A lipoic acid ester containing a benzotriazole structure and a preparation method and application thereof

Abstract

The application discloses a lipoic acid ester containing a benzotriazole structure and a preparation method and application thereof. On the basis of retaining excellent photoconversion capacity of a benzotriazole system, the dynamic disulfide ring structure of lipoic acid is introduced, so that the photo-functional molecule has polymerizable and covalent bonding capacity with a substrate, the technical problems of easy migration and easy loss of a traditional small-molecule photo-functional agent are solved, photo-degradation failure is effectively reduced, and the long-term stability and service life of the material are significantly improved. The compound has excellent stability, anti-migration and processability, and is suitable for fields of photo-functional materials, stabilization systems and functional polymers.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a thioclate containing a benzotriazole structure, its preparation method, and its application. Background Technology

[0002] Benzotriazole compounds possess excellent UV absorption and photostability, and are widely used in light stabilizers, photofunctional materials, and organic electronic materials. Currently, most benzotriazole photofunctional materials are small-molecule compounds. While they exhibit good UV protection, they suffer from significant drawbacks in practical applications: small molecules are prone to migration, volatilization, or solvent extraction within the material matrix, and are susceptible to photodegradation during long-term service, leading to a decline in photostability and failing to meet the stringent requirements for long-term stability and anti-migration properties in high-end materials.

[0003] To address the problem of small molecule migration, existing technologies often employ methods such as polymer grafting, blending modification, and encapsulation. For example, grafting benzotriazole groups onto polymer chains such as acrylic resins and polyurethanes can inhibit migration to some extent, but the grafting reaction conditions are harsh, the cost is high, and it easily damages the optical activity of benzotriazole. Physical blending is a simple process, but the small molecules have poor compatibility with the matrix, and there is still a risk of migration in the long term. Encapsulation, on the other hand, has problems such as easy damage to the coating layer and affecting the light transmittance of the material, which limits its versatility.

[0004] Lipoic acid is a naturally occurring dithiocarboxylic acid containing a 1,2-disulfide five-membered ring structure. The disulfide bond exhibits dynamic and reversible properties: under conditions of heat, light, or reducing agents, it can open to form a thiol group. This thiol group can participate in free radical polymerization, addition reactions, or covalently bind to metals or substrate materials containing double bonds / epoxy groups. Furthermore, it can close the ring again after opening, endowing materials with self-healing and reconfigurable properties. Currently, lipoic acid and its derivatives have shown great application potential in self-healing materials, biomedical materials, and dynamic covalent polymers. However, there are no reports of combining lipoic acid with benzotriazole-based photofunctional molecules to construct functional molecules that combine UV protection, anti-migration, and polymerizability.

[0005] In summary, current technologies lack a benzotriazole derivative that is structurally simple, easy to prepare, and possesses both excellent optical properties and polymerizable immobilization capabilities. This makes it difficult to simultaneously address the issues of easy migration and poor stability of small-molecule photofunctional molecules, and also hinders its adaptability to various application scenarios, including photofunctional materials, stabilization systems, and functional polymers. Therefore, developing a compound that organically combines the optical properties of benzotriazole with the dynamic polymerizability of lipoic acid has significant theoretical and practical value. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems and provide a thioctic ester containing a benzotriazole structure, its preparation method, and its application. This invention introduces thioctic acid groups into the photofunctional structure of benzotriazole, enabling the photofunctional molecule to possess polymerizability and dynamic covalent bonding capabilities, thus achieving stable immobilization in the material system and significantly improving the long-term stability and service life of the material.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] The first aspect of this invention provides a thioclate containing a benzotriazole structure, wherein the structural formula of the thioclate containing the benzotriazole structure is as follows:

[0009] Where R is methyl or isobutyl.

[0010] The benzotriazole-containing thioctic acid ester provided by this invention is a functional molecule formed by linking a benzotriazole derivative to a thioctic acid molecule via an ester bond through an alkyl chain. This molecular structure retains the excellent optical properties of the benzotriazole system while introducing the disulfide ring structure of thioctic acid; its disulfide bonds can undergo further polymerization via ring-opening reactions or covalently bond with a substrate material, thereby achieving stable immobilization of the photofunctional molecule in the material system. Compared to existing technologies, the compounds of this invention possess excellent stability, anti-migration properties, and processability, making them suitable for applications in photofunctional materials, stabilization systems, and functional polymers.

