Preparation method and application of multi-stimulus response spiropyran photochromic material

Abstract

The application provides a preparation method and application of a multi-stimulus response spiropyran photochromic material, and belongs to the technical field of heterocyclic compounds. TDBA-2 is obtained through catalytic reaction by taking TDBA and ethylenediamine as raw materials, TDBA-2 and a spiropyran are placed in a catalytic environment, and a multi-stimulus response spiropyran photochromic material TDBA-SP2 is obtained through catalytic preparation. The prepared material exhibits excellent reversible stimulus response performance and fatigue resistance performance in a powder state, and does not show obvious performance attenuation after at least 5 cycles, can be used for multi-level information encryption, helps to further guarantee information security, and has a wide application prospect in the field of information storage and encryption.

Description

Technical Field

[0001] This application relates to a method for preparing and applying a multi-stimulus responsive spiropyran-based photochromic material, belonging to the field of heterocyclic compound technology. Background Technology

[0002] Due to their broad and sensitive responsiveness, multi-stimuli-responsive spiropyran derivatives have become a widely studied class of smart materials. Benzene rings and long alkyl chains play important roles in the molecular structure of spiropyran derivatives, allowing the molecules to stack loosely and be easily disrupted by external stimuli, thus producing responsive behaviors (such as changes in color, fluorescence, and absorbance). This also involves the influence of intermolecular interactions (π-π stacking and van der Waals forces). These relatively weak non-covalent interactions are important assembly driving forces for building aggregated structures. Applying external forces will disrupt these non-covalent interactions, altering the molecular stacking pattern of spiropyran derivatives and thus affecting the photophysical properties of the material. Hydrogen bonds are also a special type of intermolecular force, playing an important role in the self-assembly of molecules. Mo et al. combined carboxyl-substituted spiropyran with naphthalimide through amide bonds, generating strong hydrogen bond interactions and achieving tunable mechanically driven self-assembly with both photochromic and mechanochromic responses. Mechanical forces can enhance π-π stacking and disrupt hydrogen bonds by inducing crystal phase transitions and rearrangement of π-conjugated groups, thereby causing changes in the microstructure and optical properties of spiropyran. Therefore, the disruption of hydrogen bonds by external stimuli can also lead to changes in the molecular stacking pattern. In other words, hydrogen bonds are an important driving force in the spiropyran stimulus-response process, and the introduction of hydrogen bonds can help design spiropyran molecules with multiple stimulus responses.

[0003] Compared to single-stimulus-responsive fluorescent materials, multi-stimulus-responsive materials possess diverse responsiveness and a wider range of applications. Furthermore, developing such multi-stimulus-responsive materials is crucial for understanding color-changing mechanisms and opening up avenues for novel smart luminescent materials. Unfortunately, due to their diverse response mechanisms and luminescence capabilities, a universal strategy for preparing multi-stimulus-responsive fluorescent materials is lacking. Moreover, ensuring the compatibility and diversity of various response behaviors while effectively combining different reactivity within a multi-stimulus-responsive system remains a significant challenge. Therefore, the development and application of multi-stimulus-responsive organic materials still have a long way to go. Summary of the Invention

[0004] In view of this, this application firstly provides a method for preparing a multi-stimulus responsive spiropyran-based photochromic material.

[0005] Specifically, this application is implemented through the following scheme:

[0006] A method for preparing a multi-stimulus responsive spiropyran-based photochromic material includes two steps:

[0007] 1) TDBA-2 was obtained by catalytic reaction using TDBA and ethylenediamine as raw materials.

[0008] 2) TDBA-2 and spiropyran (SP-COOH) were placed in a catalytic environment to catalytically prepare a multi-stimulus responsive spiropyran-based photochromic material, denoted as TDBA-SP2.

