A photochromic material containing a pyridine derivative triarylethene and its preparation and application method

Abstract

The present invention relates to a pyridine derivative-containing triarylethylene photochromic material and its preparation and application methods. A pyridine ring or its derivative containing a formaldehyde substituent at one end is subjected to a Corey-Funchs reaction to synthesize its dibromosubstituted product; then, the dibromosubstituted product is reacted with an aromatic compound or heterocyclic compound containing a boric acid or pinacol borate group through a Suzuki reaction; or a benzophenone derivative is reacted with a pyridine ring or its derivative containing a diethyl phosphate group through a Wittig reaction to obtain the pyridine derivative-containing triarylethylene photochromic material. The present invention has low-cost raw materials and a simple and easy synthesis process. The prepared photochromic material has the advantages of dual light / proton response, high color purity, a wide color change wavelength range, and long color change durability. This expands the original triarylethylene photochromic material with a single stimulus response to a light / proton dual-responsive photochromic material, and also expands the color change range from orange to red and purple. The material is suitable for multiple fields such as inspection, storage encryption, and biological imaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of color-changing materials, and relates to a photochromic material containing a pyridine derivative triarylethene and its preparation and application method, which is used in the fields of pH testing, optical switching, optical information storage, encryption and anti-counterfeiting, decorative and protective packaging, and biological imaging. Background Art

[0002] Photochromism is a phenomenon in which two compounds undergo reversible structural and color transformations under exposure to light of different wavelengths (Pure and Applied Chemistry. 2001, 73, 639-665). This structural interconversion is often accompanied by changes in a range of physical or chemical properties, such as refractive index, dielectric constant, conductivity, solubility, surface wettability, luminescence, or mechanical properties. Therefore, in addition to their widespread use in everyday applications such as color-changing glass and clothing, photochromic materials also have great potential for applications in areas such as encryption and anti-counterfeiting, optical switches, and molecular logic gates, and have garnered widespread attention from both the scientific and industrial communities in recent years.

[0003] Among the many photochromic systems, organic photochromic materials have good fatigue resistance, are easy to modify, and can be applied to flexible devices compared to inorganic systems. They have the advantages of rich colors and fast light response, and therefore have broader application prospects. At present, typical organic photochromic systems include azobenzenes, spiropyrans, fulgides, and diarylethenes (Chem.Soc.Rev., 2018, 47, 1044-1097). However, these materials are subject to varying degrees of limitations such as complex synthesis process, poor thermal stability, and weak fatigue resistance, and face great challenges in a wide range of practical applications. Therefore, there is an urgent need for a new organic photochromic system with fast response.

[0004] In recent years, triphenylethylene derivatives are expected to become a new type of organic photochromic molecules due to their advantages such as simple synthesis and easy modification. Since Yu et al. first reported triarylethenes photochromic molecules (Ou D, Yu T, Yang Z, et al. Combined aggregation induced emission (AIE), photochromism and photoresponsive wettability in simple dichloro-substituted triphenylethylene derivatives. Chem. Sci., 2016, 7, 5302-5306), recent years have reported the light-controlled interface of this system (Wang L, Yu T, Xie Z, et al. Design, synthesis and photochromism studies of thienyl-containing triarylethylene derivatives and their applications in real-time photoresponsive surfaces. J. Mater. Chem. C, 2018, 6, 8832-8838), color-changing and fluorescence dual response (Zhang X, Yu T, Huang C, et al. Switching excitons between the emissive and photochromic pathways in the triphenylethylene However, the reported triarylethenes have a limited color range (orange to red) and a single stimulus response (only to light), which restricts their application in fields such as optical information storage. Further development of multi-stimulus responsive photochromic materials is needed. Summary of the Invention

[0005] Technical problems to be solved

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a photochromic material containing a pyridine derivative triarylethene and a preparation and application method thereof.

[0007] The purpose of the present invention is to provide a photochromic material containing a pyridine derivative triarylethene, which has the advantages of light / proton dual response, high color purity, wide color change wavelength range, and long color change durability.

