A pyrene-based viologen and its preparation method, and an electrochromic device

Abstract

The present invention discloses a pyrene-based viologen, a preparation method thereof, and an electrochromic device. The pyrene-based viologen comprises a compound represented by the general formula (I): #imgabs0#, wherein R is one of methyl, benzyl, methylnaphthalene, methylanthracene, methylbenzo[a]pyrene, methylpyrene, methylphenanthrene, and methylperylene. The pyrene-based viologen molecular design of the present invention forms a unique electron donor-donor-donor conjugated structure by introducing pyrene, benzyl, methylnaphthalene, methylanthracene, methylbenzo[a]pyrene, methylpyrene, methylphenanthrene, or methylperylene and utilizing the hyperconjugation effect of methylene groups. This significantly improves the optical and electrical properties of the viologen, in particular the fluorescence performance and coloring efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochromic device development, and relates to a pyrene-based viologen and a preparation method thereof, and an electrochromic device. Background Art

[0002] Electrochromism refers to the stable and reversible change of the optical properties of a material (absorption wavelength, reflectivity, transmittance, etc.) under the action of an external voltage, which manifests itself as a reversible change in color and transparency. Electrochromic devices have been widely used in self-powered smart windows, photoelectric switches and optical sensors, electronic writing, anti-glare glass, etc. At present, the commonly used organic electrochromic material is viologen, which is a type of diquaternized bipyridyl salt. This type of compound has three stable redox states. The most stable state of the viologen molecule is the divalent cation (RV 2+ ), after two distinct step-by-step, stable and reversible single-electron reduction processes, a radical cation (RV +● ) and a neutral species (RV), accompanied by a two-step distinct color change. Viologen molecules achieve reversible coloring and fading through redox reactions involving electron gain and loss. Compared to inorganic electrochromic materials, viologen-based organic electrochromic materials offer advantages such as fast color change, wide viewing angles, and high coloring and fading contrast. Viologen-based materials also feature low driving voltage, energy savings, and the ability to maintain color after power failure (a memory function). Consequently, research on viologen-based electrochromic materials has made significant progress.

[0003] However, viologen compounds readily self-aggregate in the radical cationic state, forming dimers, which degrades their color-changing properties. Furthermore, the wide energy gap, low degree of conjugation, and poor luminescence properties of viologen molecules result in low fluorescence emission efficiency in the excited state, making them difficult to observe effectively in night vision or low-light environments. Furthermore, existing electrochromic devices have complex structures, typically consisting of a multilayer composite structure consisting of a transparent conductive electrode (such as indium tin oxide conductive glass), an electrochromic layer, an electrolyte layer, and an ion storage layer. This multilayer composite structure requires precise fabrication of each layer, with clear and smooth interfaces between layers. This not only increases fabrication difficulty and process complexity, but also requires precise control of process steps such as deposition, coating, and heat treatment between layers to ensure device performance and stability. Each layer in the multilayer structure may have defects or flaws, which can lead to device performance degradation or failure. Interfaces between layers may also be subject to instabilities, such as chemical reactions and diffusion, which can affect the long-term stability and reliability of the device. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a pyrene-based viologen and a preparation method thereof, as well as an electrochromic device, thereby solving the technical problem in the prior art that the fluorescence efficiency of the viologen molecule is low, resulting in it being difficult to effectively observe in night vision or low-light environments. At the same time, it also solves the technical problems in the prior art that the electrochromic device has a complicated structure, a complex preparation process, and poor reliability.

[0005] The present invention is achieved through the following technical solutions:

[0006] A pyrene-based viologen, comprising a compound represented by the general formula (I):

[0007]

[0008] Wherein, R is one of methyl, benzyl, methylnaphthalene, methylanthracene, methylbenzopyrene, methylpyrene, methylphenanthrene and methylperylene.

[0009] Preferably, the method comprises the following steps:

[0010] S1: Cs2CO3, 1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, 2,7-dibromopyrene and pyridine-4-boronic acid were added to DMF and stirred to react to obtain compound 1;

[0011] S2: Compound 1 is dissolved in an ultra-dry organic solvent, and methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene are added dropwise to the reaction system, and the mixture is stirred for reaction to obtain Compound 2;

[0012] S3: Compound 2 is placed in a saturated aqueous solution of NH4PF6 and stirred to obtain the compound represented by the general formula (I).

[0013] Preferably, in step S1, after the stirring reaction is completed, the organic phase is extracted with chloroform and water, and then the organic phase is decompressed to remove the solvent, and finally washed with n-hexane to obtain the compound 1.

