CN114605317B

CN114605317B - Cyanostyrene molecule based on free radical photochromism and application thereof in intelligent glass

Info

Publication number: CN114605317B
Application number: CN202210349783.9A
Authority: CN
Inventors: 魏培发; 丁杨蓝; 何玄
Original assignee: Anhui University
Current assignee: Anhui University
Priority date: 2022-04-02
Filing date: 2022-04-02
Publication date: 2023-07-07
Anticipated expiration: 2042-04-02
Also published as: CN114605317A

Abstract

The invention discloses a cyano-styrene molecule based on free radical photochromism and application thereof in intelligent glass, wherein the structural general formula of the cyano-styrene molecule based on free radical photochromism is shown as follows:

in the general formula: ar represents a benzene ring or other aromatic compound; r is R ₁ Is an aromatic ring or an aromatic heterocyclic ring and derivatives thereof. The cyanostyrene molecule has the characteristic of photo-induced generation of free radicals, shows obvious photochromism, can be doped in a polymer in a low proportion, still keeps good reversible performance, can be applied to the fields of photochromism glass, photo-patterning, information encryption, storage and the like, and has wide application prospect.

Description

Cyanostyrene molecule based on free radical photochromism and application thereof in intelligent glass

Technical Field

The invention relates to a preparation method and application, in particular to a cyano-styrene molecule based on free radical photochromism and application thereof in intelligent glass.

Background

To save energy, to achieve a healthy and natural atmosphere, smart color shifting glasses capable of reversibly adjusting the energy of visible light and solar radiation passing through the glass have been developed. The color of the material can be changed under certain conditions such as illumination, temperature, electric field or current, surface pressure and the like, the color can be changed correspondingly along with the change of the conditions, and the material can be reversibly and automatically restored to the initial state after the applied conditions disappear.

Photochromic materials based on organic molecules have a rich number of modifiable sites, creating the potential for multi-color modulation. The mechanism of color change is mainly a photo-induced chemical reaction, including: isomer formation (proton transfer tautomerization, cis-trans isomerization), cleavage and combination of double bonds (bond isoschizomers and homomeroles), pericyclic reactions, redox reactions, and the like. Most of the researches at present mainly focus on molecules such as azobenzene, diarylethene, fulgide, spiropyran, spirooxazine, schiff base and the like which are main structures, and have good application potential in the aspects of photochemistry, biology, nanotechnology and the like. However, the cis-trans isomerism system such as azobenzene often has hetero atoms (such as N, S and O), which results in complex synthesis and high cost, and limits practical application. The electron transfer tautomerism mechanism based on Schiff base has poor thermal stability, and the condition of the product in solution can be detected by means of advanced and expensive transient absorption spectrum. The charge-concentrated zwitterionic structure is a color-changing intermediate of the spiropyran and a main structure of an open loop, and oxidation degradation of singlet oxygen is easy to occur, which becomes a great disadvantage for preventing the practical application of the spiropyran. Based on typical circumferential reaction of diaryl ethylene, the open ring has two configurations of parallel and antiparallel, and the parallel structure can not form symmetrical ring to become color body, so that the light quantum yield of the system is greatly reduced. Redox mechanisms based on fused ring systems often need to face poor solubility issues, making them difficult and heavy during material preparation. It is further noted that many photochromic molecules can be converted to a desired state in solution, but in a more practical environment, such as doping into a solid matrix (e.g., a polymer matrix), the photochromic properties of the intercalating molecules are strongly affected by the surrounding environment, such as steric hindrance, polarity, etc., and the discoloration reaction is even directly blocked.

The photo-generated free radical color-changing material is a full research direction, and particularly, the photo-generated free radical color-changing material is combined with special magnetism brought by free radicals to accelerate the generation of novel cross leading edge fields (figure 2). The organic compound has the characteristics of adjustable structure, easy modification and the like, and gives various colors of the photo-generated free radicals and adjustable natural advantages, for example, by increasing the conjugation degree of a molecular system, the wavelength of the color development of the free radicals can be red shifted, and the stability of the obtained free radicals can be enhanced, so that the service life of the free radicals is prolonged. There are also some studies focused on anti-counterfeiting and information encryption of photoradical discoloration, etc. The free radical is often darker in color from the property of the free radical itself, and the generation of the photo-induced free radical is less influenced by environmental hindrance and the like than other photo-induced chemical reactions, and is particularly suitable as a photosensitive additive for reducing light transmittance.

