Molecular optical switches based on dasas that enable solid thin film isomerization and methods of synthesis and use thereof

Abstract

The application discloses a DASAs molecular optical switch capable of realizing solid thin film isomerization and a synthesis method and application thereof. Z ,4 E )-5-(benzyl((4-methylpyridin-2-yl)methyl)amino)-2-hydroxypenta-2,4-dien-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione is synthesized by reacting 4-methylpyridine-2-carboxaldehyde and benzylamine and then reducing by sodium borohydride N -benzyl-1-(4-methylpyridin-2-yl)methylamine, and then reacting with 5-(furan-2-ylmethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione in methanol. The DASAs molecular optical switch has a quick and reversible isomerization response to visible light, and exhibits a significant selective color response to metal ions, and in addition, the molecular optical switch can realize reversible photochromism in a polymer substrate in a solid state. More importantly, a pure phase solid thin film prepared from the molecular optical switch can realize photoisomerization, and has great application potential in the fields of optical information storage and information permanent encryption, metal ion detectors and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and relates to a DASA molecular optical switch capable of realizing solid film isomerization and a synthesis method and application thereof. BACKGROUND

[0002] Donor-acceptor Stenhouse adducts (DASAs) are a class of photochromic molecules that can rapidly respond under visible light irradiation, and can rapidly convert from a colored chain structure to a colorless ring structure. This process can be reversed by heat under dark conditions. Compared with traditional color-changing materials that require high-energy ultraviolet light response, DASAs exhibit significant advantages. The light response characteristics of DASAs include negative photochromism, visible light absorption, synthesis adjustability, and significant property changes between photoisomers. These characteristics make DASAs ideal candidates for photochromic materials. Another significant advantage of DASAs is their excellent synthesis adjustability. By changing the molecular structure, the light response characteristics can be adjusted to achieve optimal performance in a specific wavelength range. This adjustability provides a wide space for designing photochromic materials with specific application requirements.

[0003] However, existing researches mostly focus on the photochromic properties of DASAs molecules. In addition, like traditional photoresponsive compounds, DASAs exhibit fast, reversible and efficient isomerization in solution, but in solid state, such isomerization is often hindered due to factors such as π-π stacking of chromophores or inherent mobility limitation, which undoubtedly limits the development and application of solid-state DASAs photoresponsive materials. ([1] Photoswitching using visible light: A new class of organic photochromic molecules. Helmy, Sameh, et al. Journal of the American Chemical Society, 2014, 136(23): 8169-72. [2] Design and Synthesis of Donor-Acceptor Stenhouse Adducts: A Visible Light Photoswitch Derived from Furfural. Sameh Helmy, et al. Journal of the Organic Chemistry, 2014, 79, 11316-11329. [3] Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches. Mallo, Neil, et al. Chemical Science, 2018, 43, 8242-8252.) Therefore, it is necessary to further explore new molecular design strategies and material synthesis methods in order to break through the existing limitations, improve the multi-stimulus response behavior and solid-state isomerization performance of DASAs photochromic materials, and develop new photochromic molecules that respond to more elements and adapt to multiple states, so as to realize the in-depth expansion of DASAs molecular switch function. SUMMARY

[0004] The purpose of the present application is to provide a DASAs molecular optical switch capable of realizing solid thin film isomerization and its synthesis method and application.

[0005] The technical solution for achieving the purpose of the present application is as follows:

[0006] The DASAs molecular optical switch capable of realizing solid thin film isomerization is 5-((2Z,4E)-5-(benzyl((4-methylpyridin-2-yl)methyl)amino)-2-hydroxy-penta-2,4-dien-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione, and its structural formula is shown as formula III:

[0007]

[0008] The synthesis method of the above-mentioned DASAs molecular optical switch capable of realizing solid thin film isomerization comprises the following steps:

[0009] (1) 4-methylpyridine-2-carboxaldehyde and benzylamine are reacted in methanol as a solvent at 78±5℃, after the reaction is completed, sodium borohydride is added under ice water bath condition for reduction, then heated to reflux, after the reaction is completed, cooled, methanol is removed by rotary evaporation, extracted, and rotary evaporated to obtain N-benzyl-1-(4-methylpyridin-2-yl)methylamine, and the synthesis route is as follows:

[0010]

[0011] (2) 5-(furan-2-ylmethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione and N-benzyl-1-(4-methylpyridin-2-yl)methylamine are subjected to electrophilic addition reaction in methanol as a solvent at room temperature to prepare 5-((2Z,4E)-5-(benzyl((4-methylpyridin-2-yl)methyl)amino)-2-hydroxy-penta-2,4-dien-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione, and the synthesis route is as follows:

[0012]

[0013] Further, in step (1), the molar ratio of 4-methylpyridine-2-carboxaldehyde to benzylamine is 1:1.05-1.1.

[0014] Further, in step (1), the reduction reaction time is more than 1 h, and the reflux reaction time is more than 20 h.

[0015] Further, in step (1), the extraction solvent is CH2Cl2.

[0016] Further, in step (2), the molar ratio of 5-(furan-2-ylmethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione to N-benzyl-1-(4-methylpyridin-2-yl)methylamine is 1:1.05-1.1.

[0017] Further, in step (2), the reaction temperature is 23±3℃, and the reaction time is 25-30 min.

[0018] Further, the application provides application of the above-mentioned DASAs molecular optical switch in Fe 3+ , Al 3+ or Cu 2+ detection.

[0019] Further, the application provides the use of the above-mentioned DASAs molecular optical switch in the preparation of a rewritable material or an information encryption material.

[0020] Further, the specific method of the above-mentioned use is as follows: dissolving the DASAs molecular optical switch in an organic solvent, then engraving information in the process of forming a solid film by volatilization of the organic solvent, forming a solid film after the complete volatilization of the organic solvent, erasing the engraved information by visible light stimulation, and preparing an information permanent encryption material composed of a DASAs molecular optical switch solid film; or mixing a polymer and the DASAs molecular optical switch in an organic solvent, forming a solid polymer film after the complete volatilization of the organic solvent, and engraving and erasing information by alternating stimulation of visible light and heat, to prepare a rewritable material or an information encryption material composed of a DASAs molecular optical switch solid polymer film.

[0021] Further, the organic solvent used for preparing the DASAs molecular optical switch solid film is 1,1,1,3,3,3-hexafluoro-2-propanol; the organic solvent used for preparing the DASAs molecular optical switch solid polymer film is chloroform, and the polymer used is polymethyl methacrylate (PMMA).

[0022] Compared with the prior art, the application has the following advantages:

[0023] (1) The synthesis method of the application is simple, the raw materials used are environmentally friendly and low in cost, the reaction conditions are mild, the reaction speed is fast, the yield of the target product is high, and the purification process is simple.

[0024] (2) In the synthesis of the target molecular optical switch, methanol solvent is selected instead of tetrahydrofuran solvent used in the existing synthesis technology. By using methanol solvent, the synthesis conditions are optimized, and compared with tetrahydrofuran, methanol has relatively low toxicity, greatly avoiding the safety risk in the use process, and being suitable for industrialized production application scenarios.

[0025] (3) The molecular optical switch of the application has multiple stimulation response behaviors in different environments, including light responsiveness, selective metal ion responsiveness (based on a solution environment), and light isomerization responsiveness in a solid state environment, and can realize photochromism in a solid film state, having great application potential in the fields of metal ion detectors, information storage and encryption, and rewritable materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of compound I.

[0027] Figure 2 is the nuclear magnetic resonance hydrogen spectrum of compound III.

[0028] Figure 3 is the two-dimensional COSY spectrum of compound III.

[0029] Figure 4 is the infrared spectrum of compound III.

[0030] Figure 5 is the UV-vis absorption spectrum of compound III in dichloromethane, where a) is the full spectrum of absorbance vs. concentration, and b) is the linear relationship of absorbance vs. concentration.

