Boron difluoride imidazole heterocyclic compound and electroluminescent device thereof

Abstract

The invention belongs to the technical field of organic light-emitting materials and semiconductors, and particularly relates to a difluoro-boron imidazole heterocyclic compound and an electroluminescent device thereof. The structural general formula of the difluoro-boron imidazole heterocyclic compound is as shown in the general formula 1. According to the difluoro-boron imidazole heterocyclic compound provided by the invention, a TADF object structure material taking a benzimidazole difluoro-boron heterocyclic ring as a skeleton is subjected to precise functional modification on a 12-site of a host structure, so that the TADF object structure material can be used as an electron acceptor when being connected with an electron-donating group; and when connected with an electron withdrawing group, the compound can be used as an electron donor to form a bidirectionally adjustable D-A type TADF molecular design, so that the difluoro-boron imidazole heterocyclic compound and an electroluminescent device prepared by taking the difluoro-boron imidazole heterocyclic compound as a guest luminescent material are obtained, and the technical problems that the existing TADF is low in luminous efficiency, short in service life and poor in luminous color purity are solved.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting materials and semiconductor technology, specifically relating to a difluoroboron zimidazole heterocyclic compound and its electroluminescent device. Background Technology

[0002] In recent years, organic light-emitting diodes (OLEDs) have attracted much attention in the lighting and display fields due to their outstanding characteristics such as self-emission, high brightness, high contrast, flexibility, and low power consumption. With continuous technological advancements, thermally activated delayed fluorescence (TADF) materials, as third-generation OLED light-emitting materials, have gradually become a research hotspot. These materials possess a relatively small singlet-triplet energy level difference (Δ...). E st It can convert triplet excitons into singlet excitons through an anti-intersystem crossing mechanism, theoretically achieving 100% internal quantum efficiency, and is therefore regarded as a highly promising new generation of luminescent materials.

[0003] Currently, most organic TADF materials employ a donor-acceptor (DA) molecular configuration to reduce the overlap between HOMO and LUMO orbitals, thereby reducing Δ E st However, these materials generally exhibit intramolecular charge transfer effects, making them prone to structural relaxation in the excited state. This leads to problems such as large Stokes shift, broadened emission spectra, and increased full width at half maximum (FWHM). These optical defects mean that OLED devices based on TADF materials still face challenges such as rapid efficiency degradation and insufficient device lifetime in practical applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a difluoroboron zimidazole heterocyclic compound and its electroluminescent device, thereby solving the technical problems of low luminous efficiency and low device lifetime of existing boron-oxygen-containing compounds as luminescent materials.

[0005] The first object of the present invention is to provide a difluoroboron zimidazole heterocyclic compound, the general structural formula of which is shown in Formula 1: .

[0006] Ar1 is selected from one of substituted or unsubstituted C5-C40 aryl groups or substituted or unsubstituted C5-C40 heteroaryl groups, wherein the heteroatom in the heteroaryl group is N, O, S, Si or P; X is selected from CR1R2, O, S, Se or SiR1R2; R1 and R2 are each independently selected from C1-C20 straight-chain alkyl groups, C1-C20 alkoxy groups, C1-C20 thioalkoxy groups, C3-C20 branched alkyl groups, C3-C20 cyclic alkyl groups, C3-C20 branched alkoxy groups, C3-C20 cyclic alkoxy groups, C3-C20 branched thioalkoxy groups or C3-C20 cyclic thioalkoxy groups.

[0007] Furthermore, R1 and R2 are each independently selected from C1~C6 straight-chain alkyl, C1~C6 straight-chain alkoxy, C3~C6 branched alkyl, C3~C6 cyclic alkyl, C3~C6 branched alkoxy, C3~C6 cyclic alkoxy, and C1~C3 straight-chain thioalkoxy.

[0008] Furthermore, Ar1 is selected from one of the following groups: ; in," "This is the bonding site. In each Ar1 group, there is a bonding site through any one of the " "Bonded with the main structure; R0 is selected from H, D, substituted or unsubstituted C3-C30 aromatic groups, substituted or unsubstituted C3-C30 heteroaromatic groups, substituted or unsubstituted C3-C30 aromatic amine groups, straight-chain alkyl groups having C1-C20, branched alkyl groups having C1-C20, alkoxy groups having C1-C20, thioalkoxy groups having C1-C20, and substituted silyl groups having C1-C20; the substituent is selected from at least one of carbonyl, alkoxy, aromatic carbonyl, cyano, formyl, isocyano, and -CF3."

[0009] Furthermore, R0 is selected from H, D, substituted or unsubstituted C6~C16 aromatic groups, C6~C16 heteroaromatic groups, C6~C16 aromatic amine groups, C1~C8 straight-chain alkyl groups, C3~C8 branched-chain alkyl groups, C1~C8 straight-chain alkoxy groups, C3~C8 branched-chain alkoxy groups, C1~C4 thioalkoxy groups, and C1~C8 substituted silyl groups; wherein, the substituent is selected from one or two of carbonyl, -CF3, cyano, and formyl groups, and the substituent on the C6~C16 aromatic group, C6~C16 heteroaromatic group, or C6~C16 aromatic amine group is substituted only on the aromatic group, heteroaromatic group, or aromatic amine group.

[0010] Furthermore, the difluoroboronimidazole heterocyclic compound is selected from one of the following compounds: .

