Circularly polarized TADF material based on carbon-nitrogen axial chirality

Abstract

The invention discloses a circularly polarized TADF material based on carbon-nitrogen axial chirality, and belongs to the field of organic luminescent materials. The preparation method of the carbon-nitrogen axial chirality circular polarization TADF material comprises the following steps: mixing C1 and C2 in glacial acetic acid, and reacting to obtain C3; c3, C4 and a catalyst are mixed in an organic solvent and react to obtain C5; mixing C5, C6 and a catalyst in an organic solvent, and reacting to obtain the circularly polarized TADF material based on carbon-nitrogen axial chirality. In the product structure designed by the invention, a phthalimide structure is used as an acceptor, and a chiral carbon-nitrogen axial chiral TADF molecule is constructed through resistance conversion isomerization of a substituent group on the ortho-position of carbazole and has an aggregation-induced emission property. According to the invention, [delta] ESTlt; the circular polarization TADF material with the concentration of 0.1 eV provides a carbon-nitrogen axial chiral measurement for the construction of chiral TADF molecules, and provides a new chiral parent nucleus for a circular polarization OLED device.

Description

Technical Field

[0001] The invention relates to the field of organic light-emitting materials, and in particular to a circularly polarized TADF material based on carbon-nitrogen axial chirality. Background Art

[0002] As organic light-emitting diode (OLED) technology matures, the demand for new luminescent materials is also growing, especially materials that can improve efficiency, stability and color quality, which urgently need further research. The discovery of the TADF (thermally activated delayed fluorescence) mechanism provides a new way to improve the luminescence efficiency of OLEDs. Through the anti-intersystem crossing process, TADF materials can convert triplet excitons that usually transition non-radiatively into luminescent singlet excitons and achieve luminescence. Thermally activated delayed fluorescence materials are a class of metal-free luminescent materials with important potential in OLED and other optoelectronic applications. In recent years, the use of chiral TADF materials for the preparation of organic light-emitting diodes has become the mainstream direction of TADF material improvement. The introduction of chirality into TADF materials aims to use the characteristics of chiral molecules to control the luminescence process and then achieve circularly polarized luminescence, which has potential applications in optical communications, 3D displays, and bioimaging.

[0003] Chiral TADF materials have chiral centers or chiral structures, which enable them to emit light with a specific polarization direction, i.e. left-handed or right-handed circularly polarized light. Their chirality can be derived from the point chirality, axial chirality, planar chirality or helical chirality of the molecule (e.g. Figure 1 As shown in Figure 2 ). With the development of circularly polarized thermally activated delayed fluorescent materials, how to construct luminescent materials that have both circular polarization properties and high device performance has become a problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a circularly polarized TADF material based on carbon-nitrogen axial chirality to solve the above-mentioned problems in the background technology. In the product structure designed by the present invention, the phthalimide structure is used as a receptor, and a chiral carbon-nitrogen axial chiral TADF molecule is constructed by a transversion isomerization of the substituents on the ortho position of carbazole, and has aggregation-induced emission properties. The present invention prepares a circularly polarized TADF material with ΔEST<0.1eV, provides a carbon-nitrogen axial chirality strategy for the construction of chiral TADF molecules, and provides a new chiral mother core for circularly polarized 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 is to provide a circularly polarized TADF material based on carbon-nitrogen axial chirality, wherein the circularly polarized TADF material is a phthalimide derivative, and the structural formula is as follows:

[0007]

[0008] Among them, R1 and R3 are halogen or electron-rich aromatic amine substituents, and R1 and R3 contain at least one electron-rich aromatic amine substituent, and the amino nitrogen of the electron-rich aromatic amine substituent is connected to phthalimide; R2 is a halogen or electron-rich aromatic amine substituent, and the amino nitrogen of the electron-rich aromatic amine substituent is connected to phthalimide; R4 is a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heteroaromatic hydrocarbon group.