[0011] A second aspect of this invention provides a method for preparing the thioctic ester containing the benzotriazole structure described in the first aspect, comprising the following steps:

[0012] (1) 4,7-dihalobenzotriazole was reacted with haloalkylcarboxylic acid esters in the presence of base and organic solvents to carry out a bimolecular nucleophilic substitution reaction, and the N-substituted benzotriazole derivative was obtained by post-treatment purification.

[0013] (2) The N-substituted benzotriazole derivative was subjected to a Suzuki coupling reaction with arylboronic acid in the presence of a palladium catalyst, a first base and a solvent, and the intermediate product was obtained after post-treatment purification; the intermediate product was subjected to a hydrolysis reaction in the presence of a second base and an organic solvent, and the hydroxyl-containing benzotriazole derivative was obtained after post-treatment.

[0014] (3) The hydroxyl-containing benzotriazole derivative is subjected to esterification reaction with thioctic acid in the presence of condensing agent, catalyst and organic solvent, and the thioctic ester containing benzotriazole structure is obtained by post-treatment purification.

[0015] Further, in step (1), the 4,7-dihalobenzotriazole is 4,7-dibromobenzotriazole, and the haloalkylcarboxylic acid ester is 4-iodobutylacetic acid ester.

[0016] Further, in step (1), the base is potassium carbonate, and the molar ratio of the base to 4,7-dihalobenzotriazole is (3-5):1.

[0017] Further, in step (1), the organic solvent is N,N-dimethylformamide.

[0018] Furthermore, in step (1), the temperature of the bimolecular nucleophilic substitution reaction is 50-70 °C and the time is 10-14 h.

[0019] Further, in step (1), the post-processing purification is carried out by column chromatography, and the eluent is a mixed solvent of ethyl acetate and petroleum ether, wherein the volume ratio of ethyl acetate to petroleum ether is 1:(40-60).

[0020] Further, in step (2), the arylboronic acid is p-methylphenylboronic acid or p-isobutylphenylboronic acid, and the molar ratio of the arylboronic acid to the N-substituted benzotriazole derivative is (2.0-2.4):1.

[0021] Further, in step (2), the first base is potassium carbonate, and the molar ratio of the first base to the N-substituted benzotriazole derivative is (2.5-3.5):1.

[0022] Further, in step (2), the palladium catalyst is tetra(triphenylphosphine)palladium, and the molar ratio of the palladium catalyst to the N-substituted benzotriazole derivative is (0.0008-0.0012):1.

[0023] Further, in step (2), the solvent is a mixed solvent of 1,4-dioxane and water, and the volume ratio of 1,4-dioxane to water is (2-4):1.

[0024] Furthermore, in step (2), the temperature of the Suzuki coupling reaction is 80-90 °C and the time is 24-36 h.

[0025] Furthermore, in step (2), the organic solvent is methanol.

[0026] Further, in step (2), the second base is potassium hydroxide, and the molar ratio of the second base to the intermediate product is (1-2):1.

[0027] Furthermore, in step (2), the hydrolysis reaction is carried out at a temperature of 15-30 °C for 4-8 h.

[0028] Further, in step (3), the molar ratio of the hydroxyl-containing benzotriazole derivative to thioctic acid is 1:(1-1.5).

[0029] Further, in step (3), the condensing agent is dicyclohexylcarbodiimide, and the molar ratio of the condensing agent to the hydroxyl-containing benzotriazole derivative is (1.5-2.5):1; the catalyst is 4-dimethylaminopyridine, and the molar ratio of the catalyst to the hydroxyl-containing benzotriazole derivative is (0.05-0.2):1.

[0030] Further, in step (3), the organic solvent is dichloromethane.

[0031] Furthermore, in step (3), the esterification reaction is carried out at a temperature of 45-55 °C for 20-28 h.

[0032] The third aspect of this invention provides the application of the thioctic ester containing the benzotriazole structure described in the first aspect in the preparation of photofunctional materials.

[0033] The thioctic acid ester containing a benzotriazole structure provided by this invention can be directly added as a light stabilizer to various polymer materials. It can also be used to prepare functional polymers with a benzotriazole structure in the main chain or side chain through polymerization reaction. It can also be used in the fields of anti-corrosion coatings for metal surfaces and organic light-emitting diode packaging materials, and has broad market application prospects.

