A thermally activated delayed fluorescent material and its preparation method and application

Abstract

The invention discloses a thermally activated delayed fluorescent material and a preparation method and application thereof. The structural formula of the thermally activated delayed fluorescent material is: #imgabs0# wherein R1 is hydrogen, tert-butyl or aromatic group; R2 is aromatic group; R3 is aromatic group; X and Y are each independently ‑CH‑ or nitrogen. The thermally activated delayed fluorescent material provided by the invention is a gold (I) complex, which uses a carbazole ligand with greater rigidity as an electron donor and an electron-withdrawing carbene ligand as an electron acceptor, and the two use metal gold (I) as a bridge, the electron donor and the electron acceptor are located on the two ligands, the metal accounts for a small proportion, and the thermally activated delayed fluorescence is achieved by charge transfer between the carbazole donor and the carbene acceptor.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials, and in particular to a thermally activated delayed fluorescent material and a preparation method and application thereof. Background Art

[0002] In recent decades, gold complexes have attracted extensive attention due to their rich optical reaction properties, including unique electronic structure (full d orbital electrons) and special intermolecular interactions (metal interactions), and have had a significant impact in many fields such as homogeneous catalysis, medicinal chemistry and materials science. Gold (I) complexes have spin-orbit coupling (SOC) constants second only to those of precious metals such as iridium and platinum, and the d 10 The special electron layer structure can avoid the splitting of the coordination field d orbital, and the emission is usually dominated by triplet excited state phosphorescence. Compared with some metal complexes with low spin-orbit coupling constants (such as copper (I), silver (I), etc.), gold (I) complexes have higher spin-orbit coupling constants, which makes it difficult to achieve thermally activated delayed fluorescence emission (and the photoluminescence quantum yield is low, and the number of ligands is small), and mainly phosphorescence emission is the main emission. Moreover, gold (I) complexes are more likely to exist in a polymerized form due to their strong gold (I)...gold (I) interaction force, forming multi-nuclear phosphorescent metal complexes with poor solubility, which greatly limits the application of gold (I) complexes in optoelectronic materials.

[0003] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a thermally activated delayed fluorescence material and a preparation method and application thereof, aiming to solve the problem that the existing gold (I) complexes are difficult to achieve thermally activated delayed fluorescence emission due to their high spin-orbit coupling constant.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect of the present invention, a thermally activated delayed fluorescent material is provided, wherein the structural formula of the thermally activated delayed fluorescent material is:

[0007]

[0008] Wherein, R1 is hydrogen, tert-butyl or aromatic group; R2 is aromatic group; R3 is aromatic group; X and Y are each independently -CH- or nitrogen.

[0009] The thermally activated delayed fluorescence material provided by the present invention is a gold (I) complex, which uses a carbazole ligand with relatively large rigidity as an electron donor and an electron-withdrawing carbene ligand as an electron acceptor, the two of which use metal gold (I) as a bridge, the electron donor and the electron acceptor are located on the two ligands, the metal accounts for a small proportion, and thermally activated delayed fluorescence is achieved through charge transfer between the carbazole donor and the carbene acceptor.

[0010] Specifically, by introducing large steric hindrance R2 groups on both sides of the carbazole donor, on the one hand, the gold (I)-carbene part can be rotated, physically reducing the overlap of the HOMO and LUMO of the donor and the acceptor, reducing the singlet and triplet energy gaps, and increasing the reverse intersystem crossing rate constant; on the other hand, there is a certain intermolecular interaction between the R2 group on the carbazole and the carbene, so that the thermally activated delayed fluorescent material forms a stable vertical structure, achieving high photoluminescence quantum efficiency and low luminescence lifetime, while preventing the aggregation of molecules, making it difficult to form multi-nuclear phosphorescent complexes. Further, by introducing different steric hindrance groups on the carbene nitrogen to adjust the stability of the molecule (increasing the molecular weight and improving the thermal stability), and by changing the X and Y elements of the carbene to adjust the color of the luminescence, the luminescence color of the gold (I) complex is further adjusted by adjusting the push-pull electron ability of the ligand.

[0011] In addition, the molecular structure of the thermally activated delayed fluorescent material is relatively three-dimensional and has a large molecular weight, which makes the material have good thermal stability, and its decomposition temperature is higher than 260°C, which is comparable to the thermal decomposition temperature of the currently reported monetary metal (gold, silver, copper) complexes. The delayed fluorescence lifetime of the thermally activated delayed fluorescent material is close to 1μs, which is the optimal lifetime value for achieving thermally activated delayed fluorescence (TADF) luminescence, ensuring the stability of the excited state, and can be used to prepare high-efficiency, low-roll-off electroluminescent devices.

