A thermally stable and photoisomerizable compound and its preparation method

Abstract

A thermally stable and photoinduced chiral inversion compound and its preparation method, wherein the preparation method includes: obtaining an aldehyde compound by dehydrative condensation reaction of phenylglyoxylic acid and binaphthol; carrying out an aldehyde-amine condensation reaction between the aldehyde compound and a phenylhydrazine compound under acidic catalytic conditions to generate a hydrazone compound. The present invention can rapidly respond under visible light or ultraviolet light irradiation, resulting in the disappearance and establishment of the molecular planar conjugated structure, thereby causing reversible changes in the magnitude and direction of molecular chirality, having rapid photo-responsiveness and good cycling performance, and the hydrazone functional group linked by a covalent bond can ensure good chiral switching ability of the chiral molecule. Through a series of synthetic reactions, the present invention synthesizes a photoinduced chiral inversion compound with single or multiple hydrazone functional groups, and the magnitude and direction of the chirality of the photoinduced chiral inversion compound can be regulated by light irradiation.

Description

Technical Field

[0001] The present invention relates to the field of organic fluorescent small molecules, and particularly relates to a compound with high thermal stability and capable of photoinduced chiral inversion and a preparation method thereof. Background Art

[0002] Photoisomerizable hydrazone compounds are a research hotspot in the field of photochemistry. Compared with other photo-responsive molecules, the advantages of hydrazone compounds are high thermal stability, simple synthesis, and easy structural modification. The hydrogen atom at the photoactivation site of hydrazone compounds can form hydrogen bond interactions with adjacent oxygen atoms or nitrogen atoms, etc., and then form a large conjugated planar structure. By irradiating light to cause cis-trans isomerization of hydrazone molecules, the conjugated planar structure of the molecules can be changed.

[0003] Utilizing the change of this conjugated planar structure of hydrazone compounds to construct a new type of photo-responsive molecule with chiral change properties is a newly emerging research direction in recent years. Such photo-responsive chiral molecules have great potential in the fields of chiral information storage, cholesteric liquid crystal regulation, etc.

[0004] However, the current hydrazone chiral molecules have the disadvantages of small chiral change and non-invertible chirality. Developing new hydrazone chiral molecules with chiral inversion characteristics is still a field to be studied at present. Summary of the Invention

[0005] Based on this, the present invention provides a compound with high thermal stability and capable of photoinduced chiral inversion and a preparation method thereof, so as to solve the technical problems that the existing hydrazone chiral molecules have small chiral change and non-invertible chirality, resulting in limited applications.

[0006] To achieve the above object, the present invention provides a compound with high thermal stability and capable of photoinduced chiral inversion and a preparation method thereof. The general formula of the structure of the compound is shown as follows:

[0007]

[0008] Wherein, X1 to X6 are the same or different and independently selected from H or the group and at least one of X1 to X6 is the group The R functional group in this group is selected from any of the groups shown in formulas (1)-(4), and n in formulas (1)-(4) is a positive integer greater than zero;

[0009]

[0010] Y1 to Y4 are the same or different and independently selected from H or any of the groups shown in formulas (5)-(13), and n in formulas (5)-(13) is a positive integer greater than zero;

[0011]

[0012] According to another aspect of the present invention, the present invention further provides a method for preparing a thermally stable and photo-induced chiral inversion compound, comprising the following steps:

[0013] React phenylglyoxylic acid and binaphthol through dehydration condensation reaction to obtain an aldehyde compound;

[0014] React the aldehyde compound with a phenylhydrazine compound under acidic catalytic conditions to generate a hydrazone compound, wherein the structure of the phenylhydrazine compound is:

[0015]

[0016] wherein, R4-R6 are independently selected from H or any group shown in formulas (5)-(13).

[0017] As a further preferred technical solution of the present invention, the reaction of the aldehyde compound with the phenylhydrazine compound under acidic catalytic conditions to generate a hydrazone compound specifically includes:

[0018] Provide a solution of the aldehyde compound, place it in a reaction vessel, add 1-2 equivalents of the phenylhydrazine compound, heat to obtain a mixture; add a catalyst to the mixture, stir and react, and then add 2-3 equivalents of deionized water to quench the reaction; after the reaction, the solution is cooled to room temperature, and the solution is removed by suction filtration. Take the obtained precipitate by filtration, and purify it through a silica gel chromatography column.

[0019] As a further preferred technical solution of the present invention, the catalyst is an organic acidic catalyst.

