A photochromic and photo-thermal conversion bifunctional compound and a preparation method and application thereof

Abstract

This invention relates to the field of functional color-changing materials, and particularly to a bifunctional compound combining photochromism and photothermal conversion, its preparation method, and its applications. The preparation method involves reacting 2-acetyl-6-bromopyridine under alkaline conditions with anhydrous ethanol as a solvent via an aldol condensation reaction to obtain an intermediate; then, under the action of ammonia, a Hantzsch cyclization tandem reaction occurs to yield a symmetrical tris(2-bromopyridyl)methane-substituted 1,4-dihydropyridine product. This invention is the first to combine high-contrast yellow-to-blue photochromism with efficient photothermal conversion performance, overcoming the limitations of traditional materials with single functions. The preparation method of this invention is simple, mild, and has a high yield, making it suitable for large-scale production. The compound of this invention can be used in high-end anti-counterfeiting labeling, photothermal antibacterial, and photothermal actuation fields, and has unique advantages, especially in smart coatings and sensor detection.

Description

Technical Field

[0001] This invention relates to the field of functional color-changing materials technology, and in particular to a bifunctional compound that combines photochromism and photothermal conversion, its preparation method, and its applications. Background Technology

[0002] Photochromic materials are a class of smart materials whose molecular structure undergoes reversible changes under light of a certain wavelength, resulting in a color change. These materials have significant application value in fields such as optical information storage, anti-counterfeiting identification, smart windows, and sensors. Photochromic materials can be mainly divided into two categories based on their material type: organic and inorganic. Organic photochromic materials mainly include spiropyrans, diarylethylenes, azobenzenes, fumonisins, and spiroxazines, while inorganic materials include transition metal oxides, metal halides, and rare earth complexes. The color-changing ability of these organic photochromic materials stems from their unique photochemical reactions: Spiropyrans: Under ultraviolet light, the CO bonds in the molecule break, changing from colorless to colored; under visible light or heat, the ring closes again, restoring the colorless state. Azobenzenes: Under light or heat, the molecular structure can reversibly switch between cis and trans arrangements; these two structures have different colors, thus achieving color change. Diarylethylene: undergoes a reversible cyclization reaction under specific wavelengths of light, switching between open and closed ring states, resulting not only in color changes but also alterations to other physical properties such as electrical conductivity. However, photochromic materials based on pyridine derivatives have been rarely or never reported.

[0003] On the other hand, photothermal conversion materials can convert absorbed light energy into heat energy, and have received widespread attention in fields such as photothermal therapy, seawater desalination, and photothermal drive.

[0004] Currently, integrating photochromism and photothermal conversion properties into the same material system is a research hotspot in the field of functional materials. For example, Chinese Patent Publication No. CN106634942A discloses a composite material that uses the photothermal effect of gold nanoparticles to drive the color change of poly(diacetylene), but it involves multi-component composites and has the problem of complex preparation process.

[0005] Currently, there is a lack of a monomeric compound and its preparation method that is easy to synthesize, possesses specific color changes (from pale yellow to blue), and exhibits high efficiency in photothermal conversion. Based on this, the present invention develops a novel bifunctional compound. Summary of the Invention

[0006] This invention provides a bifunctional compound for photochromism and photothermal conversion, its preparation method, and its application, with the aim of solving the aforementioned problems in the background art.

[0007] To achieve the above objectives, embodiments of the present invention provide a bifunctional compound for photochromism and photothermal conversion, with the following structural formula: .

[0008] Preferably, the photochromic and photothermal conversion bifunctional compound is a light yellow solid powder.

[0009] Preferably, the photochromic and photothermal conversion bifunctional compound, when dissolved in a solution of dichloromethane, gradually changes from light yellow to blue under 365nm ultraviolet light irradiation.

[0010] Preferably, a new absorption peak appears at 625 nm in the absorption spectrum before and after irradiation with a 365 nm ultraviolet lamp.

[0011] The embodiments of the present invention also provide a method for preparing the above-mentioned photochromic and photothermal conversion bifunctional compound, the synthetic route of which is as follows: .

