A phenanthroimidazole fluorescent material with high thermal stability and high-purity blue light emission, as well as its synthesis method and application

Abstract

The present invention discloses a phenanthroimidazole fluorescent material with high thermal stability and high-purity blue light emission, as well as its synthesis method and application. The material uses phenanthroimidazole as an acceptor unit, triphenylamine as a donor unit, and different benzene ring functional groups at position 1 of phenanthroimidazole as excited state regulating groups. The present invention introduces different electron-absorbing or electron-supplying groups in the direction of the short axis of the molecule to achieve fine-tuning of the excited state properties, thereby suppressing the vibration coupling occurring in the first singlet excited state, thereby achieving high-purity blue light emission, and at the same time ensuring that the fluorescent molecule has excellent thermal stability. The preparation method of the fluorescent material of the present invention is simple and easy to purify, and its excellent photophysical properties and thermal stability make it have great potential in organic diode display applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photoelectric materials, and in particular relates to a phenanthroimidazole fluorescent material with high thermal stability and high-purity blue light emission. Background Art

[0002] OLED has huge advantages over LCD, such as faster screen response, high contrast, etc. The International Commission on Illumination defines deep blue as a color that meets the CIEy<0.08 range. The fluorescence emission peak λ of commercial blue devices is PL The wavelength should be below 450nm and the material should have a low Stokes shift to improve the luminous efficiency. How to develop more stable thermal properties (thermal decomposition temperature T d >400℃) and excellent photophysical properties of blue OLED materials still need further exploration.

[0003] Li et al. (Adv. Funct. Mater., 2012, 22, 2797-2803.) first disclosed the synthesis and application of phenanthroimidazole derivatives, in which TPA-PPI can meet the fluorescence emission peak λ PL The requirements of spectral red shift of 69 nm and decomposition temperature Td>400 ° C were met. However, the large spectral red shift of 69 nm in the solvation experiment was not conducive to the formation of low Stokes shift materials. Subsequently, Zhang et al. (Adv. Funct. Mater., 2015, 25, 1755-1762.) reported the synthesis and application of two phenanthroimidazole derivatives. Although the derivatives met the requirements of thermal properties, the photophysical properties of the molecule TPMCN in four types of solvents did not meet the requirements of fluorescence emission peak λ PL The requirements of λ<450nm and CIEy<0.08 are met, and the spectrum is red-shifted by 78nm in the solvation experiment, which is also not conducive to the formation of low Stokes shift materials, which is related to the strong substituent cyano group introduced. Peng et al. (Opt. Mater., 2020, 101, 109726.) announced the synthesis and application of three fluorescent molecules based on phenanthroimidazole derivatives. In this study, the molecule MePPIM-TPA, although it meets the requirements of λ<450nm and CIEy<0.08 in acetonitrile solution, meets the requirements of λ<450nm and CIEy<0.08 in the solvation experiment ... PL High-purity blue emission requirements of <450nm are required, but thermal performance is unstable.

[0004] Fluorescence radiative transitions primarily occur in the first singlet excited state (S1). Due to the vibrational coupling of S1 and between S1 and the ground state (S0), they are often accompanied by a broad spectrum, which undoubtedly compromises color purity. Therefore, the development of fluorescent molecules with high-purity blue light emission and excellent thermal properties is of great significance. Summary of the Invention

[0005] The present invention aims to provide a phenanthroimidazole fluorescent material with high thermal stability and high-purity blue light emission. The material adopts a rigid phenanthroimidazole structure to improve the molecular thermal stability, introduces a triphenylamine structure to suppress the quenching of the fluorescent molecules, and then introduces different functional groups to regulate the excited state properties. Ultimately, the material can meet the high-quality blue emission requirement of CIEy < 0.08 and overcome the disadvantage of insufficient thermal stability of some fluorescent molecules at high temperatures.

[0006] The structural formula of the phenanthroimidazole fluorescent material with high thermal stability and high-purity blue light emission provided by the present invention is as follows:

[0007]

[0008] In the formula, X represents O or S, and Y represents H or F.

[0009] The synthesis method of the fluorescent material of the present invention comprises the following steps: adding phenanthrenequinone, diphenylamino-4-benzaldehyde, an aniline derivative, and ammonium acetate to acetic acid, and reacting the mixture at 110-120° C. in a nitrogen atmosphere for 1-3 hours; after the reaction is complete, pouring the reaction system into saturated saline, filtering, washing with ethanol, and recrystallizing from N,N-dimethylformamide to obtain a phenanthroimidazole fluorescent material; the reaction equation is as follows:

[0010]

[0011] In the formula, X represents O or S, and Y represents H or F.

