Preparation and application of a class of four-arm type conjugated viologen electrochromic materials

Abstract

The application discloses a kind of four-arm conjugated viologen electrochromic material preparation and application, belong to electrochromic field.The four-arm conjugated viologen electrochromic material described in the application has simple synthesis route, mild reaction condition, low cost, and excellent electrochemical performance.The electrochromic device prepared by using the four-arm conjugated viologen electrochromic material designed in the application can realize the change from colorless transparent to deep color, and the color change is adjustable, with excellent electrochromic performance, high optical contrast, short response time, good cycle stability, and potential application value.The four-arm conjugated viologen molecule provided in the application provides a new idea for designing excellent conjugated viologen electrochromic material.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic technology, and relates to a method for preparing a type of four-arm conjugate violet electrochromic material, and its application in electrochromic devices. Background Technology

[0002] Electrochromic materials are a class of smart materials that exhibit reversible color changes under the influence of an applied voltage. They have wide applications in smart windows, anti-glare rearview mirrors, and optoelectronic displays. Organic electrochromic materials offer advantages such as easily customizable molecules, easily controlled color changes, fast response rates, and high optical contrast, making them promising for the market. Compared to organic conjugated polymer electrochromic materials, organic small molecule electrochromic materials are simpler to synthesize, easier to purify, and have lower production costs, attracting widespread attention in the field of electrochromism.

[0003] Violet is an N,N'-disubstituted 4,4'-bipyridine salt. Its divalent dicationic state is usually colorless, but it is readily reduced to form monocationic or dicationic radicals, thus exhibiting significant color changes, making it a high-performance electrochromic material. To enrich the color variations of violet-based electrochromic materials, conjugated structural units can be introduced between the two pyridine groups to form conjugated violet-based electrochromic materials. Currently, the main synthetic method for conjugated violet-based electrochromic materials involves preparing a dipyridine intermediate via palladium-catalyzed coupling reaction, followed by alkylation of the pyridine nitrogen atom. Summary of the Invention

[0004] This invention utilizes molecular design to prepare a class of four-armed conjugated violetin electrochromic materials through a condensation reaction of terephthalaldehyde with aryl ethyl ketone followed by alkylation. The novel conjugated violetin molecules described in this invention possess excellent electrochemical properties and can be used to fabricate electrochromic devices. Electrochromic devices prepared using the four-armed conjugated violetin electrochromic materials designed in this invention exhibit high optical contrast, fast response rate, and good cycle stability. Furthermore, the color changes of the electrochromic devices can be enriched by regulating the four-armed group structure, demonstrating potential application value.

[0005] Another objective of this invention is to provide a method for synthesizing four-armed conjugated violet, which has mild preparation conditions, low cost, high yield, avoids the use of precious metal catalysts, and has high application value.

[0006] The present invention provides a type of four-arm conjugate violet electrochromic material, the chemical structural formula (I) of which is as follows:

[0007]

[0008] The method for synthesizing the aforementioned four-arm conjugated violet electrochromic material is as follows: terephthalaldehyde, aryl ethyl ketone and ammonium acetate undergo a condensation reaction to obtain the key intermediate four-arm dipyridylbenzene, which is then alkylated with methyl trifluoromethanesulfonate to obtain the target four-arm conjugated violet molecule.

[0009] (1) Dissolve terephthalaldehyde and aryl ethyl ketone in N-sulfonic acid butylpyridine hydrogen sulfate, then add ammonium acetate, heat to 120°C under nitrogen protection, keep the temperature for reaction, after the reaction is completed, cool to room temperature, filter, wash the filter cake with water, dry under vacuum, and then purify by column chromatography to obtain the intermediate tetra-arm dipyridylbenzene.

[0010] (2) Synthesis of tetra-arm conjugated violet electrochromic material: The intermediate tetra-arm dipyridylbenzene was dissolved in 1,2-dichloroethane, methyl trifluoromethanesulfonate was added, the temperature was raised to 80°C under nitrogen protection, and the reaction was maintained at this temperature. After the reaction was completed, the solvent was removed under reduced pressure, and the crude product was purified by column chromatography to obtain the tetra-arm conjugated violet electrochromic material.

