Small-molecule photo-thermal material based on molecular rotor and preparation method of small-molecule photo-thermal material

Abstract

The invention relates to a micromolecular photothermal material based on a molecular rotor and a preparation method of the micromolecular photothermal material, and specifically, triphenylamine is taken as a core unit, is subjected to a Stille coupling reaction with a cyclopentyl bithiophene group, and is connected with a difluoro-bis-cyano indanone (FIC) group as a terminal to form the micromolecular photothermal material. The high-performance micromolecular photothermal material is obtained by regulating and controlling the torsion resistance of two benzene rings in triphenylamine. The micromolecular photothermal material is excellent in photothermal performance, the upper limit of the photothermal performance can reach 210 DEG C, the micromolecular photothermal material can be widely applied to the fields of medical treatment, chemical engineering, energy and the like, the preparation process is simple, the cost is low, and raw materials are easy to obtain.

Description

Technical Field

[0001] The present invention relates to a small molecule photothermal material based on a molecular rotor and a preparation method thereof, and specifically belongs to the technical field of organic photothermal materials. Background Art

[0002] Photothermal effect refers to the phenomenon that a substance generates heat under the action of light. It has the advantages of diverse conversion forms, high utilization value, and wide application fields. It plays an important role in energy development and utilization, medical care, chemical industry and other fields. Compared with traditional inorganic materials, organic small molecule photothermal materials have the advantages of clear structural characterization, convenient performance adjustment, good reproducibility, low manufacturing cost, no potential heavy metal ion poisoning, and the ability to convert light energy into heat energy through non-radiative attenuation. In recent years, it has received more and more attention in the fields of solar energy absorption and utilization, photothermal therapy, remote material control, etc. However, there is still huge room for improvement in its performance optimization. How to design and develop more efficient and more valuable organic photothermal molecules is still the key in this field.

[0003] For organic small molecule photothermal materials, when the material absorbs the energy of photons, its electrons can transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), and then return to the ground state through the radiative transition and non-radiative transition of excited state electrons. Among them, the non-radiative transition process often releases the energy absorbed by the material in the form of thermal energy, thereby giving the organic small molecule photothermal conversion ability. In the above process, the size of the energy gap between HOMO and LUMO is an important basis for determining the photon absorption capacity of the material, and the level of the non-radiative transition ability of the molecule directly determines the photothermal conversion efficiency. Generally speaking, with the increase in the number of π-bonds and the increase in the degree of conjugation of the material, the energy gap between HOMO and LUMO tends to decrease, and the light absorption capacity of the molecule is also enhanced. At the same time, it can release the absorbed photons in the form of molecular thermal vibration. The small molecule material formed by the connection of the donor (D) and the acceptor (A) units can further promote electron delocalization, reduce the material band gap, and improve the intermolecular stacking ability due to its strong electron push-pull effect, so it has a wide range of applications in the field of organic photothermal and optoelectronics.

[0004] Triphenylamine (TPA) is a common group with a propeller structure. The molecular skeleton based on triphenylamine is easy to be structurally modified by simple reactions. It can be coupled with a variety of functional groups through chemical modification, thereby further obtaining TPA derivatives with diverse properties. Through previous studies, it was found that it is mainly used as an end structure to improve the molecular mobility. Because of the rotor rotatability of its propeller structure, it can be given stronger absorption and intramolecular charge transfer capabilities based on the π-π conjugation of the molecule and the interaction between molecules, so that most of the energy absorbed by the molecule generates heat energy through non-radiative transition pathways. However, the upper limit of the temperature rise of small molecule photothermal materials with triphenylamine-related structures known at present can only reach about 70°C. This type of small molecule material is mostly studied in the field of photothermal medicine, and its use is limited in fields such as seawater desalination that require higher photothermal conversion temperatures. And the improvement of the photothermal performance of this type of material often requires the redesign of the structure, the study of the structure and ratio of the receptor, and its research and development cost and time are difficult to control. Therefore, the present invention changes the triphenylamine rotor originally used for the end material into a core unit, which is a new and operable path.

