Luminescent material containing cyclobutadiene as well as preparation method and application of luminescent material

Abstract

The invention provides a luminescent material containing a cyclobutadiene structure, and a preparation method and application thereof, and relates to the technical field of organic electroluminescent materials. According to the cyclobutadiene-containing luminescent material provided by the invention, the anti-aromatic cyclobutadiene is fused into a binary nitrogen-containing fused heterocyclic skeleton, and excitation state vibration relaxation is inhibited by using the special electronic structure and high ring tension of the anti-aromatic cyclobutadiene, so that narrow-band luminescence is realized. By introducing the steric hindrance effect group, the aggregation fluorescence quenching phenomenon between luminescent parent nuclei is weakened, and the fluorescence quantum yield is improved. Different from a current mainstream multi-resonance mechanism, the design of the narrow-spectrum light-emitting molecule provided by the invention does not need to depend on the construction of a B / N-fused ring, and the molecular structure can be simplified to realize full-light-color ultra-narrow-band light emission. When the organic light-emitting diode is applied to an organic light-emitting device, an ultra-narrow full-width-at-half-peak electroluminescent spectrum and high device efficiency can be realized, and a better solution is provided for an ultra-high-definition organic light-emitting diode display technology.

Description

Technical Field

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

[0002] As a new display technology, OLED (Organic Light-Emitting Diode) has become the mainstream solution in the display field by virtue of its ultra-thin, flexible, and self-luminous characteristics. Its luminescent material system has evolved through three generations: in the early stage, fluorescent materials only utilized singlet excitons for luminescence, suffering from low efficiency problems (theoretical limit 25%); phosphorescent materials achieved 100% exciton utilization by introducing heavy metal atoms to capture triplet excitons, but faced cost pressure due to the dependence on precious metals, and the blue light materials had insufficient stability; the third-generation thermally activated delayed fluorescence (TADF) materials also achieved full exciton utilization through the reverse intersystem crossing (RISC) mechanism, while getting rid of the limitation of precious metals and showing significant cost advantages.

[0003] Based on the TADF mechanism, the Multiple Resonance (MR) technology is developed. By constructing the localization distribution difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) within the molecule, the non-bonding / non-bonding (n-π*) transition characteristics are realized, thereby significantly compressing the full width at half maximum (FWHM = 25 - 35 nm) of the emission spectrum. Specifically, HOMO is mainly localized on electron-rich heteroatoms such as nitrogen and oxygen, while LUMO is concentrated on electron-deficient boron or carbonyl (C=O) and other moieties. The spatial separation of such orbitals effectively inhibits the structural relaxation between the ground state and the excited state, reducing the Stokes shift. In order to pursue a narrower spectrum, existing research can optimize the FWHM to less than 15 nm by introducing a rigid skeleton or a π-expansion strategy through molecular engineering. However, such improvements are accompanied by a sharp increase in molecular weight (MW > 1000 Da), leading to key defects such as an increase in the crystallization temperature of the material and deterioration of the film-forming performance, resulting in a significant reduction in its compatibility with the mainstream vacuum evaporation process. In addition, the core structure of the currently constructed MR system (such as boron-nitrogen fused rings) has inherent bottlenecks such as scarce substitution sites and limited derivatization, and Japanese and Korean companies have completed a systematic patent layout in this field, which forms a major technical barrier to the construction of an independent and controllable OLED industrial chain in China.

[0004] In response to the above problems, the prior art attempts to optimize the performance by modifying peripheral groups or doping heteroatoms, but with limited results: either there is a problem of a decrease in molecular weight accompanied by spectral broadening; or there is a problem of insufficient structural derivatization and difficulty in breaking through the technical blockade.

[0005] In summary, it is urgent to develop a new type of MR luminescent material with a narrow spectrum to solve the dual dilemmas of process compatibility and patent barriers. Summary of the Invention

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

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

[0008]

[0009] In formula I or formula II, L1 and L2 independently selected from substituents with steric hindrance effects, n takes 0 to 4, and n in L1 and L2 is not 0 at the same time; R is selected from H, straight-chain alkyl or aryl; W, X, Y, Z are independently selected from C or N, and at least one of W, X, Y, Z is N to form a binary nitrogen-containing fused heterocycle.

[0010] A further technical solution thereof is that the substituents with steric hindrance effects include isopropyl, tert-butyl, triarylsilyl, truxenyl, adamantyl, biphenyl, 1,2-dimethylphenyl, trifluoromethyl, diarylboron, diphenylphosphine oxide, pyridyl, pyrimidinyl, diarylamino, 9H-carbazolyl, aryloxy, alkoxy.

[0011] A further technical solution thereof is that the binary nitrogen-containing fused heterocycle includes any one of quinoline, 1,5-naphthyridine, 1,8-naphthyridine, quinoxaline, pyrido[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine.

[0012] A further technical solution thereof is that the R is selected from any one of H, methyl, ethyl, isopropyl, tert-butyl, phenyl, tert-butylphenyl, naphthyl.

