Phenanthroimidazole fused ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate and application of phenanthroimidazole fused ring blue fluorescent material

Abstract

The invention discloses a phenanthroimidazole fused ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate and application thereof, the fluorescent material uses phenanthroimidazole as a donor unit and a fused ring aromatic conjugated group as an acceptor unit to construct a blue fluorescent molecular system. According to the invention, a toluene group is introduced to the position of phenanthroimidazole N2, so that the realization of efficient blue light (430-470 nm) is ensured, different condensed ring groups are introduced to the position of C1 to adjust the luminescence color of fluorescent molecules, and the fluorescence quantum yield, the thermal stability and the radiative transition rate are improved. The preparation method of the blue fluorescent material is simple, the blue fluorescent material is easy to purify, and the blue fluorescent material has great potential in organic diode display application due to high quantum yield, radiative transition rate and excellent thermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photoelectric materials, and in particular relates to a phenanthroimidazole-based condensed-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate. Background Art

[0002] Organic light-emitting diodes (OLEDs) have significant advantages over liquid crystal displays, such as faster screen response and high contrast. How to develop high fluorescence quantum yield and thermal properties are stable (thermal decomposition temperature T d Blue OLED materials with operating temperatures >400℃ still need further exploration.

[0003] The absolute fluorescence quantum yield is often an important indicator to measure the excellent optical properties of fluorescent molecules. The higher the quantum yield of the fluorescent molecule itself, the higher the efficiency of the prepared OLED device. The preparation of OLED is often achieved by vacuum evaporation, so this requires the fluorescent molecules to have excellent thermal stability. At the same time, OLED preparation requires fluorescent molecules to have a good radiation transition rate kr. The higher the rate, the more photons in the excited state can complete the luminescence process in the form of high-speed radiation transition, reducing the accumulation of photons in the excited state, thereby effectively extending the service life of the device. The specific calculation formula is quantum yield / fluorescence decay lifetime, that is, Wang et al. (ACS Appl. Mater. Interfaces 2024, 16, 51201-51211.) announced a class of synthesis and applications of phenanthroimidazole blue fluorescent molecules. By simply changing the substituents or the position of the same substituent, the structure-activity relationship of the molecules was systematically studied. Among them, the change of the substituents or the change of the position of the same substituent will have a greater impact on the photophysical properties or thermal properties of the fluorescent molecules. For example, when the substituent at the N2 position is changed from a trifluoromethyl group to a cyano group, the thermal properties of the molecule are improved, but its quantum yield is significantly reduced; when the cyano group at the N2 position is moved to the 4th position of the biphenyl at the C1 position, the thermal properties of the molecule are improved, the fluorescence quantum yield is significantly improved, but its fluorescence emission peak or color undergoes a significant red shift. For example, PPIM-13F and PPIM-23F have good photophysical properties, but the presence of trifluoromethyl groups reduces the thermal decomposition temperature (375.0°C and 391.0°C, respectively), which is not conducive to the stability of OLED preparation. PL =441nm, T d =436.0℃) and PPIM-2CN(λ PL =478nm, T d=454.0°C). Although the change in the position of the cyano group significantly increased its fluorescence quantum yield (from 13.7% to 79.6%), and both compounds also had excellent thermal stability (from 436.0°C to 454.0°C), their original fluorescence emission peaks underwent a significant red shift (from 441nm for pure blue to 478nm, close to sky blue), which would be unfavorable for the preparation of high-purity blue OLEDs. This shows that the position and type of substituents have a significant impact on the quantum yield and thermal stability of blue fluorescent molecules. Summary of the Invention

[0004] The present invention aims to provide a phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate. The material adopts a rigid phenanthroimidazole structure to ensure the thermal stability of the molecule. By introducing a toluene group at the N2 position of the phenanthroimidazole, the emission color of the fluorescent molecule is adjusted to ensure the realization of efficient blue light. By introducing different fused-ring groups at the C1 position, the thermal stability is further improved, and the fluorescence quantum yield and radiation transition rate are increased.