Disclosure of Invention

The invention aims to provide a cyanostyrene molecule based on free radical photochromism and application thereof in intelligent glass. The invention utilizes the principle that cyano styrene is photo-induced to generate free radical to change color, and the glass surface is coated with doped polymer to prepare intelligent glass.

The technical scheme adopted for solving the technical problems is as follows:

the invention relates to a cyano styrene molecule based on free radical photochromism, which has the following structural general formula:

in the general formula: ar represents a benzene ring or other aromatic compound; r is R ₁ Is an aromatic ring or an aromatic heterocyclic ring and derivatives thereof.

Further, the formula Ar is selected from one of the following structures:

further, the formula R ₁ Selected from one of the following structures:

n＝0,1,2,3…、/>

n＝0,1,2,3…、/>

the preparation method of the cyanostyrene molecule based on free radical photochromism adopts a typical Knoevenagel condensation reaction, and the reaction route is shown as follows:

the reaction conditions are alcoholic solvents and bases, reference such as Advanced Optical Materials 2019,7,1801348; chem Sci,2021,12,15928-15934; am.chem.soc.,2018,140,1966-1975; and Phys.chem.chem.Phys. 2018,20,28279-28286.

The application of the cyanostyrene molecule based on free radical photochromism is used for preparing intelligent glass. Specifically, the cyanostyrene molecules are doped in a polymer and coated on the surface of glass to prepare the intelligent glass.

Further, the color of the generated radicals can be adjusted by protonating the pyridine groups at the end of TCS, specifically, the compound can be blended with an acid, the compound reacted with methyl iodide to generate an iodized salt, and the iodized salt of the compound exchanged anions such as hexafluorophosphate, tetrafluoroborate, and the like.

Further, the doping proportion of the cyanostyrene molecule is 1% -40%. A range may be possible without being limited to 3% in the embodiment.

The invention has the advantages of few steps of synthesizing the cyano styrene molecules, simple separation and purification operation, good stability, light-induced free radical generation, obvious photochromic performance, good reversibility when being doped in a polymer in a low proportion, wide application prospect, and the like, and can be applied to the fields of photochromic glass, photo-patterning, information encryption and storage.

Drawings

FIG. 1 shows the nuclear magnetic resonance hydrogen spectrum of TCS.

FIG. 2 is a nuclear magnetic resonance carbon spectrum of compound TCS.

Fig. 3 is a high resolution mass spectrum of compound TCS.

FIG. 4 shows the nuclear magnetic resonance hydrogen spectrum of the generated cyclobutane after photo-dimerization of TCS crystals compared with the original TCS.

FIG. 5 shows EPR spectra before and after illumination of TCS crystals after grinding.

Fig. 6 is an XRD spectrum before and after grinding of TCS crystals.

FIG. 7 is a comparison of hydrogen spectra after illumination discoloration after TCS crystal grinding with nuclear magnetic resonance hydrogen spectra after photodimerization of TCS crystals and TCS nuclear magnetic resonance hydrogen spectra.

Fig. 8 is an ultraviolet visible absorption trace spectrum of TCS solution when slowly faded in air after light discoloration.

FIG. 9 shows the absorption profile of FIG. 8 at wavelengths of 600nm and 317 nm.

FIG. 10 is an ultraviolet-visible absorption spectrum of TCS solution at various illumination times.

FIG. 11 is a graph showing fluorescence emission spectra of TCS solutions at various illumination times.

FIG. 12 shows the absorption intensity variation (left axis) and fluorescence intensity variation (right axis) at 415nm at different illumination times of 600nm and 317 nm.

FIG. 13 shows the hydrogen nuclear magnetic resonance spectra of TCS solutions at different illumination times.

FIG. 14 shows the photoreaction mechanism of TCS solution.

FIG. 15 is a nuclear magnetic resonance hydrogen spectrum of TCS photo-cyclized product TCS-SP.

FIG. 16 is a nuclear magnetic resonance carbon spectrum of TCS photo-cyclized product TCS-SP.

FIG. 17 is a high resolution mass spectrum of TCS photo-cyclized product TCS-SP.

FIG. 18 is the UV-visible spectrum of TCS in dichloromethane/methanol/trifluoroacetic acid (v/v/v, 10/1/0.05) solution (10. Mu.M) under UV irradiation at various times.

FIG. 19 is a graph showing the change in absorption intensity with time of illumination at 317nm and 655nm in FIG. 15.

