阅读说明：本技术 一种电致变色化合物及其制备方法和应用 (Electrochromic compound and preparation method and application thereof ) 是由 苏峰育 凌欢 田颜清 罗丹 刘言军 孙小卫 于 2019-11-27 设计创作，主要内容包括：本发明提供一种电致变色化合物及其制备方法和应用,所述电致变色化合物具有如式I或式II所示结构,为含有端炔基的紫精类化合物,通过取代基的特殊设计显著提升了其电致变色性能。所述电致变色化合物应用于电致变色器件的电致变色层材料,能够有效改善电致变色器件的透过率差值、变色响应速度、变色效率以及稳定性。所述电致变色器件为凝胶电致变色器件,包括两层导电层,以及位于所述两层导电层之间的复合凝胶电致变色层,所述复合凝胶电致变色层包括所述电致变色化合物、电解质和凝胶材料,具有高透过率差值、快速响应时间和高循环稳定性,能够充分满足高性能、高稳定性电致变色器件的应用需求。(The invention provides an electrochromic compound and a preparation method and application thereof, wherein the electrochromic compound has a structure shown in a formula I or a formula II, is a viologen compound containing terminal alkynyl, and obviously improves the electrochromic performance through special design of a substituent. The electrochromic compound is applied to an electrochromic layer material of an electrochromic device, and can effectively improve the transmittance difference, the color-changing response speed, the color-changing efficiency and the stability of the electrochromic device. The electrochromic device is a gel electrochromic device and comprises two conductive layers and a composite gel electrochromic layer between the two conductive layers, wherein the composite gel electrochromic layer comprises an electrochromic compound, an electrolyte and a gel material, has high transmittance difference, quick response time and high cycle stability, and can fully meet the application requirements of the electrochromic device with high performance and high stability.)

1. An electrochromic compound having a structure according to formula I or formula II:

wherein, X₁、X₂Each independently selected from halogen;

n₁、n₂each independently selected from integers of 1 to 7.

2. Electrochromic compound according to claim 1, characterised in that said X₁、X₂Each independently is chlorine or bromine;

preferably, said n₁、n₂Each independently selected from integers of 1 to 3.

3. Electrochromic compound according to claim 1 or 2, characterised in that it has any of the following compounds:

4. a method for preparing an electrochromic compound according to any one of claims 1 to 3, wherein when the electrochromic compound has a structure represented by formula I, the preparation method is method (a); when the electrochromic compound has a structure as shown in formula II, the preparation method is a method (b);

the method (a) is as follows: reacting 4,4' -bipyridine with a compound shown as a1 to obtain the electrochromic compound shown as the formula I, wherein the reaction formula is as follows:

the method (b) is as follows: reacting 4,4' -bipyridine with a compound shown as a formula b1 to obtain an electrochromic compound shown as a formula II, wherein the reaction formula is as follows:

wherein, X₁、X₂Each independently selected from halogen;

n₁、n₂each independently selected from integers of 1 to 7.

5. The preparation method according to claim 4, wherein the molar ratio of 4,4' -bipyridine to the compound represented by the formula a1 in the method (a) is 1 (0.8-1.0);

preferably, the reaction temperature in the method (a) is 85-95 ℃;

preferably, the reaction time in the method (a) is 12-18 h;

preferably, the reaction in the process (a) is carried out in an organic solvent;

preferably, the organic solvent is N, N-dimethylformamide.

6. The preparation method according to claim 4, wherein the molar ratio of 4,4' -bipyridine to the compound represented by the formula b1 in the method (b) is 1 (2.0-3.0);

preferably, the temperature of the reaction in the method (b) is 105-115 ℃;

preferably, the reaction time in the method (b) is 30-40 h;

preferably, the reaction in the method (b) is carried out in an organic solvent;

preferably, the organic solvent is N, N-dimethylformamide.

7. An electrochromic device, characterized in that the electrochromic layer of the electrochromic device comprises an electrochromic compound according to any one of claims 1 to 3.

8. The electrochromic device according to claim 7, wherein the electrochromic device is a gel electrochromic device comprising two conductive layers, and a composite gel electrochromic layer located between the two conductive layers, the composite gel electrochromic layer comprising the electrochromic compound according to any one of claims 1 to 3, an electrolyte and a gel material.