[0011] The second objective of this invention is to provide an electroluminescent device comprising an anode layer and a cathode layer, and an organic layer disposed between the anode layer and the cathode layer; the organic layer, from bottom to top along the direction from the anode layer to the cathode layer, comprises a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and the light-emitting layer is prepared from a host light-emitting material and a guest light-emitting material, the guest light-emitting material comprising the aforementioned difluoroboronimidazole heterocyclic compound.

[0012] Furthermore, the mass of the guest luminescent material accounts for 0.1 wt.% to 3.0 wt.% of the mass of the luminescent layer.

[0013] In this invention, the electroluminescent device comprises, from the anode layer to the cathode layer, a substrate, an anode layer, a hole injection layer (HIL), a hole transport layer, an electron blocking layer (EBL), an emission material layer (EML), a hole blocking layer (HBL), an electron transport layer, an electron injection layer (EIL), and a cathode layer, which are stacked sequentially. The substrate needs to possess high mechanical strength, excellent thermal stability, excellent water resistance, and excellent transparency. As a preferred embodiment of this invention, the substrate is made of polyethylene terephthalate (PET) plastic.

[0014] In this invention, to facilitate the injection of holes into the organic layer, the anode layer material is preferably a material with a high work function, achieved by sputtering or depositing a specific functional layer material on the substrate. Specific examples of anode layer materials that can be used in this invention include: metals such as vanadium, chromium, copper, zinc, and gold, or their alloys; oxides such as zinc oxide, aluminum oxide, or tin dioxide; and conductive polymers such as polypyrrole and polyaniline.

[0015] In this invention, the compounds in the organic layers, except for the light-emitting layer, can be small organic molecules, large organic molecules, polymers, or combinations thereof. The materials used for the hole injection layer, hole transport layer, electron blocking layer, electron transport layer, and electron injection layer are selected from industry-leading cost-effective materials. The compatibility between the layers needs to be determined through a series of tests and screening processes.

[0016] Preferably, the material of the hole injection layer in this invention is: .

[0017] Preferably, the hole transport layer in this invention is selected from one of the following materials: .

[0018] Preferably, the material of the electron blocking layer in this invention is selected from one of the following materials: .

[0019] Preferably, the material of the hole-blocking layer in this invention is selected from one of the following materials: .

[0020] Preferably, the electron transport layer in this invention is selected from one of the following materials: .

[0021] In this invention, the material of the electron injection layer is Liq.

[0022] In this invention, the cathode layer material is preferably a material with a low work function in order to facilitate the injection of electrons into the functional organic layer. Specific examples of cathode layer materials that can be used in this invention include: metals or alloys thereof such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and lead, for example, Mg-Al, Mg-Ag, etc.

[0023] Furthermore, the host luminescent material is selected from one or two of the following compounds: .

[0024] Compared with the prior art, the present invention has the following beneficial effects: The difluoroboron difluoroboron heterocyclic compounds provided by this invention are centered on a class of TADF materials with a benzimidazole difluoroboron heterocycle as the backbone. The key to their molecular design lies in the precise functionalization modification of the 12-position of the main structure: when an electron-donating group is attached, the main unit can act as an electron acceptor; when an electron-withdrawing group is attached, it can act as an electron donor. This bidirectionally tunable molecular design provides a broad platform for achieving highly efficient TADF properties. The main structure, the benzimidazole difluoroboron heterocycle, itself has a certain rigidity, and the steric hindrance of the 12-position substituent effectively restricts intramolecular vibrations and rotations, reduces non-radiative transition pathways, improves radiative transition efficiency, and enhances luminescence efficiency.

[0025] The difluoroboronimazole heterocyclic compound provided by this invention has a main structure of benzimidazole difluoroboron heterocyclic. Through the rational design of the substituent at the 12-position, the degree of conjugation and the range of electron delocalization of the molecule are adjusted, which helps to achieve narrow-band emission and thus improve the color purity of the emitted light.

[0026] This invention uses difluoroboronimazole heterocyclic compounds as guest light-emitting materials to prepare electroluminescent devices. The luminous efficiency of the devices is effectively improved, the service life is extended, the light emitted by the devices has good color purity, and the emission wavelength of the electroluminescent devices is in the blue light range. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the electroluminescent device of the present invention.

[0028] Figure 2 This is the NMR spectrum of compound 1 of the present invention.

[0029] Figure 3 This is the NMR spectrum of compound 10 of the present invention.

[0030] Figure 4 This is the NMR spectrum of compound 23 of the present invention.

[0031] Figure label: 1-Substrate, 2-Anode layer, 3-Hole injection layer, 4-Hole transport layer, 5-Electron blocking layer, 6-Light emitting layer, 7-Hole blocking layer, 8-Electron transport layer, 9-Electron injection layer, 10-Cathode layer. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] It should be noted that the following embodiments use conventional instruments and equipment in the art. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Process equipment or apparatus in the following embodiments, unless otherwise specified, are all conventional equipment or apparatus in the art. All raw materials used in the following embodiments are conventional commercially available products with specifications in the art.

[0034] It should be noted that the English name for high performance liquid chromatography is High Performance Liquid Chromatography, abbreviated as HPLC; and the English name for liquid chromatography-mass spectrometry is Liquid Chromatograph-Mass Spectrometer, abbreviated as LC-MS.

[0035] This invention uses a series of difluoroboron zimidazole heterocycles as the matrix, and through substitution and functionalization modification at the 12-position, introduces a series of electron-donating / electron-withdrawing substituents to construct DA-type TADF molecules. The raw materials for difluoroboron zimidazole heterocycle compounds are simple and readily available, the preparation method is simple, the reaction route is short, the post-processing is simple, the yield is high, and it is easy to realize the large-scale production of difluoroboron zimidazole heterocycle compounds.

