Pure organic room-temperature phosphorescent material and preparation method thereof

Abstract

The invention relates to the technical field of phosphorescent materials, and discloses a pure organic room-temperature phosphorescent material and a preparation method thereof.The preparation method comprises the steps that amidation reaction is conducted on a compound biphenyl anhydride, an amino substitute, triethylamine and 4-dimethylaminopyridine in dichloromethane; after the reaction is finished, adding HCl to carry out quenching reaction; then, dichloromethane is used for extraction; drying the organic phase with anhydrous Na2SO4, and removing the solvent under reduced pressure after drying to obtain a crude product; adding acetic anhydride into the crude product, and heating and refluxing; removing the solvent under reduced pressure after reflowing; and purifying the obtained product through silica gel column chromatography, and eluting to obtain the pure organic room-temperature phosphorescent material. According to the preparation method, different functional groups can be introduced into the biphenyl imide structure through the reaction of amino and anhydride, the preparation method is simple, the raw materials are cheap and easy to obtain, the reaction steps are few, the reaction conditions are mild, the yield is relatively high, and industrialization is easy to realize. The pure organic room-temperature phosphorescent material prepared by the method disclosed by the invention is relatively high in luminous efficiency and long in luminous life.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphorescent materials, and particularly relates to a pure organic room temperature phosphorescent material and a preparation method thereof. Background Art

[0002] Room temperature phosphorescence (RTP) materials include organic-inorganic hybrid materials, pure organic materials and polymer RTP materials, and have become a research hotspot due to their adjustable molecular structures, long emission lifetimes and wide optical applications. Organic room temperature phosphorescent materials have been favored by researchers in biological imaging, organic optoelectronics, anti-counterfeiting labels, and sensing due to their large Stokes shifts, long lifetimes, long afterglows, and good biocompatibility, showing potential application values.

[0003] Since pure organic molecules do not contain heavy metals, their weak intersystem crossing efficiency makes it usually difficult to observe long afterglow luminescence at room temperature. Usually, at a low temperature of 77K or by doping the molecules into a rigid matrix such as a polymer, non-radiative transitions are suppressed to achieve the property of room temperature phosphorescence. However, it is difficult to conduct the research on the phosphorescent properties of single-component materials alone, which leads to difficulties in studying the molecular mechanism and further makes it difficult to develop high-performance room temperature phosphorescent materials. Therefore, the development of non-doped single-component room temperature phosphorescent materials is not only of great significance for scientific research but also very important for the development of high-performance and stable room temperature phosphorescent materials. The number of single-component room temperature phosphorescent materials in the prior art is extremely scarce, the molecular structures are single, and the luminescence performances are poor.

[0004] Based on this, it is urgent for those skilled in the art to propose a high-performance and stable pure organic room temperature phosphorescent material and a preparation method thereof. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a pure organic room temperature phosphorescent material and a preparation method thereof.

[0006] The technical solution adopted by the present invention is as follows: A pure organic room temperature phosphorescent material of the present invention has a structure as shown in Formula 1, Formula 1; wherein, X is H, F, Cl, Br, CN or I; R is H, an alkyl chain with 1-10 carbons, phenyl, methoxyphenyl, bromobenzyl, bromophenyl, iodophenyl, allyl, 2-hydroxyethyl, 2-aminoethyl, 2-fluoroethyl.

[0007] A preparation method of a pure organic room temperature phosphorescent material of the present invention, the synthesis route of the pure organic room temperature phosphorescent material is as shown in Formula 2, Formula 2; The preparation method includes the following steps: S1: Carry out an amide reaction of biphenyl anhydride with an amino substituent, a basic reagent triethylamine, and a catalyst 4-dimethylaminopyridine in a polar dichloromethane organic solvent; S2: After the amide reaction is completed, add HCl to carry out a quenching reaction; S3: Extract with dichloromethane and repeat the extraction three times; S4: Dry the organic phase with anhydrous Na2SO4, and after drying, remove the solvent under reduced pressure using a rotary evaporator to obtain a crude product; S5: Add acetic anhydride to the crude product and heat under reflux; S6: After the reflux is completed, remove the solvent under reduced pressure using a rotary evaporator; S7: Purify the product obtained in S6 by silica gel column chromatography, with the eluent being petroleum ether and dichloromethane, and obtain a pure organic room temperature phosphorescent material after the elution is completed.