[0031] Figure 6 is the UV-vis absorption spectrum of compound III in acetonitrile, where a) is the full spectrum of absorbance vs. concentration, and b) is the linear relationship of absorbance vs. concentration.

[0032] Figure 7 is the UV-vis absorption spectrum of compound III in dark equilibrium in dichloromethane.

[0033] Figure 8 is the UV-vis cyclic spectrum of compound III in dichloromethane, where the absorbance reversibly changes in response to light.

[0034] Figure 9 is the UV-vis absorption spectrum of compound III in tetrahydrofuran, where a) is the full spectrum of absorbance vs. concentration, and b) is the linear relationship of absorbance vs. concentration.

[0035] Figure 10 is the UV-vis cyclic spectrum of compound III in tetrahydrofuran, where the absorbance reversibly changes in response to light.

[0036] Figure 11 is the color change vs. metal ion response of compound III.

[0037] Figure 12 is the absorbance change of compound III in UV-vis a) and the linear relationship of absorbance vs. concentration of compound III at 531 nm b) after adding different concentrations of Fe 3+ responsive metal ions. Figure 12 Figure 12

[0038] Figure 13 is the absorbance change of compound III in UV-vis a) and the linear relationship of absorbance vs. concentration of compound III at 531 nm b) after adding different concentrations of Al 3+ responsive metal ions. Figure 13 Figure 13

[0039] Figure 14 is the absorbance change of compound III in UV-vis a) and the linear relationship of absorbance vs. concentration of compound III at 531 nm b) after adding different concentrations of Cu 2+ ​​​​UV-vis spectra of compound III in response to metal ions Figure 14 a) and the linear relationship between the absorbance of compound III at 531 nm and the concentration Figure 14 b).

[0040] Figure 15 Schematic diagram of reversible isomerization of compound III with PMMA as substrate under light and heat stimuli.

[0041] Figure 16 UV-vis spectra of isomerization of compound III solid film under light and heat stimuli. DETAILED DESCRIPTION

[0042] The application will be further described below in conjunction with the drawings and examples.

[0043] The structural formula of 5-(furan-2-ylmethyl)-2,2-dimethyl-1,3-dioxane-4,6-dione (compound I) is as follows: The compound I can be prepared by the following steps:

[0044] In a double-neck flask, according to the molar ratio of 2-furaldehyde: propylene glycol isopropylidene ester = 1.1:1, propylene glycol isopropylidene ester is first added to the flask, deionized water is used as the solvent, 2-furaldehyde is slowly added dropwise under stirring at room temperature, and the reaction is carried out at 25°C for 2.5h. After the reaction is completed, CH2Cl2 is added to extract the crude product, CH2Cl2 is used to extract the aqueous phase (25ml*3), and then the organic phase is collected. Saturated NaHSO4 and saturated NaHCO3 solution are added in sequence, and the CH2Cl2 phase is washed for 3 times, respectively, then anhydrous sodium sulfate is added to dry the small amount of water in the organic phase, the organic solvent is removed under reduced pressure, the oil pump is vacuumed, and yellow oil compound I is obtained. Nuclear magnetic resonance characterization is carried out, and the results are shown in Figure 1 .

[0045] Example 1

[0046] (1) Compound II is N-benzyl-1-(4-methylpyridin-2-yl)methylamine, and the molecular structure is as follows:

[0047]

[0048] The compound II is prepared by the following steps:

[0049] In a double-neck flask, according to the molar ratio of 4-methylpyridine-2-formaldehyde Benzylamine First, 4-methyl-2-pyridine carboxaldehyde was added into a flask, and benzylamine was slowly added dropwise under stirring at 78±5°C in methanol as solvent. After the reaction was completed, sodium borohydride was added under ice-water bath for 1 h, and then the reaction flask was heated to reflux for 22 h. After the reaction was completed, the organic solvent was removed by rotary evaporation. CH2Cl2was added to dissolve the crude product, and saturated NaCl solution and saturated NH4Cl solution were added. The CH2Cl2phase was washed for 3 times, and the lower organic phase was collected and rotary evaporated to obtain N-benzyl-1-(4-methylpyridin-2-yl)methylamine.