[0005] On the other hand, the introduction of a thiophene ring with relatively low polarity into the small molecule structure can adjust the solubility of the molecule by combining with cyclopentane, so that it has better solubility in different solvents, which is convenient for the processing and application of materials. In addition, the present invention introduces a fluorocyanoindanone end group, the fluorine atom has a strong electronegativity, and there are weak interactions such as hydrogen bonds, which can enhance the electron-pulling ability of the end group and promote intramolecular charge transfer, thereby broadening the absorption spectrum; it can also enhance intermolecular interactions and molecular stacking, thereby improving electron mobility. Therefore, the present invention designs small molecules from the above three structures to form an ADA type (acceptor-donor-acceptor type) structure. Because it has two receptors, it breaks the traditional DA type (donor-acceptor type) structure, which can promote stronger intramolecular charge transfer (ICT), enhance light absorption and heat generation, and show more effective photothermal conversion efficiency, which has profound research value for the structural selection and regulation of the donor. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned technologies, the purpose of the present invention is to provide a small molecule photothermal material based on molecular rotors and a preparation method thereof, aiming to construct a functional small molecule material with efficient and adjustable photothermal properties.

[0007] The structural formula of a small molecule photothermal material based on a molecular rotor of the present invention is as follows:

[0008] A method for preparing a small molecule photothermal material based on a molecular rotor specifically comprises the following steps: Step 1: Stille coupling reaction Using tetrakis(triphenylphosphine)palladium as a catalyst, DMF and anhydrous toluene as solvents, a triphenylamine derivative and 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene are subjected to Stille coupling reaction at a temperature of 110 to 120° C. for 12 to 15 hours; wherein the molar ratio of the triphenylamine derivative and 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene is 1:2.4; Step 2: Vilsmeier-Haack reaction The reaction product of step 1 is subjected to a Vilsmeier-Haack reaction using phosphorus oxychloride as a catalyst, N,N-dimethylformamide and 1,2-dichloroethane as a solvent; during the reaction, the reaction is first performed at 85° C. for 4 hours and then at 50° C. for 5 hours; Step 3: Knoevenagel reaction Using titanium tetrachloride and pyridine as catalysts and tetrahydrofuran as solvent, the reaction product of step 2 and difluorobiscyanoindanone are subjected to Knoevenagel reaction at 70-75° C. for 1 hour, and the product is post-treated to obtain a small molecule photothermal material; wherein the material ratio of the reaction product of step 2 to difluorobiscyanoindanone is 1:2.4.

[0009] The triphenylamine derivative is N,N-bis(4-bromophenyl)aniline or 3-bromo-9-(4-bromophenyl)-9H-carbazole.

[0010] The synthetic route of the small molecule of the present invention consists of three steps: Stille coupling reaction, Vilsmeier-Haack reaction and Knoevenagel reaction, as follows: ; Note: The final product is a small molecule photothermal material, codenamed zq. The structure formed by the dotted line in the above structural formula refers to the triphenylamine derivative formed by connecting carbon No. 2 and carbon No. 8 in the triphenylamine structure (see zq-2 structural formula for details). The structure of difluorobiscyanoindanone (FIC) is shown in the figure below:

[0011] The present invention uses triphenylamine as a core unit and a difluorobiscyanoindanone (FIC) group as a terminal group. The core unit is introduced under reaction conditions to construct a functional small molecule material with new high performance and highly adjustable photothermal properties. The purpose of regulating molecular properties is achieved by controlling the degree of distortion of the two benzene rings in triphenylamine in the structure, thereby reducing the HOMO-LUMO energy gap of the molecule, obtaining excellent photothermal properties, and preparing a small molecule photothermal material based on molecular rotors with adjustable performance.

[0012] Beneficial effects of the present invention: The present invention develops a photothermal small molecule construction strategy based on a polyarylamine core, which can significantly regulate the molecular optical and thermal properties through simple structural changes.

[0013] The present invention can change the photothermal performance by controlling the twisting degree of the two benzene rings in the core unit triphenylamine of the small molecule compound, thereby achieving control of the photothermal performance. It can be seen from the two examples that at 0.1 W cm -2 When irradiated with a 638 nm near-infrared laser for about 2 min, the upper limits of the temperature rise of the two small molecule powders were 175°C and 215°C, respectively, and the heating efficiency was greatly improved (see step 4 in Example 1). BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : UV-visible absorption spectra of small molecule photothermal materials zq-1 and zq-2 prepared in Examples 1 and 2 of the present invention; Figure 2 : CV graph of the small molecule photothermal material zq-1 prepared in Example 1 of the present invention; Figure 3 : CV graph of the small molecule photothermal material zq-2 prepared in Example 2 of the present invention; Figure 4 : Photothermal image of the solution of the small molecule photothermal material zq-1 prepared in Example 1 of the present invention; Figure 5 : Photothermal image of the solution of the small molecule photothermal material zq-2 prepared in Example 2 of the present invention; Figure 6 : Powder photothermal image of the small molecule photothermal material zq-1 prepared in Example 1 of the present invention; Figure 7 : Powder photothermal image of the small molecule photothermal material zq-2 prepared in Example 2 of the present invention; Figure 8 : Temperature rise images of the small molecule photothermal materials zq-1 powder and zq-2 powder of the present invention under 1.0 W cm-2 638 nm near-infrared laser irradiation. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below in conjunction with the embodiments and drawings.