[0011] The synthesis process is as follows:

[0012]

[0013] In step (1), the molar ratio of terephthalaldehyde, aryl ethyl ketone, and ammonium acetate is 1:4.2:10, the reaction time is 12-24 h, and the column chromatography eluent is a mixed solvent of n-hexane and dichloromethane with a volume ratio of 1:1.

[0014] In step (2), the molar ratio of the intermediate tetra-arm dipyridylbenzene to methyl trifluoromethanesulfonate is 1:6, the reaction time is 6-12 h, and the column chromatography eluent is a mixed solvent of dichloromethane and methanol with a volume ratio of 30:1.

[0015] The four-arm conjugate violet electrochromic material prepared in this invention is used as an electrochromic material in an electrochromic device. The electrochromic device is composed of a transparent conductive electrode, an electrochromic material, ferrocene, and an electrolyte. The specific preparation steps are as follows:

[0016] (1) Cut the transparent conductive substrate into a fixed size and perform etching. Clean the etched conductive substrate in different solvents by ultrasonic cleaning and then perform ultraviolet ozone cleaning. Place a piece of sarin membrane with a hollow center and a small hole on one side between two transparent conductive electrodes and heat-shape it under a hot press to prepare the device.

[0017] (2) Dissolve the electrochromic material, ferrocene and electrolyte in an organic solvent to prepare a solution, inject it into the device under reduced pressure, and then seal the reserved small hole with UV curing adhesive.

[0018] The transparent conductive substrate is one of indium tin oxide conductive glass or indium tin oxide flexible conductive substrate.

[0019] The electrochromic material is a type of four-arm conjugate violet electrochromic material;

[0020] The electrolyte is one of tetrabutylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate;

[0021] The organic solvent used in the preparation of the electrochromic device is N-methylpyrrolidone; the concentrations of the electrochromic material, ferrocene, and electrolyte in the preparation of the electrochromic device are 0.05 mol / L, 0.05 mol / L, and 0.50 mol / L, respectively.

[0022] This invention has the following advantages:

[0023] The four-armed conjugated violet electrochromic material designed in this invention has a simple synthesis route, mild reaction conditions, and low cost. Electrochromic devices prepared using this four-armed conjugated violet electrochromic material can achieve color changes from colorless and transparent to dark colors, and the color change is adjustable. They exhibit excellent electrochromic performance, high optical contrast, short response time, and good cycle stability. Attached Figure Description

[0024] Figure 1 The molecular structure of the tetra-arm conjugated violet electrochromic material with R being phenyl synthesized in Example 1 of this invention is shown.

[0025] Figure 2 The absorption spectra of the electrochromic device based on the tetra-arm conjugated violet electrochromic material with R being phenyl synthesized in Example 1 of this invention at different voltages are shown.

[0026] Figure 3 The image shows the response time of an electrochromic device based on the tetra-armed conjugated violet electrochromic material with R being phenyl synthesized in Example 1 of this invention.

[0027] Figure 4 The diagram shows the cyclic stability of the electrochromic device based on the four-arm conjugated violet electrochromic material with R being phenyl synthesized in Example 1 of this invention. Detailed Implementation

[0028] Example 1: Four-arm conjugated violet electrochromic material with R being phenyl

[0029] (1) Preparation of a four-armed dipyridylbenzene intermediate in which R is a phenyl group

[0030] Terephthalaldehyde (500 mg, 3.73 mmol) and acetophenone (1.88 g, 15.7 mmol) were dissolved in 5 mL of N-butylpyridine sulfonate. Ammonium acetate (2.87 g, 37.3 mmol) was added under stirring at room temperature. The mixture was then heated to 120 °C under nitrogen protection and kept at this temperature for 14 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with water and dried under vacuum. The dried filter cake was dissolved in dichloromethane and purified by column chromatography using n-hexane / dichloromethane (volume ratio 1:1) as the eluent. After vacuum drying, a tetra-armed dipyridylbenzene intermediate with R as phenyl was obtained (1.12 g, yield 56%). 1 H NMR (600MHz, CDCl3) δ 8.24 (d, J=7.2Hz, 8H), 7.96 (s, 4H), 7.92 (s, 4H), 7.55 (t, J=7.2Hz, 8H), 7.48 (t, J=7.8Hz, 4H).

