbon atoms.

[0115] The "aryl" in the present invention refers to an unsaturated hydrocarbon group having a specified number of carbon atoms and containing a benzene ring, for example: C6~C 30 The aryl group refers to an unsaturated hydrocarbon group having 6 to 30 carbon atoms and containing a benzene ring.

[0116] The term "heteroaryl" as used herein refers to an aromatic group whose ring atoms contain one or more heteroatoms nitrogen, oxygen and sulfur. BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Figure 1 Schematic diagram of the structure of an organic electroluminescent device.

[0118] Description of the accompanying drawings: 10, ITO anode; 20, hole injection layer; 30, first hole transport layer; 40, second hole transport layer; 50, light-emitting layer; 60, first electron transport layer; 70, second electron transport layer; 80, electron injection layer; 90, metal cathode.

[0119] Figure 2 This is the electroluminescence spectrum of an organic electroluminescent device based on the boron nitrogen compound BN-1. DETAILED DESCRIPTION

[0120] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0121] The synthetic raw materials of boron nitrogen compounds are as follows:

[0122] Raw materials A-1 to A-7:

[0123]

[0124] Raw materials B-1 to B-3:

[0125]

[0126] Raw materials C-1 to C-3:

[0127]

[0128] Ligand:

[0129] Ligand-1 to Ligand-6:

[0130]

[0131] Ligand-7 to Ligand-12:

[0132]

[0133] Ligand-13 to Ligand-17:

[0134] Ligand-18 to Ligand-24:

[0135] Synthesis of ligand:

[0136] Synthesis and characterization of ligand-1:

[0137]

[0138] Synthesis of Intermediate 1: Raw material A-1 (10.0 g, 40.6 mmol) and di-tert-butyl dicarbonate (9.8 g, 48.7 mmol) were dissolved in 400 mL of tetrahydrofuran solution. 4-Dimethylaminopyridine (0.5 g, 4.1 mmol) was added under nitrogen and refluxed for 6 h. After the reaction, tetrahydrofuran was removed by rotary evaporation, and the mixture was extracted with dichloromethane and water. The organic phase was concentrated and purified by column chromatography to obtain 12.4 g of a white solid with a yield of 85.3%. Mass spectrometry confirmed the target product, Intermediate 1, with MS: 345.05 (calculated value: 345.04).

[0139] Synthesis of Intermediate 2: Raw material B-1 (4.0 g, 43.0 mmol) and raw material C-1 (11.0 g, 51.5 mmol) were dissolved in 200 mL of toluene. Under nitrogen, sodium tert-butoxide (8.2 g, 86.0 mmol), palladium acetate (0.2 g, 0.9 mmol) and tri-tert-butylphosphine (3.6 mL, 1.8 mmol, 10% hexane solution) were added and heated to reflux for 12 h. After the reaction was completed and returned to room temperature, the mixture was washed with dichloromethane and water. The organic phase was concentrated and purified by column chromatography to obtain 9.3 g of a white solid with a yield of 96.1%. The target product, Intermediate 2, was confirmed by mass spectrometry analysis, MS: 225.08 (calculated value: 225.06).

[0140] Synthesis of Intermediate 3: Intermediate 1 (12.0 g, 34.7 mmol), Intermediate 2 (8.6 g, 38.1 mmol) and sodium tert-butoxide (5.5 g, 57.2 mmol) were dissolved in 150 mL of toluene. Under nitrogen, palladium acetate (0.2 g, 1.0 mmol) and tri-tert-butylphosphine (4.0 mL, 2.0 mmol, 10% hexane solution) were added and heated to reflux for 12 h. After the reaction was completed and returned to room temperature, the mixture was washed with dichloromethane and water. The organic phase was concentrated and purified by column chromatography to obtain 15.7 g of a white solid with a yield of 92.3%. The target product, Intermediate 3, was confirmed by mass spectrometry analysis with MS: 490.19 (calculated value: 490.17).

[0141] Synthesis of Ligand-1: Intermediate 3 (15.0 g, 30.6 mmol) was dissolved in 200 mL of tetrahydrofuran. Under nitrogen, trifluoroacetic acid (4.5 mL, 61.2 mmol) was added dropwise at room temperature and stirred for 6 h. After the reaction, the tetrahydrofuran was removed by rotary evaporation, and the solid was poured into saturated sodium bicarbonate solution. A white solid precipitated and was filtered. The filter cake was rinsed with methanol to obtain 10.3 g of a white solid with a yield of 86.3%. Mass spectrometry confirmed the target product, Ligand-1, with an MS of 390.10 (calculated value: 390.12).

