A red light luminescent material and its preparation method and application

Abstract

The present invention discloses a red light emitting material and a preparation method and application thereof, belonging to the technical field of organic light emitting materials. The present invention introduces a phthalimide structure as an acceptor and uses N,N,N',N'-tetraphenyl-9H-carbazole-2,7-diamine as a donor to reduce ∆E ST , promoting anti-gap crossing and enhancing the electron-donating ability of the donor, and successfully preparing ∆E ST Red light TADF materials with a wavelength of <0.05eV are beneficial for improving the efficiency of red light OLED devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic luminescent materials, and in particular relates to a red luminescent material and a preparation method and application thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs) have great application prospects in the fields of flat panel displays and solid-state light sources due to their many advantages such as full solid-state, self-luminescence, wide viewing angle, fast response, low driving voltage, and low power consumption. At present, although significant progress has been made in the research on OLEDs, the luminescent materials of traditional OLEDs are mainly fluorescent materials and phosphorescent materials: the first generation of OLEDs based on fluorescent emission materials only utilizes singlet excitons for luminescence, and its internal quantum efficiency (IQE) is only 25%; the second generation of OLEDs are based on phosphorescent emission materials containing precious metals, and through the spin-orbit coupling (SOC) between precious metals and their ligands, singlet (25%) and triplet (75%) excitons are comprehensively utilized, and its IQE can reach 100%. However, phosphorescent emission materials still have the following problems: the high prices of metals such as Ir(III), Pt(II) and Os(II), and the serious efficiency roll-off of OLEDs based on phosphorescent emission at high currents. In recent years, by designing and synthesizing singlet (S I ) and triplet state (T l ) between the energy levels (ΔE ST ) small thermally activated delayed fluorescence (TADF) material, so that its triplet state (75%) excitons can cross the reverse intersystem to S l This type of TADF material can simultaneously utilize singlet excitons with a generation probability of 25% and triplet excitons with a generation probability of 75% to obtain high luminescence efficiency, and its IQE can also reach 100%, which is expected to become the next generation of OLED luminescent materials. At present, the efficiency of blue and green OLED luminescent materials is already very high, but the small overlap between HOMO and LUMO reduces the oscillator strength and radiation decay rate (kr), which usually leads to reduced luminescence efficiency. Therefore, high-efficiency red TADF materials with an electroluminescence (EL) peak of more than 600nm are very scarce.

[0003] Up to now, although there have been some reports on red light TADF materials and their applications in OLEDs, the reported TADF materials generally have problems such as long synthesis steps, low preparation efficiency, and difficulty in large-scale preparation. In addition, the types of electron-withdrawing fragments in the molecules are very small, mainly concentrated in cyano, carbonyl, sulfone (sulfoxide) groups, etc. Summary of the invention

[0004] Based on the current situation that the efficiency of red light OLED devices is generally lower than that of blue light and green light, the present invention proposes a red light emitting material and its preparation method and application. The present invention introduces a phthalimide structure as an acceptor by reducing ∆E ST , promoting anti-gap crossing and enhancing the electron-donating ability of the donor, and successfully preparing ∆E ST Red light TADF materials with a wavelength of <0.05eV are beneficial for improving the efficiency of red light OLED devices.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A red light luminescent material, characterized in that the structural formula is as follows:

[0008] or .

[0009] The red light luminescent material of the present invention has both thermally activated delayed fluorescence effect and aggregation induction effect.

[0010] The second technical solution of the present invention:

[0011] The present invention also provides a method for preparing the red light luminescent material. When the structural formula is When, it is recorded as AI-1DPACz, and its preparation method comprises the following steps:

[0012] Compound C1, aniline and glacial acetic acid (CH3COOH) are mixed, heated to reflux (Reflux) for reaction, cooled, placed in a 0°C environment to precipitate a white solid, filtered to obtain a first crude product, washed with water (for removing the remaining glacial acetic acid), to obtain white crystals, the white crystals are compound C3, the compound C3, compound C4 and cesium carbonate (CS2CO3) are mixed, dimethylformamide (DMF) is added, heated to 65°C for reaction for 12 hours, cooled, water and dichloromethane are added for extraction, the organic phase after extraction is dried, filtered and distilled to obtain a second crude product, the second crude product is purified by column chromatography to obtain AI-1DPACz;

[0013] When the structural formula is When, it is recorded as AI-2DPACz, and its preparation method comprises the following steps:

[0014] Compound C5, aniline and glacial acetic acid are mixed, heated to reflux for reaction, cooled to room temperature, placed in a 0°C environment to precipitate a white solid, filtered to obtain a first crude product, washed with water (for removing the remaining glacial acetic acid), to obtain white crystals, the white crystals are compound C6, the compound C6, the compound C4 and CS2CO3 are mixed, DMF is added, heated to 65°C for reaction for 12 hours, cooled, water and dichloromethane are added for extraction, the organic phase after extraction is dried, filtered and distilled to obtain a second crude product, the second crude product is purified by column chromatography to obtain AI-2DPACz;

[0015] The structural formula of the compound C1 is , the structural formula of the compound C3 is The structural formula of the compound C4 is , the structural formula of the compound C5 is , the structural formula of the compound C6 is .

[0016] Preferably, the temperature of the heating reflux reaction is 120° C. and the time is 4 hours.

[0017] Preferably, the mass volume ratio of the compound C1, aniline and glacial acetic acid is 5g: 3.3mL: 100mL;

[0018] The mass ratio of the compound C3, the compound C4 and CS2CO3 is 0.5:1.09:0.6881;

[0019] The mass volume ratio of the compound C5, aniline and glacial acetic acid is 6 g: 3.56 mL: 100 mL;

[0020] The mass ratio of the compound C6, the compound C4 and CS2CO3 is 0.5:2.03:1.32.

[0021] Preferably, the volume ratio of water to dichloromethane is 7:1.

[0022] Preferably, the organic phase after extraction is dried using anhydrous sodium sulfate.

[0023] More preferably, when the red light emitting material is AI-1DPACz, its synthesis route is as follows:

[0024]

[0025]

[0026] The preparation method of AI-1DPACz is as follows: 5 g of compound C1, 3.3 mL of aniline (i.e., C2) and 100 mL of glacial acetic acid are sequentially added to a 250 mL round-bottom flask, heated under reflux at 120° C. for 4 hours, cooled to room temperature, placed in a 0° C. environment to precipitate a white solid, filtered to obtain a first crude product, washed with water to remove the remaining glacial acetic acid, and obtained white crystals, wherein the white crystals are compound C3; a 100 mL round-bottom flask is taken for anhydrous and oxygen-free treatment, 500 mg of the compound C3, 1.09 g of compound C4 and 688.1 mg of CS2CO3 are weighed and sequentially added to the above round-bottom flask, 30 mL of DMF is added, heated to 65° C. for reaction for 12 hours, cooled to room temperature, water and dichloromethane are added for extraction, the organic phase after extraction is dried with anhydrous sodium sulfate, filtered, and then the organic liquid phase is distilled to obtain a second crude product, and the second crude product is purified by column chromatography to obtain AI-1DPACz;

[0027] When the red light emitting material is AI-2DPACz, its synthesis route is as follows:

[0028]

[0029] The preparation method of AI-2DPACz is as follows: 6 g of compound C5, 3.56 mL of aniline (i.e., C2) and 100 mL of glacial acetic acid are added to a 250 mL round-bottom flask in sequence, heated under reflux at 120°C for 4 hours, cooled to room temperature, placed in a 0°C environment to precipitate a white solid, filtered to obtain a first crude product, washed with water to remove the remaining glacial acetic acid, and obtained white crystals, wherein the white crystals are compound C6; a 250 mL round-bottom flask is treated with anhydrous and oxygen-free conditions, 500 mg of compound C6, 2.03 g of compound C4 and 1.32 g of CS2CO3 are weighed and added to the above round-bottom flask in sequence, 100 mL of DMF is added, heated to 65°C for reaction for 12 hours, cooled to room temperature, water and dichloromethane are added for extraction, the extracted organic phase is dried with anhydrous sodium sulfate, filtered, and then the organic liquid phase is distilled to obtain a second crude product, and the second crude product is purified by column chromatography to obtain AI-2DPACz.

[0030] The third technical solution of the present invention:

[0031] The present invention also provides application of the red light emitting material in preparing a red light organic light emitting diode (OLED) device.

[0032] The fourth technical solution of the present invention:

[0033] The present invention also provides the use of the red light luminescent material in preparing a red thermally activated delayed fluorescence material (TADF).