[0050] (2) The target compound III is 5-((2Z,4E)-5-(benzyl((4-methylpyridin-2-yl)methyl)amino)-2-hydroxy-penta-2,4-dien-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione, and the molecular structure is shown as follows:

[0051]

[0052] Prepared by the following steps:

[0053] At room temperature, a single-necked flask was used to prepare compound III according to the molar ratio of compound II N-benzyl-1-(4-methylpyridin-2-yl)methylamine Methanol was added, and after 25-30 minutes of reaction at 25°C, purple-red solid was produced. The solid was washed with anhydrous ether under ice-water bath, filtered, and the precipitate was collected to obtain high-purity target compound III with a yield of 93.5%. Nuclear magnetic resonance and infrared characterization were performed, and the infrared spectrum data of compound III were measured by potassium bromide tablet method, and the results are shown in FIGS. Figures 2-4

[0054] Example 2

[0055] Concentration-dependent effect of compound III:

[0056] Under the irradiation of visible light λ max =550 nm, compound III was added dropwise in dichloromethane solution according to the same concentration gradient, and the concentration-dependent characterization results were measured and shown in FIGS. Figure 5

[0057] Figure 5 FIG. a) in the figures is a UV-vis absorption spectrum of compound III in dichloromethane with varying concentrations, and the maximum absorbance is at 546 nm. Figure 5 FIG. b) in the figures is a linear relationship diagram of the absorbance of compound III at 546 nm and the concentration. This indicates that the dichloromethane solution of compound III has a good linear relationship (R 2 =0.99761), and the maximum absorption wavelength does not change with the concentration.​​

[0058] Figure 6 The UV-vis absorption spectrum of compound III in acetonitrile as a function of concentration, and the linear relationship between the absorbance of compound III at 546 nm and concentration, are shown. 2 =0.99995.

[0059] Example 3

[0060] Reversible photoresponse test of compound III:

[0061] Compound III was dissolved in dichloromethane (DCM) and tetrahydrofuran (THF) respectively to prepare a solution with c = 1.0 × 10⁻⁶. - 3 The solution was prepared by further preparing a solution of compound III in each solvent by placing the solutions in 3 ml cuvettes, resulting in a concentration of c = 1.0 × 10⁻⁶ mol / L. -5 A solution of mol / L (the solution is purple-red) was tested, and its UV-vis absorption spectra at dark equilibrium in DCM and THF solutions were obtained, as follows: Figure 7 and Figure 9 As shown.

[0062] Figure 8 The UV-vis graph shows the reversible light-switching cycle performance of compound III in DCM. From... Figure 7 It can be seen that compound III in λ max The absorbance at 546 nm decreased from 0.9999 to 0.7397. Irradiation of the solution with a 550 nm visible xenon lamp revealed a rapid fading from purplish-red to colorless, at which point the absorbance was measured to be 0.0179. After 7.2 h in the dark, the isomerization of compound III reached equilibrium, resulting in the highest absorbance value (at which point the solution was purplish-red). Figure 8 As shown in Figure b). Repeated testing revealed that after 7-8 cycles or more, the dark recovery of compound III in DCM solution showed a low degree of attenuation, indicating good cyclic fatigue resistance. The experimental results are as follows: Figure 8 As shown in Figure c).

[0063] Figure 10 The UV-vis graph shows the reversible light-switching cycle performance of compound III in THF. From... Figure 9 It can be seen that compound III in λ max The absorbance at 546 nm decreased from 0.9746 to 0.7821. Irradiation of the solution with a 550 nm visible xenon lamp revealed a rapid fading from purplish-red to colorless, at which point the absorbance was measured to be 0.0196. After being placed in the dark for 9.8 hours to allow it to reach equilibrium, the change in the maximum absorption peak in THF over time was measured as follows: Figure 10As shown in Figure b), the cycle was repeated to test its fatigue resistance. It was found that after more than four cycles, the dark recovery of compound III in THF solution showed almost no decrease, indicating good cyclic fatigue resistance. It can serve as a good molecular optical switch. The experimental results are shown in Figure b). Figure 10 As shown in Figure c).