[0009] The structural formula of the TDBA is as follows:

[0010] The structural formula of TDBA-2 is as follows:

[0011] The structural formula of SP-COOH is:

[0012] The structural formula of TDBA-SP2 is as follows:

[0013]

[0014] The above method connects a rigid benzene ring and a flexible long chain to spiropyran (SP-COOH) via amide bonds, and by adjusting intermolecular interactions (hydrogen bonds), prepares a spiropyran-based photochromic material (TDBA-SP2) exhibiting triple stimulus-responsiveness (photochromic, mechanochromic, and thermochromic). UV-Vis absorption and fluorescence emission spectroscopy analysis results show that TDBA-SP2 exhibits excellent reversible stimulus-responsiveness and fatigue resistance in the powder state. This rapid and reversible multiple stimulus-responsiveness is very rare in a single molecule and can be used for multi-level information encryption, helping to further ensure information security, and has broad application prospects in the field of information storage encryption.

[0015] Furthermore, as a preferred option:

[0016] In step 1):

[0017] The catalyst is benzotriazole-1-oxytris(dimethylamino)phosphine hexafluorophosphate (BOP), with an addition amount (molar amount) of 111% relative to TDBA.

[0018] The catalytic reaction time was 4.5 h at room temperature.

[0019] Step 1) can be expressed using the following reaction formula:

[0020]

[0021] In step 2):

[0022] The catalyst is a mixture of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU) and N,N-diisopropylethylamine (DIPEA). The amount of HATU added relative to SP-COOH is 200% (molar amount), and the mixing ratio (molar ratio) of HATU and DIPEA is 1:5.06.

[0023] The catalytic reaction time was 48 hours at room temperature.

[0024] Step 2) can be expressed using the following reaction formula:

[0025]

[0026] In the reaction processes of steps 1) and 2) above, dichloromethane is added as a solvent, and the reaction is carried out in a protective nitrogen atmosphere.

[0027] The above-mentioned multi-stimulus responsive spiropyran-based photochromic materials prepared by the above method have applications in the fields of information storage encryption and anti-counterfeiting.

[0028] In the above application process:

[0029] The multi-stimulus responsive spiropyran-based photochromic material is in powder form.

[0030] The aforementioned multi-stimulus responsive spiropyran-based photochromic material exhibits a photosensitive effect, meaning it is sensitive to ultraviolet light stimulation and recovers upon exposure to white light or in a dark environment.

[0031] The multi-stimulus responsive spiropyran-based photochromic material exhibits a mechanosensitive effect, meaning it is sensitive to stimuli such as grinding and displays a color-switching effect, which recovers under recrystallization conditions.

[0032] The multi-stimulus responsive spiropyran-based photochromic material exhibits a thermo-responsive effect, meaning that it undergoes a color-switching effect when heated and recovers after being irradiated with white light.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] This invention prepares a spiropyran-based photochromic material (TDBA-SP2) exhibiting triple-stimulus responsiveness (photochromic, mechanochromic, and thermochromic) by linking a rigid benzene ring and a flexible long chain to spiropyran (SP-COOH) via amide bonds and adjusting intermolecular interactions (hydrogen bonds). The introduction of hydrogen bonds significantly improves the multi-stimulus responsiveness of spiropyran and enhances its response sensitivity; TDBA-SP2 powder changes color after 2 seconds of UV irradiation. Simultaneously, TDBA-SP2 also responds to mechanical and thermal stimuli, exhibiting rapid, reversible, and high-contrast color and fluorescence changes. In its powder state, TDBA-SP2 demonstrates excellent reversible stimulus response and fatigue resistance. This rapid and reversible multi-stimulus response is extremely rare in single molecules and can be used for multi-level information encryption, contributing to further information security and showing broad application prospects in the field of information storage encryption. Attached Figure Description

[0035] Figure 1 The UV absorption spectra of TDBA-SP2 prepared in Example 1 after different grinding times and recrystallization are shown.

[0036] Figure 2 The fluorescence emission spectra of TDBA-SP2 prepared in Example 1 were recovered under 410 nm excitation at different grinding times and recrystallization times.

[0037] Figure 3 The diagram shows the cycle of TDBA-SP2 prepared in Example 1 under alternating conditions of milling for 30 min and recrystallization recovery, as well as the changes in physical color and fluorescent color.