[0005] The structural formula of the phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate provided by the present invention is as follows:

[0006]

[0007] Where Ar represents Any one of them.

[0008] Further preferably, the phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiative transition rate of the present invention is selected from any one of the following compounds A to C:

[0009]

[0010] The synthesis steps of the above-mentioned phenanthroimidazole fused-ring blue fluorescent material are as follows:

[0011] Step 1: Add phenanthrenequinone, p-bromobenzaldehyde, p-methylaniline, and ammonium acetate to acetic acid in a molar ratio of 1:1:2-4:3-5, and react at 110-120°C under a nitrogen atmosphere for 1-3 hours. After the reaction is complete, cool to room temperature, pour the reaction system into saturated brine, filter, wash with ethanol, and dry to obtain the compound MePIBr. The reaction equation is as follows:

[0012]

[0013] Step 2: Compound MePIBr, an aromatic boronic acid derivative represented by Formula I, tetrabutylammonium bromide (TBAB), and dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium (II) (Pd132) are added to N,N-dimethylformamide in a molar ratio of 1:1 to 2:1 to 2:0.01, and an aqueous potassium carbonate solution is slowly added dropwise. The mixture is reacted at 70-90°C under a nitrogen atmosphere for 2-8 hours. After the reaction is complete, the mixture is extracted with dichloromethane (DCM), and the organic phase is washed with water until neutral. The organic phase is dried over anhydrous magnesium sulfate and concentrated by evaporation. The crude product is washed with ethanol and petroleum ether, recrystallized from a toluene / ethanol (volume ratio 1:1), and decolorized with activated carbon to obtain the phenanthroimidazole-based fused-ring blue fluorescent material represented by Formula II. The reaction equation is as follows:

[0014]

[0015] The present invention also provides a method for preparing an organic light-emitting diode by using the phenanthroimidazole condensed ring blue fluorescent material as a guest molecule of a light-emitting layer in an OLED.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention uses phenanthroimidazole as a donor unit and a fused-ring aromatic group as an acceptor unit. By introducing a toluene group at the N2 position of the phenanthroimidazole, efficient blue light emission (430nm to 470nm) is achieved. By introducing different fused-ring groups at the C1 position, the fluorescent molecule's emission color is adjusted, and its fluorescence quantum yield, thermal stability, and radiative transition rate are improved. The preparation method of the fluorescent material is simple and easy to purify. Its high quantum yield, radiative transition rate, and excellent thermal stability address the problem of some OLED materials decomposing at lower temperatures, making it highly promising for applications in blue organic diode displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the fluorescence emission spectrum of compounds A, B, C synthesized in Examples 1, 2, 3 and compound MePI synthesized in Comparative Example 1.

[0019] Figure 2 It is the thermogravimetric analysis spectrum of compounds A, B, C synthesized in Examples 1, 2, 3 and compound MePI synthesized in Comparative Example 1. DETAILED DESCRIPTION

[0020] 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.

[0021] Comparative Example 1

[0022]

[0023] 10.00 g (48 mmol) of 9,10-phenanthrenequinone, 5.15 g (48 mmol) of p-methylaniline, 17.50 g (96 mmol) of 4-biphenylaldehyde, 18.51 g (240 mmol) of ammonium acetate, and 200 mL of acetic acid were added sequentially to a 500 mL three-necked flask with a thermometer and reacted at 120°C for 2 hours under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature and poured into 200 mL of saturated brine, stirred, and filtered. The crude product was then washed twice with 200 mL of ethanol, recrystallized with 50 mL of DMF, and finally washed with 200 mL of PE to obtain 12.41 g of a white solid compound, MePI, with a yield of 56.13%. Its structural characterization data are as follows: 1 H NMR(500MHz,Chloroform-d)δ8.90(d,J=9.4Hz,1H),8.78(d,J=8.3Hz,1H),8.71(d,J=8.3Hz,1H),7.75(t,J=6.9Hz,1H),7.71-7.63( m,3H),7.60(d,J=7.1Hz,2H),7.53(dd,J=19.0,7.5Hz,3H),7.46-7.39(m,6H),7.35(t,J=7.3Hz,1H),7.31-7.25(m,2H),2.55(s,3H).