[0036] The specific synthetic route for intermediate A1 is shown below: .

[0037] The specific synthesis process is as follows: Step 1: Synthesis of intermediate A1-1: Under nitrogen protection, a1 (10.81 g, 0.1 mol), a2 (32.10 g, 0.1 mol), and 250 mL of toluene were added to a 500 mL three-necked flask. The mixture was stirred until the solution was clear. Pd2(dba)3 (1.83 g, 2 mmol), Am-phos (1.33 g, 5 mmol), and sodium tert-butoxide (19.22 g, 0.2 mol) were added. The reaction mixture was heated to 120 °C and reacted for 10 h. After the reaction was completed, the mixture was filtered while hot using diatomaceous earth. The filtrate was cooled to room temperature and washed with purified water. After separation, the organic phase was retained, and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, concentrated, and column filtered (petroleum ether / dichloromethane = 15:1) to obtain intermediate A1-1, weighing 28.28 g, with a yield of 81%, HPLC purity of 98%, and LC-MS showing a molecular weight of 349.16.

[0038] Step 2, Synthesis of Intermediate A1-2: Intermediate A1-1 (34.92 g, 0.1 mol), triethyl orthoformate (32 mL, 0.2 mol), THF (tetrahydrofuran: 500 mL), and p-toluenesulfonic acid (0.38 g, 2 mmol) were added sequentially to a 1000 mL three-necked flask. The mixture was stirred and heated to 80 °C for 0.5 hours. After the reaction was completed, 20 mL of water was added to quench the reaction, followed by 300 mL of ethyl acetate and 300 mL of saturated brine. The mixture was extracted, and the aqueous phase was extracted twice more with 300 mL of ethyl acetate each. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (petroleum ether / dichloromethane = 12:1) to obtain intermediate A1-2, weighing 28.01 g, with a yield of 78%, HPLC purity of 98%, and LC-MS showing a molecular weight of 359.14.

[0039] Step 3, Synthesis of Intermediate A1: A1-2 (35.91 g, 0.1 mol) and 250 mL THF were added to a 500 mL flask and stirred. Freshly prepared lithium diisopropylamino (approximately 1.5 M tetrahydrofuran solution, 73.3 mL, 0.11 mol) was carefully added at -78 °C. The reaction mixture was stirred at the same temperature for 1 hour. Then, iodine (27.89 g, 0.11 mmol) was added in a single addition at -78 °C. The resulting mixture was slowly heated to room temperature, and the reaction was terminated with water-soluble Na2S2O3 solution. After extraction with ethyl acetate, the combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure to obtain a crude solid. This solid was then purified by silica gel column chromatography (n-hexane / ethyl acetate = 5 / 1) to obtain intermediate A1, weighing 35.41 g, with a yield of 73%, HPLC purity of 98%, and LC-MS showing a molecular weight of 485.04.

[0040] The synthesis method and specific synthetic route of intermediate A2 are shown below: .

[0041] The specific synthesis process is as follows: Step 1: Synthesis of intermediate A2-1: Under nitrogen protection, a1 (10.81 g, 0.1 mol), a3 (32.30 g, 0.1 mol), and 250 mL of toluene were added to a 500 mL three-necked flask. The mixture was stirred until the solution was clear. Pd2(dba)3 (1.83 g, 2 mmol), Am-phos (1.33 g, 5 mmol), and sodium tert-butoxide (19.22 g, 0.2 mol) were added. The reaction mixture was heated to 120 °C and reacted for 10 h. After the reaction was completed, the mixture was filtered while hot using diatomaceous earth. The filtrate was cooled to room temperature and washed with purified water. After separation, the organic phase was retained, and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, concentrated, and column filtered (petroleum ether / dichloromethane = 15:1) to obtain intermediate A2-1, weighing 29.85 g, with a yield of 85%, HPLC purity of 98%, and LC-MS showing a molecular weight of 351.17.

[0042] Step 2, Synthesis of Intermediate A2-2: Intermediate A2-1 (35.12 g, 0.1 mol), triethyl orthoformate (32 mL, 0.2 mol), and TMF (500 mL) were added sequentially to a 1000 mL three-necked flask. Toluenesulfonic acid (0.38 g, 2 mmol) was added, and the mixture was stirred. The reaction system was heated to 80 °C and reacted for 0.5 hours. After the reaction was complete, 20 mL of water was added to quench the reaction, followed by 300 mL of ethyl acetate and 300 mL of saturated brine. The mixture was extracted, and the aqueous phase was extracted twice more with 300 mL of ethyl acetate (2 mL each). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (petroleum ether / dichloromethane = 12:1) to obtain intermediate A2-2, weighing 31.78 g, with a yield of 88%, HPLC purity of 98%, and LC-MS showing a molecular weight of 361.16.

[0043] Step 3, Synthesis of Intermediate A2: A2-2 (36.12 g, 0.1 mol) and 250 mL of THF were added to a 500 mL flask and stirred. Freshly prepared lithium diisopropylamino (approximately 1.5 M tetrahydrofuran solution, 73.3 mL, 0.11 mol) was carefully added at -78 °C. The reaction mixture was stirred at the same temperature for 1 hour. Then, iodine (27.89 g, 0.11 mmol) was added in a single addition at -78 °C. The resulting mixture was slowly heated to room temperature, and the reaction was terminated with water-soluble Na2S2O3 solution. After extraction with ethyl acetate, the combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure to obtain a crude solid. This solid was then purified by silica gel column chromatography (n-hexane / ethyl acetate = 5 / 1) to obtain intermediate A2, weighing 36.53 g, with a yield of 75%, HPLC purity of 98%, and LC-MS showing a molecular weight of 487.05.