[0013] In the second aspect, the present invention provides a preparation method of a luminescent material containing cyclobutadiene as described in the first aspect, including the following steps:

[0014] Reacting a dihalohydrocarbon with a furan derivative under the action of a metal lithium reagent through a Diels-Alder addition reaction to generate an intermediate;

[0015] After the intermediate undergoes C-H activation under the action of a transition metal catalyst, it is subjected to a coupling reaction with a haloaromatic hydrocarbon molecule to obtain the end product of general formula (I) or general formula (II);

[0016] Among them, the dihalohydrocarbon has the structure shown in the general formula (III), and in the general formula (III), A and B are independently selected from the halogen elements Cl, Br or I:

[0017]

[0018] The furan derivative has the structure shown in the general formula (IV):

[0019]

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

[0021]

[0022] A further technical solution thereof is that the metal lithium reagent includes at least one of n-butyllithium and tert-butyllithium.

[0023] A further technical solution thereof is that 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, bis(triphenylphosphine)chloropalladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, and 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-trichloromethane complex.

[0024] In a third aspect, the present invention also provides the application of the cyclobutadiene-containing luminescent material described in the first aspect, or the cyclobutadiene-containing luminescent material prepared by the preparation method described in the second aspect, in the preparation of organic electroluminescent devices and color conversion materials.

[0025] In a fourth aspect, the present invention provides an organic light-emitting layer thin film, and the organic light-emitting layer thin film includes the cyclobutadiene-containing luminescent material described in the first aspect, or the cyclobutadiene-containing luminescent material prepared by the preparation method described in the second aspect.

[0026] In a fifth aspect, the present invention provides an organic electroluminescent device, including the cyclobutadiene-containing luminescent material described in the first aspect, and the cyclobutadiene-containing luminescent material prepared by the preparation method described in the second aspect, and is preferably applied to the light-emitting layer in the organic electroluminescent device.

[0027] Compared with the prior art, the technical effects that the present invention can achieve include:

[0028] The luminescent material containing cyclobutadiene provided by the present invention fuses antiaromatic cyclobutadiene (CBD) into a π-conjugated fluorescent skeleton. By utilizing its high ring strain and restricted electron delocalization characteristics of antiaromaticity, the rigidity of the molecular conjugated skeleton is significantly enhanced. The present invention uses the antiaromatic CBD fusion technology, which can increase the activation energy barrier of atomic stretching vibration within the molecule, effectively inhibit the excited-state configuration relaxation, and reduce the Stokes shift. By using the design of localized frontier molecular orbitals and the strategy of spatial separation of HOMO / LUMO orbitals, the difference in electron cloud distribution between the ground state and the excited state is reduced, directly reducing the energy loss during the transition process, and achieving the full width at half maximum (FWHM) of the emission spectrum compressed to 11-16 nm, effectively realizing the narrowing of the full width at half maximum of the emission spectrum and improving the external quantum efficiency of the light-emitting device.

[0029] Furthermore, the luminescent material containing cyclobutadiene of the present invention weakens the antiaromaticity of CBD (such as the NICS value) through steric hindrance effects by introducing large steric hindrance groups (such as triptycene, adamantane, etc.) and strong electron-donating / withdrawing groups (such as cyano, carbazole, etc.) around the binary nitrogen-containing heterocycle, improves the molecular rigidity, shrinks the molecular plane, weakens the molecular quenching effect, and at the same time can regulate the electron cloud density distribution, weaken the delocalization of the frontier orbital molecules, and enhance the solid-state quantum efficiency of the light-emitting device.

[0030] Furthermore, the luminescent material containing cyclobutadiene of the present invention contains a cyclobutadiene skeleton and can provide 4-6 modifiable sites. According to different introduced modifying groups, at least 72 structures can be derived, which has high derivatization compared with the prior art. It can also be coupled with auxiliary groups to further improve the molecular processing characteristics, reduce the fluorescence quenching effect between the luminescent groups, and regulate the molecular chemical stability and aromaticity, etc., to achieve an extremely narrow full width at half maximum (FWHM) and high device efficiency.

[0031] The preparation method of the luminescent material containing cyclobutadiene provided by the present invention adopts the Diels-Alder / Suzuki coupling method, and the raw materials have a wide source and have been industrialized, greatly reducing the production cost.

[0032] The luminescent material containing cyclobutadiene provided by the present invention is applied in an electroluminescent device, which can achieve strong stability, an extremely narrow full width at half maximum (FWHM), and high device efficiency. The present invention provides an autonomous material solution for high-resolution OLED display and lighting applications. Description of the Drawings

[0033] Figure 1 It is the optimized ground-state configuration diagram of the CBD-5 molecule provided by the embodiment of the present invention. In the figure, a) is the top view and b) is the side view.

[0034] Figure 2The LUMO and HOMO frontier orbital distribution diagrams of the CBD-5 molecule provided by the embodiments of the present invention.

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

[0036] Figure 4 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-9 molecule provided by the embodiments of the present invention.

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

[0038] Figure 6 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-13 molecule provided by the embodiments of the present invention.

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

[0040] Figure 8 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-35 molecule provided by the embodiments of the present invention.

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

[0042] Figure 10 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-45 molecule provided by the embodiments of the present invention.

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

[0044] Figure 12 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-66 molecule provided by the embodiments of the present invention.

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

[0046] Figure 14 The LUMO and HOMO frontier orbital distribution diagrams of the CBD-67 molecule provided by the embodiments of the present invention.

