JP2023133170A - Viologen derivative with regular structure, and redox flow battery including the same - Google Patents

Abstract

To provide a compound with high solubility for use in an active material of a redox flow battery, and further provide a redox flow battery that includes the compound and exhibits significantly reduced capacity loss due to crossover.SOLUTION: A viologen derivative is represented by general formula (I) (where Ar is a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a bipyridinium group, a is an integer of 0 or 1, b is an integer of 0-5, c is an integer of 1-6, d is an integer of 1-5, e is an integer of 1-6, n is an integer required to maintain the molecular electrical neutrality, X is a counter anion, and Y is a hydrophilic substituent).SELECTED DRAWING: Figure 1

Description

The present invention relates to a functional material for improving the performance of a redox flow battery, and an electrochemical device using the same.

In order to make renewable energies such as solar and wind power the main power sources, it is necessary not only to introduce a large number of power generation systems that use them, but also to introduce high-performance storage batteries (secondary batteries) to adjust the constantly fluctuating output. There is. However, the development of high-performance storage batteries that meet cost, safety, and resource considerations has not been sufficient, and large-scale implementation has not yet been achieved. Redox flow batteries have a long life, safety, and high degree of freedom in design, so they are considered to be a promising means of leveling out renewable energy. However, there are challenges in improving energy density and further reducing costs.

A redox flow battery is a battery that was successfully developed by NASA in the 1970s. At the beginning of development, iron/chromium systems were the mainstream, but development did not proceed smoothly because of the drawback that the cross-over of positive and negative electrolytes mixing through a diaphragm reduced the capacity of the battery. Since the vanadium type was reported in 1985, this type has now become mainstream and is being put into practical use in some areas. However, when considering the large-scale introduction of vanadium-based electrolytes in the future, it is said that there remains a problem in cost reduction due to resource constraints, and the development of new electrolytes for large-scale introduction is underway all over the world. It is actively carried out in In recent years, there have been many reports on the use of organic compounds instead of inorganic metal ions. In the case of organic compounds, compounds with different structures for the positive and negative electrodes are generally used in order to widen the redox potential generated at both the positive and negative electrodes and improve energy density.

However, in that case, it is necessary to suppress crossover that causes a reduction in capacity. As one of the methods, there are reports using polymerized compounds and compounds containing a structure that forms part of a Bethe lattice or a Cayley tree (Non-Patent Documents 1 and 2, and Patent Document 1); At present, it is difficult to exceed the energy density of vanadium-based materials due to the difficulty of ensuring sufficient solubility and the unavoidable precipitation due to aggregation of molecules associated with redox. Against this background, there is a need for the development of new materials that have the dual functions of high solubility to avoid agglomeration and crossover suppression.

T. Janoschka, N. Martin, U. Martin, C. Friebe, S. Morgenstern, H. Hiller, M. D. Hager and U. S. Schubert, Nature 2015, 527, 78-81. T. Hagemann, J. Winsberg, M. Grube, I. Nishang, T. Janoschka, N. Martin, M. D. Hager, U. S. Schubert, J. Power Sources 2018, 378, 546-554.

Japanese Patent Application Publication No. 2020-170697

The present invention was made in view of the above-mentioned situation in the prior art, and its purpose is to provide a compound with high solubility for use as an active material of a redox flow battery, and furthermore, to provide a compound with high solubility for use as an active material of a redox flow battery, and furthermore, to An object of the present invention is to provide a redox flow battery in which capacity reduction is significantly reduced.

The present inventors conducted extensive studies to solve the above problems. As a result, they discovered that the above problems can be solved by using a compound in which viologen derivatives are regularly arranged and a hydrophilic substituent is introduced at the end of the molecule as an active material for a redox flow battery, and the present invention has been completed. That is, one embodiment of the present invention has general formula (I):

(wherein, Ar is a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a bipyridinium group, a is an integer of 0 or 1, b is an integer of 0 to 5, c is an integer of 1 to 6, d is an integer of 1 to 5, e is an integer of 1 to 6, n is an integer necessary to maintain the electrical neutrality of the molecule, and X is an integer of 1 to 6. From the group consisting of halogen anions, BF ₄ ^- , PF ₆ ^- , ClO ₄ ^- , SO ₄ ^2- , NO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- , CF ₃ SO ₃ ^- , and CF ₃ CO ₂ ^- Y is a counter anion selected from the group consisting of a hydroxy group, an alkylammonium group, a sulfonic acid group, a phosphonic acid group, a phosphoric acid group, a carboxy group, a boric acid group, and a group corresponding to a salt thereof. It is a viologen derivative represented by the following hydrophilic substituent.