[0024] Example 1

[0025]

[0026] Step 1: 15.00 g (72 mmol) of 9,10-phenanthrenequinone, 7.70 g (72 mmol) of p-methylaniline, 26.66 g (144 mmol) of 4-bromobenzaldehyde, 27.77 g (360 mmol) of ammonium acetate and 200 mL of acetic acid were added sequentially into a 500 mL three-necked flask with a thermometer, and the mixture was reacted at 120° C. in a nitrogen atmosphere for 1 hour. After the reaction, the mixture was cooled to room temperature, and the reaction solution was poured into 200 mL of saturated brine, stirred thoroughly, filtered, washed with ethanol, and dried to obtain 25.73 g of a pink solid compound MePIBr with a yield of 77.08%.

[0027] The structural characterization data of MePIBr are: 1H NMR(600MHz,Chloroform-d)δ8.75(d,J=8.0Hz,1H),8.66(d,J=8.3Hz,1H),8.60(d,J=8.3Hz,1H),7.64(s,1H),7.55(s,1H),7.41(s,1 H),7.37(d,J=8.2Hz,2H),7.33(d,J=8.3Hz,2H),7.30(d,J=7.9Hz,2H),7.27(d,J=7.9Hz,2H),7.18(s,1H),7.13(s,1H),2.45(s,3H).

[0028]

[0029] Step 2: To a three-necked flask equipped with a thermometer, 100 mL of DMF, 10.00 g (21.58 mmol) of MePIBr, 5.57 g (32.37 mmol) of 1-naphthaleneboronic acid, 13.91 g (43.16 mmol) of TBAB, and 130 mg (0.22 mmol) of Pd123 were added in sequence, and stirred until the raw materials were completely dissolved. 17.90 g (17.9 mmol) of K2CO3 was dissolved in 10 mL of deionized water and slowly added dropwise to the reaction system. The reaction was continued at 75 ° C for 3 hours. After the reaction, it was extracted with DCM, and the organic phase was washed with water to neutrality. The organic phase was dried over anhydrous magnesium sulfate and concentrated by evaporation to obtain a crude product. The crude product was washed with ethanol and petroleum ether, and purified by recrystallization from toluene / ethanol (volume ratio 1: 1). Activated carbon was used for decolorization to finally obtain 9.03 g of white solid compound A with a yield of 81.97%.

[0030] The structural characterization data of compound A are: 1 H NMR(500MHz,Chloroform-d)δ8.93(d,J=8.0Hz,1H),8.76(d,J=8.4Hz,1H),8.70(d,J=8.3Hz,1H),7.88(dd,J=8.9,2.9Hz, 2H),7.84(d,J=8.2Hz,1H),7.75(dd,J=11.8,8.1Hz,3H),7.65(t,J=7.7Hz,1H),7.54-7.46(m,3H),7.46-7.37(m,8H),7.32 -7.24(m,2H),2.54(s,3H).

[0031] Example 2

[0032]

[0033] In step 2 of this example, 1-naphthaleneboric acid in step 2 of Example 1 was replaced with an equal molar amount of 9-anthraceneboric acid. The other steps were the same as in Example 1 to obtain 5.29 g of white solid B with a yield of 43.69%. The structural characterization data are as follows: 1 H NMR(500MHz,Chloroform-d)δ8.96(d,J=8.0Hz,1H),8.81(d,J=8.4Hz,1H),8.74(d,J=8.3Hz,1H),8.49(s,1H),8.04(d,J=8.5Hz,2H),7.84(d,J=8.2Hz,2 H),7.78(t,J=7.5Hz,1H),7.67(dd,J=18.7,7.8Hz,3H),7.57-7.50(m,3H),7 .46(d,J=8.4Hz,4H),7.42-7.34(m,4H),7.32(d,J=6.2Hz,2H),2.57(s,3H).