[0047] Figure 15 Absorption / Emission Spectrogram of CBD-9 Molecule in Toluene Solution provided by Embodiment of the Invention

[0048] Figure 16 Absorption / Emission Spectrogram of CBD-13 Molecule in Toluene Solution provided by Embodiment of the Invention

[0049] Figure 17 Absorption / Emission Spectrogram of CBD-45 Molecule in Toluene Solution provided by Embodiment of the Invention

[0050] Figure 18 Absorption / Emission Spectrogram of CBD-66 Molecule in Toluene Solution provided by Embodiment of the Invention

[0051] Figure 19 Molecular Structures of Luminescent Guests DABNA-1 and CBD-00 of Comparative Example 1 and Comparative Example 2

[0052] Figure 20 Molecular Structures of Functional Layer Materials Involved in Preparation of Organic Electroluminescent Devices

[0053] Figure 21 Current-Voltage-Brightness Curve Graph of Luminescent Devices Prepared with Luminescent Materials of Embodiment of the Invention and Comparative Examples

[0054] Figure 22 Power Efficiency-Brightness and Current Efficiency-Brightness Curve Graphs of Luminescent Devices Prepared with Luminescent Materials of Embodiment of the Invention and Comparative Examples

[0055] Figure 23 External Quantum Efficiency-Brightness Curve Graph of Luminescent Devices Prepared with Luminescent Materials of Embodiment of the Invention and Comparative Examples

[0056] Figure 24 Schematic Diagram of Structure of OLED Device provided by Embodiment of the Invention

[0057] Figure 25 Synthesis Route Diagram of Luminescent Material Containing Cyclobutadiene provided by Embodiment of the Invention Detailed Implementation Modes

[0058] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the invention. Similar component numbers in the drawings represent similar components. Obviously, the embodiments to be described below are only a part of the embodiments of the invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the invention without making creative efforts fall within the scope of protection of the invention.

[0059] An embodiment of the present invention provides a luminescent material containing cyclobutadiene, having a molecular structure represented by the following general formula (I) or general formula (II):

[0060]

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

[0062] In specific embodiments, the substituent with steric effect can be a neutral substituent with steric effect, such as isopropyl, tert-butyl, triarylsilyl, truxenyl, adamantyl, biphenyl, 1,2-dimethylphenyl and other groups; it can also be a large steric substituent with an electron-withdrawing effect, including trifluoromethyl, diarylboron, diphenylphosphine oxide, pyridyl, pyrimidinyl and other groups; it can also be a large steric substituent with an electron-donating effect, including diarylamino, 9H-carbazolyl, aryloxy, alkoxy and other groups.

[0063] In specific embodiments, the binary nitrogen-containing fused heterocycle can regulate the distribution of frontier orbitals, and its structure can be centrosymmetric, axially symmetric and other structures. For example, the binary nitrogen-containing fused heterocycle includes any one of quinoline, 1,5-naphthyridine, 1,8-naphthyridine, quinoxaline, pyrido[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine.

[0064] In specific embodiments, the R is selected from any one of H, methyl, ethyl, isopropyl, tert-butyl, phenyl, tert-butylphenyl, naphthyl. 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] An embodiment of the present invention also provides a preparation method of the above luminescent material containing cyclobutadiene, and the synthesis route is shown in Figure 25 .

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

[0067] React a dihalohydrocarbon with a furan derivative under the action of a metal lithium reagent through a Diels-Alder addition reaction to generate an intermediate;

[0068] After the intermediate undergoes C-H activation under the action of a transition metal catalyst, it undergoes a coupling reaction with a haloaromatic hydrocarbon molecule to obtain the end product of general formula (I) or general formula (II);

[0069] Among them, the dihalohydrocarbon has the structure shown in the general formula (III), and in the general formula (III), A and B are independently selected from the halogen elements Cl, Br or I:

[0070]

[0071] The furan derivative has the structure shown in the general formula (IV):

[0072]

[0073] The haloaromatic hydrocarbon molecule has the structure shown in the general formula (VI) or the general formula (VII), and in the general formula (VI) or the general formula (VII), A and B are independently selected from the halogen elements Cl, Br or I:

[0074]

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

[0076] In specific implementation, 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, bis(triphenylphosphine)chloropalladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, and 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-chloroform complex.

[0077] Since the cyclobutadiene skeleton can provide 4-6 modifiable sites, according to the different binary nitrogen-containing heteroaromatic ring structures and modifying groups, there are at least 72 kinds of cyclobutadiene-containing luminescent materials in the present invention, 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 solution of the present invention, cyclobutadiene-containing luminescent materials with narrow-band luminescence effects other than the above structural formulas CBD-1 to CBD-72 can be obtained.

[0081] The luminescent material containing cyclobutadiene provided in this embodiment realizes narrow-band luminescence by fusing antiaromatic cyclobutadiene to a binary nitrogen-containing heteroaromatic ring skeleton and utilizing its special antiaromatic electronic structure and high ring strain to inhibit excited-state vibrational relaxation. By introducing a steric hindrance effect group, the aggregation fluorescence quenching phenomenon between luminescent nuclei is weakened, and the fluorescence quantum yield is improved. From any specific embodiment of the above structural formulas CBD-1 to CBD-72, the molecular structure of the luminescent material containing cyclobutadiene of the present invention is different from the current mainstream multiple resonance mechanism. The present invention does not need to rely on the construction of B / N-heteroaromatic rings, and can simplify the molecular structure to achieve ultra-narrow spectral band luminescence of the entire visible light spectrum. The luminescent material containing cyclobutadiene provided in the embodiments of the present invention is applied in an organic electroluminescent device, and can achieve an electroluminescent spectrum with an ultra-narrow full width at half maximum and high device efficiency, providing a better solution for ultra-high definition organic light-emitting diode display technology.

