Bi-state emission phenanthroimidazole blue light material with high radiative transition rate and application of bi-state emission phenanthroimidazole blue light material

Abstract

The invention discloses a bi-state emission phenanthroimidazole blue light material with high radiation transition rate and application thereof, the molecular structure of the blue light material takes phenanthroimidazole with bipolar characteristic as a core unit and takes different functional groups as electron donor or acceptor units to construct an efficient blue fluorescence system. Specifically, a methyl phenyl group is introduced to the C2 position of phenanthroimidazole, so that the blue light-emitting characteristic of the material is effectively maintained; meanwhile, different functional groups are introduced to the N1 site, so that the fine adjustment of the emitted light color is realized, and the radiative transition rate is remarkably improved. The preparation method of the blue-light-emitting material is simple and convenient, the blue-light-emitting material is easy to purify, and the blue-light-emitting material has the advantages of high radiation transition rate and high fluorescence quantum yield and has important application prospects in the field of organic light-emitting diode display.

Description

A dual-state emission phenanthreneimidazole-based blue light material with high radiative transition rate and its applications. Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials technology, specifically relating to a dual-state emission phenanthrimidazole blue light material with a high radiative transition rate and its applications. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have significant advantages over liquid crystal displays, such as faster response times and higher contrast ratios. However, the development of blue OLED materials that combine high fluorescence quantum yield and high radiative transition rate still requires further exploration and breakthroughs.

[0003] Absolute fluorescence quantum yield is one of the core indicators for evaluating the optical performance of fluorescent molecules. Generally speaking, the higher the quantum yield φ of a fluorescent molecule, the higher the efficiency of the resulting OLED device tends to be. High-performance fluorescent molecules typically exhibit efficient two-state emission characteristics, meaning they maintain high quantum yields in both solution and solid film states. Furthermore, to achieve efficient and stable device performance, fluorescent molecules also need to possess a high radiative transition rate k. r k r A higher value indicates a faster process where excited-state photons return to the ground state and emit light via radiative transition, thus reducing the accumulation of excited-state particles and extending the lifespan of OLED devices. Radiative transition rate k r The specific calculation formula is: k r= φ / τ. Where φ is the fluorescence quantum yield and τ is the fluorescence decay lifetime. Jayabharathi et al. (New J. Chem., 2014, 38, 4321-4335) reported that the phenanthrimidazole derivative Compd.1 had a low quantum yield (5.5%) in the solid state. Li and Song et al. (J. Mole. Struct., 2026, 1355, 145041) reported the synthesis of a series of phenanthrimidazole-based blue fluorescent molecules and systematically studied the effects of different substituents on the photophysical properties of the molecules. Although the molecules reported in this study overcame the problem of low fluorescence quantum yield in the solid film state reported by Jayabharathi, the fluorescence quantum yield in the solution state was generally low. For example, although the target molecule MeACFy achieved a high fluorescence quantum yield of 76.9% in the solid film state, the fluorescence quantum yield in DMF solution was only 18.6%. This phenomenon can be attributed to the increased nonradiative energy loss caused by strong solute-solvent interactions in solution. Furthermore, the phenanthreneimidazole core group readily forms a large torsion angle at the N2 position, effectively suppressing aggregation-induced fluorescence quenching in the solid state. This large torsion angle also facilitates the formation of typical charge-transfer states, thereby improving triplet exciton conversion efficiency. Therefore, molecular configuration and structural modifications significantly influence its photophysical dynamics. Summary of the Invention

[0004] The purpose of this invention is to provide a phenanthrimidazole-based blue light material with high radiative transition rate and dual-state emission. By introducing a methylphenyl group at the C2 position, the molecular emission color is adjusted to ensure the realization of deep blue light; different functional groups are introduced at the N1 position of phenanthrimidazole to improve its fluorescence quantum yield and radiative transition rate.

[0005] The structural formula of the dual-state emission phenanthrimidazole-based blue light-emitting material with high radiative transition rate provided by this invention is shown below:

[0006]

[0007] In the formula, represent , , , , , , , , , and Any one of them.