[0044] The synthesis method and specific synthetic route of intermediate A3 are shown below: .

[0045] The specific synthesis process is as follows: Step 1: Synthesis of intermediate A3-1: Under nitrogen protection, a1 (10.81 g, 0.1 mol), a4 (33.70 g, 0.1 mol), and 250 mL of toluene were added to a 500 mL three-necked flask. The mixture was stirred until the solution was clear. Pd2(dba)3 (1.83 g, 2 mmol), Am-phos (1.33 g, 5 mmol), and sodium tert-butoxide (19.22 g, 0.2 mol) were added. The reaction mixture was heated to 120 °C and reacted for 10 h. After the reaction was completed, the mixture was filtered while hot using diatomaceous earth. The filtrate was cooled to room temperature and washed with purified water. The organic phase was separated and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, concentrated, and column filtered (petroleum ether / dichloromethane = 15:1) to obtain intermediate A3-1, weighing 31.04 g, with a yield of 85%, an HPLC purity of 98%, and a molecular weight of 365.15 as shown by LC-MS.

[0046] Step 2, Synthesis of Intermediate A3-2: Intermediate A3-1 (36.52 g, 0.1 mol), triethyl orthoformate (32 mL, 0.2 mol), tetrahydrofuran (500 mL), and p-toluenesulfonic acid (0.38 g, 2 mmol) were added sequentially to a 1000 mL three-necked flask. The mixture was stirred and the reaction system was heated to 80 °C for 0.5 hours. After the reaction was completed, 20 mL of water was added to quench the reaction, followed by 300 mL of ethyl acetate and 300 mL of saturated brine. The mixture was extracted, and the aqueous phase was extracted twice more with 300 mL of ethyl acetate each. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (petroleum ether / dichloromethane = 12:1) to obtain intermediate A3-2, weighing 33.01 g, with a yield of 88%, HPLC purity of 98%, and LC-MS showing a molecular weight of 375.14.

[0047] Step 3, Synthesis of Intermediate A3: A3-2 (37.51 g, 0.1 mol) and 250 mL THF were added to a 500 mL flask and stirred. Freshly prepared lithium diisopropylamino (approximately 1.5 M tetrahydrofuran solution, 73.3 mL, 0.11 mol) was carefully added at -78 °C. The reaction mixture was stirred at the same temperature for 1 hour. Then, iodine (27.89 g, 0.11 mmol) was added in a single batch at -78 °C. The resulting mixture was slowly heated to room temperature, and the reaction was terminated with water-soluble Na2S2O3 solution. After extraction with ethyl acetate, the combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure to obtain a crude solid. This solid was then purified by silica gel column chromatography (n-hexane / ethyl acetate = 5 / 1) to obtain intermediate A3, weighing 39.08 g, with a yield of 78%, HPLC purity of 98%, and LC-MS showing a molecular weight of 501.03.

[0048] The synthesis of other intermediates (A4~A34) is based on the synthesis process of intermediates A1, A2, and A3. The corresponding starting material compound a (a1~a35) is selected during the synthesis process.

[0049] The structural formulas of compounds a1~a35 are shown below: .

[0050] The structural formulas of intermediates A4 to A34 are shown below: .

[0051] The specific synthetic route for intermediate M1 is shown below: .

[0052] The specific synthesis process is as follows: Under nitrogen protection, add b1 (22.60 g, 0.1 mol) to a flask containing 250 mL THF. Start stirring and lower the reaction temperature to -78 °C. Then, add n-butyllithium (approximately 2.5 M tetrahydrofuran solution, 44 mL, 0.11 mol) dropwise. After the addition is complete, continue stirring at -78 °C for 30 min. At this point, the solution is pale yellow. Then, add trimethyl borate (11.43 g, 0.11 mol) dropwise. After the addition is complete, continue stirring at -78 °C for 1 h. Then, slowly raise the temperature to 0 °C (ice bath) and stir for 2 h. After the reaction was completed, the reaction mixture was allowed to naturally heat to room temperature. Dilute hydrochloric acid was added to quench the reaction, followed by extraction with ethyl acetate and saturated brine. The aqueous phase was then extracted twice more with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (petroleum ether / dichloromethane = 12:1) to obtain intermediate M1, weighing 16.33 g, with a yield of 85%, an HPLC purity of 98%, and a molecular weight of 192.06 as shown by LC-MS.

[0053] The synthesis method of intermediate M2, and the specific synthetic route are shown below: .

[0054] The specific synthesis process is as follows: Under nitrogen protection, add b2 (24.39 g, 0.1 mol) to a flask containing 250 mL THF. Start stirring and lower the reaction temperature to -78 °C. Then, add n-butyllithium (approximately 2.5 M tetrahydrofuran solution, 44 mL, 0.11 mol) dropwise. After the addition is complete, continue stirring at -78 °C for 30 min. At this point, the solution is pale yellow. Then, add trimethyl borate (11.43 g, 0.11 mol) dropwise. After the addition is complete, continue stirring at -78 °C for 1 h. Then, slowly raise the temperature to 0 °C (ice bath) and stir for 2 h. After the reaction was completed, the reaction mixture was allowed to naturally heat to room temperature. Dilute hydrochloric acid was added to quench the reaction, followed by extraction with ethyl acetate and saturated brine. The aqueous phase was then extracted twice more with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (petroleum ether / dichloromethane = 12:1) to obtain intermediate M2, weighing 17.27 g, with a yield of 83%, HPLC purity of 98%, and LC-MS showing a molecular weight of 208.04.