[0082] To facilitate the full understanding of this technical solution by those skilled in the art, the synthesis route, basic photophysical properties, and its application in circularly polarized organic light-emitting diodes (CP-OLEDs) of the luminescent material containing cyclobutadiene provided by the present invention will be systematically described below in conjunction with specific examples and drawings.

[0083] Example 1 Synthesis of Luminescent Material CBD-9

[0084] The synthesis route is as follows:

[0085]

[0086] Add 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) into a dry 100 mL round-bottom flask. Pump to vacuum with an oil pump and then fill with nitrogen gas, repeating three times. Cool the solution to -75 °C, and slowly add a 2.5 M hexane solution of n-butyllithium (0.88 mL, 2.2 mmol) using a syringe pump. After the addition, restore to room temperature and stir for 12 h. After the reaction is completed, quench with water, extract with ethyl acetate, combine the organic phases and dry. After removing the excess solvent by rotary evaporation under reduced pressure, add silica gel powder and evaporate the solvent to dryness, and then separate and purify by column chromatography using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 481 mg of a colorless powder, namely intermediate 1-1 (yield 85%). HRMS (ESI) theoretical calculation C 20 H 26 O, [M+H] + 283.2062, the measured value is 283.2061.

[0087] In a dry 25 mL pressure-resistant tube, palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added. The mixture was stirred at room temperature for 5 minutes and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. Through column chromatography, separation and purification were carried out using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 575 mg of a white solid, namely CBD-11 (yield 86%). HRMS (ESI) theoretical calculation C 48 H 50 N2, [M+H] + 655.4052, the measured value was 655.4049.

[0088] 1 1H 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] Example 2 Synthesis of Luminescent Material CBD-5

[0090] The synthesis route is as follows:

[0091]

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

[0093] In a dry 25 mL pressure-resistant tube, palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added. The mixture was stirred at room temperature for 5 minutes and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. Through column chromatography, separation and purification were carried out using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 582 mg of a white solid, namely CBD-21 (yield 88%). HRMS (ESI) theoretical calculation C 48 H 50N2, [M+H] + 655.4052, the measured value is 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 in Example 3

[0096] The synthesis route is as follows:

[0097]

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

[0099] Add palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent into a dry 25 mL pressure-resistant tube. Stir the mixture at room temperature for 5 minutes, and then heat it to 130 °C for reaction for 24 h. After the reaction solution is cooled to room temperature, filter it through a thin layer of diatomaceous earth to remove inorganic salts, and wash the residue on the diatomaceous earth with chloroform. Separate and purify by column chromatography using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 582 mg of white solid CBD-31 (yield 88%). HRMS (ESI) theoretical calculation C 48 H 50 N2, [M+H] + 655.4052, the measured value is 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 in Example 4

[0102] The synthesis route is as follows:

[0103]

[0104] The process for preparing Intermediate 1-1 is the same as the steps described in Example 1.

[0105] Palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added to a dry 25 mL pressure-resistant tube. The mixture was stirred at room temperature for 5 minutes and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. By column chromatography, separation and purification were carried out using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 584 mg of a white solid, namely CBD-61 (yield 88%). HRMS (ESI) theoretical calculation C 46 H 48 N4, [M+H] + 657.3957, the measured value was 657.3960.

[0106] 1 1H NMR (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 Luminescent Material CBD-66 in Example 5

[0108] The synthesis route is as follows:

[0109]

[0110] Diphenylethanedione (420.01 mg, 2.00 mmol), 5-bromopyrazine-2,3-diamine (378.02 mg, 2.00 mmol) and 50 mL of water were added to a dry 150 mL two-necked flask. It was evacuated to vacuum with an oil pump and then filled with nitrogen, and this was repeated three times. The mixed system was heated to 105 °C and stirred for 15 min. After the reaction ended, the organic phases were extracted and combined and dried. After removing the excess solvent by rotary evaporation under reduced pressure, silica gel powder was added and the solvent was rotary evaporated to dryness. Then, separation and purification were carried out by column chromatography to obtain 442 mg of a powder, namely Intermediate 5-1 (yield: 50%), HRMS (ESI) theoretical calculation C 18 H 11 BrN4, [M+H] + 363.0245, the measured value was 363.0247.

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

[0112] 4″,5″-Dibromo-1,1':2',1″:2″,1‴:2‴,1″″-quaterphenyl (1.08 g, 2.00 mmol) and 2,5-dimethylfuran (972 mg, 10.0 mmol) were evacuated with an oil pump and then filled with nitrogen gas, and this was repeated three times. The solution was cooled to -75 °C, and a 2.5 M hexane solution of n-butyllithium (0.88 mL, 2.2 mmol) was slowly added dropwise using a syringe pump. After the addition was complete, the mixture was allowed to return to room temperature and stirred for 12 h. After the reaction was completed, water was added to quench the reaction, and the mixture was extracted with ethyl acetate. The organic phases were combined and dried. After removing the excess solvent by rotary evaporation under reduced pressure, silica gel powder was added and the solvent was evaporated to dryness. Then, column chromatography was performed using ethyl acetate / n-hexane (1:20, v / v) as the eluent for separation and purification to obtain 481 mg of a colorless powder, namely intermediate 5-2 (yield: 50%). HRMS (ESI) theoretical calculation for C 36 H 28 O, [M + H] + 477.2218, the measured value was 477.2220.

