A class of viologen compounds, their preparation methods and applications

Abstract

The present invention belongs to the field of organic optoelectronic functional materials and devices, and discloses a class of viologen compounds, their preparation methods and applications. This class of compounds is composed of the acceptor 4,4'-bipyridine, the donor 1,10-phenanthroline and different counter anions. The synthesis method of the viologen compound is to introduce the rigid-structured luminescent body 1,10-phenanthroline as an N-substituent onto 4,4'-bipyridine, and then perform ion exchange to obtain novel viologen compounds with different counter anions. The synthesis is simple, and purification and separation are easy, which is suitable for large-scale production. In addition to having rich redox states, good redox reversibility and rich color changes, the viologen compounds provided by the present invention also exhibit adjustable luminescent color changes. Therefore, such novel viologen compounds can be used as electroactive materials for preparing large-area multi-color electrochromic / electroluminescent color-changing devices.

Description

Technical Field

[0001] The present invention belongs to the field of organic optoelectronic functional materials and devices. More specifically, it relates to a viologen compound, a preparation method thereof, and an application thereof. Background Art

[0002] Stimulus-responsive materials have attracted much attention due to their great potential applications in the fields of data storage, sensors, biomedicine, and information display. The applied external stimuli include temperature, light, mechanical force, solvent or vapor, electric field, and magnetic field. Among them, the electric field is an important external stimulus that can be easily combined with various optical and electronic devices. Moreover, due to the advantages of easy detection, high sensitivity, and high contrast, electro-stimulus-responsive materials have broad prospects in the fields of display, energy, and information storage.

[0003] Electrochromism (EC) refers to the phenomenon that the optical properties (reflectivity, transmittance, absorbance, etc.) of a material change stably and reversibly under an electric stimulus, which is manifested as a reversible change in color and transparency in appearance.

[0004] Similarly, electrochemiluminescence color change (ELC) refers to the phenomenon that the luminescence properties (such as emission intensity, wavelength, and lifetime) of a material undergo a reversible transformation under an electric stimulus. This luminescence switching property can detect both electric signals and optical signals and can be applied to various multifunctional intelligent devices. Exploring new electrochemiluminescence color-changing materials is very important for the development of this field. However, currently, electrochemiluminescence color-changing materials exhibit low fluorescence characteristics and poor stability under an electric stimulus, which is not conducive to practical applications in daily life.

[0005] As an organic electrochromic material, viologen has an easily modified chemical structure, rich redox states, good redox reversibility, and excellent electron-accepting ability, and has been widely used in the fields of smart windows, anti-glare rearview mirrors, and energy storage devices. As a kind of good electron acceptor, viologen generally does not exhibit fluorescence under light stimulation. By introducing a lumophore with a rigid structure, it can have both color-changing and electrochemiluminescence color-changing properties. It is of great significance to develop viologen compounds with rich luminescence color changes by modifying the chemical structure of viologen and apply them to large-area displays and luminescent displays.

[0006] For the electrochromic phenomenon of viologen compounds, although different color conversions under electrical stimulation can be easily achieved by regulating the types of their N-substituents or counter anions. However, due to the inherent strong electron-withdrawing ability of viologens, the regulation of their electroluminescent properties is not simple. Appropriate N-substituents or counter anions must be selected to lower the frontier orbital energy levels of viologen compounds to endow them with fluorescence. To achieve the luminescence regulation of viologen compounds, refer to the patent document with the publication number CN110526861 A. The provided viologen derivatives are formed by introducing some aromatic groups into the middle of the 4,4'-bipyridine skeleton to form π-expanded viologen derivatives with luminescent properties. However, such viologen derivatives only exhibit the phenomenon of fluorescence on→off or fluorescence off→on, and do not have the mutual conversion of multiple fluorescence colors.