[0142] Note:

[0143] The mass spectrometry test was conducted using the Maldi-TOF (Autoflex Speed) instrument from Bruker.

[0144] The ligands used in the synthesis examples of boron nitrogen compounds were all prepared according to the above preparation method, and the products were verified by mass spectrometry, as shown in the following table:

[0145] Table 1 Synthesis of ligands

[0146] ligand Raw material A Raw material B Raw material C Mass spectrometry analysis Comprehensive yield (%) Ligand-1 A-1 B-1 C-1 390.10 65.3 Ligand-2 A-2 B-1 C-1 404.15 58.4 Ligand-3 A-3 B-1 C-1 446.20 70.2 Ligand-4 A-4 B-1 C-1 446.19 66.8 Ligand-5 A-5 B-1 C-1 460.20 50.6 Ligand-6 A-6 B-1 C-1 502.22 54.1 Ligand-7 A-1 B-2 C-1 446.17 52.6 Ligand-8 A-1 B-3 C-1 418.16 53.4 Ligand-9 A-2 B-2 C-1 460.20 66.2 Ligand-10 A-5 B-2 C-1 516.25 61.3 Ligand-11 A-2 B-3 C-1 432.18 58.0 Ligand-12 A-5 B-3 C-1 488.22 59.2 Ligand-13 A-1 B-1 C-2 446.17 54.6 Ligand-14 A-2 B-1 C-2 460.18 60.1 Ligand-15 A-3 B-1 C-2 502.25 62.5 Ligand-16 A-4 B-1 C-2 502.24 61.1 Ligand-17 A-7 B-1 C-1 466.17 65.7 Ligand-18 A-1 B-1 C-3 500.22 63.2 Ligand-19 A-2 B-1 C-3 514.24 57.2 Ligand-20 A-1 B-2 C-3 556.27 55.0 Ligand-21 A-4 B-1 C-3 556.29 58.0 Ligand-22 A-1 B-2 C-2 502.23 58.9 Ligand-23 A-2 B-2 C-2 516.27 62.0 Ligand-24 A-5 B-2 C-2 572.32 64.5

[0147] Synthesis examples of boron nitrogen compounds BN-1 to BN-28:

[0148] Synthesis and characterization of boron nitrogen compound BN-1:

[0149]

[0150] Synthesis and Characterization of Compound BN-1-A: 1,5-Dibromo-2,4-difluorobenzene (3.0 g, 11.0 mmol), Ligand-1 (9.5 g, 24.3 mmol), and cesium carbonate (11.9 g, 36.4 mmol) were dissolved in 300 mL of N,N-dimethylformamide. The mixture was heated to 120°C under nitrogen and maintained for 12 hours. After the reaction was complete and cooled to room temperature, the reaction solution was poured into ice water, resulting in the precipitation of a large amount of white solid. The filter cake was then recrystallized from dichloromethane and methanol to yield 10.8 g of a white solid in a 96.6% yield. Mass spectrometry confirmed the target product, BN-1-A, with an MS of 1012.25 (calcd. 1012.17).

[0151] Synthesis and characterization of boron nitrogen compound BN-1: Compound BN-1-A (5.1 g, 5.0 mmol) was dissolved in 100 mL of tert-butylbenzene and stirred at room temperature for 30 min under nitrogen. Tert-butyllithium (11.5 mL, 1.3 M, 15.0 mmol) was then added dropwise at 0°C. After the addition was complete, the temperature was raised to 60°C and heated with stirring for 2 h. The reaction system was then lowered to 0°C and BBr3 (5.0 g, 20.0 mmol) was added dropwise. The reaction system was returned to room temperature and stirred for 1 h. The reaction system was then lowered to 0°C and N,N-diisopropylethylamine (3.1 g, 24.0 mmol) was added dropwise. The reaction system was heated to 120°C and stirred for 24 h. After the reaction was completed, methanol and water were added dropwise to quench the reaction. The system was washed with dichloromethane and water. The organic phase was concentrated and purified by column chromatography to obtain 0.5 g of a light yellow solid with a yield of 11.5%. Mass spectrometry and elemental analysis confirmed the target product, boron nitrogen compound BN-1. MS: 870.25 (calculated: 870.23); elemental analysis: C, 79.95; H, 3.78; N, 6.45; S, 7.38 (calculated: C, 80.01; H, 3.70; B, 2.48; N, 6.44; S, 7.36).