[0034] Specifically, the compounds of this invention can replace traditional small-molecule light conversion aids in the preparation of light conversion functional film materials. Utilizing the dynamic covalent bonding and in-situ polymerization characteristics of the thioctic acid disulfide ring in the molecular structure, they can be covalently anchored to the film substrate, significantly improving the long-term stability of the functional film. After this functional film is bonded and assembled onto the surface of a solar cell module, it can achieve efficient conversion of incident ultraviolet light into visible light. This not only blocks the photo-aging damage of ultraviolet light to the photovoltaic encapsulation layer and cells, thus extending the lifespan of the solar panel, but also improves the photoelectric conversion efficiency of the photovoltaic device through spectral optimization, meeting the application requirements for long-term maintenance-free operation of solar panels.

[0035] The above-described technical solution of the present invention has the following beneficial effects:

[0036] 1. This invention, while retaining the excellent photoconversion capacity of the benzotriazole system, introduces the dynamic disulfide ring structure of lipoic acid, enabling photofunctional molecules to polymerize and covalently bond with the substrate. This solves the technical problems of easy migration and loss of traditional small molecule photofunctional agents, effectively reduces photodegradation failure, and significantly improves the long-term stability and service life of the material.

[0037] 2. The thioctic ester structure containing benzotriazole provided by this invention has strong designability, and the dynamic reversible ring-opening characteristics of its disulfide bond also endow the material system with self-healing and reconfigurable capabilities, further expanding its application space in the field of functional materials. Attached Figure Description

[0038] Figure 1 The 1H NMR spectrum of 4-(4,7-dibromo-2H-benzo[d][1,2,3]triazol-2-yl)butylacetate in Example 1 is shown.

[0039] Figure 2 The 1H NMR spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]but-1-ol in Example 1.

[0040] Figure 3 The 1H NMR spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate ester prepared in Example 1.

[0041] Figure 4 The UV-Vis absorption spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1 is shown.

[0042] Figure 5 The fluorescence emission spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1 is shown.

[0043] Figure 6 The fluorescence quantum yield spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1 is shown.

[0044] Figure 7 The images show the solidified sample and its UV-excited fluorescence effect in Example 2; where (a) is a solidified sample image and (b) is a UV-excited fluorescence effect image. Detailed Implementation

[0045] Unless otherwise defined, 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. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0047] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0048] Example 1

[0049] A method for preparing a thiooctanoic acid ester (4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate) containing a benzotriazole structure, comprising the following steps:

[0050] (1) Add 1 equivalent (eq) of 4,7-dibromobenzotriazole to a pear-shaped flask, using N,N-dimethylformamide (DMF) as the reaction solvent, and then add 4 eq of potassium carbonate; under stirring, add 1 eq of 4-iodobutylacetic acid dropwise to the system, heat to 60 ℃ and stir for 12 h. After the reaction is complete, cool to room temperature, quench the reaction with water, extract the reaction solution with ethyl acetate, combine the organic phases and dry and concentrate to obtain the crude product; the crude product is purified by column chromatography, using a 1:50 volume ratio of ethyl acetate / petroleum ether mixed solvent as the eluent to separate 4-(4,7-dibromo-2H-benzo[d][1,2,3]triazol-2-yl)butylacetic acid, with a reaction yield of 40%, and the 1H NMR spectrum is shown below. Figure 1 As shown; the reaction equation is as follows:

[0051] .

[0052] (2) 1 eq of 4-(4,7-dibromo-2H-benzo[d][1,2,3]triazol-2-yl)butyl acetate was added to a pear-shaped flask. A 1,4-dioxane / water mixed solvent (volume ratio 3:1) was used as the reaction medium. 2.2 eq of p-methylphenylboronic acid and 3 eq of potassium carbonate (K2CO3) were added. Then, 0.001 eq of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) was added as a catalyst. The mixture was heated to 85 °C and stirred for 30 h. After the reaction was completed, the mixture was cooled to room temperature, diluted with water, extracted with ethyl acetate, and the organic phases were combined, dried, and concentrated to obtain the crude product. The crude product was purified by column chromatography using a 1:5 volume ratio ethyl acetate / petroleum ether mixed solvent as the eluent to obtain the intermediate product.