[0007] In addition, refer to the published paper: Ren Xiuli. Electrochromic Materials and Devices Based on Terpyridine-Modified Viologen Compounds [D]. Nanjing: Nanjing University of Posts and Telecommunications, 2022: 24-39. For the viologen compounds modified with terpyridine previously disclosed by this research group, although they also have rich redox centers and good redox reversibility and can be used for large-area multi-color displays, such viologen compounds modified with terpyridine still have the problems of relatively cumbersome synthesis, difficult separation and purification of intermediates, relatively high overall preparation cost, and long production cycle, and are not suitable for large-scale production. Summary of the Invention

[0008] Aiming at the above existing problems, the present invention aims to provide a kind of viologen compound. Using relatively simple 1,10-phenanthroline as the N-substituent, a class of viologen compounds with adjustable color and luminescence color is synthesized. Its synthesis steps are relatively simple, separation and purification are relatively easy, and based on the viologen compound, a large-area multi-color electrochromic / electroluminescent color-changing device is fabricated, which is suitable for large-scale production.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] Utilizing the rich redox states, good redox reversibility and excellent electron-accepting ability of viologens, a luminophore is modified in the viologen structure so that its luminescence and color can be regulated under electrical stimulation. 1,10-Phenanthroline is introduced onto 4,4'-bipyridine, and then ion exchange is carried out to obtain novel viologen compounds with different counter anions. The prepared novel viologen compounds not only have the inherent photophysical and electrochemical properties of viologens, but also exhibit excellent luminescent properties. Under electrical stimulation, such viologen compounds undergo good redox reversible reactions and are accompanied by rich color and luminescence color changes. By optimizing the device structure, a large-area multi-color electrochromic / electroluminescent color-changing device is fabricated, which has great application potential in the field of intelligent display / light-emitting display.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] In a first aspect, the present invention provides a novel viologen compound Vio-X, with the structural formula:

[0013]

[0014] Wherein, X - is PF6 - , BF4 - , TFSI - , OTf - is any one of them; R can be independently selected from cyclic, branched, or straight-chain alkyl chains or ether chains with a positive integer number of carbon atoms.

[0015] As a preferred embodiment of the viologen compound of the present invention, the structural formula of the viologen compound is as follows:

[0016]

[0017] In a second aspect, the present invention provides a preparation method for the above novel viologen compound, and the preparation method includes the following synthetic route:

[0018]

[0019] The specific steps of the preparation method include: reacting the asymmetric pyridinium salt intermediate 1 with compound 2 to obtain compound 3; performing a nucleophilic substitution reaction on compound 3 and the halide, and finally performing an ion exchange with any one of hexafluorophosphate, tetrafluoroborate, bis(trifluoromethanesulfonyl)imide salt, and trifluoromethanesulfonate to obtain the novel viologen compound Vio-X.

[0020] As a preferred embodiment, the specific synthesis steps of the above novel viologen compound are as follows:

[0021] (1) Preparation of compound 1: React 1-chloro-2,4-dinitrobenzene and 4,4'-bipyridine in a reflux reaction in acetone, acetonitrile, or ethanol solvent for within 80 h. After the reaction is completed, filter, concentrate and dry the filtrate, wash it three times with acetone first, then three times with ether, and then dry it under vacuum to obtain compound 2;

[0022] (2) Preparation of compound 3: React compound 1 with compound 2 in a mixed solvent of alcohol and deionized water in a reflux reaction for 24 - 84 h; cool to room temperature, rotary evaporate to remove the solvent, add a small amount of alcohol to completely dissolve the solid, then add a large amount of ethyl acetate and acetone for sedimentation, filter, and wash it three times with a mixed solvent of ethyl acetate and acetone to obtain compound 3;

[0023] (3) Preparation of Compound Vio-X: Compound 3 reacts with a halide in solvents such as acetonitrile, alcohol, DMSO, DMF, etc. under a nitrogen atmosphere at 40 - 50 °C for 12 - 36 h; after the reaction, the solvent is removed by rotary evaporation; the solid is dissolved in a good solvent, and any one of hexafluorophosphate, tetrafluoroborate, bis(trifluoromethanesulfonyl)imide salt or trifluoromethylsulfonate is added, and stirred at room temperature for 4 - 12 h; after the reaction, it is filtered and recrystallized to obtain Compound Vio-X.

