A cyclobutadiene-containing light-emitting material, a preparation method and application thereof

Abstract

The application provides a luminescent material containing a cyclobutadiene structure, a preparation method and application, and relates to the technical field of organic electroluminescent materials.The luminescent material containing a cyclobutadiene provided by the application is fused to a binary nitrogen-containing fused heterocyclic skeleton by using anti-aromatic cyclobutadiene, the anti-aromatic special electronic structure and high ring tension of the anti-aromatic cyclobutadiene are utilized to inhibit excited state vibration relaxation and realize narrow-band luminescence.By introducing a steric hindrance effect group, the aggregation-induced fluorescence quenching phenomenon between luminescent mother nuclei is weakened, and the fluorescence quantum yield is improved.Different from the current mainstream multiple resonance mechanism, the narrow-spectrum luminescent molecule design provided by the application does not need to depend on the construction of B / N-hetero-fused rings, and the molecular structure can be simplified to realize full-color super-narrow-band luminescence.The application is applied to an organic electroluminescent device, and can realize an electroluminescent spectrum with a super-narrow full width at half maximum and high device efficiency, and provides a better solution for super-high-definition organic light-emitting diode display technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic electroluminescent materials, in particular to a luminescent material containing cyclobutadiene, a preparation method and application. BACKGROUND

[0002] OLED (Organic Light-Emitting Diode) as a new display technology, with ultra-thin, flexible and self-luminous characteristics, has become the mainstream solution in the display field. Its luminescent material system has evolved through three generations: early fluorescent materials only utilize singlet excitons for light emission, which has the problem of low efficiency (theoretical limit 25%); phosphorescent materials capture triplet excitons through the introduction of heavy metal atoms to achieve 100% exciton utilization, but face cost pressure due to dependence on noble metals, and the stability of blue light materials is insufficient; the third generation of thermally activated delayed fluorescence (TADF) materials also achieve full exciton utilization through the reverse intersystem crossing (RISC) mechanism, while breaking away from the restriction of noble metals, showing significant cost advantage.

[0003] Multiple resonance (MR) technology developed based on TADF mechanism, by constructing the localized distribution difference of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) within the molecule, realizing the n-π* transition characteristics, thereby significantly compressing the full width at half maximum (FWHM = 25-35 nm) of the emission spectrum. Specifically, the HOMO is mainly localized on electron-rich nitrogen, oxygen and other heteroatoms, while the LUMO is concentrated on electron-deficient boron or carbonyl (C=O) elements. Such orbital spatial separation effectively suppresses the structural relaxation between the ground state and the excited state, reducing the Stokes shift. To pursue a narrower spectrum, existing research introduces rigid skeletons or π expansion strategies through molecular engineering, which can optimize the FWHM to less than 15 nm, but such improvements are accompanied by a sharp increase in molecular weight (MW>1000 Da), causing key defects such as increased crystallization temperature and deteriorated film-forming performance, resulting in a significant reduction in compatibility with mainstream vacuum evaporation processes. In addition, the core structure of the MR system constructed at present (such as boron-nitrogen fused ring) has inherent bottlenecks such as lack of substitution sites and limited derivatization, while Japanese and Korean companies have completed systematic patent layout around this field, which poses a major technical barrier to the construction of a self-contained OLED industrial chain in China.

[0004] To solve the above problems, existing technologies attempt to optimize performance through peripheral group modification or heteroatom doping, but the effect is limited: either the molecular weight is reduced with the problem of spectral broadening; or the structure derivatization is insufficient to break through the technical blockade.

[0005] In summary, there is an urgent need to develop a new MR luminescent material with narrow spectrum to solve the dual dilemma of process compatibility and patent barriers. SUMMARY

[0006] The technical problem to be solved by the present application is the deficiency of existing MR molecules in spectral narrowing. To solve the above problems, the present application proposes the following technical solutions:

[0007] In a first aspect, the present application provides a cyclobutadiene-containing luminescent material having a molecular structure represented by the following general formula (I) or general formula (II):

[0008]

[0009] In formula I or formula II, L1, L2 are independently selected from a substituent having a steric effect, n is 0-4, and n in L1 and L2 is not simultaneously 0; R is selected from H, linear alkyl or aryl; W, X, Y, Z are independently selected from C or N, and at least one N in W, X, Y, Z to form a binary nitrogen-containing fused heterocycle.

[0010] Further technical solutions are that the substituent having a steric effect includes isopropyl, tert-butyl, triarylsilane, triptycene, adamantyl, biphenyl, 1,2-dimethylphenyl, trifluoromethyl, diarylboron, diphenylphosphine oxide, pyridyl, pyrimidyl, diarylamine, 9H-carbazolyl, aryloxy, alkoxy.

[0011] Further technical solutions are that the binary nitrogen-containing fused heterocycle includes any one of quinoline, 1,5-naphthylidine, 1,8-naphthylidine, quinoxaline, pyrido[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine.

[0012] Further technical solutions are that R is selected from any one of H, methyl, ethyl, isopropyl, tert-butyl, phenyl, tert-butylphenyl, naphthyl.

[0013] In a second aspect, the present application provides a preparation method of the cyclobutadiene-containing luminescent material according to the first aspect, comprising the following steps:

[0014] Diels-Alder addition reaction of dihalogenated hydrocarbon under the action of lithium metal reagent and furan derivative to generate an intermediate;

[0015] C-H activation of the intermediate under the action of a transition metal catalyst, and coupling reaction with a halogenated aromatic hydrocarbon molecule to obtain the final product of general formula (I) or general formula (II);

[0016] The dihalogenated hydrocarbon has a general formula (III), wherein A and B are independently selected from halogen elements Cl, Br or I:

[0017]

[0018] The furan derivative has a general formula (IV):

[0019]

[0020] The halogenated aromatic hydrocarbon molecule has a general formula (VI) or a general formula (VII), wherein A and B are independently selected from halogen elements Cl, Br or I:

[0021]

[0022] Further, the metal lithium reagent includes at least one of n-butyllithium and tert-butyllithium.