[0014] Preferably, in step S2, methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene are added dropwise at 0°C, and the stirring reaction temperature is 25-110°C.

[0015] Preferably, in step S2, after stirring the reaction, the solid is collected by centrifugation, dried and dissolved in acetonitrile, and then n-hexane is added to precipitate the solid, the precipitate is collected by centrifugation, and the precipitate is washed with dichloromethane and n-hexane to obtain the compound 2.

[0016] Preferably, in step S2, the ultra-dry organic solvent is ultra-dry dichloromethane or ultra-dry N,N-dimethylformamide.

[0017] A method for preparing an electrochromic device comprises sandwiching the above-mentioned pyrene-based viologen in a sealed conductive layer.

[0018] Preferably, the pyrenyl viologen is dissolved in N,N-dimethylformamide and then sandwiched in a closed conductive layer.

[0019] Preferably, the conductive layer is conductive glass or conductive film.

[0020] An electrochromic device is prepared by the above method.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The present invention discloses a pyrene-based viologen. Pyrene is a polycyclic aromatic hydrocarbon containing four fused benzene rings. The introduction of pyrene into the viologen molecule creates an electron donor-acceptor structure that effectively improves charge transfer efficiency and reduces the band gap, thereby enhancing the viologen's optical and electrical properties. Simultaneously, benzyl, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene, or bromomethylperylene are attached to either side of the pyrene. This hyperconjugation effect of the methylene groups further expands the conjugated system, forming an electron donor-donor-donor conjugated structure. This further evenly distributes the electron cloud, effectively improving the coloring efficiency of the electrochromic device and the fluorescence properties of the viologen molecule, resulting in excellent visibility in night vision or low-light environments. By introducing pyrene as an electron donor, which combines with the viologen's electron acceptor, the present invention forms an efficient electron transfer channel, significantly improving charge transfer efficiency. The optimized molecular structure reduces the band gap, making it easier for electrons to be excited and transmitted, thereby improving the optical and electrical properties of viologen. The electron donor-donor-donor conjugated structure makes the electron cloud uniformly distributed inside the molecule, improving the coloring efficiency of the electrochromic device. By expanding the conjugated system and optimizing the electron distribution, the fluorescence performance of the viologen molecule has been significantly improved, so that the device has good visibility in night vision or low light environments. The pyrenyl viologen molecule design of the present invention introduces pyrene, benzyl, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene, and utilizes the hyperconjugation effect of the methylene group to form a unique electron donor-donor-donor conjugated structure, which significantly improves the optical and electrical properties of viologen, especially the fluorescence performance and coloring efficiency.

[0023] Furthermore, the present invention discloses a method for preparing the aforementioned pyrenyl viologen. First, Cs2CO3, 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride, 2,7-dibromopyrene, and pyridine-4-boronic acid are added to DMF and stirred for reaction to obtain compound 1. Compound 1 is then dissolved in an ultra-dry organic solvent, and methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene, or bromomethylperylene are slowly added to the reaction system and stirred for reaction to obtain compound 2. Finally, compound 2 is placed in a saturated aqueous solution of NH4PF6 and stirred to obtain the compound represented by general formula (I). This method is easy to control and improves the accuracy and repeatability of the preparation. In step S1, Cs2CO3 is used as the alkaline source and 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride is used as the catalyst. The selection of these materials helps promote the reaction and improve reaction efficiency. At the same time, the introduction of 2,7-dibromopyrene and pyridine-4-boronic acid provides the foundation for the subsequent construction of the pyrenyl viologen molecule. In step S2, by slowly adding methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene, or bromomethylperylene to the reaction system, the structure of compound 1 can be modified and different functional groups can be introduced, thereby obtaining compound 2 with different properties. Finally, in step S3, by placing compound 2 in a saturated aqueous solution of NH4PF6, the target product can be conveniently separated from the reaction system and purified. This purification method is simple and effective, helping to improve the purity and quality of the product. The pyrenyl viologen prepared by the above method has an excellent electron donor-acceptor structure, which can effectively improve charge transfer efficiency and reduce the band gap, thereby improving the optical and electrical properties of the viologen. In addition, by introducing structural units such as pyrene and benzyl, the coloring efficiency and fluorescence performance of electrochromic devices can be further improved, making them have good visibility in night vision or low-light environments.