[0012] Optionally, the aromatic group includes a substituted C6-C60 aromatic ring group or an unsubstituted C6-C60 aromatic ring group.

[0013] Optionally, the R2 is selected from one of the following structures:

[0014]

[0015] Among them, "---" represents the connection site, and Ph, DPXZ, etc. below the structural formula are the abbreviations of the corresponding structural formula above it.

[0016] Optionally, the R3 is selected from one of the following structures:

[0017]

[0018] Among them, "---" represents the connection site, and Ph, DMe, etc. below the structural formula are the abbreviations of the corresponding structural formula above it.

[0019] Optionally, the thermally activated delayed fluorescent material is selected from one of the following structures:

[0020]

[0021]

[0022]

[0023] Among them, CHPh-Ph, CHPh-DPXZ, etc. below the structural formula are the abbreviations of the corresponding structural formulas above them.

[0024] The second aspect of the present invention provides a method for preparing the thermally activated delayed fluorescent material as described above, wherein the thermally activated delayed fluorescent material is prepared by the following general reaction formula:

[0025]

[0026] The preparation method comprises the steps of:

[0027] Will and Adding into an organic solvent, after reaction, the thermally activated delayed fluorescent material is obtained, wherein R is a halogen atom, R1 is hydrogen, tert-butyl or aromatic group; R2 is an aromatic group; R3 is an aromatic group; X and Y are independently -CH- or nitrogen.

[0028] The method provided by the present invention is simple to operate, easy to control, and does not require overly complicated separation and purification processes. By increasing the molecular weight, the material can have good thermal processing ability, ensuring the film-forming stability of the material, and is expected to manufacture new optical devices.

[0029] Optionally, R is a chlorine atom.

[0030] Optionally, the organic solvent is selected from at least one of tetrahydrofuran, ethanol and acetonitrile.

[0031] The third aspect of the present invention provides a use of the thermally activated delayed fluorescent material as described above in an electroluminescent device.

[0032] Optionally, the electroluminescent device is an organic light emitting diode (OLED).

[0033] The present invention can obtain a thermally activated delayed fluorescent material with excellent performance and adjustable luminescent color by regulating the molecular structure of the thermally activated delayed fluorescent material. In addition, the thermally activated delayed fluorescent material provided by the present invention has good thermal processing ability and film-forming stability, and can be used as a luminescent material for electroluminescent devices such as OLEDs, so that the electroluminescent devices have the advantages of high quantum yield, low roll-off, etc.

[0034] Beneficial effects: The thermally activated delayed fluorescent material provided by the present invention is a fluorescent gold (I) complex, which uses a carbazole ligand with relatively large rigidity as an electron donor and an electron-withdrawing carbene ligand as an electron acceptor, and the two use metal gold (I) as a bridge, and the electron donor and the electron acceptor are located on the two ligands, and the metal accounts for a small proportion. The present invention expands the types of electron acceptors and electron donors of the gold (I) complex and realizes thermally activated delayed fluorescence through charge transfer between the carbazole donor and the carbene acceptor. Specifically, by introducing a large steric hindrance R2 group on both sides of the carbazole donor, on the one hand, the gold (I)-carbene part can be rotated, and the overlap of the HOMO and LUMO of the donor and the acceptor can be physically reduced, the singlet and triplet energy gaps can be reduced, and the reverse intersystem crossing rate constant can be increased; on the other hand, the R2 group on the carbazole and the carbene have certain intermolecular interactions, so that the thermally activated delayed fluorescent material forms a stable vertical structure, achieves high photoluminescence quantum efficiency and low luminescence lifetime, and prevents the aggregation of molecules, making it difficult to form a multi-nuclear phosphorescent compound. Furthermore, by introducing different steric groups on the carbene nitrogen to adjust the stability of the molecule (increasing the molecular weight and improving thermal stability), and by changing the X and Y elements in the carbene to adjust the color of the luminescence, the luminescence color of the gold (I) complex is further adjusted by adjusting the push-pull electron ability of the ligand. In addition, the molecular structure of the thermally activated delayed fluorescent material is relatively three-dimensional and has a large molecular weight, so that the material has good thermal stability, and its decomposition temperature is higher than 260°C, which is comparable to the thermal decomposition temperature of the currently reported monetary metal (gold, silver, copper) complex. The delayed fluorescence lifetime of the thermally activated delayed fluorescent material is close to 1μs, which is the optimal lifetime value for achieving TADF luminescence, ensuring the stability of the excited state, and has the potential to prepare high-efficiency, low-roll-off electroluminescent devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The absorption spectra of the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 in 2-MeTHF with a complex concentration of 10 μM.