In a preferred embodiment, the substituent of the substituted aryl group or substituted heteroaryl group in general formula (I) is an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxy group, a haloalkoxy group, or an aryloxy group. , acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen The viologen derivative is a group selected from the group consisting of atoms, cyano groups, and heterocyclic groups. In other embodiments, Ar may be an unsubstituted aryl group, an unsubstituted heteroaryl group, or a bipyridinium group. In a preferred embodiment, Ar is a phenyl group, a bipyridinium group, a pyrazinium group, a triazinium group, or the like.

In a further preferred embodiment, the viologen derivative represented by the general formula (I) is a compound represented by any of the following formulas (II) to (IX).

In another aspect of the present invention, an electrochemical device comprising any of the viologen derivatives described above is provided. Preferably, the electrochemical device is a redox flow battery or a redox capacitor.

According to the present invention, a novel compound for use in an active material of a redox flow battery is provided. Furthermore, it is possible to provide a redox flow battery using this compound in which capacity reduction due to crossover is significantly reduced.

FIG. 1 is a configuration diagram of a redox flow battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a small test cell of a redox flow battery according to another embodiment of the invention. FIG. 3 is a schematic diagram of the apparatus used in the crossover test. FIG. 4 is a graph showing the results of the crossover test.

Next, each embodiment of the present invention will be described with reference to the drawings. It should be noted that each embodiment described below does not limit the claimed invention, and all of the various elements and combinations thereof described in each embodiment are the solution of the present invention. is not necessarily required.

The viologen derivative according to one embodiment of the present invention is
General formula (I):

(wherein, Ar is a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a bipyridinium group, a is an integer of 0 or 1, b is an integer of 0 to 5, c is an integer of 1 to 6, d is an integer of 1 to 5, e is an integer of 1 to 6, n is an integer necessary to maintain the electrical neutrality of the molecule, and X is an integer of 1 to 6. , counter anions (halogen anions (F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ ), BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , N(CF ₃ SO ₂ ) ₂ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ ), and Y is a hydrophilic substituent (hydroxy group, alkylammonium group, sulfonic acid group, phosphonic acid group, phosphoric acid group, carboxy group, or boric acid group). or a group corresponding to a salt thereof), and can be a variety of compounds. At least one type of viologen derivative of this embodiment can be introduced into the negative electrode electrolyte, and it is also possible to introduce a plurality of types.

In one embodiment, Ar in the above general formula (I) is an unsubstituted aryl group, an unsubstituted heteroaryl group, or a bipyridinium group. Here, the term "aryl" means an aryl having 6 to 14 carbon atoms (C _6-14 aryl). Aryl groups are not particularly limited, but include, for example, phenyl, naphthyl, or ortho-fused bicyclic groups having 8 to 10 ring atoms and at least one ring being an aromatic ring (such as indenyl). can be mentioned. Since e is an integer of 1 to 6, the aryl group may be a monovalent to hexavalent group, preferably a monovalent to trivalent group, more preferably a trivalent group.

In addition, the term "heteroaryl" refers to a 5- to 7-membered aromatic group containing 1 to 4 heteroatoms of 1 to 3 types selected from nitrogen atoms, sulfur atoms, and oxygen atoms in addition to carbon atoms as ring atoms. Means a heterocyclic (monocyclic) group, for example 1-6 derived from pyridine, pyrazine, pyrimidine, pyridazine, triazine, pyrrole, thiophene, furan, imidazole, pyrazole, thiazole, isothiazole, oxazole, isoxazole, etc. It can be a valent group, preferably a monovalent to trivalent group, more preferably a divalent group. Specifically, furyl, thienyl, pyrrolyl, thiazolyl, pyrazolyl, oxazolyl, isoxazolyl, isothiazolyl, imidazolyl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, 1,2,3-triazolyl, 1,2 , 4-triazolyl, 1,2,4-thiadiazolyl, 1,3,4-thiadiazolyl, tetrazolyl, pyridyl, pyridinium, pyrimidinyl, pyrimidinium, pyrazinyl, pyrazinium, pyridazinyl, pyridazinium, triazinyl, triazinium, azepinyl, diazepinyl, etc. . In addition, "heteroaryl" refers to a 5- to 7-membered aromatic heteroaromatic compound containing 1 to 4 heteroatoms of 1 to 3 types selected from nitrogen atoms, sulfur atoms, and oxygen atoms in addition to carbon atoms as ring atoms. Also included are groups whose ring is derived from a benzene ring or an aromatic heterocycle (bicyclic or more) fused to the above-mentioned aromatic heterocycle (monocyclic) group, such as indolyl, isoindolyl, benzo[ b]furyl, benzo[b]thienyl, benzimidazolyl, benzoxazolyl, benzisoxazolyl, benzothiazolyl, benzisothiazolyl, quinolyl, isoquinolyl, and the like.