[0113] Palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added to a dry 25 mL pressure-resistant tube. The mixture was stirred at room temperature for 5 minutes, and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. Column chromatography was performed using ethyl acetate / n-hexane (1:20, v / v) as the eluent for separation and purification to obtain 652 mg of a white solid, namely CBD-76 (yield 88%). HRMS (ESI) theoretical calculation for C 54 H 36 N4, [M + H] + 741.3018, the measured value was 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] Example 6 Synthesis of Luminescent Material CBD-45

[0116] The synthetic route is as follows:

[0117]

[0118] The process for preparing Intermediate 1-1 is the same as the steps described in Example 1.

[0119] Palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added to a dry 25 mL pressure-resistant tube. The mixture was stirred at room temperature for 5 minutes and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. By column chromatography, separation and purification were carried out using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 473 mg of a white solid, namely CBD-45 (yield 86%). HRMS (ESI) theoretical calculation C 40 H 36 N2, [M+H] + 545.2957, the measured value was 545.2955.

[0120] 1 1H 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 Luminescent Material CBD-67 in Example 7

[0122] The synthetic route is as follows:

[0123]

[0124] In a dry 150 mL two-necked flask, add [1,1'-biphenyl]-2-carbaldehyde (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 with an oil pump and then fill with nitrogen gas, repeating three times. Heat the mixed system to 105 °C and stir for 15 min. After the reaction is completed, extract and combine the organic phases and dry. Remove the excess solvent by rotary evaporation under reduced pressure, add silica gel powder and dry the solvent by rotary evaporation. Then separate and purify by column chromatography to obtain 258 mg of powder, namely intermediate 7-1 (yield: 50%). HRMS (ESI) theoretical calculation C 30 H 19 BrN4, [M+H] + 515.0871, the measured value is 515.0873.

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

[0126] In a dry 25 mL pressure-resistant 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 minutes, then heat to 130 °C and react for 24 h. After the reaction solution is cooled to room temperature, filter through a thin layer of diatomaceous earth to remove inorganic salts, and wash the residue on the diatomaceous earth with chloroform. Separate and purify by column chromatography using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 621 mg of white solid, namely CBD-78 (yield 88%). HRMS (ESI) theoretical calculation C 50 H 42 N4, [M+H] + 699.3488, the measured value is 699.3490.

[0127] 1 1H 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 in Example 8

[0129] The synthesis route is as follows:

[0130]

[0131] In a dry 150 mL round-bottom flask, add (1r,3r,5r,7r)-2-phenyladamantane (424.68 mg, 2.00 mmol), iron(III) bromide (295.56 mg, 1.00 mmol), liquid bromine (639.23 mg, 4.00 mmol), and 50 mL of dichloromethane. Stir the mixture at room temperature for 12 h. After the reaction is completed, extract and combine the organic phases and dry them. Remove the excess solvent by rotary evaporation under reduced pressure, add silica gel powder, and dry the solvent by rotary evaporation. Then, separate and purify by column chromatography to obtain 518 mg of powder, namely intermediate 8-1 (yield: 70%). HRMS (ESI) theoretical calculation for C 16 H 18 Br2, [M+H] + 368.9854, the measured value is 368.9856.

[0132] In a dry 100 mL round-bottom flask, add intermediate 8-1 (740.26 mg, 2.00 mmol) and 2,5-dimethylfuran (972 mg, 10.0 mmol). Pump to vacuum and then fill with nitrogen three times. Cool the solution to -75 °C and slowly add a 2.5 M hexane solution of n-butyllithium (0.88 mL, 2.2 mmol) using a syringe pump. After the addition is complete, restore to room temperature and stir for 12 h. After the reaction is completed, add water to quench, extract with ethyl acetate, combine the organic phases and dry them. Remove the excess solvent by rotary evaporation under reduced pressure, add silica gel powder, and dry the solvent by rotary evaporation. Then, separate and purify by column chromatography using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 521 mg of colorless powder, namely intermediate 8-2 (yield 85%). HRMS (ESI) theoretical calculation for C 22 H 26 O, [M+H] + 307.2062, the measured value is 307.2065.

[0133] In a dry 25 mL pressure-resistant tube, palladium acetate (22.56 mg, 0.1 mmol), (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 of solvent were added. The mixture was stirred at room temperature for 5 minutes and then heated to 130 °C for reaction for 24 h. After the reaction solution was cooled to room temperature, it was filtered through a thin layer of diatomaceous earth to remove inorganic salts, and the residue on the diatomaceous earth was washed with chloroform. Through column chromatography, separation and purification were carried out using ethyl acetate / n-hexane (1:20, v / v) as the eluent to obtain 625 mg of a white solid, namely CBD-79 (yield 88%). HRMS (ESI) theoretical calculation C 52 H 50 N2, [M+H] + 703.4052, the measured value was 703.4055.