[0008] Further, in step S1, the molar ratio of biphenyl anhydride to the amino substituent is 1:1.2, the molar ratio of biphenyl anhydride to the basic reagent triethylamine is 1:3, the molar ratio of biphenyl anhydride to the catalyst 4-dimethylaminopyridine is 1:0.2, and the molar ratio of biphenyl anhydride to the volume ratio of dichloromethane is 1:20.

[0009] Further, in step S1, the amide reaction is stirred at room temperature for 12 h.

[0010] Further, in step S2, the molar ratio of HCl to biphenyl anhydride is 1:3.

[0011] Further, in step S4, the reduced pressure condition of the rotary evaporator is -0.095 MPa.

[0012] Further, the acetic anhydride (Ac2O) is a ring-closing reagent.

[0013] Further, in step S5, the reflux reaction temperature is 150 °C and the reaction time is 6 - 24 h.

[0014] Further, in step S6, the reduced pressure condition of the rotary evaporator is -0.095 MPa.

[0015] Further, in step S7, the volume ratio of the eluent petroleum ether to dichloromethane is 2:1.

[0016] Compared with the prior art, the beneficial effects of the present invention: The present invention generates a pure organic room temperature phosphorescent material with a twisted benzilimide structure by reacting a biphenyl anhydride compound with an amino substituent in a polar solvent. The preparation method of the present invention can easily introduce different functional groups into the benzilimide structure through the reaction of amino groups and anhydrides. The preparation method is simple, the raw materials are cheap and easily available, the reaction steps are few, the reaction conditions are mild, the yield is high, and industrialization is easy to achieve. The pure organic room temperature phosphorescent material with a twisted benzilimide structure prepared by the method of the present invention has high luminescence efficiency and long luminescence lifetime. The preparation method of the present invention is conducive to introducing different functional groups at the end of the amine side chain, promoting the application of pure organic room temperature phosphorescent materials in organic electroluminescent devices, chemical sensing, biological imaging, data encryption and anti-counterfeiting marking, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. Figure 1 is the luminescence image of the crystal of compound A1 in this example under ultraviolet light (365 nm) irradiation and after turning off the light source; FIG. Figure 2 is the superimposed diagram of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 10 ms delay of compound A1 in the crystalline state in this example; FIG. Figure 3 is the time-resolved phosphorescence emission decay curve of compound A1 in the crystalline state in this example; FIG. Figure 4 is the superimposed diagram of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 10 ms delay of compound A2 in the crystalline state in this example; FIG. Figure 5 is the time-resolved phosphorescence emission decay curve of compound A2 in the crystalline state in this example; FIG. Figure 6 is the superimposed diagram of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 10 ms delay of compound A3 in the crystalline state in this example; FIG. Figure 7 is the time-resolved phosphorescence emission decay curve of compound A3 in the crystalline state in this example; FIG. Figure 8 is the superimposed diagram of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 5 ms delay of compound A4 in the crystalline state in this example; FIG. Figure 9 is the time-resolved phosphorescence emission decay curve of compound A4 in the crystalline state in this example; FIG. Figure 10 is the superimposed diagram of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 10 ms delay of compound A5 in the crystalline state in this example; FIG. Figure 11 is the time-resolved phosphorescence emission decay curve of compound A5 in the crystalline state in this example; FIG. Figure 12It is a superimposed graph of the steady-state fluorescence spectrum and the steady-state emission spectrum with a 10-ms delay of Compound A6 in the crystalline state in this example; Attached Figure 13 It is the time-resolved phosphorescence emission decay curve of Compound A6 in the crystalline state in this example; Attached Figure 14 It is of Compound A1 in this example 1 1H NMR spectrum; Attached Figure 15 It is of Compound A2 in this example 1 1H NMR spectrum; Attached Figure 16 It is of Compound A3 in this example 1 1H NMR spectrum; Attached Figure 17 It is of Compound A4 in this example 1 1H NMR spectrum; Attached Figure 18 It is of Compound A5 in this example 1 1H NMR spectrum; Attached Figure 19 It is of Compound A6 in this example 1 1H NMR spectrum; Attached Figure 20 It is a schematic diagram of the application of Compound A5 in high-level data protection and anti-counterfeiting labels in this example. Specific implementation manners

[0018] In order to make the purpose and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. 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.