[0023] Further, the transition metal catalyst includes at least one of palladium acetate, palladium chloride, tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)palladium, bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium, dichlorobis(triphenylphosphine)palladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-trichloromethane complex.

[0024] In a third aspect, the application further provides an application of the cyclobutadiene-containing light-emitting material of the first aspect or the cyclobutadiene-containing light-emitting material prepared by the preparation method of the second aspect in preparing an organic electroluminescent device or a color conversion material.

[0025] In a fourth aspect, the application provides an organic light-emitting layer film, which includes the cyclobutadiene-containing light-emitting material of the first aspect or the cyclobutadiene-containing light-emitting material prepared by the preparation method of the second aspect.

[0026] In a fifth aspect, the application provides an organic electroluminescent device, which includes the cyclobutadiene-containing light-emitting material of the first aspect or the cyclobutadiene-containing light-emitting material prepared by the preparation method of the second aspect, and is preferably applied to a light-emitting layer of the organic electroluminescent device.

[0027] Compared with the prior art, the application can achieve the following technical effects:

[0028] The cyclobutadiene-containing light-emitting material provided by the present application significantly improves the rigidity of the conjugated molecular skeleton by fusing the anti-aromatic cyclobutadiene (CBD) to the pi-conjugated fluorescent skeleton, using the high ring strain and the limited electron delocalization characteristics of the anti-aromatic CBD, the present application uses the anti-aromatic CBD fusion technology, which can increase the potential barrier of the intramolecular atomic stretching vibration, effectively suppress the excited state configuration relaxation, and reduce the Stokes shift. By using the localization design of the frontier molecular orbital, through the HOMO / LUMO orbital space separation strategy, the difference between the electron cloud distribution of the ground state and the excited state is reduced, the energy loss in the transition process is directly reduced, the emission spectrum full width at half maximum (FWHM) is compressed to 11-16 nm, the emission spectrum full width at half maximum is effectively narrowed, and the external quantum efficiency of the light-emitting device is improved.

[0029] Further, the cyclobutadiene-containing light-emitting material of the present application can introduce large steric hindrance groups (such as triptycene, adamantane, etc.), strong electron push / pull groups (such as cyano, carbazole, etc.) on the periphery of the binary nitrogen-containing fused heterocycle, weaken the anti-aromaticity of CBD (such as NICS value) through steric hindrance effect, improve the rigidity of the molecule, reduce the molecular plane, weaken the quenching effect of the molecule, and at the same time, can adjust the electron cloud density distribution, weaken the delocalization of the frontier orbital molecule, and improve the solid-state quantum efficiency of the light-emitting device.

[0030] Further, the cyclobutadiene-containing light-emitting material of the present application contains a cyclobutadiene skeleton, which can provide 4-6 modifiable sites, and at least 72 structures can be derived according to the different introduced modification groups, which has high derivatization compared with the prior art, and auxiliary groups can also be coupled to further improve the molecular processing properties, reduce the fluorescence quenching effect between the light-emitting groups, adjust the chemical stability and aromaticity of the molecule, and realize extremely narrow full width at half maximum (FWHM) and high device efficiency.

[0031] The preparation method of the cyclobutadiene-containing light-emitting material provided by the present application adopts Diels-Alder / Suzuki coupling method, the raw materials are widely available and have been industrialized, which greatly reduces the production cost.

[0032] The cyclobutadiene-containing light-emitting material provided by the present application can realize strong stability, extremely narrow full width at half maximum (FWHM) and high device efficiency when applied in electroluminescent devices. The present application provides a self-contained material solution for high-resolution OLED display and lighting applications. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The optimized ground state configuration diagram of the CBD-5 molecule provided by the present application is shown in the figure, wherein a) is a top view and b) is a side view.

[0034] Figure 2LUMO and HOMO frontier orbital distribution diagram of the CBD-5 molecule provided by the embodiment of the present application.

[0035] Figure 3 The optimized ground state configuration diagram of the CBD-9 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0036] Figure 4 LUMO and HOMO frontier orbital distribution diagram of the CBD-9 molecule provided by the embodiment of the present application.

[0037] Figure 5 The optimized ground state configuration diagram of the CBD-13 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0038] Figure 6 LUMO and HOMO frontier orbital distribution diagram of the CBD-13 molecule provided by the embodiment of the present application.

[0039] Figure 7 The optimized ground state configuration diagram of the CBD-35 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0040] Figure 8 LUMO and HOMO frontier orbital distribution diagram of the CBD-35 molecule provided by the embodiment of the present application.

[0041] Figure 9 The optimized ground state configuration diagram of the CBD-45 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0042] Figure 10 LUMO and HOMO frontier orbital distribution diagram of the CBD-45 molecule provided by the embodiment of the present application.

[0043] Figure 11 The optimized ground state configuration diagram of the CBD-66 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0044] Figure 12 LUMO and HOMO frontier orbital distribution diagram of the CBD-66 molecule provided by the embodiment of the present application.

[0045] Figure 13 The optimized ground state configuration diagram of the CBD-67 molecule provided by the embodiment of the present application, wherein a) is a top view and b) is a side view.

[0046] Figure 14 LUMO and HOMO frontier orbital distribution diagram of the CBD-67 molecule provided by the embodiment of the present application.

[0047] Figure 15 Absorption / emission spectrum of CBD-9 molecule provided by the embodiment of the present application in toluene solution.

[0048] Figure 16 Absorption / emission spectrum of CBD-13 molecule provided by the embodiment of the present application in toluene solution.

[0049] Figure 17 Absorption / emission spectrum of CBD-45 molecule provided by the embodiment of the present application in toluene solution.

[0050] Figure 18 Absorption / emission spectrum of CBD-66 molecule provided by the embodiment of the present application in toluene solution.