[0055] The synthesis of other intermediates (M3~M5) follows the same process as that of intermediates M1 and M2, with the corresponding starting material compound b (b3~b5) selected during the synthesis process.

[0056] The structural formulas of compounds b3~b5 are shown below: .

[0057] The structural formulas of intermediates M3 to M5 are shown below: .

[0058] The following describes the specific method for synthesizing difluoroboronimidazolium heterocyclic compounds using the aforementioned intermediates A and M.

[0059] Example 1 The synthetic route for the difluoroboronimidazole heterocyclic compound (compound 1) is shown below: .

[0060] The specific synthesis process is as follows: Step 1: Synthesis of intermediate compound 11: Under nitrogen protection, intermediate M1 (192.06 g, 1 mol), intermediate A1 (485.04 g, 1 mol), potassium phosphate (424.67 g, 2.0 mol), 3 L of tetrahydrofuran, 0.5 L of deionized water, and Pd(PPh3)4 (11.67 g, 0.01 mol) were added to a 5 L three-necked flask. The system was heated to reflux and the reaction was continued for 18 h until completion. The reaction solution was washed with water and separated. The organic phase was passed through a diatomaceous earth funnel, and the filtrate was collected. The filtrate was concentrated under reduced pressure to obtain a crude solid. 3 L of an appropriate proportion of ethyl acetate / petroleum ether solution was added, and the mixture was dispersed and slurried. The mixture was filtered to obtain intermediate compound 11, weighing 378.89 g, with a yield of 75%, HPLC purity of 99%, and LCMS showing a molecular weight of 505.18.

[0061] Step 2, Synthesis of Intermediate Compound 12: Under nitrogen protection, intermediate compound 1-1 (5.05 g, 0.01 mol) and 250 mL of dichloromethane (DCM) were added to a 500 mL three-necked flask. After cooling to 0 °C in an ice-water bath, BBr3 (1 mL, 0.01 mol) was added dropwise with thorough stirring. After the addition was complete, the reaction solution was allowed to slowly rise to room temperature and the reaction continued for 12 h until completion. The reaction solution was washed with water and separated. The organic phase was passed through a diatomaceous earth funnel, and the filtrate was collected. The filtrate was concentrated under reduced pressure to obtain a crude solid. 1 L of an appropriate proportion of ethyl acetate / petroleum ether solution was added, and the mixture was dispersed and slurried. The mixture was filtered to obtain intermediate compound 12, weighing 3.93 g, with a yield of 80%, HPLC purity of 99%, and LCMS molecular weight of 491.16.

[0062] Step 3: Synthesis of difluoroboronimidazolium heterocyclic compound (compound 1): Under nitrogen protection, 1-2 (4.91 g, 0.01 mol), 500 mL of dry DCM, and 12.56 mL of Et2O·BF3 (0.1 mol) were added to a 500 mL three-necked flask. The mixture was stirred at room temperature for 9 h, then DIPEA (N,N-diisopropylethylamine: 26.1 mL, 0.15 mol) was added, and the mixture was stirred for another 35 h. The reaction was monitored by TLC until the starting material was completely consumed. The reaction was then quenched with water, followed by extraction three times with CH2Cl2, drying with Na2SO4, filtering, and concentrating the filtrate under reduced pressure. The mixture was then concentrated, and the residue was purified by silica gel column chromatography using petroleum ether / ethyl acetate = 20:1 and petroleum ether / dichloromethane = 10:1-1:1 as eluents to give compound 1, weighing 4.37 g, with a yield of 81%, HPLC purity of 99%, and LCMS showing a molecular weight of 539.16.

[0063] The 1H NMR data of compound 1 are as follows Figure 2 As shown: 1 H NMR (500 MHz, Chloroform-d ) δ 8.10(dd, J = 7.8, 1.2 Hz, 2H), 8.02 (dt, J = 7.1, 0.6 Hz, 1H), 7.80 (dt, J = 9.2, 0.8Hz, 1H), 7.69 (dd, J = 6.3, 1.6 Hz, 2H), 7.63 – 7.51 (m, 3H), 7.45 – 7.39 (m,2H), 7.38 – 7.32 (m, 4H), 7.32 – 7.23 (m, 3H), 7.19 (td, J = 7.0, 0.7 Hz, 1H), 6.96 (td, J = 7.1, 1.7 Hz, 1H).

[0064] Example 2 The synthetic route for the difluoroboronimidazole heterocyclic compound (compound 10) is shown below: .

[0065] The specific synthesis process is as follows: Step 1: Synthesis of intermediate compound 10-1: Under nitrogen protection, intermediate M5 (234.09 g, 1 mol), intermediate A2 (487.05 g, 1 mol), potassium phosphate (424.67 g, 2.0 mol), 3 L of tetrahydrofuran, 0.5 L of deionized water, and Pd(PPh3)4 (11.67 g, 0.01 mol) were added to a 5 L three-necked flask. The system was heated to reflux and the reaction was continued for 18 h until completion. The reaction solution was washed with water and separated. The organic phase was passed through a diatomaceous earth funnel, and the filtrate was collected. The filtrate was concentrated under reduced pressure to obtain a crude solid. 3 L of an appropriate proportion of ethyl acetate / petroleum ether solution was added, and the mixture was dispersed and slurried. The mixture was filtered to obtain intermediate compound 101, weighing 455.85 g, with a yield of 83%, HPLC purity of 99%, and LCMS showing a molecular weight of 549.22.