[0064] Example 4

[0065] Metal ion response of compound III:

[0066] Figure 11 This is a comparison of the color changes in response to metal ions of compound III. Compound III was dissolved in methanol to prepare a concentration of 1×10⁻⁶. -4 A solution of mol / L (the solution is purple-red) was prepared, and then a 10 mol / L solution was prepared in methanol. -3 mol / L of metal ions (Na) + Mg 2+ Al 3+ Mn 2+ Fe 3+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ The solution was prepared by mixing compound III with metal ions at a molar ratio of 1:4. The experimental results are as follows: Figure 11 As shown, it was found that adding Fe... 3+ The compound solution, after being added, rapidly changed from purplish-red to colorless within 5 minutes; 3+ Cu 2+ The solution gradually faded to colorless after 3.5 hours.

[0067] To further confirm the relationship between compound III and Fe 3+ Al 3+ Cu 2+ Does a linear relationship exist between metal ions? Fe is added in proportion. 3+ After metal ions, from Figure 12 It can be seen that the absorbance of compound III decreases rapidly (the solution eventually becomes colorless), and the absorbance of compound III at 531 nm shows a linear relationship with its concentration (y = -0.31582x + 1.00346, R). 2 =0.91887); from Figure 13 and Figure 14 It can also be seen from this that compound III, upon the addition of Al 3+ Cu 2+ After the metal ion was removed, the absorbance decreased rapidly (the solution eventually became colorless), and the absorbance of compound III at 531 nm showed a linear relationship with concentration (y = -0.08614x + 0.95861, R).2 = 0.95093; y = -0.10069x + 0.98813, R 2 = 0.98021). This shows that compound III has a special isomerization response to Fe 3+ and Al 3 + , Cu 2+ , and the response time is different, and a good linear relationship is presented, which can selectively detect the presence of these three types of ions in the solution according to the response time, and be used for preparing a high-selectivity and high-sensitivity metal ion detection sensor.

[0068] Example 5

[0069] Solid phase conversion performance of compound III molecular switch in polymer:

[0070] Figure 15 The reversible isomerization schematic diagram of compound III with PMMA as the substrate under light stimulation and heating stimulation. In order to further explore the isomerization response of compound III in different environments, it is found through research that the functional groups in the polymer closely affect the kinetics and equilibrium of DASAs isomerization, and various ester-containing polymers can enhance the isomerization of DASAs in the polymer film. Therefore, PMMA is selected as the polymer substrate to explore the isomerization performance of compound III in the solid phase environment. 0.5 g of PMMA is taken in a beaker, 5 mg of compound III is added, dissolved in chloroform, ultrasonically dissolved, placed in a cubic mold, naturally air-dried, and the solvent is volatilized to form a film to prepare a compound III polymer film. From the UV-vis spectra of the compound III polymer film before and after visible light (JB450 nm) irradiation, it can be seen that the polymer film fades from purple red to colorless. Figure 15 It can be seen that compound III in the solid film with PMMA as the substrate fades from purple red to colorless by visible light (JB450 nm) irradiation, and then the film is placed in an oven for heating, and it is found that the film returns from colorless to purple red. Experiments prove that the polymer solid film exhibits reversible color change response and good cycle performance by alternating stimulation of visible light and heating. This finding provides a new idea for solving the isomerization problem of DASAs in the solid state, and indicates that compound III has broad application prospects in the fields of optical information storage and repeatable erasing materials.