[0051] Figure 19 Molecular structure of the light emitting guest DABNA-1 and CBD-00 of Comparative Example 1 and Comparative Example 2.

[0052] Figure 20 Molecular structure of the functional layer material involved in the preparation of the organic electroluminescent device.

[0053] Figure 21 Current-voltage-brightness curve of the light emitting device prepared by using the light emitting material of the embodiment of the present application and the comparative example.

[0054] Figure 22 Power efficiency-brightness and current efficiency-brightness curve of the light emitting device prepared by using the light emitting material of the embodiment of the present application and the comparative example.

[0055] Figure 23 External quantum efficiency-brightness curve of the light emitting device prepared by using the light emitting material of the embodiment of the present application and the comparative example.

[0056] Figure 24 Structure schematic diagram of the OLED device provided by the embodiment of the present application.

[0057] Figure 25 Synthetic route diagram of the cyclobutadiene-containing light emitting material provided by the embodiment of the present application. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application, and similar component numbers in the drawings represent similar components. Obviously, the embodiments described below are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] The embodiment of the present application provides a luminescent material containing cyclobutadiene, which has a molecular structure shown in the following general formula (I) or general formula (II).

[0060]

[0061] In formula I or formula II, L1 and L2 are independently selected from a substituent having a steric hindrance effect, n is 0-4, and n in L1 and L2 is not 0 at the same time; R is selected from H, a linear alkyl group or an aryl group; W, X, Y and Z are independently selected from C or N, and at least one N in W, X, Y and Z is to form a binary nitrogen-containing fused heterocycle.

[0062] In specific implementation, the substituent having a steric hindrance effect can be a neutral substituent having a steric hindrance effect, such as an isopropyl group, a tert-butyl group, a triaryl silyl group, a triptycene group, an adamantyl group, a biphenyl group, a 1,2-dimethylphenyl group and the like; can also be a large steric hindrance substituent having an electron-withdrawing effect, including a trifluoromethyl group, a diaryl boron group, a diphenyl phosphine oxide group, a pyridyl group, a pyrimidyl group and the like; and can also be a large steric hindrance substituent having an electron-donating effect, including a diarylamine group, a 9H-carbazole group, an aryloxy group, an alkoxy group and the like.

[0063] In specific implementation, the binary nitrogen-containing fused heterocycle can regulate the front orbital distribution, and the structure can be a central symmetry structure, an axial symmetry structure and the like. For example, the binary nitrogen-containing fused heterocycle includes any one of quinoline, 1,5-naphthylidine, 1,8-naphthylidine, quinoxaline, pyrido[2,3-b]pyrazine and pyrazino[2,3-b]pyrazine.

[0064] In specific implementation, the R is selected from any one of H, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a phenyl group, a tert-butyl phenyl group and a naphthyl group. The R group can further improve the molecular processing properties, reduce the fluorescence quenching effect between luminescent groups, and regulate the molecular chemical stability and aromaticity.

[0065] The embodiment of the present application also provides a preparation method of the luminescent material containing cyclobutadiene, and a synthesis route is shown in the following formula (I) or formula (II). Figure 25 .

[0066] The preparation method specifically includes the following steps:

[0067] Diels-Alder addition reaction of a dihalogenated hydrocarbon under the action of a metal lithium reagent and a furan derivative to generate an intermediate;

[0068] C-H activation of the intermediate under the action of a transition metal catalyst, and coupling reaction with a halogenated aromatic hydrocarbon molecule to obtain a final product of general formula (I) or general formula (II);

[0069] The dihalogenated hydrocarbon has a general formula (III), wherein A and B are independently selected from halogen elements Cl, Br or I:

[0070]

[0071] The furan derivative has a general formula (IV):

[0072]

[0073] The halogenated aromatic hydrocarbon molecule has a general formula (VI) or a general formula (VII), wherein A and B are independently selected from halogen elements Cl, Br or I:

[0074]

[0075] In specific embodiments, the metal lithium reagent includes at least one of n-butyllithium and tert-butyllithium.

[0076] In specific embodiments, the transition metal catalyst includes at least one of palladium acetate, palladium chloride, tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)palladium, bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium, dichlorobis(triphenylphosphine)palladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, and 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-trichloromethane complex.

[0077] Due to the ability of the cyclobutadiene skeleton to provide 4-6 modifiable sites, there are at least 72 types of cyclobutadiene-containing luminescent materials according to different binary nitrogen-containing fused heterocyclic structures and modification groups, specifically any one of the following structural formulas CBD-1 to CBD-72:

[0078]

[0079]

[0080] It should be noted that based on the technical solutions of the present application, cyclobutadiene-containing luminescent materials with narrow-band luminescence effect other than the above structural formulas CBD-1 to CBD-72 can be obtained.

[0081] The luminescent material containing cyclobutadiene provided by the embodiment suppresses excited state vibration relaxation to realize narrow-band luminescence by fusing anti-aromatic cyclobutadiene to a binary nitrogen-containing fused heterocyclic skeleton and using the special electronic structure and high ring strain of the anti-aromatic cyclobutadiene. The fluorescence quenching phenomenon of the luminescent mother nucleus is weakened by introducing a steric hindrance effect group, and the fluorescence quantum yield is improved. From any one of the specific embodiments of the above structural formulae CBD-1 to CBD-72, the molecular structure of the luminescent material containing cyclobutadiene of the present application is different from the current mainstream multiple resonance mechanism. The present application does not need to rely on the construction of B / N-hetero fused ring, and can simplify the molecular structure to realize full-color super-narrow-band luminescence. The luminescent material containing cyclobutadiene provided by the embodiment of the present application can realize super-narrow full-width at half maximum electroluminescence spectrum and high device efficiency when applied to an organic electroluminescent device, and provides a better solution for ultra-high-definition organic light-emitting diode display technology.