[0024] Furthermore, in step S1, after the stirring reaction is completed, the organic phase is extracted with chloroform and water, and then the organic phase is decompressed to remove the solvent, and finally washed with n-hexane to obtain the compound 1. The use of chloroform and water for extraction can efficiently separate the reaction product from the reaction system. Since the solubility of compound 1 in the organic phase is high, while the by-products and unreacted substances remain more in the aqueous phase, this extraction method can achieve effective product separation. By removing the solvent under reduced pressure, most of the solvent in the reaction system can be removed, so that the concentration of compound 1 is increased. At the same time, the decompression operation also helps to remove some volatile impurities, thereby further improving the purity of the product. Using n-hexane to wash compound 1 can take advantage of its solubility differences in different solvents to remove residual unreacted substances, by-products and other impurities. This step is crucial for improving the purity and quality of the product. After the above purification steps, the obtained compound 1 has higher purity and better properties. This provides a basis for its further reaction and application in subsequent steps, and helps to prepare pyrenyl viologen with better performance. This process improves preparation efficiency and product quality.

[0025] Further, in step S2, methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene are slowly added at 0 ° C, and the temperature of the stirring reaction is 25 ~ 110 ° C. Slowly adding methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene at 0 ° C is beneficial to controlling the initial rate of the reaction, reducing the occurrence of side reactions, thereby improving the selectivity of the target product compound 2. The reaction temperature is 25 ~ 110 ° C, which makes the reaction more stable and avoids the problems of increased by-products and decreased product purity caused by violent reactions. Stirring the reaction at 25 ~ 110 ° C is beneficial for the reactants to be fully mixed and the reaction to proceed. In addition, the reaction rate at 25 ~ 110 ° C is moderate, which is beneficial for the complete reaction, thereby improving the yield of product 2. The reaction is divided into two stages: slow addition and stirring, and carried out at different temperatures, which is beneficial to optimize the entire preparation process. This staged reaction process can better control the reaction conditions and progress, and improve preparation efficiency and product quality.

[0026] Furthermore, in step S2, after the stirring reaction, the solid is collected by centrifugation, dried and dissolved with acetonitrile, then normal hexane is added to precipitate the solid, the precipitate is collected by centrifugation, and the precipitate is washed with dichloromethane and normal hexane to obtain the compound 2. By centrifugation, the solid product in the reaction system can be efficiently isolated. After drying, acetonitrile is used to dissolve it, which can further remove the solvent and impurities that may remain in the solid. Then, normal hexane is added to precipitate the solid, and the difference in solubility of the compound by different solvents is utilized to achieve effective separation and purification of the product. The precipitate is washed with dichloromethane and normal hexane, which can further remove impurities and unreacted substances attached to the solid surface. This washing process helps to improve the purity of product 2 and provide high-quality raw materials for subsequent steps. By steps such as centrifugation, dissolving, precipitation and washing, efficient separation and purification of product 2 can be achieved. This process optimization not only improves preparation efficiency, but also reduces production costs. At the same time, the use of common solvents such as acetonitrile, normal hexane and dichloromethane also reduces raw material costs. Compound 2, obtained through the aforementioned treatment steps, possesses high purity and favorable properties, making it suitable for subsequent reactions and applications. This will contribute to the preparation of even more superior pyrenyl viologens and expand their applications in fields such as electrochromic devices.

[0027] Furthermore, in step S2, the ultra-dry organic solvent is ultra-dry dichloromethane or ultra-dry N,N-dimethylformamide. The ultra-dry organic solvent has an extremely low moisture content, which helps reduce side reactions caused by moisture, improving reaction efficiency and the purity of the target product (Compound 2). In the preparation of pyrenyl viologen, the presence of moisture can affect the selectivity of the reaction and the stability of the product. The use of an ultra-dry solvent can effectively avoid this problem. Ultra-dry dichloromethane and DMF both have excellent solubility properties, ensuring uniform distribution of Compound 1 in the reaction system and promoting smooth reaction progress. The synthesis of pyrenyl viologen requires sufficient contact and mixing between the reactants, and ultra-dry solvents play a key role in this regard. The low impurity content in ultra-dry solvents can minimize the impact on product stability, resulting in the final pyrenyl viologen with better stability and chemical properties. The use of ultra-dry solvents also helps reduce safety issues caused by solvent impurities, such as the risk of fire and explosion. Choosing ultra-dry dichloromethane or DMF as solvents can optimize the preparation process and improve production efficiency. Although the cost of ultra-dry solvents may be slightly higher, they are economical in the entire preparation process because they can improve reaction efficiency and purity and reduce subsequent processing steps and costs.