[0038] Figure 4 The image shows an overlay of the fluorescence spectrum and the UV absorption spectrum of TDBA-2 in the open-ring state of spiropyran prepared in Example 1. Excitation wavelength: 410 nm.

[0039] Figure 5 The ultraviolet absorption spectra of TDBA-SP2 prepared in Example 1 under 365nm ultraviolet light irradiation for different times;

[0040] Figure 6 The fluorescence emission spectra of TDBA-SP2 prepared in Example 1 after different times of irradiation with 365nm ultraviolet light and excitation at 410nm wavelength;

[0041] Figure 7 The diagram shows the cycle of TDBA-SP2 prepared in Example 1 under alternating stimulation of 365nm ultraviolet light irradiation for 10 min and visible light irradiation for 40 min, as well as the changes in physical color and fluorescent color.

[0042] Figure 8The ultraviolet absorption spectra of TDBA-SP2 prepared in Example 1 after heating for different times and visible light recovery are shown.

[0043] Figure 9 The fluorescence emission spectra of TDBA-SP2 prepared in Example 1 under different heating times and visible light recovery at 410 nm excitation wavelength are shown.

[0044] Figure 10 The diagram shows the cycle of TDBA-SP2 prepared in Example 1 under alternating stimulation of heating for 10 min and visible light recovery, as well as the changes in physical color and fluorescent color. Detailed Implementation

[0045] Exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0050] The room temperature referred to in this invention is the indoor temperature, which is well known to those skilled in the art and will not be described in detail here; in particular, it should be noted that the room temperature referred to in the embodiments of this invention is 25°C.

[0051] Example 1

[0052] This embodiment describes the preparation of a photochromic material, and the process is as follows:

[0053] (1) Synthesis of TDBA-2:

[0054] Under a nitrogen atmosphere, TDBA (1.00 g, 1.48 mmol) and benzotriazine-1-oxytris(dimethylamino)phosphine hexafluorophosphate (BOP reagent, 0.10 g, 1.64 mmol) were dissolved in 20 mL of ultra-dry dichloromethane. Ethylenediamine (0.45 g, 7.48 mmol) was then added to the reaction mixture, and the mixture was stirred at room temperature for 4.5 h. After the reaction was complete, the mixture was extracted with deionized water (20 mL × 3). The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the filtrate was collected. The solvent was removed by vacuum distillation. At 0 °C, the crude product was recrystallized in a 50 mL solution of dichloromethane / methanol (v / v, 1 / 10). After standing overnight, a large amount of solid precipitated. The solid was filtered and dried to obtain 0.74 g of white powder, which was TDBA-2, with a yield of 70%.

[0055] The above process can be expressed as a reaction equation as follows:

[0056]

[0057] Compound TDBA-2 was characterized by 1H NMR spectroscopy, and the specific data are as follows: 1 H NMR (400MHz, CDCl3) δ7.00 (s, 2H), 4.03-3.96 (m, 6H), 3.56-3.45 (m, 2H), 2.98 (t, J = 5.0H z,2H),1.85-1.70(m,6H),1.51-1.41(m,6H),1.34-1.22(m,48H),0.88(t,J=6.7Hz,9H).

[0058] (2) Synthesis of TDBA-SP2:

[0059] Under a nitrogen atmosphere, SP-COOH (0.30 g, 0.79 mmol), 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU, 0.60 g, 1.58 mmol), and N,N-diisopropylethylamine (DIPEA, 1.32 mL, 8.00 mmol) were added to 20 mL of ultra-dry dichloromethane, stirred until dissolved, and incubated on ice for 0.5 h. Then, TDBA-2 (0.60 g, 0.84 mmol) was added, and the mixture was stirred at room temperature for 48 h. The reaction mixture was extracted with deionized water (20 mL × 3), and the organic phase was collected and evaporated to dryness to remove the solvent. The crude product was purified by silica gel column chromatography using petroleum ether / ethyl acetate (v / v, 10 / 1) as the eluent to obtain 0.76 g of a light brown solid, TDBA-SP2, in 89% yield.