FIG. 20 is a graph showing the transmittance of TCS@PMMA film before and after UV irradiation and after heating.

FIG. 21 is a graph showing the transmittance of TCS/TFA@PMMA film before and after UV irradiation and after heating.

FIG. 22 is a graph showing the cycle times of the discoloration and fading process for TCS/TFA@PMMA films.

FIG. 23 is a graph showing the effect of temperature on the fade time of TCS/TFA@PMMA film.

Fig. 24 is a schematic diagram of an encryption and optical information storage procedure.

FIG. 25 is a nuclear magnetic resonance hydrogen spectrum of the compound TDCS hexafluorophosphate.

FIG. 26 is an ultraviolet-visible absorption spectrum of a TDCS solution of a compound illuminated for various times.

FIG. 27 is a nuclear magnetic resonance hydrogen spectrum of Compound TSCS.

FIG. 28 is a nuclear magnetic resonance carbon spectrum of compound TSCS.

Fig. 29 is a high resolution mass spectrum of compound TSCS.

FIG. 30 is an ultraviolet visible absorption spectrum of a solution of the compound TSCS illuminated for various periods of time.

Detailed Description

For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention uses a cyano-styrene molecule with photo-induced free radical color change, and the chemical general formula is:

in the general formula: ar is benzene ring or other aromatic compound; r is R ₁ Is an aromatic ring or an aromatic heterocyclic ring and derivatives thereof.

Further, the formula Ar is preferably one of the following structures:

further, formula R ₁ One of the following structures is preferred:

n＝0,1,2,3…、/>

n＝0,1,2,3…、/>

example 1:

the synthetic route for compound TCS is as follows:

synthesis of compound TCS: trimesic aldehyde (0.10 g,0.62 mmol), 4-pyridine acetonitrile hydrochloride (0.24 g,1.28 mmol) and sodium hydroxide (0.20 g,4.93 mmol) were dissolved in 10ml methanol solution and after ultrasonic treatment at room temperature for 10 min, a white precipitate formed; the resulting mixture was filtered, washed with methanol, and the filter cake was purified by silica gel column chromatography (eluent: dichloromethane: methanol=100:3, V/V) to give TCS (0.10 g, 35%) as a white solid. Characterization of the white solid obtained, characterization data obtained: ¹ H NMR(400MHz,DMSO-d ₆ as in fig. 1), delta (ppm): 8.72 (s, 6H), 8.51 (s, 6H), 7.79 (s, 6H). ¹³ C NMR(100MHz,CDCl ₃ /CD ₃ OD, v/v,5/1, FIG. 2), delta (ppm): 150.50,143.42,141.56,135.08,132.49,120.67,116.38,112.58.HRMS: m/zcalcd.for C ₃₀ H ₁₈ N ₆ 462.1593, found:462.1599. As in FIG. 3.

Example 2:

the compound TCS prepared in example 1 was tested for properties by the following procedure:

(1) Colorless prismatic TCS crystals can be easily obtained by slow vapor evaporation from a mixed solution of methylene chloride and methanol.

(2) The TCS crystals can photodimerize under light to form cyclobutane, as evidenced by nuclear magnetic resonance hydrogen spectroscopy, as shown in FIG. 4.

(3) The TCS crystals after milling change from white to blue after illumination and fade slowly in air, and the process can be repeated multiple times. FIG. 5 shows Electron Paramagnetic Resonance (EPR) test of samples before and after illumination, the samples after illumination have obvious EPR signals, and the TCS samples after ultraviolet light induced grinding are proved to generate free radicals, and g value is 2.004, which corresponds to typical carbon free radicals. The samples before and after milling were subjected to powder X-ray diffraction testing, as shown in fig. 6, demonstrating that milling disrupts the manner in which TCS crystals are stacked. Comparing the blue-colored TCS sample with the TCS crystals before and after illumination (see fig. 7), the blue sample did not undergo chemical reaction and the TCS structure was maintained. In conclusion, grinding damages the stacking mode of TCS crystals, and under the induction of ultraviolet rays, white TCS powder generates relatively stable blue free radicals.

(4) For TCS solutions, photoreaction also occurs under irradiation of ultraviolet lamps. The short illumination turns the colorless transparent solution to a deep blue color and easily fades in air, and the fading process is monitored using the uv-vis spectrum as shown in fig. 8 and 9, which is not only reversible but can be repeated several times.