[0028] In addition, the present invention also discloses a method for preparing an electrochromic device, in which the above-mentioned pyrene-based viologen is sandwiched in a sealed conductive layer to obtain the device. The electron donor-donor-donor conjugated structure of the pyrene-based viologen in the present invention allows the electron cloud to be evenly distributed inside the molecule, effectively improving the coloring efficiency of the electrochromic device. At the same time, this structure also enhances the fluorescence properties of the viologen molecules, so that the device has good visibility in night vision or low-light environments. The pyrene-based viologen is sandwiched in a sealed conductive layer to ensure the stability of the internal environment of the device and reduce the impact of external environmental factors on the device performance. This structure can also protect the pyrene-based viologen molecules from physical and chemical damage, thereby improving the reliability and service life of the device. The use of the sandwich method to prepare electrochromic devices simplifies the preparation process and reduces production costs. At the same time, this preparation method can also achieve precise control of the device structure and further optimize the performance of the device.

[0029] Furthermore, the pyrenyl viologen is dissolved in N,N-dimethylformamide (DMF), an excellent organic solvent with good solubility for many organic compounds, including pyrenyl viologen. This allows the pyrenyl viologen to dissolve uniformly and fully in DMF, forming a stable solution. The pyrenyl viologen dissolved in DMF can be evenly coated on the conductive layer using various coating techniques (such as spin coating, spray coating, and dip coating). This uniform coating ensures uniform distribution of the pyrenyl viologen within the electrochromic device, thereby enhancing device performance. The pyrenyl viologen solution in DMF easily forms a uniform, dense film on the conductive layer. This film not only exhibits excellent electrical properties but also effectively prevents direct contact between the internal materials of the electrochromic device and the external environment, improving device stability. Dissolving pyrenyl viologen in DMF and then coating it within the conductive layer simplifies the fabrication process of the electrochromic device. This simple fabrication method reduces production costs and improves efficiency.

[0030] Furthermore, the conductive layer is made of conductive glass or conductive film. Both conductive glass and conductive film have excellent electrical conductivity, ensuring efficient charge transfer during operation of the electrochromic device, thereby achieving rapid and stable color changes. Both conductive glass and conductive film typically have high transparency. This ensures that the electrochromic device changes color without significantly affecting its light transmittance, enabling it to maintain excellent visual quality in applications requiring high light transmittance, such as smart windows. Conductive glass and conductive film typically have high mechanical strength, capable of withstanding a certain degree of physical shock and vibration. This makes the electrochromic device more stable and reliable during use, extending its service life. Conductive glass and conductive film both have excellent processability and can be precisely processed through processes such as cutting and etching, thereby meeting the requirements of electrochromic devices of various sizes and shapes. High-quality conductive glass and conductive film materials generally have good chemical stability, capable of resisting a certain degree of chemical corrosion and oxidation. This enables the electrochromic device to maintain stable performance even in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 Schematic diagram of a process for preparing pyrenyl viologen in the present invention;

[0033] Figure 2 Schematic diagram of the structure of an electrochromic device in the present invention;

[0034] Figure 3 The cyclic voltammograms of the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention at different scan rates are shown, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0035] Figure 4 The UV-visible absorption spectra of the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention after reduction with metallic zinc and sodium are shown, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0036] Figure 5 The fluorescence spectra of the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention after reduction with metallic zinc and sodium are shown, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0037] Figure 6 The UV-visible absorption spectra of the electrochromic devices prepared using the pyrene viologen prepared in Examples 1 to 3 of the present invention after power is applied, wherein (a to b) are respectively the UV-visible absorption spectra of the electrochromic devices V and V of the pyrene viologen prepared using Example 1 of the present invention. 2+ →V +• and V +• →UV-visible spectra during the two changes of V, (c~d) are respectively the electrochromic device V prepared by using the pyrene viologen prepared in Example 2 of the present invention 2+ →V +• and V +• The UV-visible spectra during the two changes of V are shown in Figure 1, (e~f) are respectively the UV-visible spectra of the electrochromic device V prepared by using the pyrene viologen prepared in Example 3 of the present invention. 2+ →V +• and V +• →UV-visible spectra during the two changes of V;

[0038] Figure 7 The relationship between the transmittance of electrochromic devices prepared using the pyrene violet prepared in Examples 1 to 3 of the present invention at a wavelength of 670 nm and time, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0039] Figure 8 The coloring efficiency of the electrochromic device prepared using the pyrene violet prepared in Examples 1 to 3 of the present invention, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0040] Figure 9 The voltage response curves of the electrochromic devices prepared using the pyrene-containing violet prepared in Examples 1 to 3 of the present invention, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0041] Figure 10 The following are the color changes of electronic warning signs prepared using the pyrene viologen prepared in Examples 1 to 3 of the present invention under different conditions, where (a) is Example 1, (b) is Example 2, and (c) is Example 3;

[0042] Figure 11 These are the flexibility test results of flexible electrochromic devices prepared using the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention; wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3.