[0060] The above process can be expressed as a reaction equation as follows:

[0061]

[0062] Compound TDBA-SP2 was characterized by 1H NMR spectroscopy, and the specific data are as follows: 1 H NMR (400MHz, CDCl3) δ8.00-7.91 (m, 2H), 7.16 (m, 1H), 7.06 (d, J = 7.3Hz, 1H), 6.98 (s, 2H) ,6.89-6.85(m,1H),6.82(d,J=10.4Hz,1H),6.70(d,J=8.9Hz,1H),6.61(d,J=7.8Hz,1H) ,5.77(d,J=10.4Hz,1H),4.00(m,6H),3.68-3.38(m,6H),2.47(m,2H),1.83-1.70(m,6H) ,1.52-1.40(m,6H),1.40-1.26(m,48H),1.22(s,3H),1.09(s,3H),0.88(t,J=6.7Hz,9H).

[0063] The performance of TDBA-SP2 prepared in Example 1 above was tested, and the results are as follows: Figures 1-10 As shown.

[0064] TDBA-SP2 exhibits high color contrast when subjected to grinding stimulation (simply grinding it in a mortar), which is crucial for anti-counterfeiting and encryption materials. Combined with... Figure 1 , Figure 2 and Figure 3 It can be seen that by extending the grinding time, a more significant color switching was achieved (see...). Figure 3(Inset: Solid powder changes from brownish-yellow to orange and then to red). This is also reflected in the UV-Vis absorption and fluorescence emission spectra, including the increase in absorbance and the appearance of fluorescence resonance energy transfer. Using a recrystallization method (dissolving the ground powder in a mixed solution of DCM and n-hexane (v / v, 1 / 1) and allowing the solvent to evaporate naturally at room temperature), the absorption peak at 550 nm and the fluorescence emission peak at 528 nm (SP form) were found to be largely restored. Based on this, we further tested the reversibility of the mechanochromic change of TDBA-SP2 powder. The results show that it can withstand at least 5 grinding-color change-recrystallization recovery cycles. This stable and excellent stimulus response will bring more convenience to practical applications.

[0065] Depend on Figure 4 , Figure 5 , Figure 6 The ultraviolet absorption and fluorescence emission spectra show that the novel photochromic material prepared in this embodiment is highly sensitive to ultraviolet light. During ultraviolet light irradiation from 0 s to 10 min, TDBA-SP2 exhibits a high-contrast color change (see...). Figure 7 Middle illustration: The solid powder changes from brownish-yellow to purplish-black, accompanied by the appearance and enhancement of red fluorescence. Furthermore, this color change can be recovered by exposure to white light or exposure to darkness (see [reference needed]). Figure 7 Further tests on its fatigue resistance showed that TDBA-SP2 powder could withstand at least 20 cycles of UV irradiation (10 min) followed by white light irradiation (40 min) without significant absorbance decay. Under continuous UV irradiation, the fluorescence emission peak of TDBA-SP2 powder in the shorter wavelength range gradually weakened and almost disappeared, while the emission peak (MC state) in the longer wavelength range continuously strengthened, resulting in a significant redshift (from 657 nm to 672 nm). The emission peak of TDBA-2 largely overlapped with the absorption peak of MC, meaning that the energy emitted by TDBA-2 was absorbed by the SP-COOH portion (MC state), causing a significant decrease in the fluorescence emission peak of TDBA-2 around 530 nm, while the emission peak of the MC state around 660 nm increased sharply, indicating fluorescence resonance energy transfer.