9. The electrochromic device of claim 8, wherein the composite gel electrochromic layer further comprises a counter electrode material;

preferably, the counter electrode material is selected from any one of ferrocene, tetramethyl p-phenylenediamine, triphenylamine or diphenylamine;

preferably, the molar ratio of the counter electrode material to the electrochromic compound is (1-10): 1;

preferably, the electrolyte is selected from any one of trifluoromethyl sulfimide lithium salt, lithium perchlorate, tetrabutyl ammonium perchlorate or lithium hexafluorophosphate;

preferably, the gel material is a thermoplastic polymer;

preferably, the thermoplastic polymer is poly (propylene butyral).

10. Use of an electrochromic device according to any one of claims 7 to 9 in a color-changing window, an automotive rear view mirror or a display.

Technical Field

The invention belongs to the technical field of organic compounds, and particularly relates to an electrochromic compound and a preparation method and application thereof.

Background

Electrochromism (EC) refers to that the optical properties of a material generate stable and reversible color change under the action of an external electric field, and the color and the transparency are reversible change from appearance, a device prepared based on the Electrochromism material is an electrochromic device, the performance of the electrochromic device is directly related to the type and the performance of the Electrochromism material, and the suitable Electrochromism material can endow the Electrochromism device with the advantages of large and controllable color change range, steady state, low driving voltage and the like, so the Electrochromism material has wide application prospect in intelligent windows, automobile rearview mirrors and low-power-consumption displays.

The color change principle of the electrochromic material mainly depends on the energy band structure and the redox property of the chemical composition of the material, and the absorption property of the material in a visible light region can be regulated and controlled through the injection and extraction of ions and electrons, or the carrier concentration and the plasma oscillation frequency are changed, so that the modulation of the infrared reflection property is realized. Electrochromic materials can be classified into three major classes according to structure: transition metal oxide, organic micromolecular compound and high molecular polymer, wherein viologen is a typical organic micromolecular electrochromic material. In 1932, Michaelis et al found for the first time that 1,1 '-dimethyl-4, 4' -bipyridine (DMP) is purple in the reduced state and is called "viologen", and later, a series of compounds of bipyridine salts are called "viologen", and viologen compounds have good reversible redox reaction performance, high contrast of color change during reaction, short color change response time, and low preparation cost, and thus have gained wide attention in the fields of electrochemistry, photochemistry, conductivity, and the like.

Currently, research on viologens is mainly structural improvement based on the purpose of performance optimization, and generally, a plurality of substituents are introduced on a bipyridyl ring to adjust the color change range and the color change color of the viologens. For example, CN102965096A discloses a viologen compound electrochromic material and an electrochromic device thereof, wherein the viologen compound electrochromic material is 1- (carbazole-N-hexyl) -1'- (diethyl phosphonate-2-ethyl) -4,4' -bipyridinium salt, can be used as a cathode electrochromic material to be applied to an electrochromic device, and has good electrochromic performance, high electrochromic transmittance difference, large difference window, good transmittance difference in a visible light region and a near infrared region, and high stability. CN110105336A discloses a viologen derivative electrochromic material and a preparation method thereof, wherein the electrochromic material has a structure of

The introduction of the pyrrole group or the carbazole group improves the electron-deficient state on the 4,4' -bipyridine core group of the viologen compound, and reduces the electrochromic voltage of the viologen compound; and the bipolar electrochromic device can be obtained, higher contrast is realized, multiple color changes are realized, and the problem of electrolyte leakage of the solution type electrochromic device can be solved. CN106928129A discloses a cathode electrochromic compound used in an electrochromic device, wherein phenyl is introduced between two pyridine groups of a viologen compound, so that the cathode electrochromic compound has the advantages of good electrochemical reversibility, high color change speed, high stability, small minimum value of visible light transmittance and the like.

The performance parameters of the electrochromic device include color change, transmittance change, color change efficiency, response time, cycling stability and the like, wherein the cycling stability is the maximum cycling frequency which can be reached when the device is switched between different voltages and the transmittance difference is maintained, and for practical application, the cycling stability is an important index, and the preparation of the device with high stability is always the target pursued by researchers. However, the cycle life of the electrochromic device disclosed in the prior art is different from tens of times to tens of thousands of times, and the electrochromic device with a long cycle life often has the disadvantage of long color-changing response time, and cannot meet the requirements for quick response and high stability in practical application at the same time.