[0012] In the above synthesis method, the molar ratio of phenanthrenequinone, diphenylamino-4-benzaldehyde, aniline derivative and ammonium acetate is preferably 1:1-1.5:2-3:4-6.

[0013] The present invention also provides use of the fluorescent material as a guest molecule of a light-emitting layer in an OLED.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention uses phenanthroimidazole as an acceptor unit to improve the thermal stability of the molecule and suppress the quenching of the fluorescent molecule. Triphenylamine is used as a donor unit. By adjusting the charge-absorbing ability of aniline derivatives containing different functional groups at the first position of phenanthroimidazole, the excited state properties of the fluorescent material are rationally controlled, thereby suppressing the vibrational coupling occurring in the first singlet excited state, thereby achieving high-purity blue light emission and ensuring the excellent thermal stability of the fluorescent molecule. The preparation method of the fluorescent material of the present invention is simple and easy to purify. It can meet the high-quality blue emission requirement of CIEy < 0.08. Its excellent photophysical properties and thermal stability solve the problem of some OLED materials decomposing at lower temperatures, making it have great potential for organic diode display applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The fluorescence emission spectra of the fluorescent material synthesized in Example 1 in four solutions (n-hexane, diethyl ether, tetrahydrofuran and acetonitrile) are shown.

[0017] Figure 2 The fluorescence emission spectra of the fluorescent material synthesized in Example 2 in four solutions (n-hexane, diethyl ether, tetrahydrofuran and acetonitrile).

[0018] Figure 3 The fluorescence emission spectra of the fluorescent material synthesized in Example 3 in four solutions (n-hexane, diethyl ether, tetrahydrofuran and acetonitrile).

[0019] Figure 4 The fluorescence emission spectra of the fluorescent material synthesized in Example 4 in four solutions (n-hexane, diethyl ether, tetrahydrofuran and acetonitrile).

[0020] Figure 5 This is the thermogravimetric analysis spectrum of the fluorescent materials synthesized in Examples 1 to 4.

[0021] Figure 6 This is the thermogravimetric analysis spectrum of the fluorescent material synthesized in Comparative Example 1. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the present invention is not limited to these examples.

[0023] Example 1

[0024]

[0025] To a 150 mL three-necked flask equipped with a magnetic stirrer, a thermometer, and a spherical condenser, 0.42 g (2 mmol) of phenanthrenequinone, 0.547 g (2 mmol) of diphenylamino-4-benzaldehyde, 0.985 g (4 mmol) of p-methoxyaniline, 0.78 g (10 mmol) of ammonium acetate, and 20 mL of glacial acetic acid were added in sequence. The mixture was stirred at 120° C. for 2 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and poured into a beaker filled with saturated brine. The mixture was stirred and filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain 0.343 g of compound I as a yellow solid powder, designated as MeO-PT, with a yield of 30.10%. Its structural characterization data are as follows: 1HNMR(600MHz,DMSO-d6)δ7.99(d,J=8.4Hz,1H),7.94(d,J=8.3Hz,1H),7.89(dd,J=8.0,1.4Hz,1H),6.90(t,J=7.5Hz,2H),6.84(t,J=7.7Hz,2H), 6.71(d,J=8.0Hz,3H),6.68-6.61(m,2H),6.47(t,J=7.9Hz,4H),6.38-6. 33(m,3H),6.25(dd,J=10.1,4.0Hz,5H),6.09-6.05(m,2H),3.12(s,3H).

[0026] Example 2

[0027]

[0028] To a 150 mL three-necked flask equipped with a magnetic stirrer, a thermometer, and a spherical condenser, 0.42 g (2 mmol) of phenanthrenequinone, 0.547 g (2 mmol) of diphenylamino-4-benzaldehyde, 1.11 g (4 mmol) of p-methylthioaniline, 0.78 g (10 mmol) of ammonium acetate, and 20 mL of glacial acetic acid were added in sequence. The mixture was stirred at 120 ° C. for 2 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and poured into a beaker filled with saturated brine. The mixture was stirred and filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain 0.236 g of yellow solid powder Compound II, designated as MTM-PT, with a yield of 20.20%. Its structural characterization data are as follows: 1 HNMR(600MHz,Chloroform-d)δ8.70(d,J=8.0Hz,1H),8.59(d,J=8.4Hz,1H),8.53(d,J=8.3Hz,1H),7.56(t,J=7.5Hz,1H),7.47(t,J=7.7H z,1H),7.38-7.20(m,7H),7.10(hept,J=8.9,8.4Hz,6H),6.93(d,J=7.9Hz,4H),6.89(t,J=7.4Hz,2H),6.80(d,J=8.7Hz,2H),2.43(s,3H).