The bipyridinium group is not particularly limited, but examples include 4,4'-bipyridinium and 3,3'-bipyridinium.

In another embodiment, Ar may have a substituent, and preferable substituents include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxy group, a haloalkoxy group, an aryloxy group, and an acyl group. group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen atom, Examples include a cyano group and a heterocyclic group. More preferred substituents include alkyl groups, alkenyl groups, alkynyl groups, amino groups, alkoxy groups, and alkylthio groups.

The term "alkyl" usually means a straight or branched alkyl having 1 to 15 carbon atoms (C _1-15 alkyl), such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec. -butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl and the like. Preferably, C _1-6 alkyl such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl or pentyl is mentioned, more preferably methyl or ethyl is mentioned, most preferably methyl. be. Furthermore, "alkenyl" includes, for example, linear or branched alkenyl having 2 to 10 carbon atoms (C _2-10 alkenyl). Specific examples include vinyl, allyl, 1-propenyl, isopropenyl, methacryl, butenyl, crotyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, and the like. Furthermore, "alkynyl" includes, for example, linear or branched alkynyl having 2 to 10 carbon atoms (C _2-10 alkynyl). Specifically, they include ethynyl, propargyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, and the like. Furthermore, "alkoxy" includes, for example, linear or branched alkoxy having 1 to 6 carbon atoms (C _1-6 alkoxy). Specifically, they are methoxy and ethoxy. Further, in the present specification, "halo-C _1-6 alkoxy" includes the above-mentioned C _1-6 alkoxy substituted with one or more halogen atoms. The number of carbon atoms in the substituent is preferably 1 to 6, more preferably 1 to 3. The position of the substituent in Ar is not particularly limited.

X is a counter anion, fluoride ion (F ⁻ ), chloride ion (Cl ⁻ ), bromide ion (Br ⁻ ), iodide ion (I ⁻ ), tetrafluoroborate ion (BF ₄ ⁻ ), Hexafluorophosphate ion (PF ₆ ⁻ ), perchlorate ion (ClO ₄ ⁻ ), sulfate ion (SO ₄ ²⁻ ), nitrate ion (NO ₃ ⁻ ), bis(trifluoromethanesulfonyl)imide ion (N(CF ₃ SO ² ) ₂ ⁻ ), bis(perfluoroethanesulfonyl)imide ion (N(C ₂ F ₅ SO ₂ ) ₂ ⁻ ), (perfluoroethanesulfonyl)(trifluoromethanesulfonyl) imide ion (N(C ₂ F ₅ SO ₂ ) (CF ₃ SO ₂ ) ⁻ ), methanesulfonate ion (CH ₃ SO ₃ ⁻ ), trifluoromethanesulfonate ion (CF ₃ SO ₃ ⁻ ), perfluoroethanesulfonate ion (C ₂ F ₅ SO ₃ ⁻ ) , formate ion (HCO ₂ ⁻ ), acetate ion (CH ₃ CO ₂ ⁻ ), trifluoroacetate ion (CF ₃ CO ₂ ⁻ ), perfluoropropionate ion (C ₂ F ₅ CO ₂ ⁻ ), etc. .

Y is a hydrophilic substituent, such as a hydroxy group, an alkylammonium group, a sulfonic acid group, a phosphonic acid group, a phosphoric acid group, a carboxy group, a boric acid group, or a group corresponding to a salt thereof. It will be done.

Specific examples of the viologen derivative of the present invention include those represented by the following formula.

When Ar is a phenyl group, the method for producing the viologen derivative of the present invention can be carried out, for example, by reacting 4,4'-bipyridyl and 1,3,5-tris(bromomethyl)benzene in advance in Example 1 described below. It can be obtained by synthesizing a skeleton like Compound 1, reacting it with 1,3-propane sultone, and then treating it with tetrabutylammonium chloride. In addition, when Ar is bipyridyl, 1,3,5-tris(bromomethyl)benzene and 4,4'-bipyridyl are reacted in advance to synthesize a skeleton such as compound 8 synthesized in Example 4 described later. It can be obtained by further reacting this with 4,4'-bipyridyl and 1,3-propane sultone and then treating with tetrabutylammonium chloride. Other viologen derivatives can also be obtained based on the above production method and conventional organic chemical synthesis techniques.