[0008] Furthermore, the dual-state emission phenanthrimidazole-based blue light material with high radiative transition rate described in this invention is preferably any one of the following compounds A to D:

[0009]

[0010] The synthesis steps of the above-mentioned dual-state emission phenanthrimidazole-based blue light-emitting materials with high radiative transition rates are as follows:

[0011] Step 1: Add 9,10-phenanthrenequinone, p-bromoaniline, 4-methylbenzaldehyde, and ammonium acetate to acetic acid in a molar ratio of 1:1–1.2:2–4:3–5, and react at 110–120°C for 1–3 hours under a nitrogen atmosphere. 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 MeBrPI. The reaction equation is as follows:

[0012]

[0013] Step 2: When represent , , When any one of the following is present, MeBrPI, spirofluorene acridine or 9,9-dimethyl acridine or carbazole, potassium carbonate, tris(dibenzylacetone)dipalladium(II) (Pd2(dba)3) and tri-tert-butylphosphine tetrafluoroborate (tBu3PHBF4) are added to toluene in a molar ratio of 1:1–1.2:1–1.5:0.045–0.055:0.09–0.12, and the mixture is refluxed under a nitrogen atmosphere for 10–14 hours; when represent , , , , , , and When any one of the following is present, compound MeBrPI, 1-naphthoboric acid, 2-naphthoboric acid, 9-anthraboric acid, 1-anthraboric acid, 2-anthraboric acid, 2-pyreneboric acid, 1-pyreneboric acid, or 4-pyreneboric acid, tetrabutylammonium bromide (TBAB), and dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium(II) (Pd132) are added to N,N-dimethylformamide (DMF) in a molar ratio of 1:1–2:1–2:0.01, and potassium carbonate aqueous solution is slowly added dropwise. The reaction is carried out at 70–90°C for 3–5 hours under a nitrogen atmosphere. After the reaction is completed, the mixture is extracted with dichloromethane (DCM), the organic phase is washed with water until neutral, the organic phase is dried with anhydrous magnesium sulfate, and then evaporated and concentrated. The crude product is washed with ethanol and petroleum ether and purified by column chromatography to obtain the corresponding phenanthreneimidazole-based blue light material.

[0014] The present invention also provides the use of the dual-state emission phenanthrimidazole blue light material with high radiative transition rate as a guest molecule in the light-emitting layer of an OLED to prepare an organic light-emitting diode.

[0015] The beneficial effects of this invention are as follows:

[0016] This invention uses phenanthreneimidazole, which possesses bipolar properties, as the core unit. By introducing a methylphenyl group at the C2 position of phenanthreneimidazole, the blue emission properties of the material are effectively ensured. Simultaneously, different functional groups are introduced at the N1 position of phenanthreneimidazole to finely adjust the emission color and improve the fluorescence quantum yield and radiative transition rate. The blue light-emitting material of this invention is simple to prepare and easy to purify, exhibiting high fluorescence quantum yield and high radiative transition rate, demonstrating significant application potential in the field of organic light-emitting diode displays. Attached Figure Description

[0017] Figure 1 shows the compounds A, B, C, and D synthesized in Examples 1, 2, 3, and 4, and compound PhPI synthesized in Comparative Example 1, in DMF solution (1×10⁻⁶). -5 Fluorescence emission spectrum of (mol / L).

[0018] Figure 2 shows the fluorescence emission spectrum of the compound PhPI synthesized in Comparative Example 1 in the solid thin film state.

[0019] Figure 3 shows the fluorescence emission spectrum of compound A synthesized in Example 1 in the solid thin film state.

[0020] Figure 4 shows the fluorescence emission spectrum of compound B synthesized in Example 2 in the solid thin film state.

[0021] Figure 5 shows the fluorescence emission spectrum of compound C synthesized in Example 3 in the solid thin film state.

[0022] Figure 6 shows the fluorescence emission spectrum of compound D synthesized in Example 4 in the solid thin film state.

[0023] Figure 7 shows the fluorescence lifetime decay curve of the compound PhPI synthesized in Comparative Example 1.

[0024] Figure 8 is the fluorescence lifetime decay curve of compound A synthesized in Example 1.

[0025] Figure 9 is the fluorescence lifetime decay curve of compound B synthesized in Example 2.

[0026] Figure 10 is the fluorescence lifetime decay curve of compound C synthesized in Example 3.

[0027] Figure 11 is the fluorescence lifetime decay curve of compound D synthesized in Example 4. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0029] Comparative Example 1

[0030] 5.00 g (24 mmol) of 9,10-phenanthrenequinone, 2.24 g (24 mmol) of aniline, 5.77 g (48 mmol) of 4-methylbenzaldehyde, 9.26 g (120 mmol) of ammonium acetate, and 150 mL of acetic acid were sequentially added to a 500 mL three-necked flask equipped with a thermometer. The mixture was heated to 120 °C under a nitrogen atmosphere and reacted at this temperature for 60 min. After the reaction was completed, the reaction solution was cooled to room temperature and poured into saturated brine. After thorough stirring, the mixture was filtered, washed with ethanol, and dried to obtain 3.11 g of a pale yellow solid compound PhPI, with a yield of 33.7%. The reaction equation is as follows:

[0031]

[0032] The structural characterization data of the obtained compound PhPI are as follows: 1H NMR (400 MHz, Chloroform-d) δ 8.89(d, J = 7.9 Hz, 1H), 8.77 (d, J = 7.3 Hz, 1H), 8.71 (d, J = 8.3 Hz, 1H), 7.79– 7.71 (m, 1H), 7.68 – 7.63 (m, 1H), 7.63 – 7.56 (m, 3H), 7.54 – 7.48 (m,3H), 7.47 (dd, J = 8.3, 1.9 Hz, 2H), 7.25 (d, J = 7.3 Hz, 1H), 7.17 (dd, J =8.3, 1.3 Hz, 1H), 7.10 (d, J = 8.0 Hz, 2H).

[0033] Example 1

[0034] Step 1: 5.00 g (24 mmol) of 9,10-phenanthrenequinone, 4.13 g (24 mmol) of p-bromoaniline, 5.77 g (48 mmol) of 4-methylbenzaldehyde, 9.26 g (120 mmol) of ammonium acetate, and 150 mL of acetic acid were sequentially added to a 500 mL three-necked flask equipped with a thermometer. The mixture was reacted at 120 °C for 1 hour under a nitrogen atmosphere. After the reaction was complete, the mixture was cooled to room temperature, poured into 200 mL of saturated brine, stirred thoroughly, filtered, washed with ethanol, and dried to obtain 7.34 g of yellow solid MeBrPI, with a yield of 65.9%. The reaction equation is as follows:

[0035]

[0036] The structural characterization data of MeBrPI obtained are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 8.87 (d,J = 7.9 Hz, 1H), 8.76 (d, J = 8.4 Hz, 1H), 8.69 (d, J = 8.3 Hz, 1H), 7.78-7.68 (m, 3H), 7.68-7.61 (m, 1H), 7.56-7.47 (m, 1H), 7.42 (d, J = 7.9 Hz, 2H), 7.36 (d, J = 8.8 Hz, 2H), 7.30 (d, J = 7.7 Hz, 1H), 7.20 (d, J = 8.3 Hz, 1H), 7.12 (d, J = 7.7 Hz, 2H), 2.34 (s, 3H).

[0037] Step 2: Add 40 mL of toluene, 1.00 g (2.16 mmol) MeBrPI, 0.864 g (2.59 mmol) spirofluorene-acetic acid, 0.45 g (3.24 mmol) potassium carbonate, 110 mg (0.11 mmol) Pd2(dba)3, and 65 mg (0.22 mmol) tBu3PHBF4 sequentially to a three-necked flask equipped with a thermometer. Stir until the starting materials are completely dissolved, then reflux under nitrogen atmosphere for 12 h. After the reaction is complete, cool to room temperature, pour the reaction solution into water, extract with DCM, wash the organic phase with water until neutral, dry with anhydrous magnesium sulfate, and concentrate by evaporation to obtain the crude product. Wash the crude product with ethanol and petroleum ether, and then purify by column chromatography to obtain 0.263 g of pale yellow solid compound A, with a yield of 17.1%. The reaction equation is as follows:

[0038]

[0039] The structural characterization data of the obtained compound A are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 8.92 (d,J = 7.9 Hz, 1H), 8.85 (d, J = 8.3 Hz, 1H), 8.76 (d, J = 8.4 Hz, 1H), 7.88 (d,J = 8.4 Hz, 2H), 7.77 (d, J = 3.5 Hz, 4H), 7.60 (dd, J = 10.0, 8.3 Hz, 4H), 7.44 (t, J = 7.6 Hz, 4H), 7.37 (d, J = 1.2 Hz, 1H), 7.30 (d, J = 1.1 Hz, 1H), 7.28 (d, J = 1.2 Hz, 1H), 7.22 (d, J = 1.2 Hz, 2H), 7.20 (d, J = 1.1 Hz, 2H), 7.19 (d, J = 1.2 Hz, 1H), 7.09 (d, J = 1.5 Hz, 1H), 7.08 – 7.05 (m, 5H), 2.40 (s, 3H).

[0040] Example 2

[0041]

[0042] In step 2 of this embodiment, equimolar carbazole was used to replace spirofluorene acridine in step 2 of Example 1. The other steps were the same as in Example 1, yielding 0.3765 g of white solid compound B, with a yield of 31.6%.