[0134] 1 1H NMR (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 and photophysical characterization

[0136] To clarify the superiority of the cyclobutadiene-containing luminescent material provided by the present invention, the following provides theoretical simulation data of the key parameters of the molecules of some of the above examples based on the Gaussian16 software, and the results are shown in Table 1 below. For the sake of simplifying the calculation, some alkyl chains were reasonably simplified to methyl groups, and the biphenyl group was simplified to a phenyl group. The optimization of all ground-state configurations was obtained based on the B3LYP / 6-311G** level, the default gas-phase single-molecule state, and considering the dispersion correction. The excited-state energy levels and configuration optimization were obtained by TD-DFT calculation based on the optimized ground-state configuration, and the basis set and functional used for the calculation were the same as those of the ground state. The visualization of all orbitals was realized based on the Gaussview 6.0 software.

[0137] Table 1. Calculation results of frontier orbital energy levels and measured electrochemical energy levels

[0138]

[0139]

[0140] Among them, a) is the data obtained by theoretical simulation calculation, and b) the HOMO is estimated by the oxidation potential of cyclic voltammetry, LUMO = HOMO - Eg, where Eg is the optical band gap.

[0141] It can be seen from the theoretical calculation results in Table 1 that the HOMO energy levels of all molecules based on the CBD structure are in the range of -5.53 to -5.91 eV, and the LUMO energy levels are between -2.30 and -2.73 eV, which are comparable to the energy levels of conventional n-type light-emitting molecules and meet the general requirements of OLED devices for the energy levels of light-emitting guest molecules. In addition, through horizontal comparison, it is found that from CBD-5, CBD-9, to CBD-35, CBD-45, and then CBD-66, CBD-67, the central nuclei change from naphthyridine and quinoxaline to pyrazino[2,3-b]pyrazine in turn, and the electron affinity of the central nuclei 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 in dichloromethane solution based on cyclic voltammetry, and the results and trends are basically consistent with the calculation. The HOMO energy levels of CBD-13 and CBD-17 based on the quinoxaline nucleus are the shallowest at -5.40 eV, and the HOMO energy level of CBD-66 based on the pyrazino[2,3-b]pyrazine nucleus is the deepest, reaching -6.08 eV. Based on the optical band gap Eg and the HOMO energy level, the LUMO energy levels of these example molecules were estimated to be in the range of -2.21 to -3.03 eV, which is beneficial to the injection of electrons from the electron transport layer into the light-emitting layer.

[0142] To further demonstrate the influence of the changes in the number or position of nitrogen atoms in the substituents and nitrogen-containing fused heterocycles on the HOMO and LUMO orbital distributions, the frontier orbital distributions of the above example molecules were calculated in the present invention, and visualized using GaussView 6.0. For the sake of simplifying the calculation, some alkyl chains were simplified to methyl groups, and the biphenyl group was simplified to a single phenyl group. Therefore, the calculation models corresponding to CBD-13 and CBD-17 are the same. The molecular preferred configuration diagrams and orbital distribution diagrams after visualization are shown in the appendix Figures 1 - 14Since the molecules designed in the present invention are all linearly extended, that is, the CBD unit is fused on both sides of the nitrogen-containing binary fused ring, and then the substituents continue to conjugate and expand along the extension direction of CBD. Thanks to this design, all molecules exhibit a rigid planar configuration and conjugate extension in a linear manner. It can be seen that the luminescent material containing cyclobutadiene provided by the present invention can effectively conjugate and extend, greatly weaken the anti-aromaticity of the CBD core, and improve the luminescent performance of the molecule. By comparing the LUMO orbital distribution maps of all example molecules, it is found that the LUMO orbitals all show obvious localization, that is, most of the LUMO is distributed on the electron-deficient N atoms and the C atoms at the resonance sites of the N atoms. In addition, a part is also distributed on the CBD moiety, indicating the contribution of the CBD moiety to the frontier orbitals and the excited state. Although the HOMO orbitals have a certain degree of delocalization, they also show a relatively isolated distribution, that is, they generally exist between 2-3 adjacent atoms. This kind of frontier orbital distribution is beneficial to reducing the proportion of bonding / antibonding orbital transitions during the HOMO-LUMO transition, thereby reducing the vibrational relaxation of the excited state and narrowing the emission spectrum. Further horizontal comparison shows that the central core has a greater influence on the frontier orbitals. With the increase in the number of N atoms, the LUMO is more localized on a single atom. In addition, the axially symmetric structure (such as quinoline) has better orbital localization than the centrosymmetric structure (such as naphthyridine). Therefore, it can be predicted that the central core with an axially symmetric structure is beneficial to output a narrower emission spectrum.