[0031] (2) Preparation of four-arm conjugated violet electrochromic materials with R being phenyl

[0032] The intermediate R, a phenyl tetra-armed dipyridylbenzene (200 mg, 0.86 mmol), was dissolved in 8 mL of 1,2-dichloroethane. Methyl trifluoromethanesulfonate (354.24 mg, 2.16 mmol) was added using a syringe under stirring. The mixture was heated to 80 °C under nitrogen protection and reacted for 6 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the product was dried under vacuum. The crude product obtained after drying was dissolved in dichloromethane and purified by column chromatography using dichloromethane / methanol (volume ratio 30:1). After vacuum drying, a phenyl tetra-armed conjugated violet electrochromic material (122 mg, yield 40%) was obtained. 1 H NMR (600MHz, DMSO-d6) δ 8.61 (s, 4H), 8.51 (s, 4H), 7.89-7.88 (m, 4H), 7.71 (t, J = 3.6Hz, 12H), 3.80 (s, 6H).

[0033] Example 2: Four-arm conjugated violet electrochromic material with R being 4-methoxyphenyl

[0034] (1) Preparation of a tetra-armed dipyridylbenzene intermediate in which R is 4-methoxyphenyl

[0035] Terephthalaldehyde (300 mg, 2.23 mmol) and 4-methoxyacetophenone (1.40 g, 9.37 mmol) were dissolved in 5 mL of N-butylpyridine sulfonate. Ammonium acetate (1.71 g, 22.3 mmol) was added under stirring at room temperature. The mixture was then heated to 120 °C under nitrogen protection and kept at this temperature for 13 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with water and dried under vacuum. The dried filter cake was dissolved in dichloromethane and purified by column chromatography using n-hexane / dichloromethane (volume ratio 1:1) as the eluent. After vacuum drying, tetra-armed dipyridylbenzene with 4-methoxyphenyl as intermediate R (800 mg, yield 52%) was obtained. 1 HNMR (600MHz, CDCl3) δ8.19 (d, J=8.4Hz, 8H), 7.90 (s, 4H), 7.84 (s, 4H), 7.05 (d, J=8.4Hz, 8H), 3.90 (s, 12H).

[0036] (2) Preparation of tetra-arm conjugated violet electrochromic materials with R being 4-methoxyphenyl

[0037] The intermediate R, a tetra-armed dipyridylbenzene with 4-methoxyphenyl (200 mg, 0.30 mmol), was dissolved in 8 mL of 1,2-dichloroethane. Methyl trifluoromethanesulfonate (299 mg, 1.82 mmol) was added using a syringe under stirring. The mixture was heated to 80 °C under nitrogen protection and reacted for 8 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the product was dried under vacuum. The crude product obtained after drying was dissolved in dichloromethane and purified by column chromatography using dichloromethane / methanol (volume ratio 30:1). After vacuum drying, a tetra-armed conjugated violet electrochromic material with 4-methoxyphenyl (167 mg, yield 49%) was obtained. 1 HNMR (600MHz, DMSO-d6) δ 8.47 (d, J=9.6Hz, 8H), 7.86 (d, J=8.4Hz, 8H), 7.25 (d, J=8.4Hz, 8H), 3.89 (s, 12H), 3.84 (s, 6H).