[0066] Step 2, Synthesis of intermediate compound 10-2: Under nitrogen protection, intermediate compound 10-1 (5.49 g, 0.01 mol) and 250 mL of DCM were added to a 1 L three-necked flask. After cooling to 0 °C in an ice-water bath, TMSI (3 mL, 0.02 mol) was added dropwise with thorough stirring. After the addition was complete, the reaction solution was allowed to slowly rise to room temperature and the reaction continued for 2 days until completion. The reaction solution was added to a saturated sodium bicarbonate aqueous solution, and the mixture was extracted with diethyl ether. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure to obtain a crude solid. The crude solid was purified by silica gel column chromatography (15% ethyl acetate / n-hexane) to obtain intermediate compound 102, weighing 4.34 g, with a yield of 81%, HPLC purity of 99%, and LCMS molecular weight of 535.21.

[0067] Step 3: Synthesis of the difluoroboronimidazolium heterocyclic compound (compound 10): Under nitrogen protection, intermediate compound 10⁻² (5.35 g, 0.01 mol), 500 mL of dry DCM, and Et₂O·BF₃ (12.56 mL, 0.1 mol) were added to a 500 mL three-necked flask. The mixture was stirred at room temperature for 9 h, then DIPEA (26.1 mL, 0.15 mol) was added, and the mixture was stirred for another 35 h. The reaction was monitored by TLC until the starting material was completely consumed. The reaction was then quenched with water, followed by extraction three times with CH₂Cl₂, drying with Na₂SO₄, filtration, and concentration of the filtrate under reduced pressure. The mixture was then concentrated, and the residue was purified by silica gel column chromatography using petroleum ether / ethyl acetate = 20:1 and petroleum ether / dichloromethane = 10:1-1:1 as eluents to give compound 10, weighing 4.96 g, with a yield of 85%, HPLC purity of 99%, and LCMS showing a molecular weight of 583.21.

[0068] The 1H NMR data of compound 10 are as follows Figure 3 As shown: 1 H NMR (500 MHz, Chloroform- d ) δ 8.08– 8.04 (m, 1H), 7.61 (dd, J = 6.9, 1.7 Hz, 1H), 7.50 (ddd, J = 8.9, 6.9, 2.1 Hz,1H), 7.43 – 7.40 (m, 2H), 7.39 – 7.35 (m, 2H), 7.32 – 7.28 (m, 5H), 7.26 –7.22 (m, 3H), 7.19 – 7.16 (m, 4H), 7.13 – 7.08 (m, 3H), 0.51 (s, 6H).

[0069] Example 3 The synthetic route for the difluoroboronimidazole heterocyclic compound (compound 23) is shown below: .

[0070] The specific synthesis process is as follows: Step 1: Synthesis of intermediate compound 23-1: Under nitrogen protection, intermediate M4 (255.98 g, 1 mol), intermediate A5 (543.06 g, 1 mol), potassium phosphate (424.67 g, 2.0 mol), 3 L of tetrahydrofuran, 0.5 L of deionized water, and Pd(PPh3)4 (11.67 g, 0.01 mol) were added to a 5 L three-necked flask. The system was heated to reflux and the reaction was continued for 18 h until completion. The reaction solution was washed with water and separated. The organic phase was passed through a diatomaceous earth funnel, and the filtrate was collected. The filtrate was concentrated under reduced pressure to obtain a crude solid. 3 L of an appropriate proportion of ethyl acetate / petroleum ether solution was added, and the mixture was dispersed and slurried. The mixture was filtered to obtain intermediate compound 231, weighing 489.15 g, with a yield of 78%, HPLC purity of 99%, and LCMS showing a molecular weight of 627.12.

[0071] Step 2, Synthesis of Intermediate Compound 23-2: Under nitrogen protection, intermediate compound 23-1 (6.27 g, 0.01 mol) and 250 mL of DCM were added to a 5 L three-necked flask. After cooling to 0 °C in an ice-water bath, TMSI (3 mL, 0.02 mol) was added dropwise with thorough stirring. After the addition was complete, the reaction solution was allowed to slowly rise to room temperature and the reaction continued for 2 days until completion. The reaction solution was added to a saturated sodium bicarbonate aqueous solution, and the mixture was extracted with diethyl ether. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure to obtain a crude solid. The crude solid was purified by silica gel column chromatography (15% ethyl acetate / n-hexane) to obtain intermediate compound 232, weighing 5.09 g, with a yield of 83%, HPLC purity of 99%, and LCMS molecular weight of 613.11.

[0072] Step 3: Synthesis of the difluoroboronimidazolium heterocyclic compound (compound 23): Under nitrogen protection, intermediate compound 23-2 (6.13 g, 0.01 mol), 500 mL of dry DCM, and Et2O·BF3 (12.56 mL, 0.1 mol) were added to a 500 mL three-necked flask. The mixture was stirred at room temperature for 9 h, then DIPEA (26.1 mL, 0.15 mol) was added, and the mixture was stirred for another 35 h. The reaction was monitored by TLC until the starting material was completely consumed. The reaction was then quenched with water, followed by extraction three times with CH2Cl2, drying with Na2SO4, filtering, and concentrating the filtrate under reduced pressure. The mixture was then concentrated, and the residue was purified by silica gel column chromatography using petroleum ether / ethyl acetate = 20:1 and petroleum ether / dichloromethane = 10:1~1:1 as eluents to obtain compound 23, weighing 5.62 g, with a yield of 85%, HPLC purity of 99%, and LCMS showing a molecular weight of 661.11.