[0012] Preferably, the preparation method includes the following steps: 2-Acetyl-6-bromopyridine was subjected to an aldol condensation reaction under alkaline conditions with anhydrous ethanol as solvent to give an α,β-unsaturated ketone intermediate. Then, under the action of ammonia, a Hantzsch cyclization tandem reaction was carried out, and NH3 was reacted with the α,β-unsaturated ketone intermediate by Michael addition (ammonolysis), which subsequently initiated intramolecular cyclization to give a symmetrical tri(2-bromopyridyl)methane-substituted 1,4-dihydropyridine product.

[0013] Preferably, the alkali in the alkaline conditions is potassium hydroxide.

[0014] Preferably, the intermediate does not require separation and directly undergoes an ammonolysis-cyclization tandem reaction.

[0015] Preferably, the entire preparation process is carried out under normal pressure.

[0016] Preferably, the preparation method specifically includes the following steps: weigh 37.98 g of 2-acetyl-6-bromopyridine, add 175 mL of anhydrous ethanol and 16 g of potassium hydroxide, and stir magnetically for 14 h; then add 150 mL of ammonia water using a constant pressure dropping funnel, and react at 85 °C for 48 h. After the reaction is completed, filter to obtain a blocky solid, dissolve in dichloromethane, recrystallize with methanol, and filter to obtain the photochromic and photothermal conversion bifunctional compound.

[0017] Embodiments of the present invention also provide an application of a bifunctional compound for photochromic and photothermal conversion in photochromic materials.

[0018] Preferably, the photochromic and photothermal conversion bifunctional compound is applied in the field of high-end anti-counterfeiting labels.

[0019] Embodiments of the present invention also provide an application of a photochromic and photothermal conversion bifunctional compound in photothermal materials.

[0020] Preferably, the photochromic and photothermal conversion bifunctional compound is applied in the fields of photothermal antibacterial and photothermal driving. In particular, the photochromic and photothermal conversion bifunctional compound is applied in the fields of smart coating and sensing detection.

[0021] Reaction mechanism: The target compound of this invention is prepared via a one-pot aldol condensation-Hantzsch cyclization tandem reaction. Under KOH / EtOH conditions, 2-acetyl-6-bromopyridine undergoes intermolecular aldol condensation to generate an α,β-unsaturated ketone intermediate. Subsequently, ammonia is added, and NH3 undergoes Michael addition (ammonolysis) with the α,β-unsaturated ketone intermediate, initiating intramolecular cyclization to construct a symmetrical tris(2-bromopyridyl)-1,4-dihydropyridine skeleton. The entire reaction is carried out in one pot, eliminating the need for intermediate separation, thus reflecting the principle of synthetic economy. Furthermore, the bromine atom remains inert throughout the reaction, preserving the crucial heavy atom effect for the photothermal function of the final product. Moreover, the presence of the bromine atom not only serves as a chromophore modifying group, but its heavy atom effect is also the structural basis for the photothermal conversion properties of this compound.

[0022] The above-described solution of the present invention has the following beneficial effects: This invention is the first to combine high-contrast photochromic properties from yellow to blue with high-efficiency photothermal conversion properties, overcoming the limitations of traditional materials with single functions.

[0023] The preparation method of the present invention is simple, mild, and has a high yield. It avoids the use of high temperature and high pressure or precious metal catalysts, and is suitable for large-scale production.