[0036] Figure 2 The absorption spectra of the complex N2DMe-DPXZ prepared in Example 3 and the complex CHiPr-PCz prepared in Example 4 in 2-MeTHF with a complex concentration of 10 μM.

[0037] Figure 3 This is the emission spectrum of the complex N2DMe-Ph prepared in Example 2 in 2-MeTHF with a complex concentration of 10 μM.

[0038] Figure 4 This is the emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in 2-MeTHF with a complex concentration of 10 μM.

[0039] Figure 5 This is the emission spectrum of the complex N2DMe-Ph prepared in Example 2 in PMMA film.

[0040] Figure 6 This is the emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in PMMA film.

[0041] Figure 7 This is the emission spectrum of the complex CHiPr-PCz prepared in Example 4 in PMMA film.

[0042] Figure 8 This is the emission spectrum of the complex NiPr-TPA prepared in Example 5 in PMMA film.

[0043] Fig. 9 This is the emission spectrum of the complex N2DMe-Ph prepared in Example 2 in mCP film.

[0044] Fig.10 This is the emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in mCP film.

[0045] Fig.11 This is the time-resolved emission spectrum of the complex N2DMe-Ph prepared in Example 2 in a PMMA film at room temperature.

[0046] Fig.12 This is the time-resolved emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in a PMMA film at room temperature.

[0047] Fig.13 The Arrhenius line relationship spectrum of the temperature and lifetime of the complex N2DMe-Ph prepared in Example 2 in the PMMA film;

[0048] Fig.14 This is the Arrhenius line relationship spectrum of temperature and lifetime of the complex N2DMe-DPXZ prepared in Example 3 in PMMA film. DETAILED DESCRIPTION

[0049] The present invention provides a thermally activated delayed fluorescent material and a preparation method and application thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0051] The following describes it in detail through specific embodiments.

[0052] Example 1 Preparation of intermediate

[0053] (1) Preparation of Intermediate 1

[0054] The reaction formula is as follows:

[0055]

[0056] 9-(4-Bromophenyl)-9H-carbazole (2.2 g, 7 mmol), bipyraclostrobin (5 g, 20 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (565 mg, 0.7 mmol), and potassium acetate (4.55 g, 46.358 mmol) were dissolved in 100 mL of ultra-dry 1,4-dioxane solvent, refluxed at 108° C. for 12 hours, the reaction solution was filtered with diatomaceous earth, the filtrate was distilled under reduced pressure, and purified by column chromatography to obtain a white solid intermediate 1 (yield 90%).

[0057] (2) Preparation of Intermediate 2

[0058] The reaction formula is as follows:

[0059]

[0060] 10-(4-bromophenyl)-9,9-dimethyl-9,10-dihydroacridine (2.5 g, 7 mmol), bipyraclostrobin (5 g, 20 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (565 mg, 0.7 mmol), potassium acetate (4.55 g, 46.358 mmol) were dissolved in 100 mL of ultra-dry 1,4-dioxane solvent, refluxed at 108° C. for 12 hours, the reaction solution was filtered with diatomaceous earth, the filtrate was distilled under reduced pressure, and purified by column chromatography to obtain a white solid intermediate 2 (yield 80%).

[0061] (3) Preparation of Intermediate 3

[0062] The reaction formula is as follows:

[0063]

[0064] 10-(4-Bromophenyl)-10H-phenoxazine (2.4 g, 7 mmol), bipyraclostrobin (5 g, 20 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (565 mg, 0.7 mmol), potassium acetate (4.55 g, 46.358 mmol) were dissolved in 100 mL of ultra-dry 1,4-dioxane solvent, refluxed at 108° C. for 12 hours, the reaction solution was filtered with diatomaceous earth, the filtrate was distilled under reduced pressure, and purified by column chromatography to obtain a white solid intermediate 3 (yield 85%).

[0065] (4) Preparation of intermediate 4

[0066] The reaction formula is as follows:

[0067]

[0068] 4-Bromo-N,N-diphenylaniline (2.3 g, 7 mmol), bipyraclostrobin (5 g, 20 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (565 mg, 0.7 mmol), potassium acetate (4.55 g, 46.358 mmol) were dissolved in 100 mL of ultra-dry 1,4-dioxane solvent, refluxed at 108° C. for 12 hours, the reaction solution was filtered with diatomaceous earth, the filtrate was distilled under reduced pressure, and purified by column chromatography to obtain a white solid intermediate 4 (yield 88%).