(5) The TCS solution was continuously irradiated for a long period of time, and the blue color slowly faded to pale yellow, and the course of the photoreaction was tracked using ultraviolet-visible absorption spectroscopy in fig. 10. First, a new absorption peak appears at 600nm after illumination, which corresponds to the process of changing the solution from colorless to blue, and the peak rises with the illumination time, and when the illumination time exceeds 20s, the peak falls with the illumination time, which corresponds to the process of fading the blue solution. When the illumination time exceeds 40s, the solution is changed from colorless to pale yellow slowly, and the peak at 317nm is raised back and gradually becomes stable. This is also a fluorescence-on procedure, which is monitored by fluorescence emission spectroscopy (PL) in fig. 11, where the emission peak at 415nm first drops, since the generated radicals quench the fluorescence, and then slowly rises with increasing illumination time, the solution changes from almost no fluorescence to bright blue fluorescence. FIG. 12 shows the change in absorbance intensity (left axis) and fluorescence intensity (right axis) at 600nm and 317nm for TCS solutions at different illumination times. The TCS solution photoreaction was monitored using nuclear magnetic resonance hydrogen spectroscopy, with two new single peaks at δ10.17ppm (Ha) and δ9.75ppm (Hb) and two peaks at δ9.11ppm (Hc) and δ8.31ppm (Hd), with a corresponding increase in their intensity with increasing illumination time, the signal of the original compound TCS decreasing dramatically (fig. 13, i-v). The product after the purification of the photoreaction was also characterized by nuclear magnetic resonance hydrogen spectroscopy (fig. 13, vi, fig. 15) and nuclear magnetic resonance carbon spectroscopy (fig. 16). Four distinct sets of split peaks in the nuclear magnetic resonance hydrogen spectrum indicate that the structure should be highly symmetrical. In addition, a new peak of m/z456.1131 appears in the mass spectrum, which corresponds to the molecular mass of TCS minus the mass of six hydrogen atoms (fig. 17). In combination with the above phenomena and data, the reaction mechanism is shown in fig. 14: the free radicals generated on the three arms are simultaneously subjected to E/Z isomerization, and then a typical styrene 6-pi electron photocyclization reaction is carried out, so that a cyclized product TCS-SP is obtained.

Example 3:

practical application of the compound TCS prepared in example 1 was designed as follows:

(1) The color of the free radical generated was adjusted by protonating the pyridine groups at the TCS terminus, as shown in fig. 18, by adding a small amount of trifluoroacetic acid to the TCS solution and tracking the photoreaction of the acidified TCS solution with uv-vis absorption spectroscopy. As can be seen from fig. 18 and 19, a new absorption peak appears at 655nm with a concomitant decrease in peak at 317nm, and the corresponding solution changes from colorless to green.

(2) TCS was homogeneously doped in a polymethyl methacrylate (PMMA) film in a proportion of 3% (TCS/PMMA, wt%) and designated TCS@PMMA. The polymer is more favorable for the stabilization of free radicals, and the white TCS@PMMA film can quickly turn blue after illumination. While heating will fade the color at 120 c, this process cannot be repeated (fig. 20).

(3) The acidified TCS was homogeneously doped in a polymethyl methacrylate (PMMA) film in a ratio of 3% (TCS/PMMA, wt%) and designated TCS/TFA@PMMA. The film changes from colorless transparent to green under the induction of ultraviolet light. However, the green color of the TCS/tfa@pmma film began to fade at a relatively low temperature of 70 ℃, figure 17 tested the effect of temperature on fade time and turned green again after re-irradiation (figure 21). This reversible process may be repeated multiple times (fig. 22). FIG. 23 is a graph showing the effect of temperature on the film discoloration time, and shows that the film was discolored within 2 minutes at 70 ℃.

(4) Fig. 24 is a schematic diagram of a pattern design encryption and optical information storage procedure, and it is apparent that other techniques such as screen printing may achieve the same effect. The TCS@PMMA and TCS/TFA@PMMA films are coated on the surface of glass, and the glass can be discolored under the irradiation of sunlight, so that the compound TCS can be applied to the field of intelligent glass.

As can be seen from the above examples, the cyano-styrene molecule provided by the invention has the characteristic of photo-induced generation of free radicals, shows obvious photochromism, can be doped in a polymer in a low proportion, still maintains good reversible performance, can be applied to the fields of photochromism glass, photo-patterning, information encryption, information storage and the like, and has wide application prospects.