[0073] The 1H NMR data of compound 23 are as follows Figure 4 As shown: 1 H NMR (500 MHz, Chloroform- d ) δ 7.91(dd, J = 7.5, 1.8 Hz, 1H), 7.86 – 7.81 (m, 1H), 7.77 (dd, J = 7.2, 1.5 Hz, 1H), 7.56 (dd, J = 6.9, 1.7 Hz, 1H), 7.40 – 7.32 (m, 10H), 7.22 – 7.17 (m, 3H), 7.08(td, J = 7.1, 1.6 Hz, 1H), 6.94 (dd, J = 6.7, 1.6 Hz, 2H), 0.50 (s, 6H).

[0074] The synthesis of other compounds follows the same methods as those described above. Compounds containing silanes are synthesized using the same procedures as compounds 10 and 23, with the corresponding intermediate compounds A (A1~A30) and M (M1~M5) selected during the synthesis. The reactant compositions of some compounds in this invention are shown in Table 1.

[0075] Table 1. Reactant composition of some compounds in this invention Using the difluoroboronimidazolium heterocyclic compound prepared above as the guest luminescent material, an electroluminescent device was fabricated. A schematic diagram of the electroluminescent device is shown below. Figure 1As shown, it includes a substrate 1 and an anode layer 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9, and a cathode layer 10, which are sequentially stacked on the substrate 1.

[0076] In the fabrication of electroluminescent devices, CBP and BCP are used as the host luminescent materials, and compounds 1, 10, 23, 15, 16, 17, 25, 29, 30, 35, 41, 45, 49, 51, 56, 65, 68, 75, 76, 80, 86, 95, 96, 101, 105, 106, 111, 128, 131, 136, 140, 141, or 153 are used as guest luminescent materials, with a mass ratio of CBP, BCP, and guest luminescent materials of 49:49:2.

[0077] In the electroluminescent device, from the anode layer to the cathode layer, the following layers are stacked sequentially: PET plastic, ITO, HAT-CN, NPB, mCBP, light-emitting layer, PPT, ET-2, Liq, and Al-Mg (Al:Mg=9:1).

[0078] The functional layer material structure used in the fabrication process of the test device is as follows: .

[0079] Application examples A method for fabricating an organic electroluminescent device includes the following steps: Using 1.5mm PET plastic as substrate 1 and 0.15mm ITO material as anode layer 2, the materials are washed sequentially by alkaline washing, pure water washing, drying, and then ultraviolet-ozone washing to remove organic residues from the surfaces of the PET plastic and ITO material.

[0080] A layer of ITO material is adhered to PET plastic. Using a vacuum evaporation device, a 20nm thick HAT-CN layer is deposited as a hole injection layer 3. Then, a 45nm thick NPB layer is deposited as a hole transport layer 4. Subsequently, a 30nm thick mCBP layer is deposited as an electron blocking layer 5. On the mCBP layer, a 60nm thick light-emitting layer 6 is formed by CBP, BCP and guest light-emitting material with a mass ratio of 49:49:2 is deposited. On the light-emitting layer 6, a 10nm thick PPT layer is deposited as a hole blocking layer 7. Then, a 30nm thick ET-2 layer is deposited as an electron transport layer 8. On the electron transport layer 8, a 16nm thick Liq layer is deposited as an electron injection layer 9. After the electron injection layer 9 is deposited, a 10nm thick Al-Mg (Al:Mg=9:1) alloy is sputtered as a cathode layer 10 using a low-temperature sputtering method.

[0081] An electroluminescent device was fabricated by vacuum encapsulating the HAT-CN, NPB, mCBP, light-emitting layer, PPT, ET-2, and Liq layers.

[0082] The guest luminescent materials are compounds 1, 10, 23, 15, 16, 17, 25, 29, 30, 35, 41, 45, 49, 51, 56, 65, 68, 75, 76, 80, 86, 95, 96, 101, 105, 106, 111, 128, 131, 136, 140, 141, or 153. These correspond to application examples 1 through 33, respectively.

[0083] Comparative Application Example 1 The fabrication method of the electroluminescent device is the same as the above application example, except that the structure of the electroluminescent device is: PET / ITO / HAT-CN / NPB / mCBP / CBP:BCP:ref-1=49:49:2 / PPT / ET-2 / Liq / Al:Mg.

[0084] Comparative Application Example 2 The fabrication method of the electroluminescent device is the same as the application example above, except that the structure of the electroluminescent device is: PET / ITO / HAT-CN / NPB / mCBP / CBP:BCP:ref-2=49:49:2 / PPT / ET-2 / Liq / Al:Mg.

[0085] Comparative Application Example 3 The fabrication method of the electroluminescent device is the same as the above application example, except that the structure of the electroluminescent device is: PET / ITO / HAT-CN / NPB / mCBP / CBP:BCP:ref-3=49:49:2 / PPT / ET-2 / Liq / Al:Mg.

[0086] Comparative Application Example 4 The fabrication method of the electroluminescent device is the same as the above application example, except that the structure of the organic electroluminescent device is: PET / ITO / HAT-CN / NPB / mCBP / CBP:BCP:ref-4=49:49:2 / PPT / ET-2 / Liq / Al:Mg.