[0069] (5) Preparation of Intermediate 5

[0070] The reaction formula is as follows:

[0071]

[0072] 3,6-di-tert-butyl-9H-carbazole (13.97 g, 50 mmol) was added to 300 mL of chloroform, and the mixture was cooled to 0°C in an ice bath. Under stirring conditions, 30 mL of a chloroform solution of N-bromosuccinimide (NBS) (17.8 g, 120 mmol) was added dropwise, and the mixture was wrapped with aluminum foil. The mixture was reacted for 16 h, and the solvent was removed by distillation under reduced pressure. The mixture was purified by dichloromethane / petroleum ether column chromatography to obtain a white solid intermediate 5 (yield 90%).

[0073] (6) Preparation of Intermediate 6

[0074] The reaction formula is as follows:

[0075]

[0076] Intermediate 5 (358 mg, 1 mmol), pinacol borane (0.8 mL, 5 mmol), [bis(triphenylphosphino)]palladium dichloride (70.2 mg, 0.1 mmol), and triethylamine (1.49 mL) were dissolved in 10 mL of ultra-dry 1,4-dioxane solvent, refluxed at 108° C. overnight, the reaction solution was filtered through diatomaceous earth, the filtrate was distilled under reduced pressure, and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio) to obtain a white solid intermediate 6 (yield 75%).

[0077] (7) Preparation of Intermediate 7

[0078] The reaction formula is as follows:

[0079]

[0080] Intermediate 5 (870 mg, 2 mmol), phenylboronic acid (360 mg, 3 mmol), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio), to obtain white solid intermediate 7 (yield 88%), the product emits sky blue light under 365 nm ultraviolet lamp. 1 HNMR(500MHz, CDCl3)δ8.33(s,1H),8.11(d,J=1.6Hz,2H),7.67(t,J=6.8Hz,4 H),7.50(dt,J=11.7,8.7Hz,6H),7.38(dd,J=16.6,9.2Hz,2H),1.50(s,18H).

[0081] (8) Preparation of Intermediate 8

[0082] The reaction formula is as follows:

[0083]

[0084] Intermediate 5 (870 mg, 2 mmol), intermediate 1 (1.1 g, 3 mmol), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio), to obtain white solid intermediate 8 (yield 82%), the product emits sky blue light under 365 nm ultraviolet lamp.

[0085] (9) Preparation of Intermediate 9

[0086] The reaction formula is as follows:

[0087]

[0088] Intermediate 5 (870 mg, 2 mmol), intermediate 2 (1.2 g, 3 mmol), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio), to obtain a white solid intermediate 9 (yield 89%).

[0089] (10) Preparation of Intermediate 10

[0090] The reaction formula is as follows:

[0091]

[0092] Intermediate 5 (870 mg, 2 mmol), intermediate 3 (1.2 g, 3 mmol), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio), to obtain a white solid intermediate 10 (yield 66%).

[0093] (11) Preparation of intermediate 11

[0094] The reaction formula is as follows:

[0095]

[0096] Intermediate 5 (870 mg, 2 mmol), intermediate 4 (1.1 g, 3 mmol), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio) to obtain a white solid intermediate 11 (yield 60%).

[0097] (12) Preparation of intermediate 12

[0098] The reaction formula is as follows:

[0099]

[0100] Intermediate 6 (1.06 g, 2 mmol), intermediate bromo-BO (1.1 g, 3 mmol, purchased), K2CO3 (1.126 g, 8.15 mmol), tetrakis(triphenylphosphine)palladium (116 mg, 0.1 mmol) were dissolved in 30 mL of ultra-dry tetrahydrofuran and 10 mL of deoxygenated water, stirred, slowly heated to 100 ° C, reacted overnight, extracted with dichloromethane and water, distilled under reduced pressure, and purified by column chromatography (eluent: petroleum ether: dichloromethane = 20:1, volume ratio) to obtain white solid intermediate 12 (yield 58%). 1 H NMR (400MHz, CDCl3) δ8.25(s,1H),8.06(s,2H),7.36(m,6H),6.86(m,16H),1.48(s,18H).