[0082] In order to enable those skilled in the art to fully understand the technical solutions, the synthesis route, basic optical physical properties and application in circularly polarized organic light-emitting diode (CP-OLED) of the luminescent material containing cyclobutadiene provided by the present application are systematically described in combination with specific embodiments and drawings.

[0083] Synthesis of luminescent material CBD-9 in Example 1

[0084] The synthesis route is as follows:

[0085]

[0086] In a dry 100 mL round-bottom flask, 6,7-dibromo-1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene (1.08 g, 2.00 mmol) and 2,5-dimethylfuran (972 mg, 10.0 mmol) were added, and the solution was pumped to vacuum and then filled with nitrogen three times. The solution was cooled to -75°C, and 2.5M n-butyllithium in hexane (0.88 mL, 2.2 mmol) was slowly added using a syringe pump. After the addition was completed, the room temperature was restored, and the solution was stirred for 12 h. After the reaction was completed, water was added to quench the reaction, and ethyl acetate was used to extract the organic phase. The combined organic phase was dried, and the excess solvent was removed by rotary evaporation under reduced pressure. Silica gel powder was added and the solvent was dried, and then column chromatography was performed using ethyl acetate / n-hexane (1:20, v / v) as the eluent to separate and purify the product. 481 mg of colorless powder, intermediate 1-1, was obtained (yield 85%). HRMS (ESI) calculated for C 20 H 26 O, [M+H] + 283.2062, and the measured value was 283.2061.

[0087] A dry 25 mL pressure tube was charged with palladium acetate (22.56 mg, 0.1 mmol) and (2-(dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 2,6-dibromo-1,5-naphthyridine (486.0 mg, 1.01 mmol), intermediate 1-1 (570.50 mg 2.02 mmol) and 8 mL solvent. The mixture was stirred at room temperature for 5 minutes, then heated to 130 °C for 24 h. After the reaction was cooled to room temperature, the inorganic salts were removed by filtration through a thin layer of celite, and the residue on the celite was washed with chloroform. Separation and purification were performed by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent to give 575 mg of CBD-11 as a white solid (yield 86%). HRMS (ESI) calculated for C 48 H 50 N2, [M+H] + 655.4052, found 655.4049.

[0088] 1 H NMR (500 MHz, Chloroform-d) δ 8.41 (s, 1H), 7.89 (s, 2H), 2.73 (s, 6H), 1.51 - 1.47 (m, 4H), 0.97 (s, 12H).

[0089] Synthesis of luminescent material CBD-5

[0090] The synthetic route is as follows:

[0091]

[0092] The procedure for preparing intermediate 1-1 was the same as the steps described in Example 1.

[0093] A dry 25 mL pressure tube was charged with palladium acetate (22.56 mg, 0.1 mmol) and (2-(dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 2,7-dibromo-1,8-naphthyridine (290.82 mg, 1.01 mmol), intermediate 1-1 (570.50 mg, 2.02 mmol) and 8 mL solvent. The mixture was stirred at room temperature for 5 minutes, then heated to 130 °C for 24 h. After the reaction was cooled to room temperature, the inorganic salts were removed by filtration through a thin layer of celite, and the residue on the celite was washed with chloroform. Separation and purification were performed by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent to give 582 mg of CBD-21 as a white solid (yield 88%). HRMS (ESI) calculated for C 48 H 50N2, [M+H] + 655.4052, found 655.4055.

[0094] 1 H NMR (500 MHz, Chloroform-d) δ 8.19 - 8.15 (m, 1H), 7.89 (s, 2H), 2.73 (s, 6H), 1.51 - 1.47 (m, 4H), 0.97 (s, 12H).

[0095] Synthesis of luminescent material CBD-13

[0096] The synthetic route is as follows:

[0097]

[0098] The process of preparing intermediate 1-1 is the same as the steps described in Example 1.

[0099] In a dry 25 mL pressure tube, palladium acetate (22.56 mg, 0.1 mmol) and (2- (dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 2,6-dibromoquinoxaline (290.8 mg, 1.01 mmol), intermediate 1-1 (570.50 mg, 2.02 mmol) and 8 mL solvent were added. The mixture was stirred at room temperature for 5 minutes, then heated to 130 °C for 24 h. After the reaction was cooled to room temperature, the inorganic salts were removed by thin layer filtration on celite, and the residue on celite was washed with chloroform. Separation and purification were performed by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent to obtain 582 mg of white solid, which was CBD-31 (yield 88%). HRMS (ESI) calcd for C 48 H 50 N2, [M+H] + 655.4052, found 655.4055.

[0100] 1 H NMR (500 MHz, Chloroform-d) δ 8.07 (s, 1H), 7.89 (s, 2H), 2.73 (s, 6H), 1.51 - 1.47 (m, 4H), 0.97 (s, 12H).

[0101] Synthesis of luminescent material CBD-35

[0102] The synthetic route is as follows:

[0103]

[0104] The procedure for preparing intermediate 1-1 is the same as the procedure described in Example 1.

[0105] In a dry 25 mL pressure tube, add palladium acetate (22.56 mg, 0.1 mmol) and (2- (dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 2,7-dibromopyrazino[2,3-b]pyrazine (289.9 mg, 1.01 mmol), intermediate 1-1 (570.50 mg, 2.02 mmol) and 8 mL solvent. Stir the mixture at room temperature for 5 min, then heat to 130 °C for 24 h. After the reaction mixture is cooled to room temperature, remove the inorganic salts by filtration through a thin layer of celite, and wash the residue on celite with chloroform. Isolate and purify by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent to give 584 mg of CBD-61 as a white solid (yield 88%). HRMS (ESI) calcd for C 46 H 48 N4, [M+H] + 657.3957, found 657.3960.

[0106] 1 HNMR (500 MHz, Chloroform-d) δ 7.89 (s, 1H), 2.73 (s, 3H), 1.51 - 1.47 (m, 2H), 0.97 (s, 6H).

