Organic framework fluorescent material based on pi bond

Abstract

The invention provides an organic framework fluorescent material based on a pi bond. Aromatic units with electron pushing and pulling properties are combined to serve as basic units, and the Pi-bond organic framework material with excellent luminescent properties is constructed in a crystallization mode. The solid powder quantum yield of the organic framework fluorescent material BCZ-TRZ based on the pi bond is close to 100%, and is obviously higher than that of most existing framework structure luminescent materials. Benefited from the rigid plane structures of the BCZ and the TRZ, a good charge transfer effect between molecules is achieved. Particularly, through a framework structure constructed among molecules, the molecules are firmly locked, the vibration inactivation of the molecules is fully inhibited, and the quantum yield is extremely high. The Pi-bond-constructed pure organic framework with 100% quantum yield is reported for the first time, and the Pi-bond-constructed pure organic framework has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent materials, specifically relating to an organic framework fluorescent material based on π bonds. Background Technology

[0002] Non-covalent π-bonded stacked organic frameworks (πOFs) are a subclass of porous materials, consisting of crystalline networks formed by organic building blocks that self-assemble through π-π interactions. In supramolecular chemistry, weak intermolecular interactions, including π-π interactions, have been extensively studied and further applied to the construction of porous molecular materials. The flexible, reversible, and conductive properties of π-π interactions, along with the π-conjugated supramolecular framework, endow πOFs with unique properties, including solution processability, self-healing ability, significant carrier mobility, and excellent stability. These properties make πOFs ideal candidate materials for traditional applications such as gas separation, molecular structure determination, and electrocatalysis; however, the extremely limited number of currently successful πOF materials undoubtedly restricts their further application. Summary of the Invention

[0003] The purpose of this invention is to provide an organic framework fluorescent material based on π bonds. This π-bond-based organic framework fluorescent material, BCZ-TRZ solid powder, achieves a quantum yield close to 100%, significantly higher than most current framework-structured luminescent materials. Benefiting from the rigid planar structure of BCZ and TRZ, excellent charge transfer effects exist between molecules. In particular, the framework structure constructed between molecules firmly locks the molecules in place, effectively suppressing vibrational inactivation and resulting in an extremely high quantum yield. This is the first reported example of a purely organic framework based on π bonds achieving 100% quantum yield.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: An organic framework fluorescent material based on π bonds, denoted as BCZ-TRZ, has the following structural formula: .

[0005] The method for preparing the π-bond-based organic framework fluorescent material includes the following steps: (1) Preparation of Cz-Br: 3,6-di-tert-butylcarbazole was added to dichloromethane and stirred thoroughly to dissolve. Under light-protected conditions, a dichloromethane solution of N-bromosuccinimide was slowly added dropwise. The reaction was carried out at room temperature in the dark for 6 hours. After cooling to room temperature, the product was concentrated and washed with saturated brine and dried with anhydrous magnesium sulfate. The concentrated organic layer was separated and separated by silica gel column chromatography to obtain the product Cz-Br. (2) DC ZPreparation of -2Br: Cz-Br was dissolved in acetone, KMnO4 was added, the reaction system was heated to 70℃, and the reaction was refluxed under nitrogen atmosphere for 10 hours. After cooling to room temperature, acetone was removed by vacuum distillation. The product was dissolved in chloroform, filtered, and the residue was washed. The resulting solution was washed successively with saturated sodium thiosulfate solution and brine, and dried over anhydrous magnesium sulfate. The concentrated organic layer was separated by silica gel column chromatography to obtain product DC. Z -2Br; (3) Preparation of BCZ-TRZ: DCz-2Br, 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl]-1,3,5-triazine, palladium chloride, 2-dicyclohexylphosphine-2',6'-dimethoxybiphenyl, and tetrabutylammonium bromide were added sequentially to the reaction vessel. Nitrogen was purged to remove oxygen, and toluene TOL and K2CO3 solution were injected. The reaction was carried out at 100℃ for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the product was washed sequentially with saturated brine, extracted with ethyl acetate, and dried with anhydrous magnesium sulfate. The concentrated organic layer was separated and separated by silica gel column chromatography to obtain the product BCZ-TRZ. (5) BCZ-TRZ crystal culture: Dissolve BCZ-TRZ in diethyl ether, heat under reflux for 1 hour, filter the solution and let it stand for two weeks, filter and collect the precipitate to obtain BCZ-TRZ crystals with a framework structure.

[0006] Furthermore, in step (1), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 20:1, by volume.

[0007] Furthermore, in step (2), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 30:1, by volume.

[0008] Furthermore, in step (3), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 35:1, by volume.