[0053] 1 eq of the intermediate was added to a pear-shaped flask, and 1.8 eq of potassium hydroxide (KOH) was added as a base in methanol (MeOH). The mixture was stirred at room temperature (rt) for 6 h. After the reaction was completed, the mixture was cooled to room temperature, quenched with water, extracted with dichloromethane, the organic phases were combined, dried and concentrated to give 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]but-1-ol, with a yield of 96%. The 1H NMR spectrum is shown below. Figure 2 As shown; the reaction equation is as follows:

[0054] .

[0055] (3) Add 1 eq of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]but-1-ol to a pear-shaped flask, and add 1.2 eq of thioctic acid in dichloromethane as solvent; add 2 eq of dicyclohexylcarbodiimide (DCC) as condensing agent and 0.1 eq of 4-dimethylaminopyridine (DMAP) as catalyst in sequence while stirring, and heat to 50 °C and stir continuously for 24 h. After the reaction was completed and cooled to room temperature, the byproducts (such as dicyclohexylurea) were removed by filtration. The filtrate was concentrated and purified by column chromatography using a 1:5 (v / v) mixture of ethyl acetate and petroleum ether as eluent to give 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiacyclopentan-3-yl)valerate. The reaction yield was 88%. The 1H NMR spectrum is shown below. Figure 3 As shown; the reaction equation is as follows:

[0056] .

[0057] According to UV-Vis absorption and fluorescence spectroscopy tests, the maximum UV absorption wavelength of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1 was 340 nm. Figure 4 As shown; the maximum fluorescence emission wavelength is 420 nm, as... Figure 5 As shown, 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate can efficiently absorb ultraviolet light and dissipate energy, thus exhibiting excellent ultraviolet protection performance.

[0058] The fluorescence quantum yield spectrum of 4-[4,7-bis(4-methylphenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1 is shown in the figure. Figure 6 As shown, the compound of this invention exhibits an absolute fluorescence quantum yield of 31.9% as measured by the integrating sphere method, corresponding to an excitation wavelength of 339.26 nm, which matches the maximum absorption wavelength of 340 nm in the UV-Vis absorption spectrum. This high fluorescence quantum yield indicates that the molecule can efficiently release absorbed UV light energy in fluorescence form, achieving energy dissipation and possessing both excellent UV absorption and photostability. Furthermore, it demonstrates that the introduction of the dynamic structure of lipoic acid did not adversely affect the photofunctional framework of benzotriazole, thus fully preserving its optical protective properties while achieving molecular immobilization and anti-migration modification.

[0059] Comparative Example 1

[0060] Add 1 eq of 4,7-dibromobenzotriazole to a pear-shaped flask, using a 3:1 volume ratio of 1,4-dioxane / water mixed solvent as the reaction medium. Add 2.2 eq of p-methylphenylboronic acid and 3 eq of K2CO3; then add 0.001 eq of Pd(PPh3)4 as a catalyst. Heat to 85 °C and stir for 30 h. The expected reaction equation is as follows:

[0061] ;

[0062] After the reaction was completed, the product was diluted with water, extracted with organic solvent, concentrated, and purified by column chromatography. The target product, 4,7-bis(4-methylphenyl)-2H-benzotriazole, was not detected. A large amount of the starting material, 4,7-dibromobenzotriazole, remained, indicating that the expected Suzuki coupling reaction did not occur.

[0063] Example 2

[0064] Weigh 0.1 g of 4-[4,7-bis(4-methyl-phenyl)-2H-benzo[d][1,2,3]triazol-2-yl]butyl-5-(1,2-dithiocyclopentan-3-yl)valerate prepared in Example 1, and place it in a brown threaded sample vial. Add 9.9 g of aliphatic polyurethane acrylate UV matrix adhesive and 0.2 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) photoinitiator sequentially while stirring, and stir in the dark until completely dissolved. Coat the mixture onto a glass slide with a wet film thickness of approximately 100 μm, using a 365 nm UV light source and 80 mW / cm². 2 Free radical copolymerization was completed by irradiation with light intensity for 180 s. The cured sample and its UV-excited fluorescence effect are as follows: Figure 7 As shown.