Therefore, it is a research focus in the field to develop an electrochromic material and an electrochromic device having fast response, high stability and high transmittance difference.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an electrochromic compound and a preparation method and application thereof, wherein the electrochromic compound greatly improves the transmittance difference, the color change response speed and the cycling stability of viologen compounds as electrochromic materials through the introduction of terminal alkynyl groups, and can fully meet the application requirements of high-performance electrochromic devices.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides an electrochromic compound having a structure represented by formula I or formula II:

wherein, X₁、X₂Each independently selected from halogen.

n₁、n₂Each independently selected from an integer of 1 to 7, such as 1, 2, 3, 4, 5, 6 or 7.

The electrochromic compound provided by the invention is a viologen compound substituted by terminal alkynyl, and the carbon chain length of the terminal alkynyl is 4-10 carbon atoms; if the number of carbon atoms is outside the range defined in the present invention, the solubility of the electrochromic compound in the device, the stability, and the performance of the electrochromic device may be adversely affected.

Preferably, said X₁、X₂Each of which isIndependently chlorine or bromine.

Preferably, said n₁、n₂Each independently selected from an integer of 1 to 3, such as 1, 2 or 3.

Preferably, the electrochromic compound has any one of the following compounds:

in another aspect, the present invention provides a method for preparing an electrochromic compound as described above, wherein when the electrochromic compound has a structure represented by formula I, the method is method (a); when the electrochromic compound has a structure as shown in formula II, the preparation method is a method (b).

The method (a) is as follows: reacting 4,4' -bipyridine with a compound shown as a1 to obtain the electrochromic compound shown as the formula I, wherein the reaction formula is as follows:

the method (b) is as follows: reacting 4,4' -bipyridine with a compound shown as a formula b1 to obtain an electrochromic compound shown as a formula II, wherein the reaction formula is as follows:

wherein, X₁、X₂Each independently selected from halogen.

n₁、n₂Each independently selected from an integer of 1 to 7, such as 1, 2, 3, 4, 5, 6 or 7.

Preferably, the molar ratio of 4,4' -bipyridine to the compound represented by the formula a1 in the method (a) is 1 (0.8-1.0), such as 1:0.82, 1:0.84, 1:0.86, 1:0.88, 1:0.9, 1:0.92, 1:0.94, 1:0.96, 1:0.98 or 1: 0.99.

Preferably, the reaction temperature in the method (a) is 85-95 ℃, such as 86 ℃, 87 ℃, 88 ℃, 89 ℃, 90 ℃, 91 ℃, 92 ℃, 93 ℃ or 94 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the range.

Preferably, the reaction time in the method (a) is 12-18 h, such as 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h or 17.5h, and the specific values therebetween are not exhaustive, and the invention is not limited to the specific values included in the range for brevity and conciseness.

Preferably, the reaction in process (a) is carried out in an organic solvent.

Preferably, the organic solvent is N, N-dimethylformamide.

Preferably, the molar ratio of 4,4' -bipyridine to the compound represented by the formula b1 in the method (b) is 1 (2.0-3.0), such as 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8 or 1: 2.9.

Preferably, the reaction temperature in the method (b) is 105-115 ℃, for example 106 ℃, 107 ℃, 108 ℃, 109 ℃, 110 ℃, 111 ℃, 112 ℃, 113 ℃ or 114 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive.

Preferably, the reaction time in the method (b) is 30-40 h, such as 30.5h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h or 39.5h, and specific values therebetween are not limited by space and for the sake of brevity, and the invention is not exhaustive.

Preferably, the reaction in the method (b) is carried out in an organic solvent.

Preferably, the organic solvent is N, N-dimethylformamide.

In another aspect, the present invention provides an electrochromic device, the electrochromic layer of which comprises an electrochromic compound as described above.

Preferably, the electrochromic device is a gel electrochromic device, the gel electrochromic device comprises two conductive layers, and a composite gel electrochromic layer located between the two conductive layers, and the composite gel electrochromic layer comprises the electrochromic compound, the electrolyte and the gel material.

Preferably, the composite gel electrochromic layer further comprises a counter electrode material.

Preferably, the counter electrode material is selected from any one of ferrocene, tetramethyl p-phenylenediamine, triphenylamine or diphenylamine.

Preferably, the molar ratio of the counter electrode material to the electrochromic compound is (1-10): 1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1 or 9.5: 1.

Preferably, the electrolyte is selected from any one of trifluoromethyl sulfimide lithium salt, lithium perchlorate, tetrabutyl ammonium perchlorate or lithium hexafluorophosphate.

Preferably, the gel material is a thermoplastic polymer.

Preferably, the thermoplastic polymer is poly (propylene butyral).

The gel electrochromic device provided by the invention is obtained by dissolving the electrochromic compound and the counter electrode material in the gel electrolyte and then injecting the gel electrolyte into the ITO box, and the preparation process is simple and easy to implement.