[0107] Synthesis of light-emitting material CBD-66

[0108] The synthetic route is as follows:

[0109]

[0110] In a dry 150 mL two-necked flask, add diphenylmethanediol (420.01 mg, 2.00 mmol), 5-bromopyrazine-2,3-diamine (378.02 mg, 2.00 mmol) and 50 mL water, and vacuumize with an oil pump and then fill with nitrogen, repeat three times. Warm the mixture to 105 °C and stir for 15 min. After the reaction is completed, extract the combined organic phases and dry, then add silica gel powder and spin dry the solvent, and then isolate and purify by column chromatography to give 442 mg of intermediate 5-1 as a powder (yield: 50%). HRMS (ESI) calcd for C 18 H 11 BrN4, [M+H] + 363.0245, found 363.0247.

[0111] In a dry 100 mL round-bottom flask, add

[0112] 4”,5”-Dibromo-1,1’:2’,1”:2”,1”’:2”’,1””-pentaphenyl (1.08 g, 2.00 mmol) and 2,5-dimethylfuran (972 mg, 10.0 mmol) were degassed with an oil pump vacuum and backfilled with nitrogen three times. The solution was cooled to -75 °C and 2.5 M n-butyllithium in hexanes (0.88 mL, 2.2 mmol) was added slowly using a syringe pump. After the addition was complete, the solution was allowed to warm to room temperature and stirred for 12 h. After the reaction was complete, water was added to quench the reaction and the mixture was extracted with ethyl acetate. The organic layers were combined and dried. After removing the excess solvent by rotary evaporation, silica gel powder was added and the solvent was removed by rotary evaporation. The product was purified by column chromatography using ethyl acetate in n-hexane (1 :20, v / v) as the eluent to give 481 mg of intermediate 5-2 as a colorless powder (yield: 50%). HRMS (ESI) calcd for C 36 H 28 O, [M+H] + 477.2218, found 477.2220.

[0113] Palladium acetate (22.56 mg, 0.1 mmol) and (2-(dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), intermediate 5-1 (442 mg, 1.00 mmol), intermediate 5-2 (481 mg 1.00 mmol) and 8 mL solvent were added into a dry 25 mL pressure tube. The mixture was stirred at room temperature for 5 min and then heated to 130 °C for 24 h. After the reaction was cooled to room temperature, the inorganic salts were removed by filtration through a thin bed of celite and the residue on the celite was washed with chloroform. The product was purified by column chromatography using ethyl acetate in n-hexane (1 :20, v / v) as the eluent to give 652 mg of CBD-76 as a white solid (yield 88%). HRMS (ESI) calcd for C 54 H 36 N4, [M+H] + 741.3018, found 741.3020.

[0114] 1 H NMR (500 MHz, Chloroform-) δ 8.14 (s, 1H), 8.00 - 7.92 (m, 4H), 7.87 - 7.75 (m, 2H), 7.61 - 7.50 (m, 3H), 7.48 - 7.42 (m, 2H), 7.42 - 7.38 (m, 1H), 7.36 - 7.31 (m, 2H), 2.56 (s, 3H).

[0115] Synthesis of light-emitting material CBD-45

[0116] The synthetic route is as follows:

[0117]

[0118] The procedure for preparing intermediate 1-1 is the same as the procedure described in Example 1.

[0119] In a dry 25 mL pressure tube, palladium acetate (22.56 mg, 0.1 mmol) and (2- (dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 6-bromo-2,3-diphenylquinoxaline (364.85 mg, 1.01 mmol), intermediate 1-1 (285.25 mg, 1.01 mmol) and 8 mL solvent were added. The mixture was stirred at room temperature for 5 minutes, then heated to 130 °C for 24 h. After the reaction mixture was cooled to room temperature, it was filtered through a thin layer of celite to remove inorganic salts, and the residue on the celite was washed with chloroform. Purification by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent gave 473 mg of CBD-45 as a white solid (yield 86%). HRMS (ESI) calcd for C 40 H 36 N2, [M+H] + 545.2957, found 545.2955.

[0120] 1 H NMR (500 MHz, Chloroform-d) δ 8.30 (s, 1H), 8.06 - 7.94 (m, 2H), 7.68 (s, 1H), 7.59 - 7.52 (m, 1H), 7.35 - 7.30 (m, 2H), 2.56 (s, 3H), 1.66 - 1.63 (m, 2H), 1.01 (s, 6H).

[0121] Synthesis of the light-emitting material CBD-67 of Example Seven

[0122] The synthetic route is as follows:

[0123]

[0124] In a dry 150 mL two-necked flask, add [1,1'-biphenyl]-2-carboxaldehyde (819.20 mg, 4.50 mmol), 5,6-dibromopyrazine-2,3-diamine (536.00 mg, 2.00 mmol) and 50 mL of water, pump to vacuum and fill with nitrogen, repeat three times. Warm the mixture to 105 °C, stir for 15 min, after the reaction is completed, extract the combined organic phase and dry, after removing the excess solvent by rotary evaporation under reduced pressure, add silica gel powder and spin dry the solvent, then purify by column chromatography to obtain 258 mg of powder, intermediate 7-1 (yield: 50%), HRMS (ESI) calculated for C 30 H 19 BrN4, [M+H] + 515.0871, found 515.0873.

[0125] The process of preparing intermediate 1-1 is the same as the steps described in Example one.

[0126] In a dry 25 mL pressure tube, add palladium acetate (22.56 mg, 0.1 mmol) and (2-(dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), intermediate 1-1 (173.95 mg, 1.01 mmol), intermediate 7-1 (600.25 mg, 1.01 mmol) and 8 mL of solvent. Stir the mixture at room temperature for 5 min, then heat to 130 °C for 24 h. After the reaction solution is cooled to room temperature, remove the inorganic salt by thin layer filtration with diatomite, and wash the residue on diatomite with chloroform. Purify by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as eluent to obtain 621 mg of white solid, CBD-78 (yield 88%). HRMS (ESI) calculated for C 50 H 42 N4, [M+H] + 699.3488, found 699.3490.