[0009] The advantages of this invention are: Current technologies for constructing pure organic πOFs primarily use simple, symmetrical conjugated aromatic units such as spirofluorene, triphenylamine, anthracene, and tetraphenylmethane as building blocks. The focus is on utilizing the rigid structure of these building blocks combined with their three-dimensional configuration to construct a porous framework. However, for aromatic systems, different combinations of aromatic units, along with adjustments to their electron-pulling and electron-pulling capabilities and conformations, can yield luminescent materials with varying properties. Clearly, current molecular designs for πOFs do not fully leverage the advantages of aromatic systems in constructing highly efficient luminescent materials. Therefore, this invention proposes a π-bonded organic framework material with excellent luminescent properties, constructed from combinations of aromatic units with electron-pulling and electron-pulling properties through crystallization. Attached Figure Description

[0010] Figure 1 Flowchart for the preparation of compound BCZ-TRZ; Figure 2 The UV-Vis absorption spectra of BCZ-TRZ in different solvents; Figure 3 This is a diagram of the BCZ-TRZ unit cell structure. Figure 4 Photographs taken under BCZ-TRZ crystal fluorescent lamp (left) and 365 nm ultraviolet lamp (right); Figure 5 Fluorescence spectra of BCZ-TRZ crystals before and after grinding; Figure 6 This is a BCZ-TRZ quantum yield diagram. Detailed Implementation

[0011] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0012] Example 1

[0013] Preparation of 1-bromo-3,6-di-tert-butylcarbazole (Cz-Br): 3,6-di-tert-butylcarbazole (1500 mg, 5.37 mmol) and 150 mL dichloromethane (DCM) were added to a 100 mL single-necked flask and stirred thoroughly to dissolve. Under light-protected conditions, 150 mL of DCM solution containing N-bromosuccinimide (1500 mg, 6.46 mmol) was slowly added dropwise. The reaction was carried out at room temperature in the dark for 6 hours, followed by cooling to room temperature. The product was concentrated to 50 mL, washed successively with saturated brine, dried over anhydrous magnesium sulfate, and the concentrated organic layer was separated by silica gel column chromatography to obtain 1600 mg of a pale yellow viscous oil, yielding 82% (eluent: PE:DCM = 20:1, volume ratio).

[0014] 1,1'-Dibromo-3,3',6,6'-Tetratert-butyl-9,9'-Dicarbazole (DC) ZPreparation of Cz-Br: Cz-Br (1215 mg, 3.39 mmol) was added to a 150 mL two-necked flask and dissolved in 30 mL of acetone. KMnO4 (1340 mg, 8.5 mmol) was added, and the reaction system was heated to 70 °C and refluxed under nitrogen atmosphere for 10 hours. After cooling to room temperature, acetone was removed by vacuum distillation. The product was dissolved in an appropriate amount of chloroform, filtered, and the residue was washed. The resulting solution was washed successively with saturated sodium thiosulfate solution and brine, and dried over anhydrous magnesium sulfate. The concentrated organic layer was separated by silica gel column chromatography to obtain 1030 mg of white solid, yield 85%. (Eluent: PE:DCM = 30:1, volume ratio).

[0015] Preparation of 2,5,10,13-Tetratert-butyll-7-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)diindol[3,2,1-de:3',2',1'-kl]phenazine (BCZ-TRZ): In a 150 mL two-necked flask, DCz-2Br (500 mg, 0.70 mmol), 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl]-1,3,5-triazine (600 mg, 1.40 mmol), palladium chloride (PdCl2) (37.2 mg, 0.21 mmol), 2-biscyclohexylphosphine-2',6'-dimethoxybiphenyl (200 mg, 0.49 mmol), and tetrabutylammonium bromide (TBAB) (33 mg, 1.40 mmol) were added sequentially. (mg, 0.21 mmol), nitrogen purging for deoxygenation, followed by the injection of toluene TOL (30 mL) and K2CO3 solution (3.4 mL, 2.0 mol / L), and reaction at 100℃ for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the product was washed successively with saturated brine, extracted with ethyl acetate, and dried over anhydrous magnesium sulfate. The concentrated organic layer was separated and purified by silica gel column chromatography to obtain 60 mg of a yellow solid product, with a yield of 10.0%. (Eluent:PE:DCM = 35:1, volume ratio) BCZ-TRZ crystal culture: Dissolve 50 mg of BCZ-TRZ in 20 mL of diethyl ether, heat under reflux for 1 h, filter the solution and let it stand for two weeks. Filter and collect the precipitate to obtain BCZ-TRZ crystals with a framework structure.

[0016] NMR data of BCZ-TRZ compounds: 1H-NMR (400 MHz, Acetone-d6) 8.85-8.80 (2 H, m), 8.80-8.74 (5 H, m), 8.06 (2 H, d, J 39.0), 7.88 (3 H, d, J 8.1), 7.78-7.44 (11 H, m), 1.62-1.43(36 H, m) 13 C-NMR (101 MHz, Chloroform-d) 171.76, 171.50, 147.26, 146.12,145.52, 145.24, 144.19, 136.48, 135.83, 135.59, 133.18, 132.64, 132.10,129.91, 129.23, 129.15, 128.79, 128.22, 127.85, 126.98, 126.80, 126.25,124.15, 123.71, 122.94, 117.37, 116.82, 112.67, 112.54, 110.59, 110.10, 106.26, 35.44, 35.04, 34.97, 34.80, 32.21, 32.11, 32.08, 31.41, 29.89. Ultraviolet absorption spectrum: UV absorption spectra of the compound in different solvents, such as Figure 2 As shown, the absorption peaks below 300 nm are mainly due to the absorption transition of π-π* in the compound, the absorption near 400 nm is mainly due to the absorption of the benzoxazole unit in the compound, and the relatively weak absorption around 450 nm is mainly due to the charge transfer state absorption of the benzoxazole unit to the triphenyltriazine unit in the compound.