[0043] The structural characterization data of the obtained compound B are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 8.80 (s,1H), 8.77 (d, J = 6.2 Hz, 1H), 8.71 (s, 1H), 8.29 (d, J = 7.7 Hz, 3H), 8.22(d, J = 7.6 Hz, 3H), 7.89 (d, J = 7.7 Hz, 3H), 7.81 (s, 2H), 7.74 (d, J = 9.2Hz, 4H), 7.65 (s, 1H), 7.63 (s, 1H), 7.54 (s, 1H), 7.33 (d, J = 7.1 Hz, 2H), 7.14 (s, 1H), 2.35 (s, 3H).

[0044] Example 3

[0045] Step 1: This step is the same as step 1 in Example 1.

[0046] Step 2: Add 50 mL of DMF, 1.00 g (2.16 mmol) of MeBrPI, 0.56 g (3.24 mmol) of 1-naphthylboronic acid, 1.39 g (4.32 mmol) of TBAB, and 30 mg of Pd132 sequentially to a three-necked flask equipped with a thermometer. Stir until the starting materials are completely dissolved. Dissolve 0.60 g (4.32 mmol) of K2CO3 in 5 mL of deionized water and slowly add it dropwise to the three-necked flask. Heat to 75°C and stir for 3 h. After the reaction is complete, extract with DCM. Wash the organic phase with water until neutral, dry with anhydrous magnesium sulfate, and concentrate by evaporation to obtain the crude product. Wash the crude product with ethanol and petroleum ether, and then purify by column chromatography to obtain 0.57 g of white solid compound C, with a yield of 31.6%. The reaction equation is as follows:

[0047]

[0048] The structural characterization data of the obtained compound C are as follows: 1H NMR (400 MHz, Chloroform-d) δ 8.94(dd, J = 8.0, 1.4 Hz, 1H), 8.83 (d, J = 8.3 Hz, 1H), 8.75 (d, J = 8.4 Hz,1H), 8.30 (d, J = 7.8 Hz, 1H), 8.25 (s, 1H), 8.23 ​​(d, J = 4.7 Hz, 1H), 8.20 (s, 1H), 8.15 (s, 2H), 8.14 (d, J = 3.6 Hz, 1H), 8.07 (d, J = 4.3 Hz, 1H), 7.84 (d, J = 8.2 Hz, 2H), 7.78 (t, J = 6.9 Hz, 1H), 7.69 (d, J = 8.2 Hz, 3H), 7.62 (d, J = 8.2 Hz, 2H), 7.58 (t, J = 7.6 Hz, 1H), 7.49 (d, J = 9.9 Hz, 1H), 7.43 (d, J = 8.1 Hz, 1H), 7.21 (d, J = 7.9 Hz, 2H), 2.41 (s, 3H).

[0049] Example 4

[0050]

[0051] In step 2 of this embodiment, 1-naphthoic acid in step 2 of Example 3 was replaced with equimolar 9-pyreneboronic acid. The other steps were the same as in Example 3, yielding 1.13 g of pale yellow solid compound D with a yield of 63.4%.

[0052] The structural characterization data of the obtained compound D are as follows: 1H NMR (400 MHz, Chloroform-d) δ 8.92(dd, J = 7.9, 1.4 Hz, 1H), 8.81 (d, J = 8.3 Hz, 1H), 8.74 (d, J = 7.9 Hz,1H), 8.02 – 7.92 (m, 3H), 7.81 – 7.74 (m, 1H), 7.74 – 7.70 (m, 2H), 7.68(ddd, J = 8.4, 7.0, 1.5 Hz, 1H), 7.65 – 7.61 (m, 3H), 7.60 (d, J = 4.2 Hz,2H), 7.57 (d, J = 2.8 Hz, 3H), 7.56 – 7.55 (m, 1H), 7.54 (d, J = 1.5 Hz, 1H), 7.47 – 7.40 (m, 1H), 7.37 (t, J = 7.0 Hz, 1H), 7.18 (d, J = 8.0 Hz, 2H), 2.38(s, 3H).