[0024] In a third aspect, the present invention also provides the application of the above-mentioned viologen compound as an active material for electrochromic and electrochromic light-emitting dual-functional devices; a novel class of viologen compounds described in the present invention has rich redox states and good redox reversibility, and can be used as an electroactive material to construct large-area multi-color electrochromic / electrochromic light-emitting devices. Specifically, in the application, the viologen compound Vio-X is used as an electroactive material, and a suitable electrolyte is doped in a suitable solvent to prepare a homogeneous solution at room temperature in air. After being assembled with two conductive electrodes, a large-area multi-color electrochromic / electrochromic light-emitting device is prepared, wherein the suitable solvent is any one of DMF, acetonitrile, DMSO or acetone; the electrolyte is a mixture of a first electrolyte and a second electrolyte, the first electrolyte is poly(vinylidene fluoride-co-hexafluoropropylene), and the second electrolyte is an imidazole salt or a lithium salt.

[0025] Preferably, the conductive electrodes are two pieces of ITO glass;

[0026] Preferably, the second electrolyte is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; further preferably, the mass ratio of poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and Vio-X is set to 8:72:3.

[0027] As a preferred embodiment, the preparation process of the above-mentioned large-area multi-color electrochromic / electrochromic light-emitting device includes the following operation steps: First, at room temperature, the ITO glass is ultrasonically cleaned with deionized water, ethanol and acetone in sequence for 10 - 30 min, and then dried for standby; Second, at room temperature, two pieces of ITO glass are bonded, leaving the required grooves and edges for injecting the electrolyte solution containing Vio-X and electrode clamping; Finally, poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and Vio-X are stirred at 50 °C until completely dissolved in anhydrous DMF as the liquid to be injected; after the reaction, it is cooled to room temperature of 25 °C, and the above-mentioned liquid to be injected is sucked with a syringe and injected into the groove of the device to prepare a large-area multi-color electrochromic / electrochromic light-emitting device.

[0028] A novel class of viologen compounds described in the present invention has rich electrochromic / electroluminescence color-changing properties and can be combined with other energy storage and sensing materials to construct energy storage or sensor devices that can be displayed in real time, such as electrochromic / electroluminescence color-changing supercapacitors, electrochromic / / electroluminescence color-changing batteries, and electrochromic / electroluminescence color-changing sensors.

[0029] A novel class of viologen compounds described in the present invention has good reversible redox ability and can be used as negative electrode materials in lithium-ion batteries, sodium-ion batteries or potassium-ion batteries and anodic electrolytes in redox flow batteries.

[0030] A novel class of viologen compounds described in the present invention has good redox states and high electrical stimulation sensitivity. Under electrical stimulation, its redox states change reversibly, causing corresponding reversible changes in its resistance states. Therefore, it can be used as active materials for various transistors (such as field-effect transistors, electrochemical transistors) and memories (including memristors) for neuromorphic computing.

[0031] The beneficial effects of the present invention are as follows:

[0032] The viologen compounds prepared by the present invention by introducing a lumophore with a rigid structure as an N-substituent onto 4,4'-bipyridine have a relatively low frontier orbital energy level difference and can achieve mutual conversion of various fluorescence colors under electrical stimulation. Specifically, the present invention introduces 1,10-phenanthroline with a rigid structure onto 4,4'-bipyridine and then obtains novel viologen compounds with different counter anions through ion exchange. Compared with the viologen compounds modified with terpyridine reported by our research group before and used for large-area multi-color display, the novel viologen compounds provided by the present invention not only have relatively simple synthesis steps, are easier to separate and purify, and are suitable for large-scale production, but also have a higher transmittance change verified by Test Example 2 and a shorter response time verified by Test Example 7. Under the action of an external electric field, the viologen compounds provided by the present invention undergo reversible redox reactions accompanied by color and luminescence color changes. By optimizing the device structure, large-area multi-color electrochromic / electroluminescence color-changing devices are successfully prepared.