[0043] Among them: 1. conductive layer, 2. nano double-sided tape, 3. pyrene-based viologen. DETAILED DESCRIPTION

[0044] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0045] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0046] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0047] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0048] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0049] The present invention provides a pyrene-based viologen, comprising a compound represented by the general formula (I):

[0050]

[0051] Wherein, R is methyl, benzyl, methylnaphthalene, methylanthracene, methylbenzopyrene, methylpyrene, methylphenanthrene or methylperylene.

[0052] In addition, the present invention also discloses a method for preparing pyrenyl viologen, such as Figure 1 The following steps are shown:

[0053] S1: Cs2CO3, 1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, 2,7-dibromopyrene, and pyridine-4-boronic acid were added to DMF, stirred for reaction, and the organic phase was extracted with chloroform and water. The solvent was then removed from the organic phase under reduced pressure, and the organic phase was washed with n-hexane to obtain compound 1;

[0054] The structural formula of the compound 1 is:

[0055] ;

[0056] S2: Compound 1 is dissolved in an ultra-dry organic solvent, and methyl trifluoromethanesulfonate, benzyl bromide, bromomethylnaphthalene, bromomethylanthracene, bromomethylbenzopyrene, bromomethylpyrene, bromomethylphenanthrene or bromomethylperylene are slowly added to the reaction system at 0°C. The reaction is stirred at 25-110°C, and the solid is collected by centrifugation. After drying, the solid is dissolved in acetonitrile, and then n-hexane is added to precipitate the solid. The precipitate is collected by centrifugation, and the precipitate is washed with dichloromethane and n-hexane to obtain compound 2;

[0057] The structural formula of the compound 2 is:

[0058] ;

[0059] R is one of methyl, benzyl, methylnaphthalene, methylanthracene, methylbenzopyrene, methylpyrene, methylphenanthrene and methylperylene;

[0060] When methyl trifluoromethanesulfonate is added and the reaction is stirred at room temperature, methyl trifluoromethanesulfonate is a strongly acidic reagent with strong corrosiveness and toxicity. Slowly adding it at 0°C can reduce its volatility and irritation, thereby reducing operational risks.

[0061] The ultra-dry organic solvent is ultra-dry dichloromethane or ultra-dry N,N-dimethylformamide.

[0062] S3: Compound 2 is placed in a saturated aqueous solution of NH4PF6 and stirred to obtain compound 3, which is the compound represented by the general formula (I).

[0063]

[0064] In addition, the present invention also discloses a method for preparing an electrochromic device, which is prepared by sandwiching the above-mentioned pyrene-based viologen in a closed conductive layer. Preferably, the pyrene-based viologen is dissolved in N,N-dimethylformamide and then sandwiched in a closed conductive layer, and the above-mentioned conductive layer is conductive glass or conductive film.

[0065] like Figure 2As shown, a specific preparation method may include: hollowing out a warning message on a sticky note, attaching the sticky note to the conductive surface of a conductive layer 1 coated with fluorine-doped tin oxide, etching the warning message into the conductive layer 1 with hydrogen, and removing the sticky note. The conductive surfaces of the glass sheets are placed facing each other, and nano double-sided tape 2 is used to adhere the conductive layer 1 around the edges to form a sealed cavity (note that the upper and lower glass sheets must leave space for the electrode clamp). Pyrenyl viologen 3 is dissolved in N,N-dimethylformamide and added to the prepared device cavity. Finally, the device is completely sealed with UV-curable adhesive to obtain the electrochromic device. In the above electrochromic device, the conductive layer 1 can be conductive glass or a conductive film, thus obtaining a flexible electrochromic device. The conductive film can be a polyethylene terephthalate conductive film coated with indium tin oxide.

[0066] This method introduces pyrene into the viologen molecule, forming an electron donor-acceptor structure that effectively improves charge transfer efficiency and lowers the band gap, enhancing the optical and electrical properties of the viologen. Further, through a substitution reaction, benzyl, methylnaphthalene, methylanthracene, methylbenzopyrene, methylpyrene, methylphenanthrene, or methylperylene are attached to both sides of the pyrene. The hyperconjugation effect of the methylene group further expands the conjugated system to form an electron donor-donor-donor conjugated structure (Compound 3), which further evenly distributes the electron cloud and effectively improves the coloring efficiency of the electrochromic device.

[0067] The invention also discloses an electrochromic device prepared by the method.