[0008] Another object of the present invention is to provide methods for synthesizing the above-mentioned photochromic materials containing triarylethenes containing pyridine derivatives. These methods are simple in process and easy to purify, and the luminescence wavelength, color after ultraviolet light excitation, fatigue resistance and other properties of the final product can be adjusted by introducing different functional groups.

[0009] Another object of the present invention is to apply the above-mentioned photochromic materials containing pyridine derivatives, triarylethenes, to the fields of pH detection, optical switching, optical information storage, encryption and anti-counterfeiting, decorative and protective packaging, and biological imaging.

[0010] Technical Solution

[0011] A photochromic material containing a pyridine derivative triarylethene, characterized by the general molecular structure formula:

[0012]

[0013] Wherein, R0 is a pyridine ring or a derivative thereof, R1 and R2 are the same or different and are selected from an aromatic ring, an aromatic heterocycle or a derivative thereof.

[0014] The R0 is selected from the following structures:

[0015]

[0016] Wherein, R3, R4, R5, and R6 are the same or different and are selected from hydrogen, alkyl, halogen, alkoxy, nitro, carboxyl, amino, aldehyde, or cyano.

[0017] The R1 and R2 are selected from the following structures:

[0018]

[0019] Among them: R7, R8, R9, R 10 、R 11 are the same or different and are selected from hydrogen, alkyl, halogen, alkoxy, nitro, carboxyl, amino, aldehyde or cyano.

[0020] A method for synthesizing the aforementioned photochromic material containing a pyridine derivative triarylethene, characterized by:

[0021] Synthesis Method 1: A pyridine ring or its derivative containing a formaldehyde substituent at one end is subjected to a Corey-Funchs reaction to synthesize its dibromosubstituted product; this is then reacted with an aromatic compound or heterocyclic compound containing a boronic acid or pinacol borate group through a Suzuki reaction to obtain a triarylethylene-based photochromic material containing a pyridine derivative;

[0022] Synthesis method 2: A benzophenone derivative is reacted with a pyridine ring containing a diethyl phosphate group or its derivative to obtain a pyridine derivative-containing triarylethylene photochromic material through a Wittig reaction.

[0023] The steps of the synthesis method 1 are as follows: ① reacting a pyridine ring or a derivative thereof containing a formaldehyde substituent at one end with triphenylphosphine and carbon tetrabromide in a dichloromethane solution at room temperature to obtain a dibromosubstituted product; ② reacting the obtained dibromosubstituted product with an aromatic compound or a heterocyclic compound containing a boric acid or pinacol borate group in a tetrahydrofuran solution in the presence of potassium carbonate and with a catalytic amount of tetrakistriphenylphosphine palladium to obtain a photochromic material containing a triarylethylene containing a pyridine derivative.

[0024] In the synthesis step 1, the pyridine ring containing a formaldehyde substituent or its derivative is 1 equivalent, triphenylphosphine is 4-5 equivalents, and carbon tetrabromide is 2-2.5 equivalents; in step 2, the dibromo substituent is 1 equivalent, and potassium carbonate is 2.5-3 equivalents.

[0025] The synthesis method 2 comprises the following steps: reacting 1-1.5 equivalents of a benzophenone derivative with 1 equivalent of a pyridine ring containing a diethyl phosphate group or a derivative thereof in a tetrahydrofuran solution in the presence of 3-3.5 equivalents of potassium tert-butoxide to obtain a pyridine derivative-containing triarylethylene photochromic material through a Wittig reaction.

[0026] In the synthesis method 2, the benzophenone derivative is 1-1.5 equivalents, the pyridine ring containing a diethyl phosphate group or its derivative is 1 equivalent, and potassium tert-butoxide is 3-3.5 equivalents.

[0027] An application of the pyridine derivative-containing triarylethene photochromic material is characterized by being used in pH testing products, optical switch products, information storage products, encryption and anti-counterfeiting products, decorative and protective packaging products or biological imaging products.