[0101] (13) Preparation of intermediate 13

[0102] The reaction formula is as follows:

[0103]

[0104] 2,3-Dichloropyrazine (4mL, 0.38mol) and 3,5-dimethylaniline (12mL, 0.962mol) were refluxed at 140°C for 6h. After the reaction was completed, the mixture was cooled to room temperature and solid was generated. The solid product was filtered to obtain a solid product, and 50mL of dichloromethane and 50mL of distilled water were added thereto and stirred for 2h. Then, the mixture was extracted three times with 3×20mL of dichloromethane (i.e., 20mL of dichloromethane was used each time for a total of three times), the organic phases were combined, dried with anhydrous sodium sulfate for 30min, sodium sulfate was removed by filtration, and the organic phase was dried with a rotary evaporator to obtain an oily product. White solid intermediate 13 (yield: 7g, yield: 60%) was precipitated by adding n-hexane. 1H NMR (400MHz, CDCl3, δ) 2.28 (s, 12H), 6.13 (s, 2H), 6.69 (s, 2H), 6.87 (s, 4H), 7.77 (s, 2H).

[0105] (14) Preparation of intermediate 14

[0106] The reaction formula is as follows:

[0107]

[0108] After the intermediate 13 (750 mg, 2.35 mmol) synthesized above and triethyl orthoformate (10 mL) were mixed evenly, concentrated hydrochloric acid with a mass concentration of 37% was added under stirring (concentrated hydrochloric acid should not be excessive, otherwise the product could not be generated). With the addition of hydrochloric acid, the solution immediately became turbid, and refluxed at 120°C until the solid dissolved to obtain a brown-yellow solution, and the reaction was continued for 6 hours. After the reaction was completed, the temperature was cooled to room temperature, 20 mL of n-hexane was added, and the product was precipitated. The solid was collected by filtration to obtain a light yellow product, namely, intermediate 13 (yield: 510 mg, yield: 60%). 1 H NMR (400MHz, CDCl3, δ) 2.34 (s, 12H), 6.65 (d, 2H), 6.73 (s, 2H), 7.07 (d, 2H), 7.41 (s, 4H).

[0109] (15) Preparation of intermediate 15

[0110] The reaction formula is as follows:

[0111]

[0112] Intermediate 14 (300 mg, 0.8 mmol) and cuprous chloride (100 mg, 1 mmol) were dissolved in ultra-dry tetrahydrofuran and refluxed at 60°C overnight. A yellow-green precipitate was generated as the reaction proceeded. After the reaction was completed, the precipitate was filtered and washed with tetrahydrofuran 4 times to remove impurities. The obtained precipitate was dissolved in dichloromethane, and tetrahydrothiophene gold chloride (330 mg, 1 mmol) was added and refluxed at 40°C for 5 hours. After the reaction was completed, the insoluble matter was filtered off to obtain a yellow-green filtrate, the filtrate was dried by rotary evaporation, and the dried solid was recrystallized with dichloromethane / petroleum ether solution to obtain a white solid, namely intermediate 15 (yield: 320 mg, yield: 61%). 1 H NMR (400MHz, CDCl3, δ) 2.46 (s, 12H), 7.23 (d, 2H), 7.37 (s, 4H), 8.62 (s, 2H).

[0113] (2) Preparation of intermediate 16

[0114] The reaction formula is as follows:

[0115]

[0116] Diisopropylphenylenediamine (860 mg, 2 mmol) and triethyl orthoformate (50 mL) were mixed evenly and refluxed at 160° C. for 6 hours. The reaction solution was then cooled to 90° C. and 10 mL of trimethylsilyl chloride (TMSCl) was added, and the reaction was continued for 12 hours. After the reaction was completed, the temperature was cooled to room temperature, and 20 mL of n-hexane was added. The product was precipitated. The solid was collected by filtration and then washed with saturated NaHCO3, extracted with dichloromethane, dried with anhydrous MgSO4, and the excess solvent was evaporated by rotary evaporation. Hexane was added to obtain a light yellow product, namely intermediate 16 (yield: 570 mg, yield: 60%).

[0117] (17) Preparation of intermediate 17

[0118] The reaction formula is as follows:

[0119]

[0120] Silver oxide (70 mg, 0.35 mmol) and intermediate 16 (285 mg, 0.60 mmol) were added to a mixed solution of dichloromethane (40 mL) and ethanol (20 mL) and stirred for 12 h under light-proof conditions. After the reaction was completed, the generated precipitate was filtered, and tetrahydrothiophene gold chloride (chemical formula THT-Au-Cl) was added to the filtrate. After the mixed solution was stirred for 12 h under light-proof conditions, the insoluble matter was filtered out, and the filtrate was dried and the obtained solid was recrystallized with dichloromethane / ether solvent to obtain a pure white solid, which was intermediate 17 (yield: 500 mg, yield: 75%).