[Electrochemical device]
The viologen derivative of the present invention can be used as a compound to be introduced into an electrochemical device. DESCRIPTION OF THE PREFERRED EMBODIMENTS A redox flow battery, which is an embodiment of the electrochemical device of the present invention, will be outlined below with reference to the drawings. FIG. 1 is a configuration diagram of a redox flow battery according to one embodiment of the present invention. Red1 and Red2 shown in FIG. 1 indicate reduced active materials, and Ox1 and Ox2 mean oxidized active materials. The ionic species are examples. Moreover, in FIG. 1, solid line arrows mean charging, and broken line arrows mean discharging.

[Redox flow battery]
The redox flow battery 11 is typically connected to a power plant (for example, a solar power generator, a wind power generator, other general power plants, etc.) via an AC/DC converter, and to a power system, a consumer, etc. It is connected to the load, charges using the power plant as the power supply source, and discharges using the load as the power supply target. In carrying out the above charging and discharging, the following battery system is constructed, which includes a redox flow battery 11 and a circulation mechanism (tank, piping, pump) that circulates an electrolyte through the battery 11.

The redox flow battery 11 includes a positive electrode cell 4 containing a positive electrode 3, a negative electrode cell 2 containing a negative electrode 1, and a diaphragm 5 that separates both cells 2 and 4 and allows appropriate ions to pass therethrough. A positive electrode electrolyte tank 8 is connected to the positive electrode cell 4 via piping. A tank 7 for negative electrode electrolyte is connected to the negative electrode cell 2 via piping. The piping is equipped with pumps 9 and 10 for circulating the electrolyte. The redox flow battery 11 circulates and supplies the positive electrolyte in the tank 8 and the negative electrolyte in the tank 7 to the positive electrode cell 4 (positive electrode 3) and negative electrode cell 2 (negative electrode), respectively, using piping and pumps. Charging and discharging are performed in conjunction with the redox reaction of organic molecules that serve as active materials in the electrode electrolyte.

FIG. 2 shows a cross-sectional view of a small test cell 21 of a redox flow battery according to another embodiment. The cell 21 has a negative electrode 30 made of carbon felt or carbon paper and a positive electrode 31 made of carbon felt or carbon paper connected to each other at approximately the center thereof using a cation exchange membrane or an anion exchange membrane (hereinafter referred to as a "diaphragm" or simply " They have a structure in which they are placed opposite each other with a membrane (referred to as "membrane") 32 interposed therebetween. The negative electrode 30 has a graphite composite current collector plate 33 made of a composite of resin and graphite disposed on the outside thereof, and a negative electrode terminal 37 further outside thereof. Similarly, the positive electrode 31 has a graphite composite current collector plate 34 made of a composite of resin and graphite disposed on the outside thereof, and a positive electrode terminal 38 further outside thereof. The negative electrode 30, the graphite composite current collector plate 33, and the negative electrode terminal 37 are in electrically conductive contact with each other. Similarly, the positive electrode 31, the graphite composite current collector plate 34, and the positive electrode terminal 38 are also in electrically conductive contact with each other. Therefore, measuring the potential difference between the negative electrode terminal 37 and the positive electrode terminal 38 can be equated with measuring the potential difference between the negative electrode 30 and the positive electrode 31.

A gasket 35 and a gasket 36 are arranged between the graphite composite current collector plate 33 and the diaphragm 32 and between the graphite composite current collector plate 34 and the diaphragm 32. The negative electrode 30 is arranged inside the gasket 35. Similarly, the positive electrode 31 is placed inside the gasket 36. The gaskets 35 and 36 have a function of effectively preventing each electrolytic solution that has soaked into the negative electrode 30 and the positive electrode 31 from leaking from the cell 21 to the outside. A back plate 39 is arranged further outside the negative electrode terminal 37. Similarly, a back plate 40 is arranged further outside the positive electrode terminal 38. The back plate 39 and the back plate 40 are clamped using, for example, bolts and nuts (not shown) in a direction that narrows the distance between them.