[0009] Preferably, the electron-rich aromatic amine substituent is The R4 is

[0010] Preferably, the structural formula is:

[0011] The second technical solution of the present invention is to provide a method for preparing the circularly polarized TADF material based on carbon-nitrogen axial chirality, comprising the following steps:

[0012] (1) C1 and C2 are mixed in glacial acetic acid and reacted to obtain C3;

[0013] (2) mixing C3, C4 and a catalyst in an organic solvent and reacting them to obtain C5;

[0014] (3) mixing C5, C6 and a catalyst in an organic solvent, reacting, and obtaining the circularly polarized TADF material based on carbon-nitrogen axial chirality;

[0015] The structural formula of C1 is The chemical formula of C2 is R1-NH2, R1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; the structural formula of C3 is R1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; the structural formula of C4 is The structural formula of C5 is R1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; and C6 is an electron-rich aromatic amine.

[0016] Preferably, in step (1), the reaction temperature is 118° C. and the reaction time is 4 h.

[0017] Preferably, in step (2): the catalyst is Cs2CO3; the reaction temperature is 25°C and the reaction time is 12h.

[0018] Preferably, in step (3): the catalyst is Cs2CO3; the reaction temperature is 25°C and the reaction time is 12h.

[0019] The third technical solution of the present invention is to provide an application of the circularly polarized TADF material based on carbon-nitrogen axial chirality in the field of thermally activated delayed fluorescence.

[0020] The beneficial technical effects of the present invention are as follows:

[0021] In the product structure designed by the present invention, the phthalimide structure is used as a receptor, and a chiral carbon-nitrogen axial chiral TADF molecule is constructed through atropisomerism of a substituent at the ortho position of carbazole, and the compound has aggregation-induced emission properties.

[0022] In the present invention, the molecular energy band gap can be regulated by modifying the carbazole derivatives, thereby changing the luminescent color and the performance of the material device.

[0023] The present invention prepares ΔE ST The circularly polarized TADF material with a chirality of <0.1eV provides a carbon-nitrogen axis chirality strategy for the construction of chiral TADF molecules and a new chiral mother core for circularly polarized OLED devices.

[0024] The present invention successfully obtains a series of luminescent molecules with circularly polarized thermally activated delayed properties by introducing carbon-nitrogen axial chirality into the construction of TADF molecules.

[0025] The chiral luminescent material designed in the present invention has broad application prospects in three-dimensional display technology, optical information storage, biological imaging and chiral sensing due to its circularly polarized luminescence characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 Schematic diagram of four types of chiral TADF materials and the application of chiral skeletons in chiral TADF materials.

[0028] Figure 2 is C3 in Example 1 1 H-NMR spectrum (a) and 13 C-NMR spectrum (b).

[0029] Figure 3 is C5 in Example 1 1H-NMR spectrum (a) and 13 C-NMR spectrum (b).

[0030] Figure 4 For the product in Example 1 1 H-NMR spectrum.

[0031] Figure 5 For the product in Example 1 13 C-NMR spectrum.

[0032] Figure 6 For the product in Example 1 19 F-NMR spectrum.

[0033] Figure 7 The absorption spectrum and emission spectrum of the product in Example 1 are shown in FIG.

[0034] Figure 8 (a) The fluorescence spectrum and (b) AIE curve of the product in Example 1.

[0035] Fig. 9 These are the CD spectra of the two configurations of Chiral-AI in Example 1.

[0036] Fig.10 Circularly polarized emission spectra of two configurations of Chiral-AI in Example 1.

[0037] Fig.11 is the g value of Chiral-AI in Example 1.

[0038] Fig.12 is the ΔE of the product of Example 1 ST Calculate the result.

[0039] Fig.13 This is the transient decay spectrum of 5wt% (rac)-AI-2TCFC:CBP doped film. DETAILED DESCRIPTION

[0040] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0041] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the 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.