[0038] Example 3: Four-arm conjugated violet electrochromic material with R being 4-fluorophenyl

[0039] (1) Preparation of a tetra-armed dipyridylbenzene intermediate in which R is a 4-fluorophenyl group

[0040] Terephthalaldehyde (300 mg, 2.23 mmol) and 4-fluoroacetophenone (1.29 g, 9.37 mmol) were dissolved in 5 mL of N-butylpyridine sulfonate. Ammonium acetate (1.71 g, 22.3 mmol) was added under stirring at room temperature. The mixture was then heated to 120 °C under nitrogen protection and kept at this temperature for 15 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with water and dried under vacuum. The dried filter cake was dissolved in dichloromethane and purified by column chromatography using n-hexane / dichloromethane (volume ratio 1:1) as the eluent. After vacuum drying, tetra-armed dipyridylbenzene with 4-fluorophenyl as intermediate R (480 mg, yield 34%) was obtained. 1 H NMR (600MHz, CDCl3) δ 8.22-8.20 (m, 8H), 7.91 (s, 4H), 7.89 (s, 4H), 7.22 (t, J = 8.4Hz, 8H).

[0041] (2) Preparation of tetra-arm conjugated violet electrochromic materials with R being 4-fluorophenyl

[0042] The intermediate R, a tetra-armed dipyridylbenzene with 4-fluorophenyl as its derivative (200 mg, 0.32 mmol), was dissolved in 8 mL of 1,2-dichloroethane. Methyl trifluoromethanesulfonate (324 mg, 1.98 mmol) was added using a syringe under stirring. The mixture was heated to 80 °C under nitrogen protection and reacted for 8 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the product was dried under vacuum. The crude product obtained after drying was dissolved in dichloromethane and purified by column chromatography using dichloromethane / methanol (volume ratio 30:1) as the eluent. After vacuum drying, a tetra-armed conjugated violet electrochromic material with 4-fluorophenyl as its derivative (110 mg, yield 36%) was obtained. 1 H NMR (400MHz, DMSO-d6) δ 8.61 (s, 8H), 7.97-7.94 (m, 8H), 7.60 (t, J = 8.8Hz, 8H), 3.80 (s, 6H).

[0043] Example 4: A four-arm conjugated violet electrochromic material with R as 2,6-difluorophenyl

[0044] (1) Preparation of a tetra-armed dipyridylbenzene intermediate with R being 2,6-difluorophenyl

[0045] Terephthalaldehyde (300 mg, 2.23 mmol) and 2,6-fluoroacetophenone (1.46 g, 9.37 mmol) were dissolved in 5 mL of N-sulfonic acid butylpyridine hydrogen sulfate. Ammonium acetate (1.71 g, 22.3 mmol) was added under stirring at room temperature. The mixture was then heated to 120 °C under nitrogen protection and kept at this temperature for 13 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with water and dried under vacuum. The dried filter cake was dissolved in dichloromethane and purified by column chromatography using n-hexane / dichloromethane (volume ratio 1:1) as the eluent. After vacuum drying, the intermediate R, a tetra-armed dipyridylbenzene with 2,6-difluorophenyl (487 mg, yield 37%), was obtained. 1 H NMR (600MHz, CDCl3) δ7.86 (s, 4H), 7.77 (s, 4H), 7.37-7.35 (m, 4H), 7.04 (t, J=7.8Hz, 8H).

[0046] (2) Preparation of tetra-arm conjugated violet electrochromic material with R being 2,6-difluorophenyl

[0047] The intermediate R, a tetra-armed dipyridylbenzene of 2,6-difluorophenyl (200 mg, 0.28 mmol), was dissolved in 8 mL of 1,2-dichloroethane. Methyl trifluoromethanesulfonate (289 mg, 1.76 mmol) was added using a syringe under stirring. The mixture was heated to 80 °C under nitrogen protection and reacted for 6 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the product was dried under vacuum. The crude product obtained after drying was dissolved in dichloromethane and purified by column chromatography using dichloromethane / methanol (volume ratio 30:1) as the eluent to obtain a tetra-armed conjugated violet electrochromic material of R, 2,6-difluorophenyl (132 mg, yield 47%). 1 H NMR (400MHz, DMSO-d6) δ9.20 (s, 4H), 8.51 (s, 8H), 7.94-7.90 (m, 4H), 7.56 (t, J = 8.4Hz, 8H), 3.99 (s, 6H).

[0048] Example 5: Four-arm conjugated violet electrochromic material with R as 2-thienyl group.