[0065] During the UV curing irradiation stage, the cyclic disulfide bonds in the thioctic acid side chain structure undergo homolytic ring-opening upon UV photon excitation, generating dithiol active sites. These thiol groups can then undergo thiol-olefin addition reactions with the acrylate double bonds in the UV matrix adhesive, enabling the photoconversion functional molecules to covalently integrate into the three-dimensional cross-linking network of the UV resin. This addresses the shortcomings of traditional small-molecule photofunctional additives, such as migration, precipitation, and blooming within the adhesive layer. The dynamic disulfide bonds that do not participate in the cross-linking reaction retain their reversible ring-opening and closing characteristics, allowing for repeated structural reconstruction under continuous UV irradiation and environmental temperature fluctuations during subsequent service, thus endowing the copolymer coating with excellent self-healing potential. Simultaneously, the thioctic acid structure participates only as a side chain unit in the cross-linking network construction, without disturbing the electron cloud distribution and energy level transition paths of the benzotriazole chromophore in the main molecular chain.

[0066] from Figure 7 As can be seen, after curing, the dynamic covalent structure of the thioctic acid side chain does not interfere with the optical energy level of the benzotriazole chromophore; the cured sample has a uniform morphology under natural light and can stably exhibit characteristic fluorescence emission after ultraviolet light excitation, proving that the cured composite coating still has stable ultraviolet absorption and fluorescence emission performance.

[0067] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A thioclate containing a benzotriazole structure, characterized in that, The structural formula of the thioclate ester containing the benzotriazole structure is as follows: Where R is methyl or isobutyl.

2. A method for preparing thiooctanoic acid ester containing a benzotriazole structure as described in claim 1, characterized in that, Includes the following steps: (1) 4,7-dihalobenzotriazole was reacted with haloalkylcarboxylic acid esters in the presence of base and organic solvents to carry out a bimolecular nucleophilic substitution reaction, and the N-substituted benzotriazole derivative was obtained by post-treatment purification. (2) The N-substituted benzotriazole derivative was subjected to a Suzuki coupling reaction with arylboronic acid in the presence of a palladium catalyst, a first base and a solvent, and the intermediate product was obtained by post-treatment purification; the intermediate product was subjected to a hydrolysis reaction in the presence of a second base and an organic solvent, and the hydroxyl-containing benzotriazole derivative was obtained by post-treatment. (3) The hydroxyl-containing benzotriazole derivative is subjected to esterification reaction with thioctic acid in the presence of condensing agent, catalyst and organic solvent, and the thioctic ester containing benzotriazole structure is obtained by post-treatment purification.

3. The preparation method according to claim 2, characterized in that, In step (1), the 4,7-dihalobenzotriazole is 4,7-dibromobenzotriazole, the haloalkylcarboxylic acid ester is 4-iodobutylacetic acid ester; the base is potassium carbonate, and the molar ratio of the base to 4,7-dihalobenzotriazole is (3-5):

1.

4. The preparation method according to claim 2, characterized in that, In step (1), the temperature of the bimolecular nucleophilic substitution reaction is 50-70 °C and the time is 10-14 h.

5. The preparation method according to claim 2, characterized in that, In step (2), the arylboronic acid is p-methylphenylboronic acid or p-isobutylphenylboronic acid, and the molar ratio of the arylboronic acid to the N-substituted benzotriazole derivative is (2.0-2.4):1; the first base is potassium carbonate, and the molar ratio of the first base to the N-substituted benzotriazole derivative is (2.5-3.5):1; the palladium catalyst is tetrakis(triphenylphosphine)palladium, and the molar ratio of the palladium catalyst to the N-substituted benzotriazole derivative is (0.0008-0.0012):

1.

6. The preparation method according to claim 2, characterized in that, In step (2), the solvent is a mixed solvent of 1,4-dioxane and water, and the volume ratio of 1,4-dioxane to water is (2-4):1; the temperature of the Suzuki coupling reaction is 80-90 °C and the time is 24-36 h.

7. The preparation method according to claim 2, characterized in that, In step (2), the organic solvent is methanol; the second base is potassium hydroxide; the hydrolysis reaction is carried out at a temperature of 15-30 °C for 4-8 h.

8. The preparation method according to claim 2, characterized in that, In step (3), the condensing agent is dicyclohexylcarbodiimide, the catalyst is 4-dimethylaminopyridine, and the organic solvent is dichloromethane.

9. The preparation method according to claim 2, characterized in that, In step (3), the esterification reaction is carried out at a temperature of 45-55 °C for 20-28 h.

10. The use of the thioctic ester containing the benzotriazole structure as described in claim 1 in the preparation of photofunctional materials.

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