[0016] Example 1 Preparation of small molecule photothermal material zq-1 Reaction equation:

[0017] Note: The final product is a small molecule photothermal material, code-named zq-1.

[0018] Step 1: Stille coupling reaction 80.62 mg (0.2 mmol) of N,N-bis(4-bromophenyl)aniline and 271.44 mg (0.48 mmol) of 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene were added to a two-necked flask, and the catalyst tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) was added. The experimental device was set up, a heat-collecting constant-temperature heating magnetic oil bath was prepared, and the two-necked flask was placed on the oil bath. Then, a condenser was set up, and the interface was sealed with sealing tape, and it was evacuated and filled with nitrogen for 30 seconds, and repeated 3 times.

[0019] Select a 10 mL syringe to extract 8 mL of DMF and a 30 mL syringe to extract 25 mL of anhydrous toluene, respectively, add all of them into the double-necked bottle, repeat the vacuum pumping and nitrogen filling for 3 times, and then seal the bottle mouth. Turn on the heat-collecting constant temperature heating magnetic oil bath, set the reaction temperature to 120℃, adjust the appropriate stirring speed, and react for 15 hours.

[0020] Step 2: Vilsmeier-Haack reaction Put phosphorus oxychloride as a catalyst into the eggplant-shaped bottle together with the reaction product of step 1. Set up the experimental device, prepare the heat-collecting constant temperature heating magnetic oil bath, place the eggplant-shaped bottle on the oil bath, and set up the condenser. Use N,N-dimethylformamide and 1,2-dichloroethane as solvents and stir at room temperature. Turn on the constant temperature heater and react at 85°C. Add deionized water to the eggplant-shaped bottle and continue stirring at 50°C.

[0021] Step 3: Knoevenagel reaction Collect the purified product of step 2 in an eggplant-shaped bottle, weigh 163.31 mg (0.15 mmol) of the product of step 2 and 82.86 mg (0.36 mmol) of difluorobiscyanoindanone, use a 20 mL syringe to draw 20 mL of tetrahydrofuran, use a 1 mL syringe to draw 0.2 mL of pyridine, and add all of them into the eggplant-shaped bottle.

[0022] Build the experimental device, prepare the heat-collecting constant temperature heating magnetic oil bath, place the eggplant-shaped bottle on the oil bath, and build the condenser. Use a 1 mL syringe with a long injection needle to extract 0.2 mL of titanium tetrachloride and add it to the reaction system from the top opening of the condenser to connect the ends of the reaction. The reaction temperature is 75°C.

[0023] Step 4: Purification and post-processing Turn off the heating and stirring of the constant temperature oil bath, remove the condenser, dissolve the product in the eggplant-shaped bottle in DCM, remove the magnetic stirrer, and extract. After the extraction is completed, column chromatography separation and purification are carried out, and the purified product is dissolved in a small amount of DCM, and then a large amount of methanol is added for precipitation. The bottle mouth is sealed with tin foil, and the flask is placed in the refrigerator. Let the solution stand and let it settle naturally for 12 hours. After the sedimentation is completed, the solution is filtered, and the filtered residue is placed in a 60°C vacuum drying oven for drying. After it is dried, it is taken out and placed in a glass bottle, and the final product is the small molecule photothermal material zq-1. At 1.0 W cm -2 Under the irradiation of 638 nm near-infrared laser, the small molecule photothermal material zq-1 powder quickly heated up to about 175°C in about 2 minutes.

[0024] Example 2 Preparation of small molecule photothermal material zq-2 Reaction equation:

[0025] Note: The final product is a small molecule photothermal material, code-named zq-2.

[0026] Step 1: Stille coupling reaction 80.22 mg (0.2 mmol) of 3-bromo-9-(4-bromophenyl)-9H-carbazole (triphenylamine derivative) and 135.72 mg (0.24 mmol) of 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene were added to a two-necked flask, and the catalyst tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) was added. The experimental device was set up, a heat-collecting constant temperature heating magnetic oil bath was prepared, and the two-necked flask was placed on the oil bath. Then, a condenser was set up, and the interface was sealed with sealing tape, and it was evacuated and filled with nitrogen for 30 seconds, and repeated 3 times.