[0143] A luminescent material containing cyclobutadiene provided by the present invention is a narrow-band luminescent molecule containing a cyclobutadiene structure. By fusing the anti-aromatic cyclobutadiene to the binary nitrogen-containing heteroaromatic ring skeleton and using its special anti-aromatic electronic structure and high ring strain, the vibrational relaxation of the excited state is inhibited to achieve narrow-band luminescence. By introducing a steric hindrance effect group, the aggregation fluorescence quenching phenomenon between the luminescent parent nuclei is weakened, and the fluorescence quantum yield is improved. Specifically, in the design of the narrow-band luminescent molecule containing a cyclobutadiene structure of the present invention, the fusion site of cyclobutadiene is limited to both sides (X-axis direction) of the binary nitrogen-containing heteroaromatic ring to form a linear conjugate extension. Although only the theoretical calculations of 8 examples are provided here, those skilled in the art can clearly know based on the existing rules. This linear conjugate extension design of the present invention can effectively provide the rigid structure of the molecule, weaken the anti-aromaticity of cyclobutadiene and improve the fluorescence efficiency on the one hand; on the other hand, it effectively inhibits the delocalization of the frontier orbitals, makes the frontier orbitals more localized on the atoms, reduces the proportion of bonding / antibonding orbital transitions, and finally realizes an ultra-narrow emission spectrum. Obviously, based on the existing theoretical calculation data provided, the above rules can be obtained.

[0144] To further clarify the advantages of the molecular design of the present invention, the present invention calculated the photophysical-related data (Table 2 in the appendix) of the above example molecules based on the Franck-condon analysis and the vibrational analysis of MOMAP.

[0145] Correspondingly, the present invention tested the absorption and emission spectra of the molecules in the above embodiments in toluene solution. Some specific values are presented in Table 2 in the appendix, and some representative absorption / emission spectrograms are presented in the appendix Figures 15 - 18 .

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

[0147]

[0148]

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

[0150] The results in Table 2 show that all the molecules in the embodiments exhibit relatively small reorganization energies (λ reorg ), but there are significant differences among different structures. For the molecules constructed with quinoxaline and pyrazino[2,3:b]pyrazine with up-down axial symmetry as the central core, such as CBD-66 and CBD-13, the λ reorg is significantly lower than that of centrosymmetric CBD-9 and left-right axially symmetric CBD-5, which is consistent with the previous frontier orbital analysis conclusion. Obviously, smaller reorganization energies will be beneficial to achieving a narrower full width at half maximum (FWHM) of the emission spectrum. On the other hand, the more N atoms there are, the stronger the aromaticity of the central core, and the more obvious the weakening of the anti-aromaticity of the adjacent fused CBD, which is beneficial to improving the luminescence efficiency. Except for CBD-5 and CBD-9, the oscillator strengths (f) of all the embodiments exceed 0.79, which is higher than that of conventional multiple resonance molecules based on B / N-heterocyclic rings and even the values of fully aromatic fluorescent cores, indicating that the molecules provided by the present invention will produce higher luminescence efficiency.

[0151] Furthermore, based on the absorption / emission spectral data in toluene solution, as expected from theoretical calculations, all these example molecules exhibit narrow-band emission characteristics, especially the molecules based on quinoline nuclei and pyrazino[2,3:b]pyrazine nuclei. The FWHM of the latter spectrum can be narrowed down to as narrow as 11 nm. This has reached and even exceeded the optimal multi-resonant molecules based on B / N-heterocyclic fused-ring skeletons reported in the current literature. In addition, the corresponding PLQY also reaches 0.98, which can fully compete with the current best ultra-narrow band emission materials - high-order B / N-heterocyclic fused-ring systems. At the same time, the molecules provided by the present invention have significantly reduced synthesis difficulty and molecular structure complexity, with easily available raw materials, which is more conducive to commercial applications.

[0152] OLED Device Application Example

[0153] To evaluate the electroluminescence performance of the CBD structure-containing luminescent molecules provided by the present invention, they are now applied to electroluminescent devices. In addition, to reflect the superiority of the molecular design of the present invention, the classic multi-resonant luminescent molecule DABNA-1 and the linear molecule CBD-00 containing the CBD unit reported in the literature are used as comparative examples to prepare OLED devices with the same structure.

[0154] The schematic structural diagram of the OLED device prepared by the present invention is shown in the appendix Figure 24 , which includes an anode layer 100, a hole injection layer 101, a first hole transport layer 102, a second hole transport layer 103, an exciton blocking layer / electron blocking layer 104, a light-emitting layer 105, an exciton blocking layer / hole blocking layer 106, an electron transport layer 107, an electron injection layer 108, and a cathode Al.

[0155] Among them, the anode layer 100 is made of indium tin oxide (ITO) material; the hole injection layer 101 has a thickness of 10 nm and the material used is HATCN; the first hole transport layer 102 has a thickness of 30 nm and the material used is TAPC; the second hole transport layer 103 has a thickness of 30 nm and the material used is TCTA; the electron blocking layer 104 has a thickness of 20 nm and the material used is mCBP; the light-emitting layer 105 has a thickness of 40 nm, the host material used is DBFPO, the sensitizer is BO5TCz, and the light-emitting guest material is the example molecule or comparative example molecule provided by the present invention. Among them, 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 3 wt%.

[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); the cathode layer 109 has a thickness of 20 nm and is made of metal Al.

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

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

[0159] First, among the devices prepared based on the present invention, the results of the devices in Comparative Example 1 and Comparative Example 2 are basically consistent with the corresponding literature reports (Adv. Mater., 2016, 28, 2777-2781), and the corresponding FWHMs are 38 and 33 nm, respectively. Compared with the comparative examples, the FWHMs of the devices prepared based on the materials of the examples of the present invention are significantly narrowed. Except for Examples 1 and 2 of the devices, the FWHMs of the remaining device examples are all lower than 16 nm, and the narrowest FWHMs of Examples 7 and 8 of the devices are as low as 12 nm, reaching the optimal value of the narrow-band OLED performance reported in the current literature.