[0020] As a further preferred technical solution of the present invention, the method for preparing the thermally stable and photo-induced chiral inversion compound specifically includes:

[0021] A: Dissolve phenylglyoxylic acid in tetrahydrofuran, place it in a reaction vessel, stir at room temperature for a period of time, add 0.2-0.5 equivalents of binaphthol, heat to 50 °C and react for 20 h; after the reaction is completed, the obtained mixture is extracted and purified to obtain white needle-like crystals, and the product is recrystallized with isopropanol to obtain the aldehyde compound.

[0022] B: Dissolve the aldehyde compound in ethanol, add 2 equivalents of the phenylhydrazine compound, add 0.1-0.2 equivalents of acetic acid catalyst, stir and react for 4 h, and then add 4-6 equivalents of deionized water to quench the reaction; after the reaction, the solution is cooled to room temperature, and the solution is removed by suction filtration. Take the obtained precipitate by filtration, and purify it through a silica gel chromatography column to obtain a thermally stable and photo-induced chiral inversion compound.

[0023] The advantages of the thermally stable and photoinduced chiral inversion compound (also known as photoinduced isomeric chiral hydrazone molecules) provided by the present invention are as follows: it can rapidly respond under visible light or ultraviolet light irradiation, resulting in the disappearance and establishment of the molecular planar conjugated structure, thereby causing reversible changes in the magnitude and direction of molecular chirality. It has rapid photo-responsiveness and good cycling performance, and the hydrazone functional group linked by covalent bonds can ensure good chiral switching ability of chiral molecules.

[0024] Through a series of synthetic reactions, the present invention synthesizes photoinduced chiral inversion compounds with single or multiple hydrazone functional groups, and the magnitude and direction of the chirality of the photoinduced chiral inversion compounds can be regulated by light irradiation.

[0025] By a general method, the present invention combines the hydrazone functional group with axially chiral binaphthol to prepare a functional molecule that can not only undergo changes in the planar conjugated structure but also achieve reversible switching of the magnitude and direction of chirality. The molecule is incorporated with single or multiple hydrazone functional groups, enabling the regulation of the magnitude and direction of chirality through the formation and disappearance of the conjugated plane during photoinduced isomerization. Therefore, this molecule is expected to be used to prepare a new generation of light-controlled intelligent materials and has broad application prospects in the field of luminescent materials. The potential applications of this molecule include:

[0026] 1) Forming cholesteric liquid crystals with small molecule liquid crystal monomers to prepare photo-responsive intelligent materials with regulatory characteristics;

[0027] 2) Based on the chiral inversion characteristics of the molecule, it can play a role in circularly polarized fluorescence emission and the control of circularly polarized fluorescence intensity and direction;

[0028] 3) It is expected to combine phenomena such as photoinduced deformation and chiral inversion in liquid crystal polymer materials to prepare new types of intelligent materials and devices. Description of the Drawings

[0029] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0030] Figure 1 It is a schematic diagram of the configuration change of the photoinduced isomeric chiral hydrazone molecule of the present invention.

[0031] Figure 2 It is the circular dichroism spectrum of the hydrazone chiral molecule in Example 1 in the initial state and under light irradiation, where the positive and negative changes of the CD curve indicate the inversion of the chirality of the chiral hydrazone molecule.

[0032] Figure 3To characterize the chiral change diagram of the hydrazone molecules prepared in Example 1 through a wedge-shaped cell, the stripe spacing in the wedge-shaped cell is inversely proportional to the chirality of the molecule. It can be seen that the chirality of the molecule is the largest in the initial state, and the chirality becomes smaller under 450 nm light irradiation. Under 365 nm light irradiation, the chirality further decreases.

[0033] The realization of the object, functional characteristics, and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Embodiments

[0034] The following further details the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention and are not intended to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods used are all conventional methods unless otherwise specified.

[0036] The present invention provides a compound that is thermally stable and can undergo photoinduced chiral inversion. The structural general formula of the compound is as follows:

[0037]

[0038] Wherein, X1 to X6 are the same or different and are independently selected from H or a hydrazone functional group The hydrazone functional group The R functional group in it is selected from any group shown in formulas (1)-(4), and n in formulas (1)-(4) is a positive integer greater than zero;

[0039]

[0040] Y1 to Y4 are the same or different and are independently selected from H or any group shown in formulas (5)-(13), and n in formulas (5)-(13) is a positive integer greater than zero;

[0041]

[0042] In the initial state, the compound (also known as a chiral molecule or chiral hydrazone molecule) has a Z configuration. Under 450 nm blue light irradiation, chiral inversion occurs, and the molecular configuration is isomerized from the Z configuration to the E configuration. Under 340 nm ultraviolet light irradiation, the E-configuration compound can undergo chiral inversion again and return to the Z-configuration state. By stimulating with light of different wavelengths, compounds with different contents of Z-configuration molecules can be obtained, and both types of configuration molecules have extremely high thermal stability. The molecular configuration change of the compound is as Figure 1 shown.