[0152] Synthesis and characterization of boron nitrogen compound BN-28:

[0153]

[0154] Synthesis and Characterization of Compound BN-28-A: 1,5-Dibromo-2,4-difluorobenzene (5.0 g, 18.4 mmol), Ligand-1 (6.5 g, 16.7 mmol), and cesium carbonate (8.2 g, 25.0 mmol) were dissolved in 200 mL of N,N-dimethylformamide. The mixture was heated to 120°C under nitrogen and maintained for 12 hours. After the reaction was complete and cooled to room temperature, the reaction solution was poured into ice water, resulting in the precipitation of a large amount of white solid. The filter cake was then recrystallized from dichloromethane and methanol to yield 10.5 g of a white solid in a 97.8% yield. Mass spectrometry confirmed the target product, BN-28-A, with an MS of 642.0 (calcd.: 641.96).

[0155] Synthesis and Characterization of Compound BN-28-B: Compound BN-28-A (10.0 g, 15.6 mmol), ligand-4 (7.6 g, 17.1 mmol), and cesium carbonate (8.4 g, 25.7 mmol) were dissolved in 300 mL of N,N-dimethylformamide. The mixture was heated to 120°C under nitrogen for 12 hours. After the reaction was complete and cooled to room temperature, the reaction solution was poured into ice water, resulting in the precipitation of a large amount of white solid. The filter cake was then recrystallized from dichloromethane and methanol to yield 15.2 g of a white solid in a 91.3% yield. Mass spectrometry confirmed the target product, BN-28-B, with an MS of 1086.05 (calculated: 1086.14).

[0156] Synthesis and Characterization of Boron Nitrogen Compound BN-28: The synthesis and characterization of compound BN-28 were similar to those of compound BN-1, except that compound BN-28-B (5.3 g, 5.0 mmol) was used instead of compound BN-1-A. The amounts of other compounds used and the synthesis method remained the same. Column chromatography yielded 0.6 g of a pale yellow solid in 13.0% yield. Mass spectrometry and elemental analysis confirmed the target product, BN-28. MS: 926.25 (calcd: 926.30); Elemental Analysis: C, 80.33; H, 4.58; N, 6.00; S, 7.01 (calcd: C, 80.35; H, 4.35; B, 2.33; N, 6.05; S, 6.92).

[0157] The synthesis of boron nitrogen compounds all followed the above preparation methods, and the products were verified by mass spectrometry, as shown in the table below:

[0158] Table 2 Synthesis of boron nitrogen compounds

[0159]

[0160]

[0161] Electroluminescent device embodiments

[0162] Representative examples of electroluminescent devices are given below, and the molecular structures of the materials involved are as follows:

[0163]

[0164] Preparation of organic electroluminescent devices:

[0165] The schematic diagram of the structure of an organic electroluminescent device is shown in Figure 1 As shown, 10 is an ITO anode, 20 is a hole injection layer, 30 is a first hole transport layer, 40 is a second hole transport layer, 50 is a light-emitting layer, 60 is a first electron transport layer, 70 is a second electron transport layer, 80 is an electron injection layer, and 90 is a metal cathode.

[0166] The preparation process of organic electroluminescent devices is as follows:

[0167] 1) Substrate Treatment: Transparent ITO glass was used as the substrate material for device preparation. It was first ultrasonically treated with a 5% ITO cleaning solution for 30 minutes, then ultrasonically cleaned with distilled water (twice), acetone (twice), and isopropyl alcohol (twice). The ITO glass was then stored in isopropyl alcohol. Before each use, the surface of the ITO glass was carefully wiped with acetone and isopropyl alcohol cotton balls, rinsed with isopropyl alcohol, and then dried. It was then treated with plasma for 5 minutes before use.

[0168] 2) A hole injection layer (4% HI:HT-1; 50 nm), a first hole transport layer (HT-1; 50 nm), a second hole transport layer (HT-2; 5 nm), a light-emitting layer (2% BN-n:BH; 20 nm), a first electron transport layer (ET-1; 5 nm), a second electron transport layer (ET-2; 25 nm), an electron injection layer (Liq; 2 nm) and a metal cathode (Al; 100 nm) were sequentially formed on the substrate using an evaporation process. The deposition rate of the organic material is The deposition rate of LiF is The deposition rate of Al is

[0169] The current, voltage, brightness, and luminescence spectrum of organic electroluminescent devices were tested synchronously using a Photo Research PR655 spectrum scanning luminance meter and a Keithley K 2400 digital source meter.