[0071] Example 6

[0072] Molecular optical switch solid film photochromic performance of compound III:

[0073] Figure 16 The UV-vis spectra of the isomerization of the compound III solid film under light stimulation and heating stimulation. The present application selects 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the solvent, grinds the compound III molecular switch synthesized above into powder, and according to its molecular weight M r= 434 g.mol -1 Quantitative calculation, take 8.68 mg dissolved in 10 ml of HFIP, using volumetric flask configuration to standard concentration is 2.0 x 10 -3 mol.L -1 The coating liquid, select flat experiment table, the prepared compound III coating liquid quantitative suspension coating on the outside of clean quartz cuvette, ensure that the cuvette surface coating uniform, natural dry, to be solvent volatilization film, successfully prepared compound III molecular optical switch solid film. Compound III solid film is placed under xenon lamp (JB450 nm) light, light time T=5min, the maximum characteristic absorption peak (lambda max =558nm) solid film absorbance decreased significantly, while observing the solid film also gradually faded from purple red, light 10min, its absorbance has reached stable no longer decreased. This shows that the colorful compound III solid film after visible light, successful photo-fading. The solid film under JB450 nm light wavelength lambda max =558nm absorbance changes with light time as shown in Figure 16 c) figure.

[0074] The solid film after light in the oven, found that with the increase of temperature, the film did not from colorless to purple red, using ultraviolet-visible absorption spectrum monitoring its absorbance changes with temperature, from Figure 16 b) figure in the red line can be observed, when the temperature rises to 95℃, the maximum absorption peak at 558nm did not rise, if the temperature is increased, will lead to the decrease of the absorbance. Speculation is compound III irradiation isomerization more easily form stable double closed loop structure, so it is difficult to realize the reversible thermal isomerization. Compound III solid film of the present application under light, heat stimulation conditions show irreversible isomerization behavior, this characteristic makes it in the field of information permanent encryption technology show great application prospects. Specifically, the film can be loaded with colorful secret information area after reading, through the simple visible light irradiation process, realize the effective fading of information, until completely changed to colorless state, thus cleverly realize the information hiding and protection. Especially important is that this fading process is irreversible, that is, once the information is hidden, even through heating and other conventional means can not make the secret information again, fundamentally eliminate the risk of information leakage, ensure the safety and reliability of information in the process of permanent encryption. Therefore, the present application not only provides a new technical means for information encryption, but also makes an important step in ensuring information security and preventing information leakage.

Claims

1. A DASA molecular optical switch that enables solid thin film isomerization, characterized in that, 5-((2) Z 4 E )-5-(benzyl((4-methylpyridin-2-yl)methyl)amino)-2-hydroxypent-2,4-diene-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione, with the structural formula shown in Formula III: 。 2. The method of synthesis of the DASA molecular photo-switch of claim 1, characterized in that, Comprising the steps of: (1) 4-methylpyridine-2-carboxaldehyde and benzylamine were reacted in methanol at 78±5°C, after the reaction was completed, sodium borohydride was added under ice water bath condition, then heated to reflux, after the reaction was completed, cooled, removed methanol by rotary evaporation, extracted, rotary evaporation to obtain N benzyl-1-(4-methylpyridin-2-yl)methylamine; (2) 5-(furan-2-ylmethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione and N - benzyl-1-(4-methylpyridin-2-yl)methylamine to give 5-((2Z,4E)-5-(benzyl((4- methylpyridin-2-yl)methyl)amino)-2-hydroxypent-2,4-dien-1-ylidene)-2,2-dimethyl- 1,3-dioxane-4,6-dione.

3. The method of synthesis according to claim 2, wherein, In step (1), the molar ratio of 4-methylpyridine-2-carboxaldehyde: benzylamine = 1:1.05~1.1; the reduction reaction time is more than 1 h, and the reflux reaction time is more than 20 h.

4. The method of synthesis of claim 2, wherein, In step (1), the extraction solvent is CH2Cl2.

5. The method of synthesis of claim 2, wherein, In step (2), the molar ratio of 5-(furan-2-ylmethyl)-2,2-dimethyl-1,3-dioxane-4,6-dione to: N - benzyl-1 -(4-methylpyridin-2-yl)methylamine = 1 : 1.05 ~ 1.

1.

6. The method of synthesis of claim 2, wherein, In step (2), the reaction temperature is 23±3℃, and the reaction time is 25~30 min.

7. Use of the DASA molecule optical switch of claim 1 in the detection of Fe 3+ , Al 3+ or Cu 2+ .​​​

Images