[0017] The structure of the single crystal obtained by BCZ-TRZ is as follows Figure 3As shown, in each BCZ-TRZ unit cell, the donor benzo[a]carbazole (BCZ) and the acceptor triphenyltriazine (TRZ) adopt a slightly twisted conformation, with a twist angle of 36.88° at their junction. Both the donor benzo[a]carbazole (BCZ) and the acceptor triphenyltriazine (TRZ) in the two BCZ-TRZ molecules exhibit close face-to-face packing, with interaction distances of 3.386 Å and 3.376 Å, respectively. Simultaneously, strong CH-π interactions exist between BCZ and TRZ molecules of different types, with a distance of 2.370 Å. All molecules construct the crystal structure through strong π-π interactions. Further analysis reveals that due to the twisted structure of the DA unit, the macroscopic crystal exhibits an open porous structure. In the overall crystal, BCZ-TRZ molecules extend along the transverse helix along the lateral direction through strong π-π interactions between BCZ and BCZ, combined with CH-π interactions of DA, constructing a transverse framework support layer. The layers are connected by TRZ-TRZ interactions, serving as a framework for vertical growth, resulting in significant pores between the transverse and longitudinal directions. Therefore, this crystal is a novel organic framework structure (πOFs) constructed based on π-bond interactions. Under a microscope, the BCZ-TRZ crystal exhibits a regular yellow color and displays bright yellow fluorescence when illuminated by a 365 nm ultraviolet lamp. Figure 4 Its fluorescence emission spectrum is as follows: Figure 5 As shown, the emission peak is located at 555 nm.

[0018] The BCZ-TRZ solid powder exhibits a quantum yield approaching 100%, significantly higher than most framework-structured luminescent materials. This is attributed to the rigid planar structure of BCZ and TRZ, which enables excellent intermolecular charge transfer. In particular, the framework structure built between molecules effectively locks them in place, suppressing vibrational inactivation and resulting in extremely high quantum yield. This is the first reported example of a purely organic framework based on π-bonds achieving 100% quantum yield.

[0019] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. An organic framework fluorescent material based on π bonds, characterized in that, The π-bond-based organic framework fluorescent material is BCZ-TRZ, and its structural formula is as follows: 。 2. The method for preparing organic framework fluorescent materials based on π bonds according to claim 1, characterized in that, Includes the following steps: (1) Preparation of Cz-Br: 3,6-di-tert-butylcarbazole was added to dichloromethane and stirred thoroughly to dissolve. Under light-protected conditions, a dichloromethane solution of N-bromosuccinimide was slowly added dropwise. The reaction was carried out at room temperature in the dark for 6 hours. After cooling to room temperature, the product was concentrated and washed with saturated brine and dried with anhydrous magnesium sulfate. The concentrated organic layer was separated and separated by silica gel column chromatography to obtain the product Cz-Br. (2) DC Z Preparation of -2Br: Cz-Br was dissolved in acetone, KMnO4 was added, the reaction system was heated to 70℃, and the reaction was refluxed under nitrogen atmosphere for 10 hours. After cooling to room temperature, acetone was removed by vacuum distillation. The product was dissolved in chloroform, filtered, and the residue was washed. The resulting solution was washed successively with saturated sodium thiosulfate solution and brine, and dried over anhydrous magnesium sulfate. The concentrated organic layer was separated by silica gel column chromatography to obtain product DC. Z -2Br; (3) Preparation of BCZ-TRZ: DCz-2Br, 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl]-1,3,5-triazine, palladium chloride, 2-dicyclohexylphosphine-2',6'-dimethoxybiphenyl, and tetrabutylammonium bromide were added sequentially to the reaction vessel. Nitrogen was purged to remove oxygen, and toluene and K2CO3 solution were injected. The reaction was carried out at 100℃ for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the product was washed with saturated brine, extracted with ethyl acetate, and dried with anhydrous magnesium sulfate. The concentrated organic layer was separated and separated by silica gel column chromatography to obtain the product BCZ-TRZ. (4) BCZ-TRZ crystal culture: Dissolve BCZ-TRZ in diethyl ether, heat under reflux for 1 hour, filter the solution and let it stand for two weeks, filter and collect the precipitate to obtain BCZ-TRZ crystals with a framework structure.

3. The preparation method according to claim 2, characterized in that, In step (1), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 20:1, by volume.

4. The preparation method according to claim 2, characterized in that, In step (2), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 30:1, by volume.

5. The preparation method according to claim 2, characterized in that, In step (3), the eluent for silica gel column chromatography is petroleum ether: dichloromethane = 35:1, by volume.

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