Example 4:

compound TDCS was synthesized in the same manner as in example 1 and by salifying protonated pyridine, the synthetic route is as follows:

trimesic aldehyde (0.10 g,0.62 mmol) and 4-pyridine benzyl cyanide (0.40 g,2.04 mmol) were dissolved in 5mL of t-butanol, 1mL of a methanol solution of tetrabutylammonium hydroxide (mass fraction: 40%) was added, stirred and refluxed overnight, then dried by spin, and recrystallized from methanol and dichloromethane for preliminary purification, followed by purification by silica gel column chromatography (eluent: dichloromethane: methanol=100:3) to give yellow solid powder TDCS.

Protonation of compound TDCS: dissolving 50mg of a compound TDCS in 8mLN, N-Dimethylformamide (DMF) solution, adding 0.4mL of methyl iodide, stirring overnight at room temperature, changing the solution from yellow to orange, adding 50mLDCM, precipitating a solid, carrying out suction filtration, washing a filter cake, and drying to obtain an iodized salt of the TDCS; dissolving the iodine salt of the TDCS in a small amount of dimethyl sulfoxide solution, then dropwise adding the solution into an excessive ammonium hexafluorophosphate aqueous solution, precipitating yellow precipitate, filtering, washing with a large amount of water, and drying to obtain the hexafluorophosphate of the TDCS.

Similar to compound TCS, the solution of compound TDCS also turned from colorless to blue after illumination, as shown in fig. 26. Whereas protonated TDCS, i.e., hexafluorophosphate solutions of TDCS, turn from colorless to green upon illumination. The properties of both compounds are highly similar.

Example 5: compound TSCS was synthesized in the same manner as in example 1, and the synthesis route was as follows:

trimesic aldehyde (0.03 g,0.185 mmol) and 2-thiopheneacetonitrile (0.08 g,0.65 mmol) were dissolved in 5mL ethanol, and after sonication for 30 min at room temperature, a yellow precipitate precipitated. The resulting mixture was filtered, washed with methanol, and the filter cake was purified by silica gel column chromatography (petroleum ether: dichloromethane=1:1, V/V as eluent) to give TSCS as a yellowish green solid (0.05 g, 57%). Characterization of the TSCS, the characterization data obtained: ¹ H NMR(400MHz,CDCl ₃ as in fig. 27), delta (ppm) 8.27 (s, 3H), 7.47-7.46 (d, j=4 hz, 3H), 7.44 (s, 3H), 7.39-7.37 (d, j=8 hz, 3H), 7.12-7.10 (dd, J) ₁ ＝5.08Hz,J ₂ ＝3.72Hz,3H). ¹³ C NMR(100MHz,CDCl ₃ As in fig. 28), delta (ppm): 138.55,137.26,135.21,130.37,128.45,128.40,127.39,116.39,108.89.Hrms: m/zcalcd.for C ₂₇ H ₁₅ N ₃ S ₃ 477.0428, found:478.0502. See FIG. 29.

Under the monitoring of an ultraviolet-visible spectrophotometer, as shown in fig. 30, a new absorption peak appears at 550nm of the methylene dichloride solution of TSCS after being irradiated by an ultraviolet lamp, and the solution can be changed into light purple after being colorless and transparent and is quickly disappeared, which shows that the TSCS is the same as TCS, and the ultraviolet light can induce the generation of free radicals at room temperature.

Synthetic representations and applications not specifically described in the specification are well known in the art and are readily ascertained and unobjectionable in practicing the present invention. The foregoing embodiments are merely illustrative of preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but can be easily implemented by anyone skilled in the art within the scope of the present invention without changing the claims to relate to the basic principle or the substitution, and the scope of the present invention shall be covered by the claims.

Claims

1. Use of a cyanostyrene molecule based on free radical photochromism, characterized in that: the cyanostyrene molecule is used as a photosensitive additive for preparing intelligent glass;

the radical photochromic-based cyanostyrene molecule is selected from the following structures:

2. the use according to claim 1, characterized in that:

the cyanostyrene molecules are doped in a polymer and coated on the surface of glass to prepare smart glass.

3. The use according to claim 1, characterized in that:

the cyanostyrene molecule has the property of photo-induced generation of free radicals, and shows obvious photochromism, and the color of the generated free radicals can be regulated by protonating pyridine groups at the tail end of the cyanostyrene molecule.