A Circularly Polarized TADF Material Based on Carbon-Nitrogen Axial Chirality

Abstract

The present invention discloses a circularly polarized TADF material based on carbon-nitrogen axial chirality, belonging to the field of organic light-emitting materials. The preparation method of the circularly polarized TADF material with carbon-nitrogen axial chirality of the present invention comprises the following steps: taking C1 and C2 and mixing them in glacial acetic acid, reacting to obtain C3; mixing C3, C4 and a catalyst in an organic solvent, reacting to obtain C5; mixing C5, C6 and a catalyst in an organic solvent, reacting to obtain the circularly polarized TADF material based on carbon-nitrogen axial chirality. In the product structure designed by the present invention, a phthalimide structure is used as the acceptor, and a chiral carbon-nitrogen axial chiral TADF molecule is constructed through the atropisomerism of the substituents at the ortho-position of carbazole, and has the property of aggregation-induced emission. The present invention prepares a circularly polarized TADF material with ΔEST < 0.1 eV, provides a carbon-nitrogen axial chirality strategy for the construction of chiral TADF molecules, and provides a new chiral mother nucleus for circularly polarized OLED devices.

Description

Technical Field

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

[0002] With the maturity of organic light-emitting diode (OLED) technology, the demand for new light-emitting materials has been continuously increasing, especially materials that can improve efficiency, stability, and color quality, and further research is urgently needed. The discovery of the thermally activated delayed fluorescence (TADF) mechanism provides a new way to improve the luminescence efficiency of OLEDs. Through the reverse intersystem crossing process, TADF materials can convert triplet excitons, which are usually non-radiative transitions, into luminescent singlet excitons and achieve luminescence. Thermally activated delayed fluorescence materials are a class of metal-free luminescent materials with important potential in OLEDs and other optoelectronic applications. In recent years, using chiral TADF materials to prepare organic light-emitting diodes has become the mainstream direction for improving TADF materials. Introducing chirality into TADF materials aims to utilize the characteristics of chiral molecules to control the luminescence process and thus achieve circularly polarized luminescence, which has potential applications in fields such as optical communication, 3D display, and biological imaging.

[0003] Chiral TADF materials have chiral centers or chiral structures, which enable them to emit light with a specific polarization direction, namely left-handed or right-handed circularly polarized light. Their chirality can originate from point chirality, axial chirality, planar chirality, or helical chirality of the molecule (as Figure 1 shown). With the development of circularly polarized thermally activated delayed fluorescence materials, how to construct luminescent materials that not only have circularly polarized properties but also high device performance has become an urgent problem to be solved. 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 problems in the background art. In the product structure designed by the present invention, using the phthalimide structure as the acceptor, a chiral carbon-nitrogen axial chiral TADF molecule is constructed through the atropisomerism of the substituents at the ortho position of carbazole, and it has the property of aggregation-induced emission. The present invention has prepared a circularly polarized TADF material with ΔEST < 0.1 eV, providing a carbon-nitrogen axial chirality strategy for the construction of chiral TADF molecules and a new chiral mother nucleus for circularly polarized OLED devices.

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

[0006] One of the technical solutions of the present invention: Provide a circularly polarized TADF material based on carbon-nitrogen axial chirality, and 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 at least one of R1 and R3 contains an electron-rich aromatic amine substituent. The amino nitrogen of the electron-rich aromatic amine substituent is connected to phthalimide; R2 is a halogen or an 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 R4 is

[0010] Preferably, the structural formula is:

[0011] The second technical solution of the present invention: Provide a preparation method of the above-mentioned circularly polarized TADF material based on carbon-nitrogen axial chirality, including the following steps:

[0012] (1) Take C1 and C2 and mix them in glacial acetic acid, react to obtain C3;

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

[0014] (3) Mix C5, C6 and a catalyst in an organic solvent, react to obtain 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, where 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; C6 is an electron-rich aromatic amine.

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

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

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

[0019] The third technical solution of the present invention: provides an application of the above-mentioned 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, with the phthalimide structure as the acceptor, chiral carbon-nitrogen axial chiral TADF molecules are constructed through the atropisomerism of the substituents at the ortho position of carbazole, and this compound has the property of aggregation-induced emission.

[0022] In the present invention, through the modification of carbazole derivatives, the regulation of the molecular energy level bandgap can be achieved, thereby changing the emission color and the performance of the material device.

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

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

[0025] The chiral luminescent material designed by the present invention, due to its circularly polarized luminescence characteristics, shows broad application prospects in three-dimensional display technology, optical information storage, biological imaging, chiral sensing and other aspects. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic diagram of the application of four types of chiral TADF materials and chiral skeletons in chiral TADF materials.

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

[0029] Figure 3 For C5 in Example 1 11H-NMR spectrum (a) and 13 13C-NMR spectrum (b).

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

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

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

[0033] Figure 7 The absorption and emission spectra of the product in Example 1.

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

[0035] Figure 9 The CD spectra of two configurations of Chiral-AI in Example 1.

[0036] Figure 10 The circularly polarized emission spectra of two configurations of Chiral-AI in Example 1.

[0037] Figure 11 The g value of Chiral-AI in Example 1.

[0038] Figure 12 The ΔE ST calculation result of the product in Example 1.

[0039] Figure 13 The transient decay spectrum of 5 wt% (rac)-AI-2TCFC:CBP doped film. Detailed Description of the Invention

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

[0041] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

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

[0043] Regarding the use of "comprising", "including", "having", "containing", etc. in this invention, they are all open-ended terms, meaning including but not limited to.