[0034] Example 3

[0035]

[0036] In step 2 of this example, 1-naphthaleneboric acid in step 2 of Example 1 was replaced with an equal molar amount of 1-pyreneboric acid. The remaining steps were the same as in Example 1, yielding 7.89 g of bright yellow solid Compound C in a yield of 62.55%. Its structural characterization data are as follows: 1 HNMR(500MHz,Chloroform-d)δ8.97(d,J=6.5Hz,1H),8.80(d,J=8.3Hz,1H),8.74(d,J=8.3 Hz,1H),8.23–8.15(m,4H),8.09(s,2H),8.05-7.99(m,2H),7.96(d,J=7.8Hz,1H),7.83(d, J=8.3Hz,2H),7.79(t,J=7.5Hz,1H),7.68(t,J=7.7Hz,1H),7.59(d,J=8.2Hz,2H),7.53(t, J=7.5Hz,1H),7.50(d,J=8.3Hz,2H),7.45(d,J=8.2Hz,2H),7.37-7.26(m,2H),2.58(s,3H).

[0037] In order to demonstrate the beneficial effects of the present invention, compounds A to C prepared in Examples 1 to 3 and compound MePI prepared in Comparative Example 1 were prepared into neat, smooth films by tableting. The fluorescence emission spectra and absolute quantum yields of the four compounds were measured using a steady-state transient fluorescence spectrometer (QuantaMaster 8000, manufactured by HORIBA, Canada). The optical and thermal properties of the phenanthroimidazole derivatives (PPIM-2CN, PPIM-13F, PPIM-23F, PPIM-1CN) reported by Wang et al. (ACS Appl. Mater. Interfaces 2024, 16, 51201-51211) were compared. The results are shown in Table 1 and Table 2. Figure 1 、 Figure 2 .

[0038] Table 1 Photophysical properties of different compounds in solid film state

[0039]

[0040]

[0041] From Table 1 and Figure 1 It can be seen that the fluorescence emission peaks λ of compounds A, B and C PL The wavelengths of the three compounds were 431nm, 447nm and 468nm, respectively, which all met the requirements of blue emission (430nm to 470nm). and The absolute fluorescence quantum yields of Excellent absolute fluorescence quantum yield will be conducive to the realization of higher efficiency in OLED devices. In order to meet the requirements of OLED preparation, the fluorescent molecules have excellent radiation transition rate requirements. According to the fluorescence quantum yield and fluorescence decay lifetime obtained by the test, the radiation transition rate is calculated from large to small: C (4.01×10 8 S -1 )>Comparative Example 1(3.58×10 8 S -1 )>B(2.73×10 8 S -1 )>A(2.62×10 8 S -1 )>PPIM-2CN(1.34×10 8 S -1)>PPIM-13F(1.15×10 8 S -1 )>PPIM-23F(0.97×10 8 S -1 )>PPIM-1CN(0.45×10 8 S -1 ). It can be seen that the radiation transition rates of compounds A~C are more than 2 times higher than those of the compounds in the literature.

[0042] Combine Figure 2 As shown in Table 1, the thermal decomposition temperatures (corresponding to 5% weight loss) of compounds A-C are 455.3°C, 425.7°C, and 467.2°C, respectively, demonstrating excellent thermal stability (all greater than 400°C). This will benefit stability during OLED device fabrication. Although compound B has a lower thermal decomposition temperature than PPIM-1CN and MePI, its thermal stability still meets the requirement of greater than 400°C and exhibits even superior photophysical properties.

[0043] In summary, the present invention introduces a toluene group at the N2 position of phenanthroimidazole to ensure the realization of efficient blue light (430nm~470nm), and achieves high fluorescence quantum yield, high radiation transition rate and excellent thermal stability by introducing a fused ring group at the C1 position.

Claims

1. A phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate, characterized in that: The structural formula of the fluorescent material is shown below: Where Ar represents Any one of them.

2. The phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate according to claim 1, characterized in that: Ar represents Any one of them.

3. Use of the phenanthroimidazole-based fused-ring blue fluorescent material with high fluorescence quantum yield and radiation transition rate according to claim 1 as a guest molecule of the light-emitting layer in OLED to prepare an organic light-emitting diode.

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