[0087] In comparative application examples 1, 2, 3, and 4, the corresponding guest luminescent materials ref-1, ref-2, ref-3, and ref-4 are all selected from prior art CN110003257A, a class of organic luminescent materials containing nitrogen difluoride-boron-oxygen heterocyclic acceptor structural units and their applications.

[0088] The structures of ref-1, ref-2, ref-3, and ref-4 are as follows: .

[0089] The electroluminescent devices from the above embodiments and comparative examples were fabricated into 30mm × 30mm samples. Then, under the same device fabrication process conditions, the anode and cathode layers were connected using an industry-known driving circuit. The luminous performance indicators of each electroluminescent device were tested. For the electroluminescent devices, at 10mA / cm... 2 The driving voltage and luminous efficiency were measured at a current density of 20 mA / cm². 2 The time required for the brightness to become 95% of its initial brightness at a given current density (LT) 95 (i.e., lifespan). The test results are shown in Table 2.

[0090] Table 2 Performance data of electroluminescent devices prepared in comparative and application examples. Note: Here, EQE refers to 1000 cd / m 2 External quantum efficiency at operating brightness.

[0091] As can be seen from the performance data in Table 2, compared with the electroluminescent devices prepared using guest luminescent materials ref-1, ref-2, ref-3 and ref-4 in the comparative application examples (comparative application examples 1 to 4), the electroluminescent devices prepared using the difluoroboron zimidazole heterocyclic compound of the present invention as the guest luminescent material have significantly improved overall luminous efficiency, with a significantly narrower half-width, an external quantum efficiency increase of about 65%, and a lifespan extension of nearly 2 times.

[0092] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0093] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A difluoroboronimidazole heterocyclic compound, characterized in that, The general structural formula of the difluoroboronimidazol heterocyclic compound is shown in Formula 1: ； Ar1 is selected from one of substituted or unsubstituted C5-C40 aryl groups or substituted or unsubstituted C5-C40 heteroaryl groups, wherein the heteroatom in the heteroaryl group is N, O, S, Si or P. X is selected from CR1R2, O, S, Se or SiR1R2; R1 and R2 are each independently selected from C1-C20 straight-chain alkyl, C1-C20 alkoxy, C1-C20 thioalkoxy, C3-C20 branched alkyl, C3-C20 cyclic alkyl, C3-C20 branched alkoxy, C3-C20 cyclic alkoxy, C3-C20 branched thioalkoxy, or C3-C20 cyclic thioalkoxy.

2. The difluoroboronimidazole heterocyclic compound according to claim 1, characterized in that, R1 and R2 are each independently selected from C1~C6 straight-chain alkyl, C1~C6 straight-chain alkoxy, C3~C6 branched alkyl, C3~C6 cyclic alkyl, C3~C6 branched alkoxy, C3~C6 cyclic alkoxy, and C1~C3 straight-chain thioalkoxy.

3. The difluoroboronimidazole heterocyclic compound according to claim 1, characterized in that, Ar1 is selected from one of the following groups: ； in," "As the bonding site, each Ar1 group is bonded through any one of the..." "bonded to the main structure; R0 is selected from H, D, substituted or unsubstituted C3-C30 aromatic groups, substituted or unsubstituted C3-C30 heteroaromatic groups, substituted or unsubstituted C3-C30 aromatic amine groups, straight-chain alkyl groups having C1-C20, branched-chain alkyl groups having C1-C20, alkoxy groups having C1-C20, thioalkoxy groups having C1-C20, and substituted silyl groups having C1-C20; the substituent is selected from at least one of carbonyl, alkoxy, aromatic carbonyl, cyano, formyl, isocyano, and -CF3.

4. The difluoroboronimidazole heterocyclic compound according to claim 3, characterized in that, R0 is selected from H, D, substituted or unsubstituted C6~C16 aromatic groups, C6~C16 heteroaromatic groups, C6~C16 aromatic amine groups, C1~C8 straight-chain alkyl groups, C3~C8 branched-chain alkyl groups, C1~C8 straight-chain alkoxy groups, C3~C8 branched-chain alkoxy groups, C1~C4 thioalkoxy groups, and C1~C8 substituted silyl groups; wherein, the substituent is selected from one or two of carbonyl, -CF3, cyano, and formyl groups, and the substituent on the C6~C16 aromatic group, C6~C16 heteroaromatic group, or C6~C16 aromatic amine group is substituted only on the aromatic group, heteroaromatic group, or aromatic amine group.

5. The difluoroboronimidazole heterocyclic compound according to claim 1, characterized in that, The difluoroboronimidazole heterocyclic compound is selected from one of the following compounds: 。 6. An electroluminescent device, characterized in that, The electroluminescent device includes an anode layer and a cathode layer, and an organic layer disposed between the anode layer and the cathode layer; the organic layer, from bottom to top along the direction from the anode layer to the cathode layer, consists of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and the light-emitting layer is prepared by a host light-emitting material and a guest light-emitting material, the guest light-emitting material including the difluoroboronimidazole heterocyclic compound as described in any one of claims 1 to 5.

7. The electroluminescent device according to claim 6, characterized in that, The mass of the guest luminescent material accounts for 0.1 wt.% to 3.0 wt.% of the mass of the luminescent layer.

8. The electroluminescent device according to claim 6, characterized in that, The main luminescent material is selected from one or two of the following compounds: 。

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