[0033] The synthesis of the viologen compound involved in the present invention is simple, with rich color changes. Under electrical stimulation, it can simultaneously achieve color and luminescence color changes, and can be made into large-area multi-color electrochromic and electro-luminescence color-changing devices, providing strong support for the further development of dual-functional materials with both electrochromic and electro-luminescence color-changing properties. Compared with single-functional devices, such dual-functional devices have two ways to achieve the response of related devices, that is, after adjusting the external voltage, the response of the device is achieved through color or luminescence color changes, and the color change or luminescence color change is applied according to actual needs. In addition, the introduction of electro-luminescence color-changing properties enables viologen-based materials to be applied in aspects such as anti-counterfeiting, electronic tags, and optical imaging. Description of the Drawings

[0034] Figure 1 For the ultraviolet absorption and emission spectrum tests of Vio-PF6 in Test Example 1 - ;

[0035] Figure 2 For the cyclic voltammetry test of Vio-PF6 in Test Example 2 - ;

[0036] Figure 3 For the cyclic voltammetry test of the large-area multi-color electrochromic / electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 4 - ;

[0037] Figure 4 For the absorption spectrum test of the large-area multi-color electrochromic / electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 5 - ;

[0038] Figure 5 For the emission spectrum test of the large-area multi-color electrochromic / electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 5 - ;

[0039] Figure 6 For the transmittance spectrum test of the large-area multi-color electrochromic / electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 6 - ; - ;

[0040] Figure 7 For the response time spectrum test of the large-area multi-color electrochromic / electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 7 - ;

[0041] Figure 8 For the demonstration of the large-area multi-color electrochromic and electro-luminescence color-changing device prepared with Vio-PF6 in Test Example 8 - ; Detailed implementation mode

[0042] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0043] Compound Vio-X - Has multiple redox states and excellent redox reversibility. Here, Vio-PF6 is taken as an example for detailed description.

[0044] Example 1: Preparation of Vio-PF6

[0045]

[0046] (1) Preparation of Compound 1: 4,4'-Bipyridine (154 mg, 1 mmol) and 1-chloro-2,4-dinitrobenzene (242 mg, 1.2 mmol) were refluxed in anhydrous acetonitrile for 72 h. After the reaction was completed, it was cooled to room temperature, filtered by suction, washed three times with acetonitrile, the filtrate was evaporated to dryness and dried under vacuum to obtain Compound 3. Yield: 72%. 1 H NMR (400 MHz, D2O) δ 9.30 (d, J = 2.5 Hz, 1H), 9.16 (d, J = 7.1 Hz, 2H), 8.84 (dd, J = 8.7, 2.5 Hz, 1H), 8.76 - 8.73 (m, 2H), 8.59 (d, J = 7.1 Hz, 2H), 8.18 (d, J = 8.7 Hz, 1H), 7.95 - 7.91 (m, 2H). 13 C NMR (100 MHz, D2O) δ 150.7, 148.8, 143.9, 139.9, 134.4, 133.2, 132.6, 123.7, 121.0.

[0047] (2) Preparation of Compound 3: Compound 2 (2.2 mmol, 429 mg) and Compound 1 (2.0 mmol, 786 mg) were refluxed in 80% ethanol solvent for 24 h; cooled to room temperature, the solvent was removed by rotary evaporation, a small amount of methanol was added to completely dissolve the solid, and then a large amount of mixed solvent of ethyl acetate and acetone was added for sedimentation to obtain Compound 4. Yield: 84%. 11H NMR (400 MHz, DMSO-d6) δ 9.65 (d, J = 6.8 Hz, 2H), 9.31 (ddd, J = 12.2, 4.2, 1.4 Hz, 2H), 9.02 - 8.96 (m, 4H), 8.70 (dd, J = 8.0, 1.6 Hz, 1H), 8.66 (s, 1H), 8.23 (dd, J = 4.6, 1.4 Hz, 2H), 8.11 (dd, J = 8.2, 1.4 Hz, 1H), 7.99 (dd, J = 8.0, 4.4 Hz, 1H), 7.89 (dd, J = 8.4, 4.2 Hz, 1H). 13 13C NMR (100 MHz, DMSO-d6) δ 150.0, 152.8, 151.9, 151.6, 147.5, 145.9, 145.5, 141.4, 138.1, 136.8, 131.1, 126.9, 126.4, 126.3, 125.1, 124.9, 123.9, 122.7。