[0170] The performance test of the organic electroluminescent device was carried out at room temperature and in air atmosphere.

[0171] The external quantum efficiency (EQE) of an organic electroluminescent device is calculated from the current density, brightness, and electroluminescent spectrum combined with the visibility function when the luminescence is a Lambertian distribution.

[0172] Test results:

[0173] 1) The electroluminescence spectrum of the organic electroluminescent device based on the boron nitrogen compound BN-1 is as follows Figure 2 shown.

[0174] Depend on Figure 2 It can be seen that the emission peak of the organic electroluminescent device is located at 461 nm, and the half-peak width is 20 nm.

[0175] 2) Organic electroluminescent device Dm (m = 1 to 28):

[0176] The structure of the organic electroluminescent device Dm is as follows:

[0177] [ITO / 4%HI:HT-1(50nm) / HT-1(50nm) / HT-2(5nm) / 2%BN-n(n=1~28):BH(20nm) / ET-1(5nm) / ET-2(25nm) / Liq(2nm) / Al(100nm)].

[0178] The performance test data of the organic electroluminescent device Dm are as follows (the driving voltage is the device current density is 10mA / cm 2 Under the voltage, the device life T 95 Refers to the current density of 10mA / cm 2 The time required for the device brightness to decrease to 95% of the initial brightness under the conditions of

[0179] Table 3 Performance test data of organic electroluminescent device Dm

[0180]

[0181]

[0182] Comparative example of organic electroluminescent device:

[0183] The same device structure was used for the preparation and characterization of comparative devices. The specific results are shown in the following table:

[0184] Table 4 Comparison of performance test data of organic electroluminescent devices

[0185]

[0186] As shown in Tables 3 and 4, the boron nitrogen compound of the present invention, when used in organic electroluminescent devices, shows obvious technical advantages in terms of driving voltage, efficiency, device life, etc. The driving voltage is as low as below 3.64 V, the maximum current efficiency is above 7 cd / A, and the device life is above 320 h.

[0187] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A boron-nitrogen compound, characterized in that: The structural formula is: In the formula, R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, C1-C 16 Alkyl, C3~C 20 Cycloalkyl, C6~C 30 Aryl, single or multiple R a Substituted C6~C 18 aryl, 5- to 18-membered heteroaryl, single or multiple R a One of the substituted 5- to 18-membered heteroaryl groups, R a For deuterium, fluorine, C1~C 12 Alkyl, C1~C 12 Alkoxy, C3~C 12 Cycloalkyl, C6~C 14 One of the aromatic groups.

2. The boron-nitrogen compound according to claim 1, wherein: The R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, Cl~C 10 Alkyl, C3~C 10 Cycloalkyl, C6~C 14 Aryl, single or multiple R a Substituted C6~C 18 aryl, 5- to 18-membered heteroaryl, single or multiple R a One of substituted 5- to 18-membered heteroaryl groups.

3. The boron-nitrogen compound according to claim 2, wherein: Said R1, R2, R3, R4, R5, R6, R7 and R8 are independently H, methyl, tert-butyl, adamantyl, cyclohexyl, phenyl, One of the following, * indicates the connection site.

4. The boron-nitrogen compound according to claim 3, wherein: The boron nitrogen compound is any one of compounds BN-1 to BN-28: Compounds BN-1 to BN-4: Compounds BN-5 to BN-8: Compounds BN-9 to BN-12: Compounds BN-13 to BN-16: Compounds BN-17 to BN-20: Compounds BN-21 to BN-24: Compounds BN-25 to BN-28:

5. A method for preparing a boron nitrogen compound according to claim 1, characterized in that: The following steps are involved: 1) Preparation of intermediate 1 and intermediate 2: Preparation of intermediate 1: Di-tert-butyl dicarbonate and 4-dimethylaminopyridine are dispersed in an organic solvent to carry out amino protection reaction to obtain It is recorded as intermediate 1; Preparation of intermediate 2: Palladium catalyst, phosphine ligand and alkali metal compound are dispersed in organic solvent to carry out carbon-nitrogen coupling reaction to obtain It is recorded as intermediate 2; 2) Dispersing intermediate 1, intermediate 2 and palladium catalyst in an organic solvent to carry out carbon-nitrogen coupling reaction to obtain It is recorded as intermediate 3; 3) The intermediate 3 is added to an acidic solvent for deprotection to obtain It is recorded as intermediate 4; 4) Preparation of asymmetric boron-nitrogen compounds and symmetric boron-nitrogen compounds: Preparation of asymmetric boron-nitrogen compounds: a) 1,3-Difluoro-4,6-dibromobenzene and an alkali metal compound are dispersed in an organic solvent to undergo a nucleophilic substitution reaction to obtain It is recorded as intermediate 5; b) Intermediate 5 and an alkali metal compound are dispersed in an organic solvent to undergo a nucleophilic substitution reaction. Different, get It is recorded as intermediate 6; c) dispersing the intermediate 6, a lithiation reagent, a boration reagent, and a cyclization reagent in an organic solvent to carry out lithiation reaction, boration reaction, and cyclization reaction to obtain an asymmetric boron nitrogen compound; Preparation of symmetrical boron-nitrogen compounds: i) will 1,3-Difluoro-4,6-dibromobenzene and alkali metal compounds are dispersed in an organic solvent to undergo a nucleophilic substitution reaction. Same, get It is designated as intermediate 7; ii) The intermediate 7, a lithiation agent and a boration agent are dispersed in an organic solvent to carry out lithiation reaction, boration reaction and ring-closure reaction to obtain a boron-nitrogen compound with a symmetrical structure.

6. The preparation method according to claim 5, characterized in that: Step 1) The molar ratio of di-tert-butyl dicarbonate is 1:1-10; the amino protection reaction in step 1) is carried out under reflux of the organic solvent, and the reaction time is 4h-24h; the step 1) The molar ratio of the intermediate 1 and the intermediate 2 is 1:0.2 to 4; the carbon-nitrogen coupling reaction is carried out at a temperature of 60°C to 150°C for a reaction time of 4h to 48h; the molar ratio of the intermediate 1 and the intermediate 2 is 1:0.2 to 4; the carbon-nitrogen coupling reaction is carried out at a temperature of 60°C to 150°C for a reaction time of 4h to 48h; the step a) in step 4) The molar ratio of 1,3-difluoro-4,6-dibromobenzene is 1:0.8-2; the nucleophilic substitution reaction in step a) of step 4) is carried out at a temperature of 60°C to 180°C and the reaction time is 4h to 48h; the nucleophilic substitution reaction in step b) of step 4) is carried out at a temperature of 60°C to 180°C and the reaction time is 4h to 48h; The molar ratio of intermediate 5 is 1:0.5-1; the nucleophilic substitution reaction in step b) of step 4) is carried out at a temperature of 60°C to 180°C, and the reaction time is 4h to 48h; the lithiation reaction in step c) of step 4) is carried out at a temperature of -78°C to 80°C, and the reaction time is 0.5h to 12h; the borylation reaction in step c) of step 4) is carried out at a temperature of -60°C to 50°C, and the reaction time is 0.5h to 24h; the ring-closing reaction in step c) of step 4) is carried out at a temperature of -30°C to 180°C, and the reaction time is 8h to 24h; the step i) of step 4) is carried out The molar ratio of 1,3-difluoro-4,6-dibromobenzene is 1:0.8~1.2:1.8~2.4; the nucleophilic substitution reaction in step i) of step 4) is carried out at a temperature of 60°C to 180°C, and the reaction time is 4h to 48h; the lithiation reaction in step ii) of step 4) is carried out at a temperature of -78°C to 80°C, and the reaction time is 0.5h to 12h; the borylation reaction in step ii) of step 4) is carried out at a temperature of -60°C to 50°C, and the reaction time is 0.5h to 24h; the cyclization reaction in step ii) of step 4) is carried out at a temperature of -30°C to 180°C, and the reaction time is 8h to 24h.

7. An organic electroluminescent composition, characterized in that The composition includes a main material and the boron nitrogen compound according to any one of claims 1 to 4; the main material is at least one of compounds H-1 to H-25 and compounds H-1 to H-25 substituted with single or multiple deuterium atoms: Compounds H-1 to H-5: Compounds H-6 to H-10: Compounds H-11 to H-15: Compounds H-16 to H-20: Compounds H-21 to H-25:

8. An organic electroluminescent device, characterized in that: The organic electroluminescent composition according to claim 7 is included.

9. The organic electroluminescent device according to claim 8, wherein: The organic electroluminescent device comprises a substrate, an anode layer, an organic light-emitting functional layer and a cathode layer stacked in sequence; the organic light-emitting functional layer comprises a light-emitting layer; and the light-emitting layer contains an organic electroluminescent composition.

10. Use of the organic electroluminescent device according to claim 8 or 9 in preparing a display or a lighting source.

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