[0121] (18) Preparation of intermediate 18

[0122] The reaction formula is as follows:

[0123]

[0124] Diisopropylpyridinediamine (860 mg, 2 mmol) and triethyl orthoformate (50 mL) were mixed and refluxed at 160°C for 6 hours, and then the reaction solution was cooled to 90°C and 10 mL of trimethylsilyl chloride (TMSCl) was added, and the reaction was continued for 12 hours. After the reaction was completed, the temperature was cooled to room temperature, and the excess solvent was evaporated off by rotary evaporation. Methanol and excess HBF4 (4 mmol) were added to the residue, and the mixture was stirred at room temperature for 1 hour. 20 mL of n-hexane was added, and the product was precipitated. The solid was collected by filtration and washed with saturated NaHCO3, extracted with dichloromethane, dried with anhydrous MgSO4, and the excess solvent was evaporated off by rotary evaporation. Hexane was added to obtain a light yellow product, which was intermediate 18 (yield: 590 mg, yield: 62%).

[0125] (2) Preparation of intermediate 19

[0126] The reaction formula is as follows:

[0127]

[0128] Intermediate 18 (422 mg, 0.8 mmol) and cuprous chloride (100 mg, 1 mmol) were dissolved in ultra-dry tetrahydrofuran and refluxed overnight at 6°C. A yellow-green precipitate was produced as the reaction proceeded. After the reaction was completed, the precipitate was filtered and washed with tetrahydrofuran 4 times to remove impurities. The obtained precipitate was dissolved in a dichloromethane solution, and tetrahydrothiophene gold chloride (330 mg, 1 mmol) was added and refluxed at 40°C for 5 hours. After the reaction was completed, the insoluble matter was filtered off to obtain a yellow-green filtrate, which was dried by rotary evaporation, and the dried solid was recrystallized with a dichloromethane / petroleum ether solution to obtain a white solid, namely intermediate 19 (yield: 445 mg, yield: 66%).

[0129] Example 2

[0130] A thermally activated delayed fluorescent material, recorded as a complex N2DMe-Ph, is obtained by the following coordination reaction formula:

[0131]

[0132] The preparation method of the complex N2DMe-Ph comprises the steps of:

[0133] The intermediate 7 (216 mg, 0.5 mmol) prepared in Example 1 and sodium tert-butoxide (100 mg, 1 mmol) were added to 20 mL of ultra-dry tetrahydrofuran and stirred at room temperature for 1 h. Then, the intermediate 15 (280 mg, 0.5 mmol) prepared in Example 1 was added. After stirring at room temperature overnight, the reaction solution was filtered through diatomaceous earth, and the filtrate was distilled under reduced pressure, washed with cold n-pentane, and then recrystallized with dichloromethane: n-hexane = 1:100 (volume ratio) to obtain a solid product (yield 60%).1 H NMR(500MHz, CDCl3)δ8.50(s,2H),8.09(d,J=2.0Hz,2H),7.39(d,J=6.9Hz,4H),7.12(s,4H),7 .08(d,J=1.9Hz,4H),7.00(t,J=7.6Hz,4H),6.88(t,J=7.4Hz,2H),2.39(s,12H),1.43(s,18H). 13 CNMR (101MHz, CDCl3) δ187.05,146.75,144.09,140.28,139.20,139.02,138.23,134.78,131 .38,130.76,127.40,127.03,125.43,124.73,124.32,123.84,114.72,34.43,32.22,21.29.

[0134] Example 3

[0135] A thermally activated delayed fluorescent material, recorded as the complex N2DMe-DPXZ, is obtained by the following coordination reaction:

[0136]

[0137] The preparation method of the complex N2DMe-DPXZ comprises the steps of:

[0138] The intermediate 12 (385 mg, 0.5 mmol) prepared in Example 1 and sodium tert-butoxide (100 mg, 1 mmol) were added to 20 mL of ultra-dry tetrahydrofuran and stirred at room temperature for 1 h. Then, the intermediate 15 (280 mg, 0.5 mmol) prepared in Example 1 was added. After stirring at room temperature overnight, the reaction solution was filtered through diatomaceous earth, and the filtrate was distilled under reduced pressure, washed with cold n-pentane, and then recrystallized with dichloromethane:n-hexane = 1:100 (volume ratio) to obtain a solid product (yield 50%). 1 H NMR (500MHz, CDCl3) δ8.17 (s, 2H), 8.10 (d, J = 2.1Hz, 2H), 7.56 (s, 4H), 7.08 (m, 4H), 7 .03(d,J=8.0Hz,4H),6.62(m,8H),6.48(d,J=4.1Hz,8H),2.30(s,12H),1.44(s,18H). 13C NMR (101MHz, CDCl3) δ185.26,146.59,146.44,144.16,139.51,139.40,139.14,138.63,138.18,135.22,131.32,128 .77,125.70,124.85,123.63,123.41,123.02,122.83,118.20,117.21,115.04,113.91,113.78,34.42,32.21,21.44.