[0068] This invention combines a redox-sensitive viologen with a highly fluorescent pyrene. Under voltage, the compound's fluorescence is gradually quenched, achieving electroluminescent color change. This pyrene-based viologen serves as the active material in an electronic warning sign. This sign boasts high color contrast, clearly displaying warning messages; dynamic information display enhances awareness; and adapts to various light and dark environments, embracing diverse applications. Furthermore, because pyrene-based viologen is unaffected by factors such as device shape and external stress, it can be applied to flexible electrochromic devices that can be bent to a certain angle.

[0069] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0070] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0071] Example 1

[0072] A method for preparing pyrenyl viologen comprises the following steps:

[0073] S1: In a Schlenk reaction flask, Cs2CO3 (1.810 g, 5.56 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (81.4 mg, 0.111 mmol), 2,7-dibromopyrene (200 mg, 0.556 mmol), and pyridine-4-boronic acid (537.2 mg, 4.37 mol) were added in DMF (20 mL). Stirring was continued at 110°C for 2 days. After completion of the reaction, the organic phase was extracted with chloroform and water, and the solvent was removed under reduced pressure. The organic phase was washed with n-hexane to obtain a reddish-brown powder, compound 1. Yield: 130.0 mg (65.66%).

[0074] S2: In a Schlenk reaction flask, dissolve 60 mg of compound 1 in 10 mL of ultra-dry dichloromethane. Slowly add 174 μL (1.68 mmol) of methyl trifluoromethanesulfonate at 0°C. Warm the mixture to room temperature and stir overnight. Collect the solid by centrifugation, dry it, and dissolve it in 5 mL of acetonitrile. Add 30 mL of n-hexane to precipitate the solid (to achieve recrystallization purification). Collect the precipitate by centrifugation, and wash the solid with dichloromethane and then with n-hexane to obtain compound 2. Yield: 111.2 mg (96.53%). Compound 2 was placed in a saturated aqueous solution of NH₄PF₆ and stirred overnight. The solid was washed with water to obtain the compound of general formula (I), where R is methyl. The product in this example can be named No. 3.

[0075] Example 2

[0076] The difference from Example 1 is that step S2 is:

[0077] S2: Dissolve 60 mg of compound 1 in 10 mL of ultra-dry dichloromethane. Slowly add 200 μL (1.68 mmol) of benzyl bromide to the mixture. Stir the reaction at 60°C overnight. Collect the solid by centrifugation, dry it, and dissolve it in 5 mL of acetonitrile. Add 30 mL of n-hexane to precipitate the solid (to achieve recrystallization purification). Collect the precipitate by centrifugation. Wash the solid with dichloromethane and then with n-hexane to obtain a yellow powder, compound 4. Yield: 106.8 mg (90.06%). Compound 4 was placed in a saturated aqueous solution of NH₄PF₆ and stirred overnight. The solid was washed with water to obtain the compound represented by general formula (I), where R is a benzyl group. The product in this example can be named No. 5.

[0078] Example 3

[0079] The difference from Example 1 is that step S2 is:

[0080] S2: Dissolve 60 mg of compound 1 and 371 mg of 2-bromomethylnaphthalene in 10 mL of ultra-dry N,N-dimethylformamide. Stir the reaction at 110°C overnight. Collect the solid by centrifugation, dry it, and dissolve it in 5 mL of acetonitrile. Add 30 mL of n-hexane to precipitate the solid (to achieve recrystallization purification). Collect the precipitate by centrifugation and wash the solid with dichloromethane and n-hexane, respectively, to obtain a yellow powder, compound 6. Yield: 110.1 mg (82%). Compound 6 was placed in a saturated aqueous solution of NH₄PF₆ and stirred overnight. The solid was washed with water to obtain the compound of general formula (I), where R is naphthylmethyl. The product in this example can be named No. 7.

[0081] In order to test the photoelectric properties of the pyrenyl viologen obtained in Examples 1 to 3 of the present invention, the following characterizations were performed, specifically:

[0082] Figure 3 The cyclic voltammograms of the pyrene-containing viologens prepared in Examples 1 to 3 of the present invention at different scanning speeds are shown in the figure. As can be seen from the figure, these compounds have three different redox centers, except for the V 2+ →V +• and V +• In addition to electron transfer from →V, there is also an electron transfer peak due to π-π stacking of the pyrene structure. This indicates that pyrene-containing viologens satisfy a two-step single-electron transfer, resulting in two processes and three distinct color states when used in electrochromic applications. However, due to the propensity for π-π stacking, the solution concentration in the electrochromic device must not be too high.