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] The present invention uses phthalimide as an acceptor and N,N,N',N'-tetraphenyl-9H-carbazole-2,7-diamine as a donor to obtain ∆E ST <0.05eV and luminescent molecules (AI-1DPACz and AI-2DPACz) with aggregation-induced effect have successfully prepared high-efficiency red TADF materials with electroluminescence (EL) peaks exceeding 600nm, which is an effective way to improve the efficiency of red light OLED devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0037] Figure 1 For AI-1DPACz 1 H NMR spectrum;

[0038] Figure 2 For AI-1DPACz 13 C NMR spectrum;

[0039] Figure 3 For AI-2DPACz 1 H NMR spectrum;

[0040] Figure 4 For AI-2DPACz 13 C NMR spectrum;

[0041] Figure 5 The absorption and emission spectra of AI-1DPACz and AI-2DPACz, where the horizontal axis is the wavelength, the left vertical axis is the absorption intensity, and the right vertical axis is the luminescence intensity;

[0042] Figure 6 The fluorescence spectra of AI-1DPACz in different THF / Ether mixtures with different ether contents (0 vol% ~99 vol%);

[0043] Figure 7 is the AIE curve of AI-1DPACz at an emission wavelength of 688 nm;

[0044] Figure 8 The fluorescence spectra of AI-2DPACz in different THF / Ether mixtures with different ether contents (0 vol% ~99 vol%);

[0045] Fig. 9 This is the AIE curve of AI-2DPACz at an emission wavelength of 724 nm. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0052] All raw materials used in the examples of the present invention are commercially available.

[0053] The technical solution of the present invention is further illustrated by the following embodiments.

[0054] Example 1 Preparation of AI-1DPACz

[0055] The synthetic route is as follows:

[0056]

[0057] The specific preparation method is as follows: 5 g of compound C1, 3.3 mL of aniline (i.e., C2) and 100 mL of glacial acetic acid are added to a 250 mL round-bottom flask in sequence, heated under reflux at 120°C for 4 hours, cooled to room temperature, placed in a 0°C environment to precipitate a white solid, filtered to obtain the first crude product, washed with water to remove the remaining glacial acetic acid, and obtained white crystals. The white crystals are compound C3, and the yield is 98%. The test results of compound C3 are as follows: 1 H NMR (500 MHz, CDCl3, δ ppm) 7.96 (dd, J = 8.0, 4.5 Hz, 1H), 7.63 (d, J = 6.5 Hz, 1H), 7.53-7.39 (m, 6H).

[0058] A 100 mL round-bottom flask was treated with anhydrous and oxygen-free conditions, 500 mg of compound C3, 1.09 g of compound C4 and 688.1 mg of CS2CO3 were weighed and added to the round-bottom flask in turn, 30 mL of DMF was added, and the mixture was heated to 65 ° C for reaction for 12 hours. After cooling to room temperature, water and dichloromethane (v / v = 7:1) were added for extraction. The organic phase after extraction was dried over anhydrous sodium sulfate and filtered, and then the organic liquid phase was removed by distillation to obtain a second crude product. The second crude product was purified by column chromatography to obtain 749 mg of orange-red powder, which was the final product AI-1DPACz, with a yield of 50%. 1 H NMR spectrum is shown in Figure 1 , 13 CNMR spectrum see Figure 2 .

[0059] Example 2 Preparation of AI-2DPACz

[0060] The synthetic route is as follows:

[0061]

[0062] The specific preparation method is as follows: 6 g of compound C5, 3.56 mL of aniline (i.e., C2) and 100 mL of glacial acetic acid are added to a 250 mL round-bottom flask in sequence, heated under reflux at 120°C for 4 hours, cooled to room temperature, placed in a 0°C environment to precipitate a white solid, filtered to obtain the first crude product, washed with water to remove the remaining glacial acetic acid, and obtained white crystals. The white crystals are compound C6, and the yield is 98%. The test results of compound C6 are as follows: 1 H NMR (500MHz, CDC13) δ7.76 (t,J =7.5Hz, 2H), 7.55-7.47 (m, 2H), 7.46-7.38 (m, 3H).

[0063] Take a 250 mL round-bottom flask for anhydrous and oxygen-free treatment, weigh 500 mg of compound C6, 2.03 g of compound C4 and 1.32 g of CS2CO3 and add them to the above round-bottom flask in sequence, add 100 mL of DMF, heat to 65 ° C for reaction for 12 hours, cool to room temperature, add water and dichloromethane for extraction, dry the extracted organic phase with anhydrous sodium sulfate, filter, and then distill to remove the organic liquid phase to obtain a second crude product, and purify the second crude product by column chromatography to obtain 707 mg of red powder, which is the final product AI-2DPACz, with a yield of 30%. 1 H NMR spectrum is shown in Figure 3 , 13 C NMR spectrum is shown in Figure 4 .