[0160] Secondly, in terms of evaluating the core optoelectronic conversion efficiency of the devices, namely the external quantum efficiency (EQE), power efficiency (PE), and current efficiency (CE). The device examples provided by the present invention are significantly superior to the comparative examples. For example, the external quantum efficiency of Example 7 (~30%) is almost twice that of Comparative Example 1 (18%) or 2 (12.9%), and the electroluminescence spectral peaks of these three devices are very close (~472 nm), which fully demonstrates the superiority of the luminescent devices constructed with the luminescent materials containing cyclobutadiene provided by the present invention, having an excellent narrow spectrum. The luminescent materials containing cyclobutadiene (ultra-narrow spectrum luminescent molecules) constructed based on the CBD fusion strategy of the present invention not only have an ultra-narrow emission spectral half-peak width and high PLQY, but also have significant advantages in their corresponding OLED performance.

[0161] Table 3. Summary of key data on the performance of OLED devices.

[0162]

[0163] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not described in detail in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0164] As described above, the above are the specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A luminescent material containing cyclobutadiene, characterized in that: It has a molecular structure represented by the following general formula (I) or general formula (II): In formula I or formula II, L1 and L2 are independently selected from substituents with steric effect, n is 0 to 4, and n in L1 and L2 are not 0 at the same time; R is selected from H, straight-chain alkyl or aryl; W, X, Y, Z are independently selected from C or N, and at least one N among W, X, Y, Z forms a binary nitrogen-containing fused heterocyclic ring.

2. The cyclobutadiene-containing luminescent material according to claim 1, characterized in that: The substituents with steric hindrance effect include isopropyl, tert-butyl, triarylsilyl, triptylenyl, adamantyl, biphenyl, 1,2-dimethylphenyl, trifluoromethyl, diarylboryl, diphenylphosphine oxide, pyridyl, pyrimidyl, diarylamine, 9H-carbazolyl, aryloxy, and alkoxy.

3. The cyclobutadiene-containing luminescent material according to claim 1, characterized in that: The binary nitrogen-containing fused heterocyclic ring includes any one of quinoline, 1,5-naphthyridine, 1,8-naphthyridine, quinoxaline, pyrido[2,3-b]pyrazine, and pyrazino[2,3-b]pyrazine.

4. The cyclobutadiene-containing luminescent material according to claim 1, characterized in that: The R is selected from any one of H, methyl, ethyl, isopropyl, tert-butyl, phenyl, tert-butylphenyl, and naphthyl.

5. The cyclobutadiene-containing luminescent material according to claim 1, characterized in that: The cyclobutadiene-containing luminescent material is any one of the following structural formulas CBD-1 to CBD-72:

6. A method for preparing a luminescent material containing cyclobutadiene according to any one of claims 1 to 5, characterized in that: The following steps are involved: The dihalogenated hydrocarbon is reacted with a furan derivative by Diels-Alder addition reaction under the action of a metallic lithium reagent to generate an intermediate; The intermediate is activated by CH under the action of a transition metal catalyst, and then coupled with a halogenated aromatic hydrocarbon molecule to obtain a final product of the general formula (I) or the general formula (II); The dihalogenated hydrocarbon has a structure shown in the general formula (III), wherein A and B in the general formula (III) are independently selected from halogen elements Cl, Br or I: The furan derivatives have the structure shown in the general formula (IV): The halogenated aromatic hydrocarbon molecule has a structure shown in the general formula (VI) or the general formula (VII), and A and B in the general formula (VI) or the general formula (VII) are independently selected from halogen elements Cl, Br or I:

7. The method for preparing a luminescent material containing cyclobutadiene according to claim 6, characterized in that: The metal lithium reagent includes at least one of n-butyl lithium and tert-butyl lithium; the transition metal catalyst includes at least one of palladium acetate, palladium chloride, tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)palladium, bis(dibenzylideneacetone)palladium, bis(acetonitrile)palladium dichloride, bis(triphenylphosphine)palladium chloride, 1,1'-bis[(diphenylphosphino)ferrocene]palladium dichloride, and 1,1'-bis[(diphenylphosphino)ferrocene]palladium dichloride-trichloromethane complex.

8. Use of the cyclobutadiene-containing luminescent material according to any one of claims 1 to 5, or the cyclobutadiene-containing luminescent material prepared by the preparation method according to any one of claims 6 to 7 in the preparation of organic electroluminescent devices and color conversion materials.

9. An organic light-emitting layer thin film, characterized in that: The organic light-emitting layer thin film comprises the cyclobutadiene-containing light-emitting material according to any one of claims 1 to 5, or the cyclobutadiene-containing light-emitting material prepared by the preparation method according to any one of claims 6 to 7.

10. An organic electroluminescent device, characterized in that: The luminescent material containing cyclobutadiene according to any one of claims 1 to 5 and the luminescent material containing cyclobutadiene prepared by the preparation method according to any one of claims 6 to 7 are preferably used in the luminescent layer of an organic electroluminescent device.

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