[0083] Figure 4The UV-visible absorption spectra of the pyrene-containing viologens prepared in Examples 1-3 of the present invention after reduction with metallic zinc and sodium are shown. As shown in the figures, after zinc reduction, the solution color of these compounds changes from yellow to blue-green, and the peak at wavelengths of 600-700 nm increases. After sodium reduction, these compounds turn dark brown, and the spectra become fully absorbed. This indicates that the color of the pyrene-containing viologen changes after being reduced to different states.

[0084] Figure 5 The fluorescence spectra of the pyrene-containing viologens prepared in Examples 1-3 of the present invention after reduction with metallic zinc and sodium are shown. As can be seen from the figures, the pyrene-containing viologens prepared in Examples 1-3 all exhibit strong fluorescence emission before reduction. After zinc reduction, the fluorescence of the compounds weakens. After sodium reduction, the fluorescence of the compounds is substantially quenched. This indicates that the fluorescence of the pyrene-containing viologens changes after being reduced to different states.

[0085] Example 4

[0086] An electrochromic device is prepared using the pyrenyl viologen prepared in Examples 1 to 3 above, specifically by hollowing out a warning message on a sticky note, sticking the sticky note to the conductive surface of conductive glass coated with fluorine-doped tin oxide, etching a warning slogan on the conductive glass with hydrogen, and removing the sticky note. The conductive surfaces of the glass are placed opposite each other, and nano double-sided tape is used to adhere the conductive glass around to form a sealed cavity (note that the upper and lower glass sheets must leave space for the electrode clamps). The pyrenyl viologen is dissolved in N,N-dimethylformamide and added to the prepared device cavity. Finally, the device is completely sealed with UV-curing glue to obtain the electrochromic device. The conductive glass coated with fluorine-doped tin oxide in the electrochromic device is replaced with a polyethylene terephthalate conductive film coated with indium tin oxide to obtain a flexible electrochromic device.

[0087] In order to test the performance of the electrochromic device obtained above, the following characterizations were performed:

[0088] Figure 6 The UV-visible absorption spectra of electrochromic devices prepared using the pyrene viologens prepared in Examples 1 to 3 of the present invention after power is applied are shown in the figure. As can be seen from the figure, the pyrene viologens prepared in Examples 1 to 3 turn green when a voltage of 3.2 or 3.6 V is applied. The absorption spectra show that the absorption between 600 and 700 nm gradually increases and turns brown at a voltage of 4.2 or 5.4 V, which is consistent with the chemical reduction spectrum.

[0089] Figure 7The relationship between the transmittance of electrochromic devices produced using the pyrene violet extracts prepared in Examples 1-3 of the present invention at a wavelength of 670 nm and time is shown. As can be seen from the figure, the response times of the electrochromic devices to voltage are 14.9 s, 13.1 s, and 14.6 s, respectively, and the recovery times are 18.4 s, 24.9 s, and 44.1 s, respectively. Due to the structure of the DAD obtained in Example 3, its free radical stability is improved, and its color retention performance after power failure is better, which helps save energy.

[0090] Figure 8 The coloring efficiency of the electrochromic device prepared by using the pyrene violet prepared in Examples 1 to 3 of the present invention is shown in the figure. The coloring efficiency of the electrochromic device is 50.46, 134.78 and 87.89 cm 2 / C, which is higher than most of the electrochromic materials reported so far. It can show high color contrast changes at low voltage and is an intelligent color-changing glass that conforms to the current development concept of green chemistry.

[0091] Figure 9 The response curves of the electrochromic devices prepared using the pyrene violet prepared in Examples 1 to 3 of the present invention to voltage are shown. As can be seen from the figure, as the voltage increases, the fluorescence of the device is gradually quenched.

[0092] Figure 10 The electronic warning sign prepared using the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention can achieve multiple color changes under visible light and ultraviolet light, adapting to different scenes. For example, at night, its eye-catching electrochromic advantage effectively alerts people.

[0093] Figure 11 The flexible electrochromic device prepared using the pyrene-containing viologen prepared in Examples 1 to 3 of the present invention can be seen from the figure that the electrochromic process of the pyrene-based viologen is not affected by factors other than voltage, such as stress and temperature, and can achieve flexible color display for human wear.

[0094] Example 5

[0095] A method for preparing pyrenyl viologen comprises the following steps:

[0096] S1: In a Schlenk reaction flask, add Cs2CO3 (1.810 g, 5.56 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (81.4 mg, 0.111 mmol), 2,7-dibromopyrene (200 mg, 0.556 mmol), and pyridine-4-boronic acid (537.2 mg, 4.37 mol) in DMF (20 mL). Stir at 110°C for 2 days. After the reaction, extract with chloroform and water, remove the organic phase, remove the solvent under reduced pressure, and wash with n-hexane to obtain a reddish-brown powder, compound 1.