[0048] (3) Preparation of Compound Vio-PF6: Compound 4 (1 mmol, 420 mg) and methyl iodide (8.0 mmol, 0.5 mL) were reacted in acetonitrile solvent under a nitrogen atmosphere at 43 °C for 24 h; after the reaction was completed, the reaction solution was concentrated to dryness to remove unreacted methyl iodide and acetonitrile solvent; subsequently, the solid was dissolved in methanol and stirred, and a saturated potassium hexafluorophosphate (5 mmol, 920 mg) solution was added dropwise until no more precipitate was formed; the mixture was stirred at room temperature for 12 h, filtered, and the filter cake was washed three times with deionized water and acetonitrile respectively, and then dried in vacuo to obtain an orange solid Vio-PF6. Yield: 65%. 1 1H NMR (400 MHz, (CD3)2SO) δ = 9.81 (d, J = 7.2 Hz, 2H), 9.37 (d, J = 6.8 Hz, 2H), 9.33 (dd, J = 4.4, 1.6 Hz, 1H), 9.29 (dd, J = 4.4, 1.6 Hz, 1H), 9.12 (d, J = 7.2 Hz, 2H), 8.90 (d, J = 6.8 Hz, 2H), 8.70 (dd, J = 8.4, 1.6 Hz, 1H), 8.63 (s, 1H), 8.06 (dd, J = 8.4, 1.6 Hz, 1H), 7.99 (dd, J = 8.0, 4.4 Hz, 1H), 7.89 (dd, J = 8.4, 4.0 Hz, 1H), 4.50 (s, 3H). 1313C NMR (100 MHz, (CD3)2SO) δ = 153.0, 152.0, 151.1, 148.5, 148.1, 147.4, 146.3, 145.8, 138.0, 136.9, 131.1, 127.5, 126.9, 126.8, 126.5, 125.1, 124.8, 124.0, 48.7. 19 19F NMR (376.5 MHz, (CD3)2SO) δ = -70.13 (d, J F-P = 711.6 HZ).

[0049] Test Example 1: Absorption and Emission Spectra Test of Vio-PF6

[0050] In this invention, the spectral test concentration is 10 μM, the test solvent is DMF, and the excitation wavelength is 365 nm; the absorption and emission spectra of Vio-PF6 are as Figure 1 shown; Vio-PF6 has a strong absorption at 269 nm, possibly due to the π→π* electronic transition of the pyridine group and the benzene ring; under the excitation of light at 365 nm, Vio-PF6 exhibits a broad emission band at 580 nm.

[0051] Test Example 2: Cyclic Voltammetry Test of Vio-PF6

[0052] The cyclic voltammetry test of Vio-PF6 adopts a three-electrode system. The reference electrode is Ag / AgNO3, the counter electrode is a platinum wire electrode, and the working electrode is a palladium-carbon electrode. The electrolyte is a DMF solution of 0.1 M tetrabutylammonium hexafluorophosphate. The scanning rate is 100 mV·s -1 .

[0053] The cyclic voltammogram of Vio-PF6 is as Figure 2 shown. It can be seen from the figure that this compound has two pairs of reversible redox peaks and two irreversible redox peaks. Among them, the reduction potentials of the two nitrogen atoms on the viologen group obtaining one electron and two electrons respectively correspond to the two pairs of reversible redox peaks with negative potentials, while the two-step electron loss reduction processes of the two nitrogen atoms on 1,10-phenanthroline correspond to the two pairs of irreversible reduction peaks.

[0054] Test Example 3: Preparation of Large-Area Multi-Color Electrochromic / Electroluminescent Color-Changing Devices

[0055] The preparation process is as follows: First, at room temperature, the ITO glass is ultrasonically cleaned with deionized water, ethanol, and acetone in sequence for 10 - 30 min, and then dried for later use. Second, at room temperature, two pieces of ITO glass are bonded with ordinary double-sided tape, leaving the required grooves and edges for injecting the electrolyte solution containing Vio-PF6 and clamping the electrodes. Finally, 40 mg of poly(vinylidene fluoride-co-hexafluoropropylene), 360 mg of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 15 mg of Vio-PF6 are stirred at 50 °C until completely dissolved in 5 mL of anhydrous DMF. After the reaction, it is cooled to room temperature of 25 °C, and the above DMF solution is sucked with a 1 mL syringe and injected into the groove of the device, successfully realizing the fabrication of a large-area multi-color electrochromic / electroluminescent color-changing device (>64 cm 2 )

[0056] Test Example 4: Cyclic voltammetry test of a large-area multi-color electrochromic / electroluminescent color-changing device prepared with Vio-PF6

[0057] As Figure 3 shown, the large-area multi-color electrochromic and electroluminescent color-changing device prepared with Vio-PF6 has two irreversible oxidation-reduction peaks, corresponding to Vio-PF6 successively gaining two electrons to generate a radical cation substance and a neutral substance respectively.