[0028] Beneficial effects

[0029] The present invention provides a pyridine derivative-containing triarylethylene photochromic material and a preparation and application method thereof. The pyridine ring or its derivative containing a formaldehyde substituent at one end is subjected to a Corey-Funchs reaction to synthesize its dibromosubstituted product; the dibromosubstituted product is then reacted with an aromatic compound or heterocyclic compound containing a boric acid or pinacol borate group through a Suzuki reaction; or a benzophenone derivative is reacted with a pyridine ring or its derivative containing a diethyl phosphate group through a Wittig reaction to obtain the pyridine derivative-containing triarylethylene photochromic material.

[0030] The present invention introduces pyridine derivatives into triarylethenes photochromic materials. Since pyridine is an important six-membered heterocyclic ring, the lone pair of electrons on the nitrogen atom in the pyridine ring does not participate in forming the conjugated system on the ring, resulting in weak alkalinity and the ability to bind to protons to produce a certain response. This creates a new triarylethene photochromic material with dual light / proton response, resolving the technical issue of the single stimulus responsiveness of existing triarylethene photochromic materials. Furthermore, this series of materials expands the color change range to red and purple, resolving the technical issue of the narrow color change range of existing triarylethene photochromics.

[0031] The raw materials required to prepare the target photochromic material of the present invention are inexpensive, and the synthesis process is simple and easy. The resulting photochromic material exhibits advantages such as dual light / proton response, high color purity, a wide color change wavelength range, and long-lasting color change. This expands the previously single stimulus-responsive triarylethene-based photochromic material to a dual light / proton responsive photochromic material, extending the color change range from orange to red and purple. The present invention is suitable for use in the production of pH testing, optical switches, optical information storage, encryption and anti-counterfeiting, decorative and protective packaging, and bioimaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Comparison pictures of the bulk crystals of the final product of Example 1 of the present invention before and after protonation and before and after photochromism, and comparison charts of their UV-visible reflectance spectra. Before protonation, the crystal on the left appears colorless before photochromism, and the crystal on the right turns red after photochromism. After protonation, the crystal on the left appears colorless before photochromism, and the crystal on the right turns orange after photochromism.

[0033] Figure 2 Comparison images of the bulk crystals of the final product of Example 2 of the present invention before and after protonation and before and after photochromism, as well as comparison images of their UV-visible reflectance spectra. The crystals themselves do not have photochromic properties before protonation. The crystals on the left after protonation appear colorless before photochromism, while the crystals on the right turn purple after photochromism.

[0034] Figure 3 These are photos of crystal luminescence and color change of the final product of Examples 2-6 of the present invention before and after protonation and deprotonation. DETAILED DESCRIPTION

[0035] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0036] The molecular structure of the triarylethene-based photochromic material containing a pyridine derivative of the present invention is shown in general formula (1):

[0037] General formula (1):

[0038]

[0039] Wherein, R0 is a pyridine ring or a derivative thereof, R1 and R2 are the same or different and are selected from an aromatic ring, an aromatic heterocycle or a derivative thereof.

[0040] Preferably, the R0 is selected from the following structures:

[0041]

[0042] Wherein, R3, R4, R5, and R6 are the same or different and are selected from hydrogen, alkyl, halogen, alkoxy, nitro, carboxyl, amino, aldehyde, or cyano.

[0043] Preferably, R1 and R2 are selected from the following structures:

[0044]

[0045] Among them: R7, R8, R9, R 10 、R 11 are the same or different and are selected from hydrogen, alkyl, halogen, alkoxy, nitro, carboxyl, amino, aldehyde or cyano.