[0042] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0044] The acetic acid concentration in the glacial acetic acid used in the following examples and comparative examples of the present invention is greater than or equal to 99.5wt%.

[0045] Unless otherwise specified, the "room temperature" in the present invention is 25°C.

[0046] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0047] Example 1

[0048] A method for preparing circularly polarized TADF materials based on carbon-nitrogen axial chirality:

[0049] (1) 10 g of C1, 5 mL of aniline and 100 mL of glacial acetic acid were added to a 500 mL round-bottom flask in sequence, and the mixture was heated under reflux at 120° C. for 4 hours. After the reaction system was cooled to room temperature, the reaction system was placed in a 0° C. environment for low-temperature crystallization, and a yellow-green solid was precipitated. The crude product was obtained by filtration, and the remaining glacial acetic acid was washed with water to obtain yellow-green crystals, which were compound C3 (yield 98%). The relevant reaction formula is as follows:

[0050]

[0051] (2) Take a 250mL round-bottom flask and treat it to be anhydrous and oxygen-free. Then weigh 2g C3, 2.48g C4 and 3.3g Cs2CO3 and add them to the reaction bottle in sequence. Then evacuate the reaction system 3 times, add 100mL DMF, and heat to 65°C for 12 hours. After the reaction system is cooled to room temperature, the reaction solution is quickly passed through a silica gel short column, and the short column is rinsed with dichloromethane to remove inorganic matter from the reaction system. Then the organic liquid phase is distilled off to obtain a crude product, which is then recrystallized with dichloromethane and petroleum ether to obtain 2g of light yellow-green powder, which is compound C5 (yield is 57%). The relevant reaction formula is as follows:

[0052]

[0053] (3) Take a 250mL round-bottom flask and perform anhydrous and oxygen-free treatment, weigh 1g C5, 2.2g C6 and 2.5g Cs2CO3 and add them to the reaction bottle in sequence, then evacuate the reaction system 3 times, add 150mL DMF, and heat to 65°C for 12 hours. After the reaction system is cooled to room temperature, the reaction solution is quickly passed through a silica gel short column, and the short column is rinsed with dichloromethane to remove inorganic substances in the reaction system. Then the organic liquid phase is distilled off to obtain a crude product, which is then purified by column chromatography to obtain 1.02g of orange-red powder, which is the final product (yield is 51%, recorded as Chiral-AI). The relevant reaction formula is as follows:

[0054]

[0055] Figure 2 is C3 in Example 1 1 H-NMR spectrum (a) and 13 C-NMR spectrum (b).

[0056] Figure 3 is C5 in Example 1 1 H-NMR spectrum (a) and 13 C-NMR spectrum (b).

[0057] Figure 4 For the product in Example 1 1 H-NMR spectrum.

[0058] Figure 5 For the product in Example 1 13 C-NMR spectrum.

[0059] Figure 6 For the product in Example 1 19 F-NMR spectrum.

[0060] Effect verification

[0061] 1. Characterization of optical properties

[0062] Figure 7 The absorption spectrum and emission spectrum of the product in Example 1 are shown in FIG.

[0063] Figure 7 In the table, Absorption represents the absorption spectrum, Film represents the emission spectrum measured in PMMA film, and Solvent represents the emission spectrum measured at a concentration of 10 -5 mol / L toluene solution.

[0064] Depend on Figure 7 It can be seen that the emission wavelength of the compound Chiral-AI is 580nm.

[0065] Table 1 shows the fluorescence quantum yield, response time and delayed fluorescence performance of the product of Example 1 in PMMA film and toluene solution.

[0066] Table 1

[0067] <![CDATA[Φ QY (%)]]> <![CDATA[τ prompt (ns)]]> <![CDATA[τ delayed (μs)]]> Solvent(Tol) 11.34 / / 5% inPMMA 15.91 9.875 1.747

[0068] 2. Characterization of Aggregation-Induced Emission Properties

[0069] The fluorescence spectra were tested in tetrahydrofuran (THF) aqueous solutions of different concentrations (water content 0 vol% to 99 vol%), and the AIE curves were tested at an emission wavelength of 688 nm. The test results are shown in Figure 2. Figure 8 shown.