[0058] Test Example 5: Absorption and emission tests of a large-area multi-color electrochromic / electroluminescent color-changing device prepared with Vio-PF6

[0059] For the large-area multi-color electrochromic and electroluminescent color-changing device prepared with Vio-PF6, the absorption and emission spectra at different voltages show that, as Figure 4 shown, at 0 V, the device has a broad absorption peak at 324 nm and appears light yellow, Figure 5 shown, the device has an emission peak at 580 nm and appears yellow. When a voltage V1 (-1.8 - -2.6 V) is applied, since Vio-PF6 gains one electron to generate a radical cation substance, as Figure 4 shown, the electrochromic and electroluminescent color-changing device has a broad absorption peak at 513 nm and appears orange, as Figure 5 shown, it has an emission peak at 600 nm and appears orange light. When the voltage V2 (-2.7 - -3.5 V) is continuously applied, with the continuous generation of the neutral substance of Vio-PF6, as Figure 5 shown, it has a broad absorption peak at 600 nm and appears dark blue, as Figure 5 shown, it has a broad emission peak centered at 498 nm and appears green light.

[0060] Test Example 6: Transmittance Spectrum Test of Large-Area Multicolor Electrochromic / Electroluminescent Color-Changing Device Prepared with Vio-PF6

[0061] For the large-area multicolor electrochromic and electroluminescent color-changing device prepared with Vio-PF6, the transmittance spectra at different voltages show that, as Figure 6 shown, at 513 nm, the transmittance change (ΔT) of Vio-PF6 at 513 nm is 42%, and at 600 nm, ΔT is 77%, which is significantly better than the previously reported viologen compounds modified with terpyridine (668 nm, ΔT = 30%; 666 nm, ΔT = 64%). For example, for the Tpy-Vio-2 device, at 668 nm, when a voltage of -2.2 V is applied, the maximum transmittance difference ΔT% of the Tpy-Vio-2 device is at most 30%; when a voltage of -3.2 V is applied, at 664 nm, the maximum transmittance difference ΔT% of the Tpy-Vio-2 device is 64%.

[0062] Test Example 7: Response Time Test of Large-Area Multicolor Electrochromic / Electroluminescent Color-Changing Device Prepared with Vio-PF6

[0063] For the large-area multicolor electrochromic and electroluminescent color-changing device prepared with Vio-PF6, the response time spectra at different step voltages show that, as Figure 7 shown in the left figure, at 513 nm, in the voltage range of 0 to -V1V, the coloring time t c is 15.1 s, and the fading time t b is 15.3 s; as Figure 7 shown in the right figure, at 600 nm, in the voltage range of 0 to -V2V, the t c is 14.0 s, and the t b is 17.4 s, which is significantly better than the previously reported viologen compounds modified with terpyridine (668 nm, when 0 to -2.2 V, t c = 31.5 s, t b = 35 s).

[0064] Test Example 8: Demonstration of Large-Area Multicolor Electrochromic / Electroluminescent Color-Changing Device Prepared with Vio-PF6

[0065] As Figure 8As shown, the large-area multi-color electrochromic and electro-luminescent color-changing devices prepared with Vio-PF6 demonstrate rich color and luminescence color changes. That is, in the initial state, the device is light yellow and emits yellow light; when a voltage of V1 V is applied, the device changes from light yellow to dark orange, and the luminescence color changes from yellow to orange; when the voltage is further increased to V2 V, the device changes from dark orange to dark blue, and the luminescence color changes from orange to green. Therefore, it has great application prospects in the field of intelligent light-emitting displays.

Claims

1. A viologen compound, characterized in that, The viologen compound is Vio-X, and its structural formula is: ； Among them, X - is PF6 - , and R is methyl.