[0049] (1) Preparation of a four-armed dipyridylbenzene intermediate with R being 2-thienyl

[0050] Terephthalaldehyde (300 mg, 2.23 mmol) and 2-acetylthiophene (1.18 g, 9.37 mmol) were dissolved in 5 mL of N-sulfonic acid butylpyridine hydrogen sulfate. Ammonium acetate (1.71 g, 22.3 mmol) was added under stirring at room temperature. The mixture was then heated to 120 °C under nitrogen protection and kept at this temperature for 15 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with water and dried under vacuum. The dried filter cake was dissolved in dichloromethane and purified by column chromatography using n-hexane / dichloromethane (volume ratio 1:1) as the eluent. After vacuum drying, a tetra-armed dipyridylbenzene with 2-thienyl group R (640 mg, yield 48%) was obtained. 1 H NMR (600MHz, CDCl3) δ7.87 (s, 4H), 7.75-7.73 (m, 8H), 7.45 (d, J=5.4Hz, 4H), 7.16 (t, J=4.2Hz, 4H).

[0051] (2) Preparation of a four-arm conjugated violet electrochromic material with R being 2-thienyl

[0052] The intermediate R, a 2-thienyl tetra-armed dipyridylbenzene (200 mg, 0.28 mmol), was dissolved in 8 mL of 1,2-dichloroethane. Methyl trifluoromethanesulfonate (351 mg, 1.68 mmol) was added using a syringe under stirring. The mixture was heated to 80 °C under nitrogen protection and reacted for 8 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the product was dried under vacuum. The crude product obtained after drying was dissolved in dichloromethane and purified by column chromatography using dichloromethane / methanol (volume ratio 30:1). After vacuum drying, a 2-thienyl tetra-armed conjugated violet electrochromic material (102 mg, yield 32%) was obtained. 1 H NMR (600MHz, DMSO-d6) δ 8.61 (s, 4H), 8.47 (s, 4H), 8.15 (d, J = 4.8Hz, 4H), 7.88 (d, J = 3.0Hz, 4H), 7.42 (t, J = 4.2Hz, 4H), 4.11 (s, 6H).

[0053] Example 6: Fabrication of an electrochromic device based on a four-arm conjugated violet electrochromic material with R being phenyl.

[0054] A 25mm × 15mm indium tin oxide (ITO) conductive glass was used as a transparent conductive electrode. It was washed with detergent and then ultrasonically cleaned sequentially with 10mL deionized water, 10mL acetone, and 10mL ethanol for 10 minutes each. Finally, it was cleaned in a UV ozone generator for 20 minutes. The treated ITO conductive glass was placed with its conductive side facing up. A sarin membrane with a small hole in the right side was placed on top, ensuring that three sides of the sarin membrane were flush with the edge of the ITO conductive glass, while the side with the small hole was spaced a certain distance from the edge. Another cleaned ITO conductive glass was then placed on the sarin membrane with its conductive side facing down. Finally, the device was encapsulated by pressing both sides at 130°C for 45 seconds each. Electrochromic solutions were prepared by dissolving 2.16 mg of a four-arm conjugated violet electrochromic material (R = phenyl), 0.5 mg of ferrocene, and 3.3 mg of tetrabutylammonium tetrafluoroborate in 50 μL of N-methylpyrrolidone solution at concentrations of 0.05 M, 0.05 M, and 0.50 M, respectively. A piece of foam was placed in a single-necked round-bottom flask as a substrate for the device, and the cavity of the prepared electrochromic device was placed on the foam substrate in the flask. The flask was evacuated for 30 s, purged with nitrogen, and this process was repeated three times. The prepared electrochromic solutions were then dropped onto pre-drilled holes in a sarin membrane, and the solution was injected into the device using a pressure differential. Finally, the pre-drilled holes were sealed using UV photopolymerization.

[0055] The electrochromic device based on the R-type phenyl tetra-arm conjugated violet electrochromic material prepared above was tested. Under an applied voltage of 1.6V, the device changed from colorless and transparent to sky blue, with an optical contrast ratio of 82% at 636nm, a coloring time of 0.26s, a fading time of 0.25s, and a coloring efficiency of 202.5cm. 2 / C, after 3000 cycles, the optical contrast retains 95% of its initial value.