[0064] The absorption and emission spectra of AI-1DPACz and AI-2DPACz are shown in Figure 5 , it can be seen that the emission wavelength of AI-1DPACz is 654nm, and the emission wavelength of AI-2DPACz is 694nm.

[0065] The fluorescence spectra of AI-1DPACz in different THF / Ether (tetrahydrofuran / ether) mixtures with different ether contents (0 vol% ~99 vol%) are shown in Figure 6 , the AIE curve at the emission wavelength of 688nm Figure 7 It can be seen that this material has aggregation-induced emission properties.

[0066] The fluorescence spectra of AI-2DPACz in different THF / Ether mixtures with different ether contents (0 vol% ~99 vol%) are shown in Figure 8 , the AIE curve at the emission wavelength of 724nm is Fig. 9 It can be seen that this material has aggregation-induced emission properties.

[0067] In summary, the present invention uses phthalimide structure (C3) as acceptor and N,N,N',N'-tetraphenyl-9H-carbazole-2,7-diamine (C4) as donor to prepare ∆E ST Red light TADF materials with a voltage of <0.05eV are an effective way to improve the efficiency of red light OLED devices.

[0068] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A red light luminescent material, characterized in that: The structural formula is as follows: or ; The ∆E of the red light emitting material ST <0.05eV, the electroluminescence peak exceeds 600nm, and it has aggregation-induced effect.

2. A method for preparing the red light luminescent material according to claim 1, characterized in that: When the structural formula is When, it is recorded as AI-1DPACz, and its preparation method comprises the following steps: Compound C1, aniline and glacial acetic acid are mixed, heated to reflux for reaction, cooled, placed in a 0°C environment to precipitate a white solid, filtered to obtain a first crude product, washed with water to obtain white crystals, the white crystals are compound C3, the compound C3, compound C4 and cesium carbonate are mixed, dimethylformamide is added, heated to 65°C for reaction for 12 hours, cooled, water and dichloromethane are added for extraction, the organic phase after extraction is dried, filtered and distilled to obtain a second crude product, the second crude product is purified by column chromatography to obtain AI-1DPACz; When the structural formula is When, it is recorded as AI-2DPACz, and its preparation method comprises the following steps: Compound C5, aniline and glacial acetic acid are mixed, heated to reflux for reaction, cooled, placed in a 0°C environment to precipitate a white solid, filtered to obtain a first crude product, washed with water to obtain white crystals, the white crystals are compound C6, the compound C6, the compound C4 and cesium carbonate are mixed, dimethylformamide is added, heated to 65°C for reaction for 12 hours, cooled, water and dichloromethane are added for extraction, the organic phase after extraction is dried, filtered and distilled to obtain a second crude product, the second crude product is purified by column chromatography to obtain AI-2DPACz; The structural formula of the compound C1 is , the structural formula of the compound C3 is , the structural formula of the compound C4 is , the structural formula of the compound C5 is , the structural formula of the compound C6 is .

3. The method for preparing the red light luminescent material according to claim 2, characterized in that: The temperature of the heating reflux reaction was 120° C. and the time was 4 hours.

4. The method for preparing the red light luminescent material according to claim 2, characterized in that: The mass volume ratio of the compound C1, aniline and glacial acetic acid is 5 g: 3.3 mL: 100 mL; The mass ratio of the compound C3, the compound C4 and the cesium carbonate is 0.5:1.09:0.6881; The mass volume ratio of the compound C5, aniline and glacial acetic acid is 6 g: 3.56 mL: 100 mL; The mass ratio of the compound C6, the compound C4 and cesium carbonate is 0.5:2.03:1.

32.

5. The method for preparing the red light luminescent material according to claim 2, characterized in that: The volume ratio of water to dichloromethane is 7:

1.

6. The method for preparing the red light luminescent material according to claim 2, characterized in that: The organic phase after extraction is dried using anhydrous sodium sulfate.

7. Use of the red light emitting material according to claim 1 in preparing a red light organic light emitting diode device.

8. Use of the red light luminescent material according to claim 1 in preparing a red thermally activated delayed fluorescent material.

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