[0024] The significant color-changing behavior of the compounds of this invention under ultraviolet light can be used for high-end anti-counterfeiting labels; their photothermal effect can be used in photothermal antibacterial, photothermal driving and other fields, and they have unique advantages in smart coating and sensing detection. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is the 1H NMR spectrum of the photochromic and photothermal bifunctional compound of the present invention. Figure 2 This is the mass spectrum of the photochromic and photothermal bifunctional compound according to an embodiment of the present invention; Figure 3 The UV-Vis absorption spectra of the photochromic and photothermal bifunctional compound of this invention dissolved in dichloromethane before and after irradiation by a 365nm UV lamp are shown. Figure 4 The diagram shows the changes of a solution of a photochromic and photothermal bifunctional compound dissolved in dichloromethane before and after irradiation with a 365nm ultraviolet lamp, as described in the embodiments of the present invention; (a) before UV irradiation, (b) after 10s of UV irradiation, and (c) after 10s of UV irradiation followed by 5s of rest. Figure 5 These are diagrams showing the changes of the photochromic and photothermal conversion bifunctional compound before and after UV irradiation according to embodiments of the present invention; (a) before UV irradiation, (b) after 10s of UV irradiation; Figure 6 These are the UV-Vis diffuse reflectance spectra of the photochromic and photothermal bifunctional compound before and after UV irradiation according to embodiments of the present invention. Figure 7 This is the ESR spectrum of the photochromic and photothermal bifunctional compound according to an embodiment of the present invention; Figure 8 This is a photothermal temperature rise curve of the photochromic and photothermal conversion bifunctional compound of this invention under 300W xenon lamp irradiation; wherein, line 1 is water sample, and line 2 is water and compound; Figure 9 The hydrogen nuclear magnetic resonance spectrum of the compound in Comparative Example 1 of this invention is shown. Figure 10 This is the UV-Vis diffuse reflectance spectrum of the compound in Comparative Example 1 of the present invention before and after UV irradiation; Figure 11 This is the UV-Vis diffuse reflectance spectrum of the compound in Comparative Example 2 of the present invention before and after UV irradiation. Detailed Implementation

[0027] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] This invention addresses existing problems by providing a bifunctional compound that combines photochromism and photothermal conversion, along with its preparation method and applications.

[0031] Example 1 This embodiment provides a method for preparing a bifunctional compound that exhibits both photochromic and photothermal conversion properties, comprising the following steps: Weigh 37.98 g of 2-acetyl-6-bromopyridine, add 175 mL of anhydrous ethanol and 16 g of potassium hydroxide, and stir magnetically for 14 h; then add 150 mL of ammonia water using a constant pressure dropping funnel, and react at 85 °C for 48 h. After the reaction is complete, filter to obtain a blocky solid, dissolve in dichloromethane, recrystallize with methanol, and filter to obtain 22 g of the target product, with a yield of 50%. The structural formula is: ; The proton NMR spectrum of the target product is as follows: Figure 1 As shown, the specific data representing the characteristics are as follows: 1 H NMR (500 MHz, CDCl3) δ 8.51 (s, 1H), 7.64 (d, J = 7.8 Hz, 2H), 7.53 (d, J = 15.6 Hz, 2H), 7.46(d, J = 15.4 Hz, 1H), 7.39 (d, J = 17.2 Hz, 3H), 7.25 (d, J = 7.8 Hz, 1H), 5.38 (s,2H), 1.69 (s, 3H). ESI-MS (561.88 calculated for C 21 H 15 Br3N4): m / z for [M + H + 563.15, calculated. 562.88, mass spectrum as shown. Figure 2 As shown.

[0032] Example 2 The photochromic performance of the bifunctional compound prepared in Example 1 was tested, specifically including the following steps: The photochromic and photothermal bifunctional compound prepared in Example 1 was dissolved in dichloromethane to prepare a solution with a concentration of 3*10. -5A solution of mol / L was prepared, and the absorption spectra before and after irradiation with a 365nm UV lamp were measured using a UV-Vis spectrophotometer. The results are as follows: Figure 3 As shown, a new absorption peak appears at 625 nm. Figure 4 As shown, the solution color changed from light yellow to blue before and after irradiation with a 365nm ultraviolet lamp, exhibiting a fast photochromic response and high-contrast photochromic behavior.

[0033] like Figure 5 As shown, the solid powder changed from yellow to blue upon UV irradiation, and the blue color was complete after 10 seconds of UV irradiation. Furthermore, a Shimadzu UV-3600 UV-Vis-NIR spectrophotometer with an integrating sphere attachment was used to perform solid-state UV-Vis DRS testing. Barium sulfate (BaSO4) was used as the reference substrate. 20 mg of the sample [the photochromic and photothermal bifunctional compound prepared in Example 1] powder was used, and the scanning wavelength range was 200-800 nm. The diffuse reflectance spectrum of the sample was collected at room temperature, and the results are shown below. Figure 6 As shown, after 30 seconds of irradiation with a 365nm ultraviolet lamp, the color of the solid powder changed from light yellow to blue, and when exposed to sunlight, the solid changed from light yellow to light green.