[0139] Example 4

[0140] A thermally activated delayed fluorescent material, referred to as the complex CHiPr-PCz, is obtained by the following coordination reaction:

[0141]

[0142] The preparation method of the complex CHiPr-PCz comprises the steps of:

[0143] The intermediate 8 (380 mg, 0.5 mmol) obtained in Example 1 and sodium tert-butoxide (100 mg, 1 mmol) were added to 20 mL of ultra-dry tetrahydrofuran, stirred at room temperature for 1 h, and then the intermediate 17 (336 mg, 0.5 mmol) obtained in Example 1 was added. After stirring at room temperature overnight, the reaction solution was filtered through diatomaceous earth, the filtrate was distilled under reduced pressure, washed with cold n-pentane, and then recrystallized with dichloromethane: n-hexane = 1:100 (volume ratio) to obtain a solid product (yield 65%). MALDI-TOF-MS (m / z): Calcd.forC 87 H 85 N5Au,1396.6470; Found,1396.6911(M+H) + .

[0144] Example 5

[0145] A thermally activated delayed fluorescent material, referred to as the complex NiPr-TPA, is obtained by the following coordination reaction:

[0146]

[0147] The preparation method of the complex NiPr-TPA comprises the steps of:

[0148] The intermediate 11 (383 mg, 0.5 mmol) and sodium tert-butoxide (100 mg, 1 mmol) prepared in Example 1 were added to 20 mL of ultra-dry tetrahydrofuran, stirred at room temperature for 1 h, and then the intermediate 15 (330 mg, 0.5 mmol) obtained in Example 1 was added. After stirring at room temperature overnight, the reaction solution was filtered with diatomaceous earth, the filtrate was distilled under reduced pressure, washed with cold n-pentane, and then recrystallized with dichloromethane: n-hexane = 1:100 (volume ratio) to obtain a solid product (yield 71%). MALDI-TOF-MS (m / z): Calcd. for C 86 H 88 N6Au,1401.6736; Found,1401.9831(M+H) + .

[0149] test:

[0150] (1) Determination of the absorption spectrum of the complex prepared in Example 2-5 in a low concentration 2-methyltetrahydrofuran (2-MeTHF) solution

[0151] Using 2-MeTHF as solvent, the complexes prepared in Examples 2-5 were added to 2-MeTHF at a concentration of 10 μM, and absorption spectrum tests were performed at room temperature. The results are as follows: Figure 1-2 As shown, Figure 1 is the absorption spectra of the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 in 2-MeTHF, Figure 2 The absorption spectra of the complex CHiPr-PCz prepared in Example 4 and the complex NiPr-TPA prepared in Example 5 in 2-MeTHF show that these complexes exhibit obvious solvation absorption peaks at 450 nm, which can be attributed to the charge transition from ligand to ligand.

[0152] (2) Determination of the emission spectrum of the complex prepared in Example 2-3 in a low concentration 2-MeTHF solution

[0153] Using 2-MeTHF as solvent, the complexes prepared in Examples 2-3 were added to 2-MeTHF at a concentration of 10 μM, and emission spectra were tested at room temperature. The results are as follows: Figure 3-4 As shown, Figure 3 is the emission spectrum of the complex N2DMe-Ph prepared in Example 2, Figure 4The emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 shows that the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 show obvious emission peaks without fine structure at 648nm and 615nnm, respectively, which can be attributed to the singlet state of charge transition from ligand to ligand.

[0154] (3) Determination of the emission spectrum of the complex prepared in Example 2-5 in a polymethyl methacrylate (PMMA) film

[0155] The doping concentration of the complex used in this test in the PMMA film is 5wt%, the excitation wavelength is 375nm, and the emission spectrum test in the PMMA film is carried out. The results are as follows: Figure 5-8 As shown, Figure 5 is the emission spectrum of the complex N2DMe-Ph prepared in Example 2 in PMMA film, Figure 6 is the emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in PMMA film, Figure 7 is the emission spectrum of the complex CHiPr-PCz prepared in Example 4 in PMMA film, Figure 8 The emission spectrum of the complex NiPr-TPA prepared in Example 5 in PMMA film shows that the spectrum presented by the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 is similar to that in solution, and is also a broad emission peak without structure, with emission maxima at 561 and 565nm, respectively, showing yellow light emission. The emission maxima of the complex CHiPr-PCz complex prepared in Example 4 and the complex NiPr-TPA prepared in Example 5 are 490nm and 535nm, respectively.