[0046] The synthesis method of the above-mentioned photochromic material containing a pyridine derivative triarylethene comprises the following steps:

[0047] Method (1): A pyridine ring or a derivative thereof containing a formaldehyde substituent at one end is subjected to a Corey-Funchs reaction to synthesize a dibromosubstituted product thereof; and then a target product is obtained by a Suzuki reaction with an aromatic compound or heterocyclic compound containing a boronic acid or pinacol borate group. Preferably, the method (1) comprises the following sequential steps: ① providing a pyridine ring or a derivative thereof containing a formaldehyde substituent at one end (1 equivalent), reacting the pyridine ring or a derivative thereof (1 equivalent) at one end in an appropriate amount of dichloromethane solution under the action of triphenylphosphine (4-5 equivalents) and carbon tetrabromide (2-2.5 equivalents) at room temperature to obtain a dibromosubstituted product thereof; ② reacting the obtained dibromosubstituted product (1 equivalent) with an aromatic compound or heterocyclic compound containing a boronic acid or pinacol borate group (2.5-3 equivalents) in an appropriate amount of tetrahydrofuran solution under the action of potassium carbonate (2.5-3 equivalents) with a catalytic amount of tetrakistriphenylphosphine palladium to obtain the target product.

[0048] Method (2): A benzophenone derivative is reacted with a pyridine ring containing a diethyl phosphate group or a derivative thereof through a Wittig reaction to obtain a target product. Preferably, method (2) comprises the following sequential steps: providing a benzophenone derivative (1-1.5 equivalents) and a pyridine ring containing a diethyl phosphate group or a derivative thereof (1 equivalent), and in an appropriate amount of tetrahydrofuran solution, in the presence of potassium tert-butoxide (3-3.5 equivalents), performing a Wittig reaction to obtain the target product.

[0049] The above-mentioned photochromic materials containing pyridine derivatives and triarylethenes can be used to prepare pH testing products, optical switch products, information storage products, encryption and anti-counterfeiting products, decorative and protective packaging products or biological imaging products.

[0050] The present invention is further described below by using specific examples, but the present invention is not limited to these specific examples.

[0051] Example 1:

[0052] (1) Synthesis of the intermediate [2-bromo-5-(bromomethyl)pyridine]

[0053]

[0054] Under an argon atmosphere, N-bromosuccinimide (5.69 g, 31.97 mmol) was added to a 250 mL dry two-necked flask. 50 mL of carbon tetrachloride solution was added and mixed thoroughly with a magnetic stirrer. 2-Bromo-5-methylpyridine (5.00 g, 29.07 mmol) was then added, followed by the initiator benzoyl peroxide (0.35 g, 1.45 mmol). The mixture was heated to 85°C and refluxed overnight. After completion of the reaction, the reaction solution was filtered, and the filtrate was distilled off the solvent under reduced pressure on a rotary evaporator. The product was then purified by silica gel column chromatography using a mixture of n-hexane and ethyl acetate in a 10:1 volume ratio as the eluent. The product was obtained as a white solid powder (2.87 g) with a yield of 39.35%.

[0055] (2) Synthesis of target product Example 1

[0056]

[0057] Under an argon atmosphere, 2-bromo-5-(bromomethyl)pyridine (1.00 g, 3.99 mmol) was added to a 250 mL dry two-necked flask, followed by triethyl phosphite (0.73 g, 4.38 mmol). The mixture was heated to 85°C on a magnetic stirrer and allowed to react for 6 hours before cooling to room temperature to yield the ylide reagent, diethyl (6-bromopyridin-3-ylmethyl)phosphonate. An appropriate amount of tetrahydrofuran solution was then added to the flask, followed by benzophenone (0.80 g, 4.39 mmol) in an ice-water bath. Once the benzophenone was completely dissolved, potassium tert-butoxide (1.34 g, 11.98 mmol) was slowly added. The reaction was stirred at room temperature for 3 hours before terminating. The tetrahydrofuran was removed from the reaction solution by vacuum distillation, followed by extraction with dichloromethane and washing with saturated brine. The organic layer was dried over anhydrous sodium sulfate, filtered to obtain a clear, transparent solution, and the solvent was removed on a rotary evaporator. Finally, the product was purified by silica gel column chromatography, with the eluent being a mixed solution of n-hexane and ethyl acetate in a volume ratio of 20:1. The obtained product was recrystallized from dichloromethane / n-hexane to obtain 0.31 g of blocky transparent crystals with a yield of 23.10%.