[0029] Example 3

[0030]

[0031] To a 150 mL three-necked flask equipped with a magnetic stirrer, a thermometer, and a spherical condenser, 0.42 g (2 mmol) of phenanthrenequinone, 0.547 g (2 mmol) of diphenylamino-4-benzaldehyde, 1.42 g (4 mmol) of p-trifluoromethoxyaniline, 0.78 g (10 mmol) of ammonium acetate, and 20 mL of glacial acetic acid were added in sequence. The mixture was stirred at 120° C. for 2 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and poured into a beaker filled with saturated brine. The mixture was stirred and filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain 0.224 g of compound III as a white solid powder, designated as TfMeO-PT, with a yield of 18.10%. Its structural characterization data are as follows: 1 H NMR(600MHz,Chloroform-d)δ8.79(d,J=8.0Hz,1H),8.70(d,J=8.4Hz,1H),8.63(d,J=8.3Hz,1H),7.66(t,J=7.4Hz,1H),7.60-7.55(m,1H),7.53-7.48 (m,2H),7.44(t,J=7.7Hz,1H),7.38(s,2H),7.31(d,J=8.4Hz,2H),7.23-7. 17(m,6H),7.07(d,J=8.4Hz,1H),7.04-6.95(m,6H),6.88(d,J=8.5Hz,2H).

[0032] Example 4

[0033]

[0034] To a 150 mL three-necked flask equipped with a magnetic stirrer, a thermometer, and a spherical condenser, 0.42 g (2 mmol) of phenanthrenequinone, 0.547 g (2 mmol) of diphenylamino-4-benzaldehyde, 1.42 g (4 mmol) of p-trifluoromethylthioaniline, 0.78 g (10 mmol) of ammonium acetate, and 20 mL of glacial acetic acid were added in sequence. The mixture was stirred at 120 ° C. for 2 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and poured into a beaker filled with saturated brine. The mixture was stirred and filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain 0.333 g of compound IV as a white solid powder, designated as TfMTM-PT, with a yield of 25.80%. Its structural characterization data are as follows: 1H NMR(600MHz,Chloroform-d)δ8.86(d,J=7.9Hz,1H),8.77(d,J=8.4Hz,1H),8.7 0(d,J=8.3Hz,1H),7.89(d,J=8.3Hz,2H),7.74(t,J=7.5Hz,1H),7.65(t,J=7.6H z,1H),7.59(d,J=8.3Hz,2H),7.51(t,J=7.0Hz,1H),7.35(d,J=8.7Hz,2H),7.2 9-7.23(m,6H),7.14(d,J=8.3Hz,1H),7.10-7.03(m,6H),6.94(d,J=8.7Hz,2H).

[0035] Comparative Example 1

[0036]

[0037] To a 150 mL three-necked flask equipped with a magnetic stirrer, a thermometer, and a spherical condenser, 0.42 g (2 mmol) of phenanthrenequinone, 0.547 g (2 mmol) of diphenylamino-4-benzaldehyde, 1.42 g (4 mmol) of p-trifluoromethylaniline, 0.78 g (10 mmol) of ammonium acetate, and 20 mL of glacial acetic acid were added in sequence. The mixture was stirred at 120° C. for 2 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and poured into a beaker filled with saturated brine. The mixture was stirred and filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain 0.333 g of compound V as a white solid powder, designated as TfMe-PT, with a yield of 25.80%. Its structural characterization data are as follows: 1 HNMR(600MHz,Chloroform-d)δ8.74(d,J=8.0Hz,1H),8.62(d,J=8.3Hz,1H),8.56(d,J=8.3Hz,1H),7.59(t,J=7.5Hz,1H),7.50(t,J=7.7Hz,1H),7.38- 7.32(m,3H),7.30-7.23(m,4H),7.12(t,J=7.7Hz,6H),7.07-7.04(m,1H),6 .96(d,J=7.3Hz,4H),6.93-6.89(m,2H),6.82(d,J=8.7Hz,2H),2.44(s,3H).

[0038] In order to demonstrate the beneficial effects of the present invention, compounds I to IV prepared in Examples 1 to 4 were dissolved in n-hexane, ether, tetrahydrofuran and acetonitrile, respectively, to prepare 1×10 -5mol / L solution. A steady-state transient fluorescence spectrometer (QuantaMaster8000, produced by HORIBA, Canada) was used to detect the four target molecules. The test content included fluorescence emission spectrum, half-maximum width (FWHM) of the fluorescence emission spectrum, fluorescence quantum yield At the same time, the performance was compared with TPMCN reported by Zhang et al. (Adv. Funct. Mater., 2015, 25, 1755-1762.), MePPIM-TPA reported by Peng et al. (Opt. Mater., 2020, 101, 109726.), and TPA-PPI reported by Li et al. (Adv. Funct. Mater., 2012, 22, 2797-2803.). The results are shown in Table 1 and Figures 1 to 4 .