[0097] S2: In a Schlenk reaction flask, dissolve 60 mg of compound 1 in 10 mL of ultra-dry dichloromethane. Slowly add 174 μL (1.68 mmol) of methyl trifluoromethanesulfonate at 0°C. Warm to room temperature and stir overnight. Collect the solid by centrifugation, dry it, and dissolve it in 10 mL of acetonitrile. Add 40 mL of n-hexane to precipitate the solid (to achieve recrystallization purification). Collect the precipitate by centrifugation, and wash the solid with dichloromethane and then with n-hexane to obtain compound 2. Place compound 2 in a saturated aqueous solution of NH4PF6 and stir overnight. Wash the solid with water to obtain the compound represented by general formula (I), where R is methyl.

[0098] Example 6

[0099] A method for preparing pyrenyl viologen comprises the following steps:

[0100] S1: In a Schlenk reaction flask, add Cs2CO3 (1.810 g, 5.56 mmol), [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (81.4 mg, 0.111 mmol), 2,7-dibromopyrene (200 mg, 0.556 mmol), and pyridine-4-boronic acid (537.2 mg, 4.37 mol) in DMF (20 mL). Stir at 110°C for 2 days. After the reaction, extract with chloroform and water, remove the organic phase, remove the solvent under reduced pressure, and wash with n-hexane to obtain a reddish-brown powder, compound 1.

[0101] S2: In a Schlenk reaction flask, dissolve 60 mg of compound 1 in 10 mL of ultra-dry dichloromethane. Slowly add 174 μL (1.68 mmol) of methyl trifluoromethanesulfonate at 0°C. Warm the mixture to room temperature and stir overnight. Collect the solid by centrifugation, dry it, and dissolve it in 8 mL of acetonitrile. Add 35 mL of n-hexane to precipitate the solid (to achieve recrystallization purification). Collect the precipitate by centrifugation, and wash the solid with dichloromethane and then with n-hexane to obtain compound 2. Place compound 2 in a saturated aqueous solution of NH4PF6 and stir overnight. Wash the solid with water to obtain the compound of formula (I), where R is methyl.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A pyrene-based viologen, characterized in that: Including compounds represented by general formula (I): Wherein, R is methyl or methylnaphthalene.

2. The method for preparing a pyrenyl viologen according to claim 1, wherein: The following steps are involved: S1: Cs2CO3, 1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, 2,7-dibromopyrene and pyridine-4-boronic acid were added to DMF and stirred to react to obtain compound 1; The structural formula of the compound 1 is: ； S2: Compound 1 is dissolved in an ultra-dry organic solvent, methyl trifluoromethanesulfonate or bromomethylnaphthalene is added dropwise to the reaction system, and the mixture is stirred for reaction to obtain Compound 2; The structural formula of the compound 2 is: ； R is methyl or methylnaphthalene; S3: Compound 2 is placed in a saturated aqueous solution of NH4PF6 and stirred to obtain the compound represented by the general formula (I).

3. The method for preparing pyrenyl viologen according to claim 2, wherein: In step S1, after the stirring reaction is completed, the organic phase is extracted with chloroform and water, and then the organic phase is decompressed to remove the solvent, and finally washed with n-hexane to obtain the compound 1.

4. The method for preparing pyrenyl viologen according to claim 2, wherein: In step S2, methyl trifluoromethanesulfonate or bromomethylnaphthalene is added dropwise at 0°C, and the stirring reaction temperature is 25-110°C.

5. The method for preparing pyrenyl viologen according to claim 2, wherein: In step S2, after stirring the reaction, the solid is collected by centrifugation, dried and dissolved in acetonitrile, and then n-hexane is added to precipitate the solid. The precipitate is collected by centrifugation and washed with dichloromethane and n-hexane to obtain the compound 2.

6. The method for preparing pyrenyl viologen according to claim 2, wherein: In step S2, the ultra-dry organic solvent is ultra-dry dichloromethane or ultra-dry N,N-dimethylformamide.

7. A method for preparing an electrochromic device, characterized in that: The method is prepared by sandwiching the pyrenyl viologen described in claim 1 in a closed conductive layer.

8. The method for preparing an electrochromic device according to claim 7, characterized in that: The pyrenyl viologen is dissolved in N,N-dimethylformamide and then sandwiched in a closed conductive layer.

9. The method for preparing an electrochromic device according to claim 7, wherein: The conductive layer is conductive glass or conductive film.

10. An electrochromic device, characterized in that: Prepared by the method according to any one of claims 7 to 9.

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