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

[0045] Unless otherwise specified, "room temperature" in this invention is calculated as 25 °C.

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

[0047] Example 1

[0048] A preparation method of a circularly polarized TADF material based on carbon-nitrogen axial chirality:

[0049] (1) Add 10 g of C1, 5 mL of aniline, and 100 mL of glacial acetic acid into a 500 mL round-bottom flask in sequence, heat under reflux at 120 °C for 4 hours, then after the reaction system cools to room temperature, place the reaction system in a 0 °C environment for low-temperature crystallization. A yellow-green solid is precipitated, filtered to obtain a crude product, and then the remaining glacial acetic acid is washed away with water to obtain a yellow-green crystal, which is compound C3 (yield: 98%). The relevant reaction formula is as follows:

[0050]

[0051] (2) Take a 250 mL round-bottom flask and perform an anhydrous and anaerobic treatment, then weigh 2 g of C3, 2.48 g of C4, and 3.3 g of Cs2CO3 and add them into the reaction flask in sequence. Then evacuate and replace the gas in this reaction system 3 times, add 100 mL of DMF, and heat to 65 °C for reaction for 12 hours. After the reaction system cools to room temperature, quickly pass the reaction solution through a short silica gel column, and rinse the short column with dichloromethane to remove the inorganic substances in the reaction system. Then distill off the organic liquid phase to obtain a crude product, and recrystallize with dichloromethane and petroleum ether to obtain 2 g of a pale yellow-green powder, which is compound C5 (yield: 57%). The relevant reaction formula is as follows:

[0052]

[0053] (3) A 250 mL round-bottom flask was subjected to anhydrous and anaerobic treatment. 1 g of C5, 2.2 g of C6, and 2.5 g of Cs2CO3 were successively added to the reaction flask. Then, the reaction system was evacuated and filled with gas three times. 150 mL of DMF was added, and the mixture was heated to 65 °C and reacted for 12 hours. After the reaction system was cooled to room temperature, the reaction solution was quickly passed through a short silica gel column, and the column was rinsed with dichloromethane to remove the inorganic substances in the reaction system. Then, the organic liquid phase was removed by distillation to obtain the crude product, which was further purified by column chromatography to obtain 1.02 g of orange-red powder, which was the final product (yield: 51%, denoted as Chiral-AI). The relevant reaction formula is as follows:

[0054]

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

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

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

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

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

[0060] Effect verification

[0061] 1. Optical property characterization

[0062] Figure 7 Absorption and emission spectra of the product in Example 1.

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

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

[0065] Table 1 shows the fluorescence quantum yield, response time, and delayed fluorescence properties 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% in PMMA 15.91 9.875 1.747

[0068] 2. Characterization of aggregation-induced emission properties

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

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

[0071] 3. Characterization of circular polarization properties

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

[0073]

[0074] Figure 9 The CD spectra of the two configurations of Chiral-AI in Example 1.

[0075] Figure 10 The circularly polarized emission spectra of the two configurations of Chiral-AI in Example 1.

[0076] Figure 11 The g value of Chiral-AI in Example 1.

[0077] Figure 12 The ΔE ST calculation results of the product of Example 1.

[0078] The product of Example 1 was mixed with 4,4'-bis(9-carbazolyl)biphenyl to prepare a doped film (the proportion of the product of Example 1 in the doped film was 5 wt%, denoted as 5 wt% (rac)-AI-2TCFC:CBP doped film), and then the transient decay spectrum of the doped film was measured. The test results are as Figure 13 shown.

[0079] Figure 13 The transient decay spectrum of 5 wt% (rac)-AI-2TCFC:CBP doped film.

[0080] From Figure 13 it can be seen that the thermally activated delayed fluorescence lifetime of this molecule is 2.167 μs.

[0081] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall 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, characterized in that: The circularly polarized TADF material is a phthalimide derivative, and the structural formula is as follows: ； Wherein, R1 and R3 are halogen or electron-rich aromatic amine substituents, and at least one of R1 and R3 contains an 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; The electron-rich aromatic amine substituent is , , , or ; The R4 is , , or .

2. The circularly polarized TADF material based on carbon-nitrogen axial chirality according to claim 1, characterized in that: The structural formula is: .

3. A method for preparing the circularly polarized TADF material based on carbon-nitrogen axial chirality according to claim 1, characterized in that: The following steps are involved: (1) Mix C1 and C2 in glacial acetic acid and react to obtain C3; (2) mixing C3, C4 and a catalyst in an organic solvent, reacting to obtain C5; (3) mixing C5, C6 and a catalyst in an organic solvent, reacting them, 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 , R4 is , , or ; The structural formula of C3 is ; The structural formula of C4 is ; The structural formula of C5 is ; The C6 is an electron-rich aromatic amine.

4. The preparation method according to claim 3, characterized in that: In step (1): the reaction temperature is 118°C and the reaction time is 4 hours.

5. The preparation method according to claim 3, characterized in that: In step (2): the catalyst is Cs2CO3; the reaction temperature is 25°C and the reaction time is 12 hours.

6. The preparation method according to claim 3, characterized in that: In step (3): the catalyst is Cs2CO3; the reaction temperature is 25°C and the reaction time is 12h.

7. Application of the circularly polarized TADF material based on carbon-nitrogen axial chirality as described in any one of claims 1 to 2 in the field of thermally activated delayed fluorescence.

Images