[0034] To investigate its photochromic mechanism, electron spin resonance (ESR) spectroscopy was performed on the target compound, and the results are as follows: Figure 7 As shown in the figure. The test results show that no ESR signal was detected in the magnetic field range of 34400-35800G before irradiation (0 min), confirming that the compound has a closed-shell structure in the initial state and does not have unpaired electrons. After irradiation with 365nm ultraviolet light for 5 min, a characteristic ESR signal appeared, and its spectral pattern was highly consistent with that of the nitrogen-centered free radical cation. After irradiation for 10 min, the signal intensity at the same position was significantly enhanced, indicating that the concentration of nitrogen cation free radicals accumulated with the extension of irradiation time. The above ESR evidence clearly shows that ultraviolet light induced a single electron transfer process within the molecule, generating a free radical cation intermediate with a nitrogen atom as the spin center.

[0035] Based on the ESR results and spectral changes (such as the appearance of a new absorption peak at 625 nm), the photochromic mechanism of the compounds in this invention can be summarized as follows: Under ultraviolet light excitation, the molecule undergoes charge separation, and a specific nitrogen atom loses an electron to form a nitrogen positron radical (the source of the ESR signal). The generation of this radical perturbs the electronic configuration of the dihydropyridine ring, thereby triggering a concerted aromatization rearrangement—originally disrupting the sp... 3 Hybrid carbon transforms into sp 2Hybridization occurs, leading to electron delocalization of the entire six-membered ring and the formation of an aromatic pyridine ring structure. This aromatization process significantly expands the conjugated system of the molecule, causing a red shift in the absorption spectrum and the appearance of a new absorption peak at 625 nm. Macroscopically, this manifests as a change in solution color from pale yellow / green to blue. In solution, upon removal of the light source, the free radicals reversibly gain electrons, restoring the aromatized structure to its initial state, achieving a reversible color change. However, in the solid state, due to the close packing of molecules and limited structural resilience, the color change is irreversible upon removal of the light source.

[0036] Although the ESR signal of the compounds in this invention also originates from free radicals, their color-changing mechanism is fundamentally different from that of typical viologen-based photochromic materials (such as the viologen free radical system reported by Liu Jingxin's team at Anhui University of Technology). In viologen-based materials, free radicals are the stable end products of the color-changing process, and their skeletons themselves do not undergo covalent bond recombination; while the nitrogen-positive ion free radicals in this invention are merely transient intermediates in the aromatization process, and the final color-changing product is a closed-shell aromatized molecule, which does not involve free radical end products. Therefore, the color-changing mechanism of the compounds in this invention belongs to "free radical-mediated aromatization," rather than the "free radical-type photochromism" of viologen-based materials.

[0037] Furthermore, this compound exhibits excellent photothermal conversion properties, primarily due to the heavy atom effect of multiple bromine atoms in the molecule. This effect significantly enhances intersystem crossing efficiency, allowing some excited-state energy to dissipate as heat through nonradiative transitions, thus achieving synergistic coexistence with the photochromic process.

[0038] Example 3 The photochromic and photothermal conversion bifunctional compound prepared in Example 1 was uniformly dispersed in an aqueous phase and placed under 300W xenon lamp irradiation. Temperature changes were monitored using a thermocouple temperature tester. The specific process is as follows: (1) Preparation of drug-loaded microspheres Weigh 25 mg of the photochromic and photothermal bifunctional compound prepared in Example 1 and dissolve it in 400 μL of dimethyl sulfoxide (DMSO) to form the inner oil phase. Separately weigh 95 mg of poloxamer-188 (P188) and dissolve it in 2 mL of dichloromethane (DCM) until fully dissolved to obtain a colorless and clear solution, which will serve as the outer oil phase. Mix the two solutions and vortex to disperse them evenly, forming a mixed oil phase.