[0043] To enable those skilled in the art to better understand and implement the technical solution of the present invention, the technical solution of the present invention will be further described in detail below through specific embodiments.

[0044] Example 1

[0045] This example provides a preparation method of a thermally stable and photoinduced chiral inversion compound. Taking the synthesis of a hydrazone chiral molecule with hydrazone functional groups at X2 and X6, H at X1, X3 - X5, H at Y1 - Y4, and the group represented by formula (1) for R in the hydrazone functional group and n being 6 as an example, the synthesis method is as follows.

[0046] 1) 1.59 g (1 mmol) of phenylglyoxylic acid is dissolved in 20 ml of anhydrous tetrahydrofuran, stirred at room temperature for 30 minutes to ensure complete dissolution, and then 2 ml of oxalyl chloride and 0.1 ml of N,N - dimethylformamide are dropped into the reaction solution. After continuing the reaction for 10 h, the solvent is removed to obtain 1.4 g of oily phenylglyoxyl chloride as the product, with a yield of 74%.

[0047] 2) 1 g of phenylglyoxyl chloride is dissolved in 20 ml of anhydrous tetrahydrofuran, stirred at room temperature for 30 min, and then 0.8 g of (S,S) - binaphthol is added. The reaction is heated to 50 °C and stirred for 20 h. After the reaction is completed, the reactant is cooled to room temperature, the solvent is removed, and it is purified through a silica gel column for chromatography (petroleum ether:ethyl acetate = 5:1) and recrystallized with isopropanol to obtain 0.8 g of an aldehyde compound as white needle - shaped solids, with a yield of 60%.

[0048] 3) 3 g of p - carboxyphenylhydrazine is dissolved in 50 ml of dichloromethane, stirred at room temperature for 30 min, then 2.06 g of DCC and 0.15 g of DMAP are added. After continuing to stir for 30 min, 2.1 g of hydroxybutyl acrylate is added. After stirring at room temperature for 24 h, the insoluble matter is removed by suction filtration and the solvent is removed, and it is purified through a silica gel column for chromatography (petroleum ether:ethyl acetate = 10:1) to obtain 2.8 g of a phenylhydrazine compound as light - gray solids, with a yield of 51%.

[0049] 4) 1 g of the aldehyde compound obtained in step 2) and 1.1 g of the phenylhydrazine compound obtained in step 3) are dissolved in 20 ml of anhydrous ethanol, and 0.1 ml of glacial acetic acid is dropped in. Stir the reaction at 90 °C in a nitrogen environment for 12 h. After the reaction, the reactant is cooled to room temperature, 80 ml of deionized water is added. Filter by suction, take the precipitate, and purify it through a silica gel column for chromatography (petroleum ether:ethyl acetate = 1:1) to obtain 1.5 g of a chiral molecule as yellow solids, with a yield of 78%.

[0050] The product obtained in step 4) is tested. The wavelength of visible light used is 450 nm, and the wavelength of ultraviolet light is 365 nm. Please refer to Figure 2, under visible light irradiation, the chirality of the molecule changes from left-handed to right-handed, and under ultraviolet light irradiation, the chirality of the molecule reverts to left-handed. Additionally, by doping chiral molecules in a wedge-shaped cell to measure the chirality magnitude, it can be found that the chirality magnitude of chiral molecules can be regulated by irradiation with 450 nm light and 365 nm light.

[0051] To further study the properties of the thermally stable and photo-induced chirality-reversible compounds of the present invention, the circular dichroism spectra of some chiral hydrazone molecules of the present invention were tested as follows, as shown in Table 1 specifically:

[0052] Table 1. Structures and properties of some chiral hydrazone molecules

[0053]

[0054] Note: The remaining X and Y groups not present in Molecules 1-7 are all H; n is 6.

[0055] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The protection scope of the present invention is only defined by the appended claims.

Claims

1. A compound that is thermally stable and can undergo photoinduced chiral inversion, Characterized in that, The structure of the compound is as follows: 。

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