[0070] Figure 8 (a) The fluorescence spectrum and (b) AIE curve of the product in Example 1.

[0071] 3. Characterization of circular polarization properties

[0072] Axially chiral molecules have two absolute configurations, as follows.

[0073]

[0074] Fig. 9 These are the CD spectra of the two configurations of Chiral-AI in Example 1.

[0075] Fig.10 Circularly polarized emission spectra of two configurations of Chiral-AI in Example 1.

[0076] Fig.11 is the g value of Chiral-AI in Example 1.

[0077] Fig.12 is the ΔE of the product of Example 1 ST Calculate the result.

[0078] The product of Example 1 was mixed with 4,4'-di(9-carbazole)biphenyl to prepare a doped film (the product of Example 1 accounted for 5wt% in the doped film, recorded as 5wt% (rac)-AI-2TCFC:CBP doped film), and then the transient attenuation spectrum of the doped film was tested. The test results are as follows: Fig.13 shown.

[0079] Fig.13 This is the transient decay spectrum of 5wt% (rac)-AI-2TCFC:CBP doped film.

[0080] Depend on Fig.13 It can be seen that the thermally activated delayed fluorescence lifetime of this molecule is 2.167μs.

[0081] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A circularly polarized TADF material based on carbon-nitrogen axial chirality, It is characterized in that The circularly polarized TADF material is a phthalimide derivative, and the structural formula is as follows: Among them, R 1 , R 3 is a halogen or electron-rich aromatic amine substituent, and R 1 , R 3 contains at least one electron-rich aromatic amine substituent, wherein the amino nitrogen of the electron-rich aromatic amine substituent is connected to phthalimide; 2 is a halogen or electron-rich aromatic amine substituent, wherein the amino nitrogen of the electron-rich aromatic amine substituent is connected to phthalimide; 4 It is a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heteroaromatic hydrocarbon group.

2. The circularly polarized TADF material based on carbon-nitrogen axial chirality according to claim 1, It is characterized in that The electron-rich aromatic amine substituent is The R4 is 3. The circularly polarized TADF material based on carbon-nitrogen axial chirality according to claim 1, It is characterized in that The structural formula is:

4. A method for preparing the circularly polarized TADF material based on carbon-nitrogen axial chirality according to any one of claims 1 to 3, It is characterized in that The following steps are involved: (1) C1 and C2 are mixed in glacial acetic acid and reacted to obtain C3; (2) mixing C3, C4 and a catalyst in an organic solvent and reacting them to obtain C5; (3) mixing C5, C6 and a catalyst in an organic solvent, reacting, and obtaining the circularly polarized TADF material based on carbon-nitrogen axial chirality; The structural formula of C1 is The chemical formula of C2 is R 1 -NH 2 , R 1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; the structural formula of C3 is R 1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; the structural formula of C4 is The structural formula of C5 is R 1 is -Ph, -cyclohexane, -n-hexyl or -pyridin; and the C6 is an electron-rich aromatic amine.

5. The preparation method according to claim 4, It is characterized in that In step (1): the reaction temperature is 118°C and the reaction time is 4 hours.

6. The preparation method according to claim 4, It is characterized in that In step (2): the catalyst is Cs 2 CO 3 ; The reaction temperature is 25°C and the reaction time is 12h.

7. The preparation method according to claim 4, It is characterized in that In step (3): the catalyst is Cs 2 CO 3 ; The reaction temperature is 25°C and the reaction time is 12h.

8. Application of the circularly polarized TADF material based on carbon-nitrogen axial chirality as described in any one of claims 1 to 3 in the field of thermally activated delayed fluorescence.

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