[0058] The final product of this example has photochromic properties in its initial state. Under irradiation with a 380nm LED ultraviolet light source, the white crystals quickly turn red. After protonation (fumigation with concentrated hydrochloric acid for 2 hours), the photochromic properties change compared to before. Under irradiation with a 380nm LED ultraviolet light source, the white crystals turn orange. Comparison photos before and after protonation and before and after photochromism and the measured UV-visible reflectance spectra are shown. Figure 1 shown.

[0059] Example 2:

[0060] (1) Synthesis of the intermediate [2-fluoro-5-(bromomethyl)pyridine]

[0061]

[0062] Under an argon atmosphere, N-bromosuccinimide (2.32 g, 13.00 mmol) was added to a 250 mL dry two-necked flask. 30 mL of carbon tetrachloride solution was added and mixed thoroughly with a magnetic stirrer. 2-Fluoro-5-methylpyridine (1.44 g, 13.00 mmol) was then added, followed by the initiator benzoyl peroxide (0.16 g, 0.65 mmol). The mixture was heated to 85°C and refluxed overnight. After completion of the reaction, the reaction solution was filtered, and the filtrate was distilled off the solvent under reduced pressure on a rotary evaporator. The product was then purified by silica gel column chromatography using a mixture of n-hexane and ethyl acetate in a 10:1 volume ratio as the eluent. The product was obtained as a yellow oily liquid (0.96 g) with a yield of 38.86%.

[0063] (2) Synthesis of target product Example 2

[0064]

[0065] Under an argon atmosphere, 2-fluoro-5-(bromomethyl)pyridine (1.00 g, 5.26 mmol) was added to a 250 mL dry two-necked flask, followed by triethyl phosphite (0.96 g, 5.79 mmol). The mixture was heated to 85°C on a magnetic stirrer and allowed to react for 6 hours before cooling to room temperature to yield the ylide reagent, diethyl (6-fluoropyridin-3-ylmethyl)phosphonate. An appropriate amount of tetrahydrofuran solution was then added to the flask, followed by benzophenone (1.05 g, 5.78 mmol) in an ice-water bath. Once the benzophenone was completely dissolved, potassium tert-butoxide (1.77 g, 15.78 mmol) was slowly added. The reaction was stirred at room temperature for 3 hours before terminating. The tetrahydrofuran was removed from the reaction solution by vacuum distillation, followed by extraction with dichloromethane and washing with saturated brine. The organic layer was dried over anhydrous sodium sulfate, filtered to obtain a clear, transparent solution, and the solvent was removed on a rotary evaporator. Finally, the product was purified by silica gel column chromatography, with the eluent being a mixed solution of n-hexane and ethyl acetate in a volume ratio of 20:1. The obtained product was recrystallized from dichloromethane / n-hexane to obtain 0.42 g of blocky transparent crystals with a yield of 29.01%.

[0066] The final product of this example has basically no photochromic properties in its initial state, but after protonation (fumigation with concentrated hydrochloric acid for 2 hours), it has photochromic properties. Under irradiation with a 380nm LED ultraviolet light source, the white crystals quickly turn purple. Comparison photos before and after protonation and before and after photochromism and the measured UV-visible reflectance spectra are as follows: Figure 2 shown.

[0067] Example 3:

[0068]

[0069] Referring to step (2) of Example 2, 4,4′-difluorobenzophenone was used to synthesize the target product Example 3 instead of benzophenone with a yield of 31.24%.

[0070] Example 4:

[0071]

[0072] Referring to step (2) of Example 2, 4,4′-dichlorobenzophenone was used to synthesize the target product Example 4 instead of benzophenone with a yield of 21.01%.

[0073] Example 5:

[0074]

[0075] Referring to step (2) of Example 2, 4,4′-dibromobenzophenone was used to synthesize the target product Example 5 instead of benzophenone with a yield of 34.20%.

[0076] Example 6:

[0077]

[0078] Referring to step (2) of Example 2, 4,4′-dimethoxybenzophenone was used to synthesize the target product Example 6 instead of benzophenone with a yield of 25.33%.

[0079] The crystal luminescence and color change photos of the final products of Examples 2-6 of the present invention before and after protonation and deprotonation are as follows: Figure 3 shown.