[0039] Table 1 Photophysical properties of compounds in Examples 1 to 4 and reference compounds in different solvents

[0040]

[0041]

[0042] Note: In the table, - indicates that the corresponding parameter is not provided.

[0043] Depend on Figures 1 to 4 It can be seen that the fluorescence emission peaks λ of MeO-PT, MTM-PT, TfMeO-PT and TfMTM-PT in tetrahydrofuran solution are PL They are 418nm, 418nm, 423nm and 429nm respectively, all of which meet the fluorescence emission peak λ PL <450nm requirement, the corresponding CIE coordinates are (0.16, 0.03), (0.16, 0.03), (0.16, 0.04) and (0.15, 0.06), all of which meet the deep blue emission requirement of CIEy<0.08. As can be seen from Table 1, compared with TPMCN, the four molecules of the present invention are superior to TPMCN in various photophysical properties under the same test conditions. The fluorescence spectra of the four molecules in the present invention are red-shifted by 32nm, 35nm, 42nm and 29nm respectively, which are all less than the 78nm red-shift of TPMCN. Compared with TPA-PPI, the red-shift of the fluorescence spectra of the four molecules in the present invention are all less than 69nm of TPA-PPI. It is proved that the introduction of different substituents in the direction of the short axis of the molecule to achieve fine control of the excited state properties is helpful for fluorescent organic molecules to form low Stokes shift materials, thereby improving photophysical properties.

[0044] In order to highlight the promoting effect of the introduction of oxygen and sulfur atoms on the thermal stability of fluorescent molecules, a professional synchronous thermal analyzer (model TGA / DSC1_*, produced by Mettler, Switzerland) was used to test the thermal properties of compounds I to IV prepared in Examples 1 to 4, compound V (TfMe-PT) prepared in Comparative Example 1, and MePPIM-TPA reported by Peng et al. (Opt. Mater., 2020, 101, 109726). The results are shown in Tables 2 and Figures 5-6 .

[0045] Table 2 Comparison of thermal performance parameters of compounds in Examples 1 to 4, Comparative Example 1 and reference compounds

[0046]

[0047] Depend on Figure 5 As shown in Table 2, the thermal decomposition temperatures (corresponding to 5% weight loss) of MeO-PT, MTM-PT, TfMeO-PT and TfMTM-PT are 439.3°C, 438.2°C, 409.0°C and 429.0°C, respectively, indicating that the four molecules have excellent thermal stability (all greater than 400°C). Figure 6 It can be seen that the thermal decomposition temperature of TfMe-PT is 366.2°C. It can be seen that after the introduction of oxygen and sulfur, the thermal decomposition temperatures of the two types of molecules TfMeO-PT and TfMTM-PT increase, indicating that the introduction of oxygen and sulfur is beneficial to improving the thermal stability of the molecules. The four types of molecules of the present invention have better thermal properties than the MePPIM-TPA reported by Peng et al. (Opt. Mater., 2020, 101, 109726.). The four types of molecules in the present invention have higher decomposition temperatures than the molecules MePPIM-TPA and TfMe-PT, which proves that the introduction of oxygen and sulfur is beneficial to improving the thermal stability of the molecules. This will be beneficial to the OLED evaporation device process, making the molecules less likely to decompose.

Claims

1. A phenanthroimidazole fluorescent material, characterized in that: The structural formula of the fluorescent material is shown below: In the formula, X represents O or S, and Y represents H or F.

2. A method for synthesizing the phenanthroimidazole fluorescent material according to claim 1, characterized in that: Phenanthrenequinone, diphenylamino-4-benzaldehyde, aniline derivatives, and ammonium acetate are added to acetic acid and reacted at 110-120°C in a nitrogen atmosphere for 1-3 hours. After the reaction is completed, the reaction system is poured into saturated brine, filtered, washed with ethanol, and recrystallized from N,N-dimethylformamide to obtain a phenanthroimidazole fluorescent material. The reaction equation is as follows: In the formula, X represents O or S, and Y represents H or F.

3. The method for synthesizing a phenanthroimidazole fluorescent material according to claim 2, wherein: The molar ratio of the phenanthrenequinone, diphenylamino-4-benzaldehyde, aniline derivative and ammonium acetate is 1:1-1.5:2-3:4-6.

4. Use of the phenanthroimidazole fluorescent material according to claim 1 as a guest molecule in a light-emitting layer of an OLED.

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