In another aspect, the present invention provides the use of an electrochromic device as described above in a colour-changing window, an automotive rear view mirror or a display.

Compared with the prior art, the invention has the following beneficial effects:

the electrochromic compound provided by the invention is a viologen compound containing terminal alkynyl, the electrochromic compound obviously improves the electrochromic performance through the special design of substituent groups, and can be prepared through Mensehutkin reaction, and the synthesis method is simple and easy. The electrochromic compound is applied to an electrochromic layer material of an electrochromic device, and can effectively improve the transmittance difference, the color-changing response speed, the color-changing efficiency and the stability of the electrochromic device. The gel electrochromic device based on the electrochromic compound shown in the formula I changes from a light yellow transparent state to a dark blue colored state under the voltage of 1.6V, the coloring and fading time is 5-6 s, the gel electrochromic device based on the electrochromic compound shown in the formula II changes from the light yellow transparent state to a grey blue colored state under the voltage of 1.2V, and further changes to purple under the voltage of 1.6V, the coloring and fading time is 2-3 s, the two have high transmittance difference and stability, the change value of the transmittance difference is lower than 8% even after 50000 times of circulation, and the application requirements of the electrochromic device with high performance and high stability can be fully met.

Drawings

FIG. 1 is a cyclic voltammogram of a gel electrochromic device of example 1;

FIG. 2 is a cyclic voltammogram of the gel electrochromic device of example 2;

FIG. 3 is a graph of the UV-VIS absorption spectrum of the gel electrochromic device in example 1 as a function of voltage;

FIG. 4 is a graph of the UV-VIS absorption spectrum of the gel electrochromic device in example 2 as a function of voltage;

FIG. 5 is a graph of the change of optical density with charge density of the gel electrochromic device in example 1, in which 1 is a graph of the change of optical density with charge density, and 2 is a slope tangent line of the curve 1 in a linear region;

FIG. 6 is a graph of the change of optical density with charge density of the gel electrochromic device in example 2, in which 1 is a graph of the change of optical density with charge density, and 2 is a slope tangent line of the curve 1 in a linear region;

FIG. 7 is a graph of transmittance versus time during color change for the gel electrochromic device of example 1;

FIG. 8 is a graph of transmittance versus time during color change for the gel electrochromic device of example 2;

FIG. 9 is a graph of current density versus time for the gel electrochromic device in example 1;

FIG. 10 is a graph of current density versus time for the gel electrochromic device in example 2;

FIG. 11 is a graph of transmittance-time response curves of the gel electrochromic device of example 1 at initial state, 5000 cycles, and 10000 cycles, respectively;

FIG. 12 is a graph showing transmittance-time response curves of the gel electrochromic device in example 2 in the initial state, 20000 cycles, 50000 cycles and 70000 cycles, respectively.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Preparation example 1

The preparation example provides an electrochromic compound MPV, which has the following structure:

the preparation method comprises the following steps:

4,4' -bipyridine (0.3g, 1.9mmol) and 5-chloro-1-pentyne (0.176g, 1.7mmol) are dissolved in 2mL of N, N-dimethylformamide, heated to 90 ℃, stirred to react for 14 hours, and after the temperature is reduced to room temperature, the solvent is dried on a rotary evaporator, and the obtained crude product is purified by a silica gel column to obtain the target product MPV which is a gray solid, 0.20g in total, and the yield is 40%.

¹H-NMR(400MHz，D₂O)：δ8.94(d,J＝6.8Hz,2H),8.66(s,2H),8.33(s,2H),7.82(s,2H),4.74(t,J＝6.8Hz,2H),2.40-1.98(m,5H)。

Preparation example 2

The preparation example provides an electrochromic compound DPV with the following structure:

the preparation method comprises the following steps:

4,4' -bipyridine (0.3g, 1.9mmol) and 5-chloro-1-pentyne (0.49g, 4.8mmol) were dissolved in 2mL of N, N-dimethylformamide, heated to 110 deg.C, stirred to react for 36 hours, and after cooling to room temperature, precipitated to give the crude product, which was washed three times with N, N-dimethylformamide to give the desired product, DPV, as a gray solid, in total 0.45g, 66% yield.

¹H-NMR(400MHz，D₂O)：δ9.09(d,J＝6.7Hz,2H),8.48(d,J＝6.3Hz,4H),4.80(t,J＝6.8Hz,4H),2.39-2.05(m,10H)。