[0156] (4) Determination of the emission spectra of the complexes prepared in Examples 2 and 3 in 1,3-dicarbazole-9-ylbenzene (mCP) films

[0157] The doping concentration of the complex used in this test in the mCP film is 5wt%, the excitation wavelength is 375nm, and the emission spectrum test in the mCP film is carried out. The results are as follows Figure 9-10 As shown, Fig. 9 is the emission spectrum of the complex N2DMe-Ph prepared in Example 2 in the mCP film, Fig.10This is the emission spectrum of the complex N2DMe-DPXZ prepared in Example 3 in the mCP film. It can be seen that the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 present spectra similar to those in the solution, which are also unstructured broad emission peaks with emission maxima at 565nm, showing yellow light emission.

[0158] (5) Testing the time-resolved emission spectra of the complexes prepared in Examples 2 and 3 in PMMA films at room temperature

[0159] The doping concentration of the complex used in this test is 5wt%, and the excitation wavelength is 375nm. The test results are as follows Fig.11 and 12 As shown in Figure 12, the time-resolved emission spectrum of the complex N2DMe-Ph prepared in Example 2 is shown. Fig.13 This is the time-resolved emission spectrum of the complex N2DMe-DPXZ prepared in Example 2.

[0160] (6) Determination of the Arrhenius curve of the temperature and lifetime of the complexes obtained in Examples 2 and 3 in the PMMA film

[0161] The doping concentration of the complex used in the test is 5wt% in the PMMA film, and the excitation wavelength is 375nm. The temperature and lifetime curves in the PMMA film are shown in Figure 2. Fig.13 and 14 As shown, after lifetime fitting, the inverse of the lifetime-temperature obtained for the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 conforms to the Arrhenius linear law, indicating that the complex N2DMe-Ph prepared in Example 2 and the complex N2DMe-DPXZ prepared in Example 3 are TADF emissions, rather than phosphorescence emissions.

[0162] The physical property data of the complexes obtained in Examples 2 and 3 in solution and PMMA film are summarized in Table 1 based on the ultraviolet absorption spectra, photoluminescence spectra and time-resolved emission spectra of the complexes prepared in Examples 2 and 3 measured as above.

[0163] Table 1 Physical properties data

[0164]

[0165] From the data in Table 1, it can be seen that the complexes prepared in Examples 2 and 3 all emit deep red light, and the decomposition temperatures at 5 wt % are all higher than 260° C., indicating that the complexes obtained in Examples 2 and 3 have good thermal stability.

[0166] In summary, the thermally activated delayed fluorescent material provided by the present invention exhibits a ligand-ligand charge transfer absorption band in a dilute solution of 2-MeTHF and exhibits deep red light emission; the thermally activated delayed fluorescent material exhibits blue light (490nm) to orange-yellow light (565nm) emission in a PMMA film; the luminescence lifetime of the thermally activated delayed fluorescent material in the PMMA film is as short as 1μs, and the luminescence lifetime and temperature of the thermally activated delayed fluorescent material in the PMMA film conform to the Arrhenius linear equation, confirming that it is TADF emission.

[0167] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A thermally activated delayed fluorescent material, characterized in that: The structural formula of the thermally activated delayed fluorescent material is: Wherein, R1 is hydrogen or tert-butyl; X and Y are each independently -CH- or nitrogen; The R2 is selected from one of the following structures: The R3 is selected from one of the following structures: Among them, "---" indicates the connection site.

2. The thermally activated delayed fluorescent material according to claim 1, characterized in that: The thermally activated delayed fluorescent material is selected from one of the following structures:

3. A method for preparing the thermally activated delayed fluorescent material according to any one of claims 1 to 2, characterized in that: The thermally activated delayed fluorescent material is prepared by the following reaction formula: The preparation method comprises the steps of: Will and The organic solvent is added thereto, and after reaction, the thermally activated delayed fluorescent material is obtained, wherein R is a halogen atom.

4. The method for preparing a thermally activated delayed fluorescent material according to claim 3, characterized in that: The R is a chlorine atom.

5. The method for preparing the thermally activated delayed fluorescent material according to claim 3, characterized in that: The organic solvent is selected from at least one of tetrahydrofuran, ethanol and acetonitrile.

6. Use of the thermally activated delayed fluorescent material according to any one of claims 1 to 2 in an electroluminescent device.

7. The use according to claim 6, characterized in that: The electroluminescent device is an organic light emitting diode.

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