[0056] Example 7: Fabrication of an electrochromic device based on a four-arm conjugated violet electrochromic material with R being 2,6-difluorophenyl.

[0057] A 25mm × 15mm indium tin oxide (ITO) conductive glass was used as a transparent conductive electrode. It was washed with detergent and then ultrasonically cleaned sequentially with 10mL deionized water, 10mL acetone, and 10mL ethanol for 10 minutes each. Finally, it was cleaned in a UV ozone generator for 20 minutes. The treated ITO conductive glass was placed with its conductive side facing up. A sarin membrane with a small hole in the right side was placed on top, ensuring that three sides of the sarin membrane were flush with the edge of the ITO conductive glass, while the side with the small hole was spaced a certain distance from the edge. Another cleaned ITO conductive glass was then placed on the sarin membrane with its conductive side facing down. Finally, the device was encapsulated by pressing both sides at 130°C for 45 seconds each. Electrochromic solutions were prepared by dissolving 2.55 mg of a four-arm conjugated violet electrochromic material (R = 2,6-difluorophenyl), 0.5 mg of ferrocene, and 3.3 mg of tetrabutylammonium tetrafluoroborate in 50 μL of N-methylpyrrolidone solution at concentrations of 0.05 M, 0.05 M, and 0.50 M, respectively. A piece of foam was placed in a single-necked round-bottom flask as a substrate for the device, and the cavity of the prepared electrochromic device was placed on the foam substrate in the flask. The flask was evacuated for 30 s, purged with nitrogen, and this process was repeated three times. The prepared electrochromic solutions were then dropped onto pre-drilled holes in a sarin membrane, and the solution was injected into the device using a pressure differential. Finally, the pre-drilled holes were sealed using UV photopolymerization.

[0058] The electrochromic device based on the four-arm conjugated violet electrochromic material with R=2,6-difluorophenyl was tested. Under an applied voltage of 1.6V, the device changed from colorless and transparent to purple, exhibiting an optical contrast ratio of 96% at 596nm, a coloring time of 0.33s, a fading time of 0.35s, and a coloring efficiency of 357.3cm. 2 / C, after 3000 cycles, the optical contrast retains 98% of the initial value.

[0059] Example 8: Fabrication of an electrochromic device based on a four-arm conjugated violet electrochromic material with R being 2-thiophene group.

[0060] A 25mm × 15mm indium tin oxide (ITO) conductive glass was used as a transparent conductive electrode. It was washed with detergent and then ultrasonically cleaned sequentially with 10mL deionized water, 10mL acetone, and 10mL ethanol for 10 minutes each. Finally, it was cleaned in a UV ozone generator for 20 minutes. The treated ITO conductive glass was placed with its conductive side facing up. A sarin membrane with a small hole in the right side was placed on top, ensuring that three sides of the sarin membrane were flush with the edge of the ITO conductive glass, while the side with the small hole was spaced a certain distance from the edge. Another cleaned ITO conductive glass was then placed on the sarin membrane with its conductive side facing down. Finally, the device was encapsulated by pressing both sides at 130°C for 45 seconds each. Electrochromic solutions were prepared by dissolving 2.20 mg of a four-armed conjugated violet electrochromic material (R = 2-thienyl), 0.5 mg of ferrocene, and 3.3 mg of tetrabutylammonium tetrafluoroborate in 50 μL of N-methylpyrrolidone solution at concentrations of 0.05 M, 0.05 M, and 0.50 M, respectively. A piece of foam was placed in a single-necked round-bottom flask as a substrate for the device, and the cavity of the prepared electrochromic device was placed on the foam substrate in the flask. The flask was evacuated for 30 s, purged with nitrogen, and this process was repeated three times. The prepared electrochromic solutions were then dropped onto pre-drilled holes in a sarin membrane, and the solution was injected into the device using a pressure differential. Finally, the pre-drilled holes were sealed using UV photopolymerization.