[0127] 1 H NMR (500 MHz, Chloroform-d) δ 8.32 - 8.17 (m, 1H), 8.02 - 7.85 (m, 1H), 7.81 - 7.71 (m, 2H), 7.71 - 7.63 (m, 2H), 7.64 - 7.59 (m, 1H), 7.50 - 7.40 (m, 3H), 2.56 (s, 3H), 1.67 - 1.63 (m, 2H), 1.01 (s, 6H).

[0128] Synthesis of luminescent material CBD-17 of Example eight

[0129] The synthesis route is as follows:

[0130]

[0131] In a dry 150 mL round-bottom flask, (1r,3r,5r,7r)-2-phenyladamantane (424.68 mg, 2.00 mmol), iron tribromide (295.56 mg, 1.00 mmol), liquid bromine (639.23 mg, 4.00 mmol), 50 mL dichloromethane were added, and the mixture was stirred at room temperature for 12 h. After the reaction was completed, the organic phase was extracted and dried, and after the excess solvent was removed by rotary evaporation under reduced pressure, silica gel powder was added and the solvent was dried, and then purified by column chromatography to obtain 518 mg of a powder, intermediate 8-1 (yield: 70%). HRMS (ESI) calculated for C14H18BrNO [M+H] 307.2062, found 307.2065. 16 H 18 Br2, [M+H] + 368.9854, found 368.9856.

[0132] In a dry 100 mL round-bottom flask, intermediate 8-1 (740.26 mg, 2.00 mmol) and 2,5-dimethylfuran (972 mg, 10.0 mmol) were added, and the oil pump was used to vacuum and then full nitrogen was passed, repeated three times. The solution was cooled to -75°C, and 2.5M n-butyllithium in hexane (0.88 mL, 2.2 mmol) was slowly added using a syringe pump, and after the addition was completed, the room temperature was restored, and stirred for 12 h. After the reaction was completed, water was added to quench, extracted with ethyl acetate, and the organic phase was combined and dried, and after the excess solvent was removed by rotary evaporation under reduced pressure, silica gel powder was added and the solvent was dried, and then purified by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 521 mg of a colorless powder, intermediate 8-2 (yield 85%). HRMS (ESI) calculated for C14H18NO [M+H] 207.1498, found 207.1499. 22 H 26 O, [M+H] + 307.2062, found 307.2065.

[0133] In a dry 25 mL pressure tube, palladium acetate (22.56 mg, 0.1 mmol) and (2- (dicyclohexylphosphino))biphenyl (0.22 mmol), cesium carbonate (654.96 mg, 1.01 mmol), 2,6-dibromoquinoxaline (290.8 mg, 1.01 mmol), intermediate 8-2 (619.03 mg 2.02 mmol) and 8 mL solvent were added. The mixture was stirred at room temperature for 5 min, then heated to 130 °C for 24 h. After the reaction mixture was cooled to room temperature, it was filtered through a thin layer of celite to remove inorganic salts, and the residue on the celite was washed with chloroform. Separation and purification were performed by column chromatography with ethyl acetate / n-hexane (1:20, v / v) as the eluent to give 625 mg of CBD-79 as a white solid (yield 88%). HRMS (ESI) calcd for C 52 H 50 N2, [M+H] + 703.4052, found 703.4055.

[0134] 1 HNMR (500 MHz, Chloroform-d) δ 8.09 - 7.85 (m, 2H), 7.80 (d, J = 2.1 Hz, 1H), 7.23 (d, J = 5.8 Hz, 1H), 3.09 - 3.00 (m, 1H), 2.56 (s, 6H), 2.53 - 2.36 (m, 2H), 2.23 - 2.18 (m, 2H), 2.04 - 1.86 (m, 7H), 1.84 - 1.78 (m, 4H).

[0135] Theoretical simulation and electrochemical, photophysical characterization

[0136] To illustrate the superiority of the cyclobutadiene-containing luminescent material provided by the present application, the following provides theoretical simulation data of some of the above-mentioned molecules based on Gaussian 16 software. In order to simplify the calculation, some alkyl chains are reasonably simplified as methyl groups, and biphenyl groups are simplified as phenyl groups. The optimization of all ground state configurations is based on the B3LYP / 6-311G** level, the results are obtained under the default gaseous monomolecular state, and the dispersion correction is considered. The energy level and configuration optimization of the excited state are obtained by TD-DFT calculation based on the optimized ground state configuration, the basis set and functional selected for calculation are consistent with the ground state, and the visualization of all orbitals is realized based on Gaussview 6.0 software.

[0137] Table 1. Calculation results of front-line orbital energy levels and measured electrochemical energy levels

[0138]

[0139]

[0140] Wherein, a) is the data calculated by theoretical simulation, b) is the HOMO estimated by the oxidation potential of cyclic voltammetry, LUMO = HOMO - Eg, Eg is the optical band gap.

[0141] From the theoretical calculation results in Table 1, it can be seen that the HOMO energy levels of all CBD structure-based molecules are between -5.53 and -5.91 eV, and the LUMO energy levels are between -2.30 and -2.73 eV, which are equivalent to the energy levels of conventional n-type light-emitting molecules, and meet the general requirements of OLED devices for light-emitting guest molecules. In addition, it is found from the lateral comparison that the central core of CBD-5, CBD-9, CBD-35, CBD-45, CBD-66 and CBD-67 changes from naphthyridine, quinoxaline to pyrazino[2,3,b]pyrazine, and the electron affinity of the central core gradually increases, which is consistent with the gradual deepening of the HOMO and LUMO energy levels in the theoretical calculation. Correspondingly, in order to verify the reliability of the theoretical calculation, the HOMO energy levels of these example molecules were measured by cyclic voltammetry in dichloromethane solution, and the results and trends were basically consistent with the calculation. The HOMO energy level of CBD-13 and CBD-17 based on quinoxaline core is the shallowest, which is -5.40 eV, and the HOMO energy level of CBD-66 based on pyrazino[2,3,b]pyrazine core is the deepest, which is -6.08 eV. Based on the optical band gap Eg and the HOMO energy level, we estimated the LUMO energy level of these example molecules, which is between -2.21 and -3.03 eV, which is conducive to the injection of electrons from the electron transport layer to the light-emitting layer.