[0080] Table 1 Changes in emission wavelength of the final products of Examples 2-6 before and after protonation and deprotonation

[0081]

[0082] Note: The emission spectrum of the solid is measured by an Ocean Optics QE65PRO spectrometer with an Ocean Optics R600-125F reflection probe.

[0083] As can be readily seen in Table 1 above, in prior literature reports, the emission wavelengths of prepared triarylethenes-based photochromic materials do not significantly change before and after protonation and deprotonation, demonstrating a lack of responsiveness to acid or base stimuli, thus exhibiting a single response characteristic, responsive only to light. In contrast to these previous studies, the final products of Examples 2-6 exhibit varying degrees of wavelength shift in their emission wavelengths before and after protonation and deprotonation, demonstrating the dual responsiveness of triarylethenes-based photochromic materials containing pyridine derivatives to both light and protons.

[0084] In summary, the present invention relates to a photochromic material containing a pyridine derivative triarylethene, which exhibits advantages such as dual light / proton response, high color purity, rapid color change response, and long-lasting color change. It can be used in the manufacture of pH testing products, optical switches, information storage products, encrypted anti-counterfeiting products, decorative and protective packaging products, or bioimaging products. Based on the above, those skilled in the art may make various corresponding modifications and variations based on the technical solutions and concepts of the present invention, and all such modifications and variations are intended to fall within the scope of protection of the claims of the present invention.

Claims

1. A photochromic material containing a pyridine derivative triarylethene, characterized in that: Selected from the following molecular structures: 、 、 、 、 。 2. A method for synthesizing the photochromic material containing a pyridine derivative triarylethene according to claim 1, characterized in that: Synthesis method 1: A pyridine ring derivative containing a formaldehyde substituent at one end is synthesized into its dibromosubstituted derivative through the Corey-Funchs reaction; Then, the pyridine derivative-containing triarylethylene photochromic material is obtained by Suzuki reaction with an aromatic compound containing boric acid or pinacol borate group; Synthesis method 2: A benzophenone derivative is reacted with a pyridine ring derivative containing a diethyl phosphate group to obtain a pyridine derivative-containing triarylethylene photochromic material through a Wittig reaction.

3. The method according to claim 2, wherein: The steps of the synthetic method 1 are as follows: ① reacting a pyridine ring derivative containing a formaldehyde substituent at one end with triphenylphosphine and carbon tetrabromide in a dichloromethane solution at room temperature to obtain a dibromosubstituted product; ② reacting the obtained dibromosubstituted product with an aromatic compound containing boric acid or pinacol borate in a tetrahydrofuran solution in the presence of potassium carbonate and with a catalytic amount of tetrakistriphenylphosphine palladium to obtain a photochromic material containing a triarylethylene containing a pyridine derivative.

4. The method according to claim 3, wherein: In the synthesis step 1, the pyridine ring derivative containing a formaldehyde substituent is 1 equivalent, triphenylphosphine is 4-5 equivalents, and carbon tetrabromide is 2-2.5 equivalents; in step 2, the dibromo substituent is 1 equivalent, and potassium carbonate is 2.5-3 equivalents.

5. The method according to claim 2, wherein: The synthesis method 2 comprises the following steps: reacting 1-1.5 equivalents of a benzophenone derivative with 1 equivalent of a pyridine ring derivative containing a diethyl phosphate group in a tetrahydrofuran solution in the presence of 3-3.5 equivalents of potassium tert-butoxide to obtain a pyridine derivative-containing triarylethylene photochromic material through a Wittig reaction.

6. The method according to claim 5, characterized in that: In the synthesis method 2, the benzophenone derivative is 1-1.5 equivalents, the pyridine ring derivative containing a diethyl phosphate group is 1 equivalent, and potassium tert-butoxide is 3-3.5 equivalents.

7. Use of the photochromic material containing a pyridine derivative triarylethene according to claim 1, characterized in that: Used in pH testing products, optical switch products, information storage products, encryption and anti-counterfeiting products, decorative and protective packaging products or biological imaging products.

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