[0039] At room temperature, the above-mentioned mixed oil phase was rapidly injected into 40 mL of deionized water (aqueous phase) using a syringe while stirring at high speed (10,000 rpm). Subsequently, the system was placed under a high-speed disperser and emulsified at 5,000 rpm for 2 min to form a stable oil-in-water (O / W) emulsion.

[0040] The resulting emulsion was transferred to a fume hood and continuously stirred on a magnetic stirrer (600 rpm, 12 h) to evaporate and remove the organic solvent dichloromethane, inducing microsphere solidification. During this process, the microspheres were observed to gradually change from their initial color to completely blue, ultimately yielding a microsphere suspension.

[0041] (2) Photothermal performance test The microsphere suspension prepared above was placed in a sample cell (glass vial), with an equal volume of deionized water as a blank control. The sample cell was fixed on the light irradiation stage, and a 300W xenon lamp equipped with a filter (spot diameter: 3.14cm) was used. 2 Irradiation distance: vertical illumination, distance 10cm) is used as a simulated sunlight source for irradiation.

[0042] During the experiment, the probes of thermocouple thermometers were inserted below the surface of the sample liquid (avoiding contact with the bottom and microsphere precipitation) and the blank control group, respectively, and the temperature changes of the sample and blank deionized water were recorded and monitored in real time. Temperature data were recorded at regular intervals (e.g., 30 seconds or 1 minute) until the temperature stabilized or the preset irradiation time was reached. Temperature change curves were plotted to evaluate the photothermal conversion performance. The results are as follows: Figure 8 As shown, the temperature rise (ΔT) was as follows: Experimental group: 3.68℃ rise within 30 minutes (temperature rise from 8.30℃ to 11.98℃); Control group: 1.85℃ rise within 30 minutes (temperature rise from 8.08℃ to 9.93℃); Net temperature rise effect: 1.83℃ (net photothermal conversion contribution after deducting solvent background absorption).

[0043] The experimental results above show that: ① Significant photothermal conversion effect: Under irradiation with a 300W xenon lamp, the aqueous dispersion containing the compound of this invention heated up by 3.68℃ within 30 minutes, and its heating rate and final temperature were significantly higher than those of the blank water sample control group. ② Net effect after background subtraction: After subtracting the temperature rise caused by the light absorption of water itself (1.85℃), the net photothermal contribution of the compound of this invention is 1.83℃, indicating that the compound can effectively absorb light energy and convert it into heat energy. ③ Time dependence: With the extension of irradiation time, the sample temperature shows a continuous upward trend and does not reach saturation within 30 minutes, indicating that the material has good sustained photothermal response capability.

[0044] Comparative Example 1 This comparative example provides a method for preparing dihydropyridine compounds. The synthetic route is as follows, and the specific preparation process includes the following steps:

[0045] Weigh 5.93 g of 2-acetyl-pyridine, add 50 mL of anhydrous ethanol and 3.47 g of potassium hydroxide, and stir magnetically for 12 h. Then add 50 mL of ammonia water using a constant pressure dropping funnel, and react at 85 °C for 24 h. After the reaction is complete, filter to obtain a solid, dissolve in dichloromethane, recrystallize with methanol, and filter to obtain 3.2 g of the target product, with a yield of 48%. Its structural formula is as follows: ; The proton NMR spectrum of this compound is as follows: Figure 9 As shown, the specific data representing the characteristics are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.86 (s, 1H), 8.65 (d, J = 4.9 Hz, 2H), 8.61 (d, J = 5.7 Hz, 1H), 7.75 (d, J = 8.2 Hz, 2H), 7.67 (d, J = 17.4 Hz, 2H), 7.62 (d, J = 9.2 Hz, 1H), 7.54 (d, J = 8.1 Hz, 1H), 7.20 (d, J = 11.1 Hz, 2H), 7.07 (d, J = 13.4 Hz, 1H), 5.44 (d, J =1.8 Hz, 2H), 1.74 (s, 3H).

[0046] The solid powder of this compound changed from yellow to deep yellow after being exposed to UV light for about 1 minute. Its solid UV diffuse reflectance spectrum is as follows: Figure 10 As shown, no new peak appeared at 625nm, and the color did not turn blue.