[0019] A kind of pure organic room-temperature phosphorescent material in this example has a structure as shown in Formula 1, Formula 1; Wherein, X is H, F, Cl, Br, CN or I; R is H, an alkyl chain with 1-10 carbons, phenyl, methoxyphenyl, bromobenzyl, bromophenyl, iodophenyl, allyl, 2-hydroxyethyl, 2-aminoethyl, 2-fluoroethyl.

[0020] The synthesis route of the above pure organic room-temperature phosphorescent material is as shown in Formula 2, Formula 2; Its preparation method specifically includes the following steps: S1: Carry out an amide reaction of biphenyl anhydride (BP) with an amino-substituted compound, the basic reagent triethylamine (Et3N), and the catalyst 4-dimethylaminopyridine (DMAP) in the polar organic solvent dichloromethane (DCM), and stir the reaction at room temperature for 12 h; wherein, the molar ratio of biphenyl anhydride (BP) to the amino-substituted compound is 1:1.2; the molar ratio of biphenyl anhydride (BP) to the basic reagent triethylamine (Et3N) is 1:3; the molar ratio of biphenyl anhydride (BP) to the catalyst 4-dimethylaminopyridine (DMAP) is 1:0.2; the volume ratio of the molar ratio of biphenyl anhydride to dichloromethane is 1:20 (i.e., 1 mmol of biphenyl anhydride corresponds to 20 ml of dichloromethane); S2: After the amide reaction is completed, add HCl to carry out a quenching reaction, wherein the molar ratio of HCl to biphenyl anhydride is 1:3; S3: Extract with dichloromethane and repeat the extraction three times; S4: Dry the organic phase with anhydrous Na2SO4, and after drying, remove the solvent by a rotary evaporator under reduced pressure to -0.095 MPa to obtain a crude product; S5: Add the ring-closing reagent acetic anhydride (Ac2O) to the crude product, heat under reflux, the reaction temperature is 150 °C, and the reaction time is 6 h - 24 h; S6: After the reflux is completed, remove the solvent by a rotary evaporator under reduced pressure to -0.095 MPa; S7: Purify the product obtained in S6 by silica gel column chromatography, the eluent is petroleum ether and dichloromethane, the volume ratio of petroleum ether to dichloromethane is 2:1, and a pure organic room temperature phosphorescent material of twisted biphenyl diimide is obtained after the elution is completed.

[0021] The following is a detailed description through specific examples.

[0022] Example 1

[0023] A pure organic room temperature phosphorescent material and a preparation method thereof in this example specifically include the following steps: S1: Sequentially add 2,2-biphenyl dicarboxylic anhydride (0.561 g, 2.5 mmol), 2-bromoaniline (0.516 g, 3.0 mmol, 1.2 equiv), triethylamine (1.043 mL, 0.759 g, 7.5 mmol, 3 equiv), 4-dimethylaminopyridine (DMAP, 61 mg, 0.5 mmol, 20 mol%) and 50 mL of anhydrous dichloromethane into a 50 mL single-necked round-bottom flask, and stir the reaction at room temperature for 12 h to carry out an amide reaction; S2: After the amide reaction is completed, add 5 mL of HCl (2M, aq) to carry out a quenching reaction, wherein the molar ratio of HCl to biphenyl anhydride is 1:3; S3: Extract with 50 mL of dichloromethane and repeat the extraction three times; S4: Dry the organic phase with anhydrous Na2SO4. After drying, remove the solvent under reduced pressure to -0.095 MPa using a rotary evaporator to obtain the crude product; S5: Add 10 mL of the ring - closing reagent acetic anhydride (Ac2O) to the crude product, heat under reflux, with the reaction temperature at 150 °C and the reaction time of 6 h; S6: After the reflux ends, remove the solvent under reduced pressure to -0.095 MPa using a rotary evaporator; S7: Purify the product obtained in S6 by silica gel column chromatography. The eluent is petroleum ether and dichloromethane, with the volume ratio of petroleum ether to dichloromethane being 2:1. After the elution ends, obtain the white solid product A1 - N-(2 - bromophenyl)-2,2 - biphenylimide (0.673 g, 1.78 mmol), with a yield of 71.2%. This product A1 has a twisted biphenylimide structure, and the structural formula of product A1 is as follows:

[0024] Example 2

[0025] A pure organic room - temperature phosphorescent material and its preparation method in this example specifically include the following steps: S1: In a 50 - mL single - necked round - bottom flask, sequentially add 2,2 - biphenyl dicarboxylic anhydride (0.448 g, 2 mmol), 4 - bromoaniline (0.413 g, 2.4 mmol, 1.2 equiv), triethylamine (0.834 mL, 0.607 g, 6 mmol, 3 equiv), 4 - dimethylaminopyridine (DMAP, 49 mg, 0.4 mmol, 20 mol%), and 40 mL of anhydrous dichloromethane. Stir and react at room temperature for 12 h for the amide reaction; S2: After the amide reaction ends, add 5 mL of HCl (2M, aq) for quenching reaction, where the molar ratio of HCl to phthalic anhydride is 1:3; S3: Extract with 5 mL of dichloromethane and repeat the extraction three times; S4: Dry the organic phase with anhydrous Na2SO4. After drying, remove the solvent under reduced pressure to -0.095 MPa using a rotary evaporator to obtain the crude product; S5: Add 10 mL of the ring - closing reagent acetic anhydride (Ac2O) to the crude product, heat under reflux, with the reaction temperature at 150 °C and the reaction time of 8 h; S6: After the reflux ends, remove the solvent under reduced pressure to -0.095 MPa using a rotary evaporator; S7: Purify the product obtained in S6 by silica gel column chromatography. The eluent is petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane is 2:1. After the elution is completed, a white solid product A2—N-(4-bromophenyl)-2,2-benzimidoyl imide (0.631 g, 1.67 mmol) is obtained, with a yield of 83.4%. This product A2 has a twisted benzimidoyl imide structure, and the structural formula of product A2 is as follows:

[0026] Example 3

[0027] A pure organic room temperature phosphorescent material and its preparation method in this example specifically include the following steps: S1: Add phthalic anhydride (0.448 g, 2 mmol), 4-bromobenzylamine (0.447 g, 2.4 mmol, 1.2 equiv), triethylamine (0.834 mL, 0.607 g, 6 mmol, 3 equiv), 4-dimethylaminopyridine (DMAP, 49 mg, 0.4 mmol, 20 mol%) and 40 mL of anhydrous dichloromethane into a 50 mL single-necked round-bottom flask in sequence, and stir and react at room temperature for 12 h for the amide reaction; S2: After the amide reaction is completed, add 5 mL of HCl (2M, aq) for quenching reaction, where the molar ratio of HCl to phthalic anhydride is 1:3; S3: Extract with 5 mL of dichloromethane and repeat the extraction three times; S4: Dry the organic phase with anhydrous Na2SO4, and then remove the solvent by a rotary evaporator under reduced pressure to -0.095 MPa to obtain a crude product; S5: Add 10 mL of the ring-closing reagent acetic anhydride (Ac2O) to the crude product, heat under reflux, the reaction temperature is 150 °C, and the reaction time is 10 h; S6: After the reflux is completed, remove the solvent by a rotary evaporator under reduced pressure to -0.095 MPa; S7: Purify the product obtained in S6 by silica gel column chromatography. The eluent is petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane is 2:1. After the elution is completed, a white solid product A3—N-(4-bromobenzyl)-2,2-benzimidoyl imide (0.699 g, 1.78 mmol) is obtained, with a yield of 89.1%. This product A3 has a twisted benzimidoyl imide structure, and the structural formula of product A3 is as follows:

[0028] Example 4

[0029] A pure organic room temperature phosphorescent material and its preparation method in this example specifically include the following steps: S1: In a 50 mL single-necked round-bottom flask, 2,2'-biphenyldicarboxylic anhydride (0.448 g, 2 mmol), 3-bromoaniline (0.447 g, 2.4 mmol, 1.2 equiv), triethylamine (0.834 mL, 0.607 g, 6 mmol, 3 equiv), 4-dimethylaminopyridine (DMAP, 49 mg, 0.4 mmol, 20 mol%) and 40 mL of anhydrous dichloromethane were added in sequence, and the mixture was stirred at room temperature for 12 h for the amide reaction; S2: After the amide reaction was completed, 5 mL of HCl (2M, aq) was added for quenching reaction, where the molar ratio of HCl to biphenyldicarboxylic anhydride was 1:3; S3: Extraction was carried out with 5 mL of dichloromethane, and the extraction was repeated three times; S4: The organic phase was dried with anhydrous Na2SO4, and after drying, the solvent was removed by a rotary evaporator under reduced pressure to -0.095 MPa to obtain a crude product; S5: 10 mL of the ring-closing reagent acetic anhydride (Ac2O) was added to the crude product, and the mixture was heated under reflux at a reaction temperature of 150 °C for 8 h; S6: After the reflux was completed, the solvent was removed by a rotary evaporator under reduced pressure to -0.095 MPa; S7: The product obtained in S6 was purified by silica gel column chromatography, and the eluent was petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane was 2:1. After the elution was completed, a white solid product A4—N-(3-bromobenzyl)-2,2'-biphenylimide (0.727 g, 1.85 mmol) was obtained, with a yield of 92.7%. This product A4 has a twisted biphenylimide structure, and the structural formula of product A4 is as follows:

[0030] Example 5

[0031] A pure organic room temperature phosphorescent material and its preparation method in this example specifically include the following steps: S1: In a 50 mL single-necked round-bottom flask, 2,2'-biphenyldicarboxylic anhydride (0.448 g, 2 mmol), 4-bromoaniline (0.447 g, 2.4 mmol, 1.2 equiv), triethylamine (0.834 mL, 0.607 g, 6 mmol, 3 equiv), 4-dimethylaminopyridine (DMAP, 49 mg, 0.4 mmol, 20 mol%) and 40 mL of anhydrous dichloromethane were added in sequence, and the mixture was stirred at room temperature for 12 h for the amide reaction; S2: After the amide reaction was completed, 5 mL of HCl (2 M, aq) was added to quench the reaction, where the molar ratio of HCl to diphenic anhydride was 1:3; S3: Extraction was carried out with 5 mL of dichloromethane and repeated three times; S4: The organic phase was dried over anhydrous Na2SO4, and after drying, the solvent was removed under reduced pressure to -0.095 MPa using a rotary evaporator to obtain a crude product; S5: 10 mL of the ring - closing reagent acetic anhydride (Ac2O) was added to the crude product, and the mixture was heated under reflux at a reaction temperature of 150 °C for 24 h; S6: After the reflux was completed, the solvent was removed under reduced pressure to -0.095 MPa using a rotary evaporator; S7: The product obtained in S6 was purified by silica gel column chromatography with the eluent being petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane was 2:1. After the elution was completed, a white solid product A5 - N-(4 - bromobenzyl)-2,2 - biphenylimide (0.737 g, 1.88 mmol) was obtained with a yield of 94.1%. This product A5 has a twisted biphenylimide structure, and the structural formula of product A5 is as follows:

[0032] Example 6

[0033] A pure organic room - temperature phosphorescent material and its preparation method in this example specifically include the following steps: S1: In a 50 - mL single - necked round - bottom flask, 2,2 - diphenic anhydride (0.448 g, 2 mmol), 3,4,5 - trimethoxybenzylamine (0.538 g, 2.4 mmol, 1.2 equiv), triethylamine (0.834 mL, 0.607 g, 6 mmol, 3 equiv), 4 - dimethylaminopyridine (DMAP, 49 mg, 0.4 mmol, 20 mol%) and 40 mL of anhydrous dichloromethane were added in sequence, and the mixture was stirred at room temperature for 12 h for the amide reaction; S2: After the amide reaction was completed, 5 mL of HCl (2 M, aq) was added to quench the reaction, where the molar ratio of HCl to diphenic anhydride was 1:3; S3: Extraction was carried out with 5 mL of dichloromethane and repeated three times; S4: The organic phase was dried over anhydrous Na2SO4, and after drying, the solvent was removed under reduced pressure to -0.095 MPa using a rotary evaporator to obtain a crude product; S5: 10 mL of the ring - closing reagent acetic anhydride (Ac2O) was added to the crude product, and the mixture was heated under reflux at a reaction temperature of 150 °C for 16 h; S6: After the reflux is completed, the solvent is removed by rotary evaporation under reduced pressure to -0.095 MPa; S7: The product obtained in S6 is purified by silica gel column chromatography. The eluent is petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane is 2:1. After the elution is completed, a white solid product A6—N-(3,4,5-trimethoxybenzyl)-2,2-benzimidamide (0.729 g, 1.71 mmol) is obtained, and the yield is 85.5%. This product A6 has a twisted benzimidamide structure, and the structural formula of product A6 is as follows:

[0034] A pure organic room temperature phosphorescent material in other specific embodiments, its structural formula In, X can be any one of H, F, Cl, Br, CN or I; R can be any one of H, an alkyl chain with 1-10 carbons, phenyl, methoxyphenyl, bromobenzyl, bromophenyl, iodophenyl, allyl, 2-hydroxyethyl, 2-aminoethyl, 2-fluoroethyl.

[0035] The products prepared in Examples 1-6 of this example were characterized by nuclear magnetic resonance (Bruker nuclear magnetic resonance NMR spectrometer 500 MHz), steady-state and transient fluorescence spectra (Edinburgh FLS1000, PerkinElmer LS 55 fluorescence spectrometer), see attached Figure 1-19 . From the attached Figure 3 It can be seen that by exponential fitting, the luminescence lifetime of compound A1 is 11.7 ms; from the attached Figure 5 It can be seen that by exponential fitting, the luminescence lifetime of compound A2 is 334 ms; from the attached Figure 7 It can be seen that by exponential fitting, the luminescence lifetime of compound A3 is 1.83 ms; from the attached Figure 9 It can be seen that by exponential fitting, the luminescence lifetime of compound A4 is 12.7 ms; from the attached Figure 11 It can be seen that by exponential fitting, the luminescence lifetime of compound A5 is 110 ms; from the attached Figure 13 It can be seen that by exponential fitting, the luminescence lifetime of compound A6 is 113 ms; from the attached Figure 1-19 It can be seen that the phosphorescent material compounds prepared in this example all have phosphorescent properties at room temperature.

[0036] Four petal-shaped films of different compounds were prepared and subjected to fluorescence testing, see attached Figure 20 , where the left petal is prepared with compound A5, and the right and upper and lower distributed petals are all prepared with conventional fluorescent compounds. From the attached Figure 20It can be seen that under the excitation of a 365 nm ultraviolet lamp, the four petals emit light simultaneously. When the light source is turned off, only the petal prepared from Compound A5 on the left has room-temperature phosphorescence properties and can still emit light continuously, while other fluorescent compounds cannot emit light when the light source is turned off due to their short luminescence lifetimes. Thus, it can be seen that the compound prepared in this embodiment can achieve the effect of an anti-counterfeiting label.

[0037] The single-component phosphorescent molecule prepared in this embodiment incorporates a carbonyl group into the system to increase the n-π electronic transition, improve the intersystem crossing efficiency from the lowest excited singlet state (S1) to the excited triplet state (Tn). At the same time, the benzilimide structure is distorted, which can avoid luminescence quenching caused by molecular aggregation, and the distorted structure can also increase the spin-orbit coupling of the π orbitals and improve the transition efficiency. By introducing different amino structures, the intramolecular charge transfer state is regulated, and then the triplet energy is adjusted, finally obtaining a series of phosphorescent materials with different luminescence colors, which have different phosphorescence efficiencies, lifetimes, and colors. This solves the problems of the extremely lack of single-component room-temperature phosphorescent materials, single molecular structure, and poor luminescence performance in the prior art.