[0053] To demonstrate the beneficial effects of the present invention, compounds A to D synthesized in Examples 1 to 4 were prepared in DMF as solvent to a concentration of 1 × 10⁻⁶. -5 A mol / L solution was prepared, or a smooth, uniform film was prepared by pellet compression. The fluorescence emission spectra, absolute quantum yield (φ), and fluorescence decay lifetime of four compounds A, B, C, D, and PhPI synthesized in Comparative Example 1 were measured using a steady-state transient fluorescence spectrometer (Quanta Master 8000, manufactured by HORIBA, Canada). Simultaneously, comparisons were made with phenanthrimidazole derivatives M1 reported by Gao et al. (Chem. Eur. J., 2013, 19, 2602–2605; Org. Electron., 2014, 15, 2667-2676.), pPhBINCP reported by Huang et al. (J. Phys. Chem. C, 2012, 116, 19458−19466.), and Li and Song et al. (J. Mole. Struct., 2026, 1355.). The optical properties of phenanthrimidazole derivatives MeACFy (reported in 145041) and Na-mP and Py-mP (reported by Song et al., J. Mole. Struct., 2026, 1352, 144503) were compared. The results are shown in Table 1 and Figures 1-11.

[0054]

[0055] M1 pPhBINCP MeACFy

[0056]

[0057] Na-mP Py-mP

[0058] Table 1. Photophysical properties of different compounds

[0059]

[0060] As can be seen from the data in Table 1 and Figures 1-6, compounds A, B, C, and D exhibit fluorescence emission peaks (λ) under solid films. PL The λ values ​​in DMF solution are 401 / 420 nm, 394 nm, 392 nm, and 400 / 424 nm, respectively. PLThe wavelengths of the light emitted are 389 nm, 362 nm, 388 nm, and 414 / 433 nm, respectively, all located in the blue light region, ensuring blue light emission. In the solid-state thin film state, the absolute fluorescence quantum yields of compounds A (φ=79.1%), B (φ=80.1%), C (φ=87.7%), and D (φ=88.4%) are all significantly higher than those of compound PhPI (φ=6.8%) in Comparative Example 1, fully demonstrating that introducing a functional group at the N2 position of phenanthrimidazole can significantly improve aggregation-induced quenching, thereby enhancing the quantum yield. Furthermore, compounds A through D exhibited increased quantum yields compared to their corresponding C1-modified compounds MeACFy, M1, Na-mP, and Py-mP: A (φ=79.1%) > MeACFy (φ=76.9%); B (φ=80.1%) > M1 (65.0%); C (φ=87.7%) > Na-mP (φ=70.8%); D (φ=88.4%) > Py-mP (φ=84.7%). In DMF solution, the quantum yields of compounds A (φ=69.5%), B (φ=75.4%), C (φ=75.1%), and D (φ=90.4%) were all significantly improved compared to compound PhPI (φ=9.4%) in Comparative Example 1. Furthermore, compared to compounds with functional groups introduced at the N2 position of phenanthrimidazole, the quantum yield in DMF solution is also higher: A (φ=69.5%) > MeACFy (φ=18.6%), C (φ=75.1%) > Na-mP (φ=68.2%), D (φ=90.4%) > Py-mP (φ=65.5%). This superior fluorescence quantum yield is beneficial for realizing higher-efficiency OLED devices. These results indicate that compounds A–D maintain high-efficiency luminescence in both solution and solid-state thin films, achieving efficient dual-state emission.

[0061] As can be seen from Table 1 and Figures 7-11, the radiative transition rates, in descending order, are: D (9.82 × 10⁻⁶). 8 S -1 ) > A (6.09 × 10 8 S -1 ) > B (5.73 × 10 8 S -1 ) > C (4.90 × 10 8 S -1 ) > MeACFy (4.50×10 8 S -1 > Py-mP (4.01×10) 8 S -1 >Na-mP (1.60×10) 8 S -1 > PhPI (0.47 × 10) 8 S-1 As can be seen, the radiative transition rates of compounds A to D are all higher than those reported in the literature, indicating that the blue light-emitting material of the present invention can return to the ground state more quickly through radiative transition in the excited state, reducing the accumulation of excitons and thus improving the luminous efficiency and stability of OLED devices.

[0062] In summary, this invention introduces a methylphenyl group at the C2 position of phenanthrimidazole to ensure efficient blue light emission, and introduces different functional groups at the N1 position to achieve high fluorescence quantum yield and high radiative transition rate, thereby achieving a high-efficiency emission state.

Claims

1. A dual-state emission phenanthrimidazole-based blue light-emitting material with a high radiative transition rate, characterized in that, The structural formula of the blue light-emitting material is shown below: In the formula represent 、 、 、 、 、 、 、 、 、 and Any one of them.

2. The dual-state emission phenanthrimidazole-based blue light-emitting material with high radiative transition rate according to claim 1, characterized in that, The structural formula of the blue light material is: 、 、 and Any one of them.

3. The use of the dual-state phenanthrimidazole blue light-emitting material with high radiative transition rate as described in claim 1 as a guest molecule in the preparation of organic light-emitting diodes.

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