[0047] The difference between the compound in this comparative example and the compound in Example 1 lies in the absence of bromine atoms in its molecular framework; that is, all bromine on the pyridine rings is replaced by hydrogen. Solid-state UV testing showed that after 1 minute of irradiation with a 365 nm UV lamp, this compound only changed from yellow to deep yellow, and no new absorption peak appeared at 625 nm, failing to exhibit blue color-changing behavior. This is due to the heavy atom effect of the lack of bromine atoms: the presence of bromine atoms can enhance intersystem crossing efficiency, promote aromatization rearrangement of the molecular framework after photoexcitation, thereby driving the expansion of the conjugated system and generating new absorption in the long wavelength region; while the bromine-free comparative example cannot effectively initiate this process, thus only a slight color change occurs and the high-contrast blue-shift color change is not achieved. This proves that the bromine atom is the key structural element for the photochromic properties of the compound of this invention.

[0048] Comparative Example 2 This comparative example provides a dihydropyridine compound with the following structural formula: , The compound was purchased from Shanghai BIDE Pharmaceutical Technology Co., Ltd., with a specification of 5g and a purity of 98%.

[0049] The solid powder of this compound changed from colorless to light yellow after being exposed to UV light for about 1 minute. Its solid UV diffuse reflectance spectrum is as follows. Figure 11 As shown, no new peak appeared at 625nm, and the color did not turn blue.

[0050] The difference between this comparative example and the compound in Example 1 lies in the absence of a bromopyridine group and an extended conjugated system in its structure. Because its conjugated system is small and lacks the heavy atom effect of bromine, it cannot drive effective aromatization rearrangement after photoexcitation. Therefore, after ultraviolet irradiation, no new absorption peak is observed at 625 nm, and the color only changes from colorless to pale yellow without exhibiting blue. This demonstrates that the extended conjugated system constructed by the 2-bromopyridine group in the compound of this invention is the key structural element for achieving the blue-shift color change.

[0051] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bifunctional compound for photochromism and photothermal conversion, characterized in that, The structural formula is: 。 2. The photochromic and photothermal bifunctional compound according to claim 1, characterized in that, The photochromic and photothermal conversion bifunctional compound is a light yellow solid powder.

3. The photochromic and photothermal bifunctional compound according to claim 1, characterized in that, The photochromic and photothermal conversion bifunctional compound, when dissolved in a solution of dichloromethane, gradually changes from light yellow to blue under 365nm ultraviolet light.

4. The photochromic and photothermal bifunctional compound according to claim 3, characterized in that, In the absorption spectra before and after irradiation with a 365nm ultraviolet lamp, a new absorption peak appears at 625nm.

5. The method for preparing the photochromic and photothermal conversion bifunctional compound according to any one of claims 1 to 4, characterized in that, The synthesis route of the preparation method is as follows: 。 6. The preparation method according to claim 5, characterized in that, The preparation method includes the following steps: 2-Acetyl-6-bromopyridine was subjected to an aldol condensation reaction under alkaline conditions with anhydrous ethanol as solvent to obtain an intermediate; then, under the action of ammonia, a Hantzsch cyclization tandem reaction was carried out to obtain a symmetrical tri(2-bromopyridyl)methane-substituted 1,4-dihydropyridine product.

7. The preparation method according to claim 6, characterized in that, The alkali in the alkaline conditions is potassium hydroxide; the intermediate does not need to be separated and directly undergoes an ammonolysis-cyclization tandem reaction.

8. The preparation method according to claim 6, characterized in that, The preparation method specifically includes the following steps: Weigh 37.98g of 2-acetyl-6-bromopyridine, add 175mL of anhydrous ethanol and 16g of potassium hydroxide, and stir magnetically for 14h; then add 150mL of ammonia water using a constant pressure dropping funnel, and react at 85℃ for 48h. After the reaction is completed, filter to obtain a blocky solid, dissolve it in dichloromethane, recrystallize it with methanol, and filter to obtain the photochromic and photothermal conversion bifunctional compound.

9. The application of the photochromic and photothermal conversion bifunctional compound as described in claim 1 in photochromic materials.

10. The application of the photochromic and photothermal conversion bifunctional compound as described in claim 1 in photothermal materials.

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