[0142] In order to further show the influence of the change of the number of nitrogen atoms or the change of the position of nitrogen atoms in the substituted group and the nitrogen-containing fused heterocycle on the HOMO and LUMO orbital distribution, the present application calculates the frontier orbital distribution of the above-mentioned example molecules, and visualizes it by GaussView 6.0. In order to simplify the calculation, part of the alkyl chain is simplified as methyl, and the biphenyl group is simplified as a single phenyl group, so the calculation model corresponding to CBD-13 and CBD-17 is the same. The molecular advantage configuration diagram and the orbital distribution diagram after visualization are shown in the following figures. Figures 1-14Due to the linear extension of the molecules designed in the present application, i.e. the CBD unit is fused on both sides of the nitrogen-containing two-membered fused ring, and then the substituent group continues to extend along the direction of the conjugated CBD, benefiting from this design, all molecules exhibit rigid planar configuration and linearly conjugated extension. It can be seen that the luminescent material containing cyclobutadiene provided by the present application can effectively extend the conjugation, greatly weaken the anti-aromaticity of the CBD core, and improve the luminescent performance of the molecule. By comparing the LUMO orbital distribution diagrams of all example molecules, it is found that the LUMO orbitals all exhibit obvious localization, i.e. most of the LUMO is distributed on the electron-deficient N atom and the C atom of the N atom resonance site, and in addition, a part is distributed on the CBD unit, indicating the contribution of the CBD unit to the frontier orbital and the excited state. Although the HOMO orbital has a certain delocalization, it also exhibits a relatively isolated distribution, i.e. it generally exists between 2-3 adjacent atoms. This frontier orbital distribution is conducive to reducing the proportion of bonding / antibonding orbital transition in the HOMO-LUMO transition process, thereby reducing the excited state vibration relaxation and narrowing the emission spectrum. Further lateral comparison shows that the central core has a greater impact on the frontier orbital, and with the increase of the number of N atoms, the LUMO tends to be more localized on a single atom, and in addition, the axially symmetric structure (such as quinoline) has better orbital localization than the centrosymmetric structure (such as naphthyridine), so it can be predicted that the central core with an axially symmetric structure is conducive to outputting a narrower emission spectrum.

[0143] The luminescent material containing cyclobutadiene provided by the present application is a narrow-band luminescent molecule containing a cyclobutadiene structure. By fusing the anti-aromatic cyclobutadiene to the two-membered nitrogen-containing fused heterocyclic skeleton, the special electronic structure and high ring strain of the anti-aromatic cyclobutadiene are utilized to suppress the excited state vibration relaxation and achieve narrow-band luminescence. By introducing a steric hindrance effect group, the aggregation-induced fluorescence quenching phenomenon between the luminescent mother nucleus is weakened, and the fluorescence quantum yield is improved. Specifically, the design of the luminescent material containing a cyclobutadiene structure provided by the present application limits the cyclobutadiene fusion site to the two sides of the two-membered nitrogen-containing fused heterocyclic ring (X-axis direction) to form linear conjugated extension. Although only the theoretical calculation of eight examples is provided here, those skilled in the art can clearly know from the existing rules that this linear conjugated extension design of the present application can effectively provide a rigid molecular structure, weaken the anti-aromaticity of the cyclobutadiene and improve the fluorescence efficiency, and on the other hand, effectively suppress the delocalization of the frontier orbital, so that the frontier orbital is more localized on the atom, the proportion of bonding / antibonding orbital transition is reduced, and finally the super-narrow emission spectrum is realized. Obviously, based on the theoretical calculation data provided, the above rules can be obtained.

[0144] In order to further illustrate the advantages of the molecular design of the present application, the present application calculates the photophysical data of the above example molecules based on Franck-condon analysis and MOMAP vibration analysis (Table 2).

[0145] Accordingly, the present application tested the above-mentioned embodiment molecules in toluene solution in the absorption and emission spectrum, part of the specific values are presented in Table 2, part of the representative absorption / emission spectrum graph is presented in the following Figures 15-18 .

[0146] Table 2. Summary of vibration analysis and photophysical characterization data.

[0147]

[0148]

[0149] In Table 2, a) is the excitation energy based on the optimized first excited singlet state (S1) structure, b) is the oscillator strength, c) is the reorganization energy in the S0 to S1 transition process, d) is the reorganization energy in the S1 to S0 transition process, e) is the emission peak in toluene solution, f) is the full width at half maximum of the emission spectrum in toluene solution, g) is the fluorescence quantum yield in toluene solution.

[0150] The results in Table 2 show that all the embodiment molecules exhibit small reorganization energy (λ reorg ), but there are significant differences between different structures. Based on the upper and lower axis symmetric quinoxaline and pyrazino[2,3:b]pyrazine as the central core, the molecules such as CBD-66 and CBD-13 have significantly lower λ reorg than the central symmetric CBD-9 and left and right axis symmetric CBD-5, which is consistent with the previous conclusion of the front-line orbital analysis, obviously, smaller reorganization energy will be conducive to achieve narrower emission spectrum FWHM. On the other hand, the more the number of N atoms, the stronger the aromaticity of the central core, and the more obvious the weakening of the anti-aromaticity of the CBD fused on the side, which is conducive to improving the luminous efficiency. In addition to CBD-5 and CBD-9, the oscillator strength (f) of all the embodiments exceeds 0.79, which is higher than the value of the conventional B / N-hetero-fused ring-based multiple resonance type molecules, and even the value of the fully aromatic fluorescent core, indicating that the molecules provided by the present application will produce higher luminous efficiency.