[0066] TDBA-SP2 also exhibited a response to temperature. Combined with Figure 8 , Figure 9 and Figure 10 After heating at 90℃ for 3 minutes, the brownish-yellow TDBA-SP2 powder turned brown and emitted orange-red fluorescence. Further heating for 10 minutes caused the powder to turn reddish-brown and emit red fluorescence (see...). Figure 10(Illustration of solid powder in the image). This high-contrast color change recovers after only 10 minutes of exposure to white light and persists for at least five color-fading cycles without absorbance decay. UV-Vis absorption and fluorescence emission spectra detailed this transition process. With prolonged heating, the absorption peak at 550 nm intensifies, the fluorescence emission peak at 528 nm weakens, and the emission peak at 652 nm intensifies and redshifts to 657 nm, demonstrating the fluorescence resonance energy transfer process.

[0067] Summarize:

[0068] The multi-stimulus responsive spiropyran-based photochromic material prepared in this case was subjected to stress effect experiments. The multi-stimulus responsive spiropyran-based photochromic material exhibited stress effects under three conditions:

[0069] (1) It exhibits a color-changing effect in response to force stimuli such as grinding. When stimulated by grinding, it also shows a high color contrast. By extending the grinding time, a significant color change can be achieved from brownish-yellow to orange and then to red. The color is restored after recrystallization. The above response can last for at least 5 grinding color change-recrystallization recovery cycles.

[0070] (2) Sensitive to ultraviolet light stimulation. During ultraviolet light irradiation from 0 s to 10 min, TDBA-SP2 exhibited high-contrast color changes, accompanied by the appearance and enhancement of red fluorescence. Furthermore, this color change could be recovered by white light irradiation or exposure to darkness; the above response could be sustained for at least 20 cycles of ultraviolet light irradiation coloration (10 min) - white light irradiation fading (40 min) without significant absorbance decay.

[0071] (3) It exhibits sensitivity to heat / temperature. When heated at 90°C for 3 minutes, the color of TDBA-SP2 changes from brownish-yellow to brown and emits orange-red fluorescence. Upon further heating for 10 minutes, it turns reddish-brown and emits red fluorescence. It recovers after 10 minutes of exposure to white light. The above response can last for at least 5 color-fading cycles without absorbance decay.

[0072] Based on the verification of the above experimental results, the multi-stimulus responsive spiropyran-based photochromic material prepared by this invention can be applied to the fields of information storage encryption and anti-counterfeiting.

[0073] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a multi-stimuli responsive spiropyran photochromic material, characterized by, The method comprises two steps: 1) obtaining TDBA-2 by catalytic reaction of TDBA and ethylenediamine as raw materials, The TDBA has a structural formula of: , The structural formula of the TDBA-2 is: , 2) obtaining the multi-stimulus-responsive spiropyran photochromic material, denoted as TDBA-SP2, by catalytic preparation of TDBA-2 and spiropyran in a catalytic environment, with a mixture of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N-diisopropylethylamine as a catalyst, The spiropyran has a structural formula of: , in the catalyst, the addition mole amount of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate relative to spiropyran is 200%, and the mixed mole ratio of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate to N,N-diisopropylethylamine is 1:5.06, the structural formula of the TDBA-SP2 is: ， the multi-stimulus-responsive TDBA-SP2 comprises: 1) stress stimulus sensitive performance showing color switching effect, and recovery under recrystallization conditions; 2) sensitive to ultraviolet light stimulus, and recovery under white light irradiation or exposure in a dark environment; 3) sensitive to temperature stimulus, and recovery under white light irradiation.

2. The method according to claim 1, wherein the method is characterized by: in step 1), the catalyst is benzotriazole-1-oxyl tris(dimethylamino)phosphonium hexafluorophosphate, and the addition mole amount relative to TDBA is 111%.

3. The method according to claim 1, wherein the method is characterized by: The reaction is a room temperature reaction, dichloromethane is added as a solvent, and the reaction is carried out in a protective nitrogen atmosphere.

4. The preparation method of a multi-stimuli responsive spiropyran photochromic material according to any one of claims 1-3, characterized in that: The multi-stimulus-responsive spiropyran photochromic material is applied to the fields of information storage encryption and anti-counterfeiting.

5. The method according to claim 4, wherein the method is characterized by: The multi-stimulus-responsive spiropyran photochromic material is in powder form.

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