[0038] The beneficial effects of this embodiment: In this embodiment, a pure organic room-temperature phosphorescent material with a distorted benzilimide structure is prepared by reacting a benzophenone anhydride compound with an amino substituent in a polar solvent. The preparation method of this embodiment can easily introduce different functional groups into the benzilimide structure through the reaction of an amino group and an acid anhydride, is easy to prepare, and is beneficial to the application of room-temperature phosphorescent materials in data encryption and anti-counterfeiting labels, etc. Moreover, the preparation method of this embodiment is simple, the raw materials are cheap and easy to obtain, the reaction steps are few, the reaction conditions are mild, the yield is high, and it is easy to realize industrialization. In addition, the pure organic room-temperature phosphorescent material with a distorted benzilimide structure prepared in this embodiment has a high luminescence efficiency and a long luminescence lifetime. The preparation method of this embodiment is beneficial to introducing different functional groups at the end of the amine side chain, promoting the application of pure organic room-temperature phosphorescent materials in organic electroluminescent devices, chemical sensing, bioimaging, and data encryption and anti-counterfeiting labels, etc.

[0039] The above is only the preferred embodiment of this application and the description of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solution formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pure organic room temperature phosphorescent material, characterized in that: The structure of the pure organic room temperature phosphorescent material is as shown in Formula 1: Formula 1; Wherein, X is H, F, Cl, Br, CN or I; R is H, an alkyl chain of 1 to 10 carbon atoms, phenyl, methoxyphenyl, bromobenzyl, bromophenyl, iodophenyl, allyl, 2-hydroxyethyl, 2-aminoethyl, 2-fluoroethyl.

2. A method for preparing a pure organic room temperature phosphorescent material according to claim 1, characterized in that: The synthesis route of the pure organic room temperature phosphorescent material is as shown in Formula 2: Formula 2; The preparation method comprises the following steps: S1: Compound biphenyl anhydride is reacted with an amino substituent, an alkaline reagent triethylamine, and a catalyst 4-dimethylaminopyridine in a polar dichloromethane organic solvent to undergo an amide reaction; S2: After the amide reaction is completed, HCl is added to quench the reaction; S3: Extract with dichloromethane, repeat the extraction three times; S4: drying the organic phase with anhydrous Na2SO4, and then removing the solvent under reduced pressure by rotary evaporation to obtain a crude product; S5: Add acetic anhydride to the crude product and heat to reflux; S6: After the reflux is completed, the solvent is removed under reduced pressure by a rotary evaporator; S7: Purify the product obtained in S6 by silica gel column chromatography, using petroleum ether and dichloromethane as eluents, and obtain a pure organic room temperature phosphorescent material after elution.

3. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: In step S1, the molar ratio of biphenyl anhydride to the amino substituent is 1:1.2, the molar ratio of biphenyl anhydride to the alkaline reagent triethylamine is 1:3, the molar ratio of biphenyl anhydride to the catalyst 4-dimethylaminopyridine is 1:0.2, and the volume ratio of the molar ratio of biphenyl anhydride to dichloromethane is 1:

20.

4. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: The amide reaction in step S1 is stirred at room temperature for 12 hours.

5. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: In step S2, the molar ratio of HCl to biphenyl anhydride is 1:

3.

6. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: The reduced pressure condition of the rotary evaporator in step S4 is -0.095 MPa.

7. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: In step S5, acetic anhydride is a ring-closing reagent.

8. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: The reflux reaction temperature in step S5 is 150° C., and the reaction time is 6-24 hours.

9. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: The reduced pressure condition of the rotary evaporator in step S6 is -0.095 MPa.

10. The method for preparing a pure organic room temperature phosphorescent material according to claim 2, characterized in that: In step S7, the volume ratio of the eluent petroleum ether to dichloromethane is 2:1.

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