2. The preparation method of a viologen compound according to claim 1, characterized in that, The synthetic route of the preparation method is as follows: ； The preparation method includes the steps: 1-chloro-2,4-dinitrobenzene reacts with 4,4'-bipyridine to obtain an asymmetric pyridinium salt intermediate 1; the asymmetric pyridinium salt intermediate 1 reacts with compound 2 to obtain compound 3; compound 3 and methyl iodide undergo a nucleophilic substitution reaction, and finally ion exchange with hexafluorophosphate to obtain the viologen compound Vio-X.

3. The preparation method according to claim 2, wherein, The specific synthesis steps of the viologen compound are as follows: (1) Preparation of compound 1: 1-chloro-2,4-dinitrobenzene and 4,4'-bipyridine are refluxed in a solvent of acetone, acetonitrile or ethanol for within 80 h. After the reaction is completed, filtration is carried out. The filtrate is concentrated and dried, washed three times with acetone first, then washed three times with ether, and then dried in vacuo to obtain compound 1; (2) Preparation of compound 3: Compound 1 and compound 2 are refluxed in a mixed solvent of alcohol and deionized water for 24 - 84 h; cooled to room temperature, the solvent is removed by rotary evaporation, a small amount of alcohol is added to completely dissolve the solid, and then a large amount of ethyl acetate and acetone are added for precipitation. Filtration is carried out, and the solid is washed three times with a mixed solvent of ethyl acetate and acetone to obtain compound 3; (3) Preparation of compound Vio-X: Compound 3 reacts with methyl iodide in a nitrogen atmosphere in solvents of acetonitrile, alcohol, DMSO, or DMF at 40 - 50 °C for 12 - 36 h; after the reaction is completed, the solvent is removed by rotary evaporation; the solid is dissolved in a good solvent, hexafluorophosphate is added, and stirring is carried out at room temperature for 4 - 12 h; after the reaction is completed, filtration is carried out, and recrystallization is carried out to obtain compound Vio-X.

4. Application of the viologen compound according to claim 1 as an active material for an electrochromic and electrochemiluminescent color-changing dual-functional device.

5. The application according to claim 4, characterized in that The application includes: using the viologen compound Vio-X as an electroactive material, doping a suitable electrolyte in a suitable solvent to prepare a homogeneous solution at room temperature in air, and assembling it with two ITO glass conductive electrodes to prepare a large-area multi-color electrochromic / electrochemiluminescent color-changing device, where the suitable solvent is any one of DMF, acetonitrile, DMSO, or acetone; the suitable electrolyte is a mixture of a first electrolyte and a second electrolyte, the first electrolyte is poly(vinylidene fluoride-co-hexafluoropropylene), and the second electrolyte is an imidazolium salt or a lithium salt.

6. The application according to claim 5, characterized in that The second electrolyte is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; and the mass ratio of poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and Vio-X is set to 8 : 72 :

3.

7. The application according to claim 5, characterized in that The preparation process of the large-area multi-color electrochromic / electroluminescent color-changing device includes the following operating steps: First, at room temperature, the ITO glass is ultrasonically cleaned with deionized water, ethanol, and acetone in sequence for 10 - 30 min, and then dried for standby; Second, at room temperature, two pieces of ITO glass are bonded, leaving the required grooves and edges for injecting the electrolyte solution containing Vio-X and electrode clamping; Finally, poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and Vio-X are stirred at 50 °C until completely dissolved in anhydrous DMF as the solution to be injected; After the reaction ends, it is cooled to room temperature of 25 °C, and the above solution to be injected is sucked with a syringe and injected into the grooves of the device to prepare a large-area multi-color electrochromic / electroluminescent color-changing device.

8. The application of the viologen compound according to claim 1 as a color-changing active material for energy storage or sensor devices, wherein the energy storage device includes an electrochromic / electroluminescent color-changing supercapacitor, and the sensor device includes an electrochromic / electroluminescent color-changing battery and an electrochromic / electroluminescent color-changing sensor.

9. The application of the viologen compound according to claim 1 as an active material for transistors and memories for neuromorphic computing, wherein the transistors include field-effect transistors and electrochemical transistors, and the memories include memristors.

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