[0061] The electrochromic device based on the four-arm conjugated violet electrochromic material with R being 2-thiophene group was tested. Under an applied voltage of 1.6V, the device changed from colorless and transparent to light blue, exhibiting an optical contrast ratio of 76% at 656 nm, a coloring time of 0.91 s, a fading time of 0.30 s, and a coloring efficiency of 181.5 cm⁻¹. 2 / C, after 3000 cycles, the optical contrast retains 97% of the initial value.

Claims

1. A class of four-armed conjugated viologen electrochromic materials characterized in that, A chemical formula of formula (I) is provided: In the formula, the R group is one of a phenyl group, a 4-methoxyphenyl group, a 4-fluorophenyl group, a 2,6-difluorophenyl group, and a 2-thiophenyl group.

2. The method for preparing a class of four-armed conjugated viologen electrochromic materials according to claim 1, characterized in that, The preparation steps include: (1) Synthesis of a four-arm dipyrrolephenyl: p-xylyleneformaldehyde and aryl ethanone are dissolved in N-sulfonic acid butyl pyridine hydrogen sulfate, then ammonium acetate is added, and the temperature is raised to 120 DEG C under nitrogen protection, and the reaction is kept for a certain time. After the reaction is completed, the temperature is cooled to room temperature, and the filter cake is washed with water and dried in vacuum. Then, column chromatography is used for purification to obtain an intermediate four-arm dipyrrolephenyl; (2) Synthesis of a four-arm conjugated viologen electrochromic material: the intermediate four-arm dipyrrolephenyl is dissolved in 1,2-dichloroethane, and methyl triflate is added, and the temperature is raised to 80 DEG C under nitrogen protection, and the reaction is kept for a certain time. After the reaction is completed, the solvent is removed under reduced pressure, and the obtained crude product is purified by column chromatography to obtain a four-arm conjugated viologen electrochromic material.

3. The method for preparing a class of four-armed conjugated viologen electrochromic materials according to claim 2, characterized in that, In the synthesis method, the molar ratio of p-xylyleneformaldehyde, aryl ethanone and ammonium acetate in step (1) is 1:4.2:10, the reaction time is 12-24 h, and the eluent for column chromatography is a mixture of n-hexane and dichloromethane with a volume ratio of 1:

1.

4. The method for preparing a type of four-arm conjugate violet electrochromic material according to claim 2, characterized in that, In the synthesis method, the molar ratio of the intermediate four-arm dipyrrolephenyl and methyl triflate in step (2) is 1:6, the reaction time is 6-12 h, and the eluent for column chromatography is a mixture of dichloromethane and methanol with a volume ratio of 30:

1.

5. The four-arm conjugated viologen electrochromic material of claim 1 is applied in an electrochromic device. The electrochromic device is composed of a transparent conductive electrode, an electrochromic material, ferrocene and an electrolyte, and the preparation steps are as follows:

6. Use according to claim 5, characterized in that, (1) The transparent conductive substrate is cut into a fixed size and etched, and then ultrasonic cleaning is performed in different solvents, followed by ultraviolet ozone cleaning. A piece of hollowed-out Saran film with a small hole on one side is placed between two transparent conductive electrodes, and the device is prepared by hot plastic setting under a hot press; (2) The electrochromic material, ferrocene and electrolyte are dissolved in an organic solvent to prepare a solution, which is injected into the device under reduced pressure, and then the small hole is sealed with ultraviolet curing glue.

7. The application of claim 6, wherein (1) the transparent conductive substrate is one of indium tin oxide conductive glass or indium tin oxide flexible conductive substrate; (2) the electrochromic material is a four-arm conjugated viologen electrochromic material; (3) the electrolyte is one of tetrabutylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate. In the preparation step (2), the organic solvent is N-methyl pyrrolidone, and the concentrations of the electrochromic material, ferrocene and electrolyte are 0.05 mol / L, 0.05 mol / L and 0.50 mol / L, respectively.

8. Use according to claim 6, characterized in that, ​

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