[0151] Further according to the absorption / emission spectrum data in toluene solution, all the example molecules exhibit narrow-band emission characteristics, as expected by the theoretical calculation, especially the molecules based on quinoline nucleus and pyrazino[2,3:b]pyrazine nucleus. The FWHM of the latter spectrum can be narrowed to 11 nm. This has reached or even exceeded the most optimal multi-resonance type molecules based on B / N-hetero-fused ring skeleton reported in the current literature. In addition, the corresponding PLQY also reaches 0.98, which is comparable to the current most excellent ultra-narrow-band light-emitting materials-high-order B / N-hetero-fused ring system. At the same time, the molecules provided by the present application significantly reduce the difficulty of synthesis and the complexity of molecular structure, and the raw materials are easy to obtain, which is more conducive to commercial application.

[0152] OLED device application examples

[0153] In order to evaluate the electroluminescent performance of the luminescent molecules containing CBD structure provided by the present application, the present application is applied to electroluminescent devices. In addition, in order to embody the superiority of the molecular design of the present application, the classic multi-resonance light-emitting molecule DABNA-1 and the linear molecule CBD-00 containing CBD unit reported in the literature are prepared as comparative examples to prepare OLED devices with the same structure.

[0154] The structure diagram of the OLED device prepared by the present application is shown in the accompanying Figure 24 , which comprises 100 anode layer, 101 hole injection layer, 102 first hole transport layer, 103 second hole transport layer, 104 exciton blocking layer / electron blocking layer, 105 light-emitting layer, 106 exciton blocking layer / hole blocking layer, 107 electron transport layer, 108 electron injection layer, 109 cathode Al.

[0155] Among them, the anode layer 100 adopts indium tin oxide (ITO) material; the hole injection layer 101, with a thickness of 10 nm, adopts HATCN material; the first hole transport layer 102, with a thickness of 30 nm, adopts TAPC material; the second hole transport layer 103, with a thickness of 30 nm, adopts TCTA material; the electron blocking layer 104, with a thickness of 20 nm, adopts mCBP material; the light-emitting layer 105, with a thickness of 40 nm, adopts DBFPO as the host material, BO5TCz as the sensitizer, and the light-emitting guest material as the example molecule or the comparative example molecule provided by the present application, wherein the host material and the sensitizer form a mixed host, and the doping ratio is 7:3 (mass ratio). The doping ratio of the light-emitting guest material in the light-emitting layer is 3wt%.

[0156] The hole blocking layer 106 has a thickness of 20 nm and is made of DBFPO; the electron transport layer 107 has a thickness of 40 nm and is made of ANT-BIZ; the electron injection layer 108 has a thickness of 1 nm and is made of lithium fluoride (Liq); and the cathode layer 109 has a thickness of 20 nm and is made of metal Al.

[0157] The structural formula of the light-emitting material molecules DABNA-1 and CBD-00 used in the comparative examples is shown in Figure 19 The structural formula of the above-mentioned materials HATCN, TAPC, TCTA, BO5TCz, mCBP, ANT-BIZ and DBFPO is shown in Figure 20 .

[0158] The structures and the materials and components used in all devices are consistent, and only the light-emitting guest materials are different, and the specific correspondence is shown in Table 3. The key performance data of all devices are summarized in Table 3, and the current-voltage, voltage-luminance, power efficiency / current efficiency-luminance and external quantum efficiency-luminance curves of Example 5, Example 7 and Comparative Examples 1 and 2 are shown in Figs. 2-5, respectively. Figure 21 , Figure 22 , Figure 23 .

[0159] Firstly, the device results of Comparative Examples 1 and 2 in the devices prepared based on the present application are basically consistent with the corresponding literature reports (Adv. Mater., 2016, 28, 2777-2781), and the corresponding FWHM is 38 and 33 nm, respectively; compared with the comparative examples, the FWHM of the devices prepared based on the material of the present application is significantly narrowed, and the FWHM of the remaining device examples is less than 16 nm except for device examples 1 and 2, and the FWHM of the narrowest device examples 7 and 8 is as low as 12 nm, reaching the optimal value of the current literature report on narrow-band OLED performance.

[0160] Secondly, in terms of evaluating the photoelectric conversion efficiency of the device core, i.e. external quantum efficiency (EQE), power efficiency (PE) and current efficiency (CE). The device examples provided by the present application are significantly better than the comparative examples, for example, the external quantum efficiency of Example 7 (~30%) is almost twice that of Comparative Example 1 (18%) or Comparative Example 2 (12.9%), and the peak values of the electroluminescence spectra of the three devices are very close (~472 nm), which fully illustrates the superiority of the light-emitting device constructed by the cyclobutadiene-containing light-emitting material provided by the present application, which has excellent narrow-band. The cyclobutadiene-containing light-emitting material (ultra-narrow-band light-emitting molecule) constructed based on the CBD fusion strategy of the present application not only has an ultra-narrow emission spectrum half-width and high PLQY, but also has a significant advantage in the corresponding OLED performance.

[0161] Table 3. Summary of key data for OLED device performance.

[0162]

[0163] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0164] The above is a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A cyclobutadiene-containing light-emitting material, characterized by, For any one of structural formulae CBD-5, CBD-9, CBD-13, CBD-17, CBD-35, CBD-45, CBD-66, CBD-67: 、 、 、 、 、 、 、 。 2. Use of the cyclodioyl-containing light-emitting material according to claim 1 in the preparation of an organic electroluminescent device, a color conversion material.

3. An organic light emitting layer film, characterized by, The organic light-emitting layer film comprises the cyclodioyl-containing light-emitting material according to claim 1.

4. An organic electroluminescent device, characterized by comprising The organic light-emitting layer film comprises the cyclodioyl-containing light-emitting material according to claim 1.

5. The organic electroluminescent device according to claim 4, wherein The organic light-emitting layer film comprises the cyclodioyl-containing light-emitting material according to claim 1.

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