[0027] Select a 10 mL syringe to extract 8 mL of DMF and a 30 mL syringe to extract 25 mL of anhydrous toluene, add all of them into the double-necked bottle, repeat the vacuum and nitrogen filling for 3 times, and then seal the bottle mouth. Turn on the heat-collecting constant temperature heating magnetic oil bath, set the reaction temperature to 110℃, adjust the appropriate stirring speed, and carry out the reaction.

[0028] Step 2: Vilsmeier-Haack reaction Put phosphorus oxychloride as a catalyst into the eggplant-shaped bottle together with the reaction product of step 1. Set up the experimental device, prepare the heat-collecting constant temperature heating magnetic oil bath, place the eggplant-shaped bottle on the oil bath, and set up the condenser. Use N,N-dimethylformamide and 1,2-dichloroethane as solvents and stir at room temperature. Turn on the constant temperature heater and react at 85°C. Add deionized water to the eggplant-shaped bottle and continue stirring at 50°C.

[0029] Step 3: Knoevenagel reaction Collect the purified product of step 2 in an eggplant-shaped bottle, weigh 163.00 mg (0.15 mmol) of the product of step 2 and 82.86 mg (0.36 mmol) of difluorobiscyanoindanone, use a 20 mL syringe to draw 20 mL of tetrahydrofuran, use a 1 mL syringe to draw 0.2 mL of pyridine, and add all of them into the eggplant-shaped bottle.

[0030] Build the experimental device, prepare the heat-collecting constant temperature heating magnetic oil bath, place the eggplant-shaped bottle on the oil bath, and build the condenser. Use a 1 mL syringe with a long injection needle to extract 0.2 mL of titanium tetrachloride and add it to the reaction system from the top opening of the condenser to connect the ends of the reaction.

[0031] Step 4: Purification and post-processing Turn off the heating and stirring of the constant temperature oil bath, remove the condenser, dissolve the product in the eggplant-shaped bottle in DCM, remove the magnetic stirrer, and extract. After the extraction is completed, perform column chromatography separation and purification, dissolve the purified product in a small amount of DCM, then add a large amount of methanol for precipitation, seal the bottle mouth with tin foil, put the flask in the refrigerator, let the solution stand, and let it settle naturally for 12 hours. After the sedimentation is completed, the solution is filtered, and the filtered residue is placed in a 60°C vacuum drying oven for drying. After it is dried, take it out and put it in a glass bottle to obtain the small molecule photothermal material zq-2. At 1.0W cm -2 Under the irradiation of 638 nm near-infrared laser, the small molecule photothermal material zq-2 powder quickly heated up to about 215°C in about 2 minutes.

Claims

1. A small molecule photothermal material based on molecular rotors, characterized in that: The structural formula of the small molecule photothermal material is as follows: 。 2. A method for preparing small molecule photothermal materials based on molecular rotors, characterized in that: The preparation method specifically comprises the following steps: Step 1: Stille coupling reaction Using tetrakis(triphenylphosphine)palladium as a catalyst, DMF and anhydrous toluene as solvents, a triphenylamine derivative and 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene are subjected to Stille coupling reaction at a temperature of 110 to 120° C. for 12 to 15 hours; wherein the molar ratio of the triphenylamine derivative and 2-trimethyltin-4,4-di(2-ethylhexyl)-dithienocyclopentadiene is 1:2.4; Step 2: Vilsmeier-Haack reaction The reaction product of step 1 is subjected to a Vilsmeier-Haack reaction using phosphorus oxychloride as a catalyst, N,N-dimethylformamide and 1,2-dichloroethane as a solvent; during the reaction, the reaction is first performed at 85° C. for 4 hours and then at 50° C. for 5 hours; Step 3: Knoevenagel reaction Using titanium tetrachloride and pyridine as catalysts and tetrahydrofuran as solvent, the reaction product of step 2 and difluorobiscyanoindanone are subjected to Knoevenagel reaction at 70-75° C. for 1 hour, and the product is post-treated to obtain a small molecule photothermal material; wherein the material ratio of the reaction product of step 2 to difluorobiscyanoindanone is 1:2.

4.

3. A method for preparing a small molecule photothermal material based on a molecular rotor according to claim 2, characterized in that: The triphenylamine derivative is N,N-bis(4-bromophenyl)aniline or 3-bromo-9-(4-bromophenyl)-9H-carbazole.

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