Graphite composite current collector plate 33, negative electrode terminal 37, and back plate 39 are provided with two through holes that communicate with them. A tube 41 is inserted into one through hole. A tube 42 is inserted into the other through hole. The tubes 41 and 42 each reach the outer surface of the negative electrode 30 without any gaps between the through holes that communicate with the graphite composite current collector plate 33, the negative electrode terminal 37, and the back plate 39. Further, the graphite composite current collector plate 34, the positive electrode terminal 38, and the back plate 40 are provided with two through holes that communicate with them. A tube 43 is inserted into one through hole. A tube 44 is inserted into the other through hole. The tubes 43 and 44 each reach the outer surface of the positive electrode 31 without any gap from the through hole that communicates the graphite composite current collector plate 34, the positive electrode terminal 38, and the back plate 40. Charging and discharging can be performed by connecting a power supply device (having a resistance circuit, not shown) between the negative terminal 37 and the positive terminal 38.

The redox flow battery according to the present invention contains a specific organic molecule, active material (A), as an active material. The organic molecules contained in the positive electrode electrolyte and the negative electrode electrolyte are not limited in type, but preferably contain a unit that exhibits a redox response in one molecule, and contain a plurality of such units in one molecule. It is characterized by having a highly symmetrical structure including a structure forming part of a Bethe lattice or a Cayley tree, in which at least the terminal end is a unit exhibiting a finite generation redox response. Due to the increased symmetry, even if the molecular weight is large, when dissolved in a solvent, the units that exhibit a redox response located on the outside are less likely to aggregate, exerting a stabilizing effect in a highly concentrated solution state. This makes it possible to suppress crossover, which increases the molecular size and causes a decrease in capacity. The concentration of the active material in the electrolytic solution used is preferably in the range of 0.1 to 3M, more preferably in the range of 0.5 to 1.5M. Further, in the present invention, the organic molecule can be used as a positive electrode or negative electrode active material, and another organic molecule or an organometallic complex can be used as a positive electrode or negative electrode active material.

Further, it is preferable that the electrolytic solution contains a supporting salt as an electrolyte. Inclusion of the supporting salt improves the electrical conductivity of the electrolytic solution, making it possible to improve the energy efficiency and energy density of the battery. Examples of the supporting salt include sodium chloride, ammonium chloride, sodium nitrate, sodium perchlorate, sodium sulfate, potassium chloride, potassium nitrate, potassium sulfate, sulfuric acid, and hydrochloric acid.

A cation exchange membrane or an anion exchange membrane can be used as the diaphragm that partitions the positive electrode cell and the negative electrode cell. In this case, during charging and discharging, for example, hydrogen ions and chlorine ions move through the diaphragm and are removed at the positive electrode. It is possible to compensate for the positive charge within the organic molecule caused by the charging reaction. Furthermore, if the only chemical species that migrates across the membrane is the supporting electrolyte, a simple porous membrane can be used. Examples of porous membranes include, but are not limited to, polysulfone membranes, polyethersulfone membranes, fluorine-containing polymer membranes, cellulose acetate membranes, nitrocellulose membranes, and the like.

Furthermore, like the organic molecules described above, the electrolytic solution may contain a complex. The complex also functions as an electrode active material in the electrolyte. Examples of complexes that can be included in the electrolytic solution include complexes that coordinate with metal atoms, incorporate metal atoms, and are stable against redox. Examples of such complexes include organic complexes such as porphyrin, phenanthroline, ferrocene, hexacyano compounds (e.g. potassium ferrocyanide), chelate compounds (e.g. sodium iron-ethylenediaminetetraacetate), as well as inorganic complexes such as graphene oxide. It will be done. Note that the electrolytic solution may contain both the organic molecule and the complex, or may contain only one of them.

The electrolytic solution may contain a surfactant for solubilizing the organic molecules and complexes in the aqueous solution. It is thought that this allows the poorly soluble organic molecules and complexes to be uniformly dispersed in the aqueous electrolyte. Specific examples of the surfactant are not particularly limited, and any surfactant may be used, such as cationic surfactants, anionic surfactants, and nonionic surfactants. Therefore, the material may be selected in consideration of the price and the degree of solubilization of the organic molecule or complex used as the active material.

Examples of cationic surfactants include quaternary ammonium salts (eg, tetramethylammonium chloride, tetrabutylammonium chloride), and polymers containing quaternary ammonium salts. Examples of anionic surfactants include polymers containing sulfonic acid (for example, sodium dodecyl sulfate), carboxylic acid, and phosphoric acid. Furthermore, examples of nonionic surfactants include ether-containing compounds such as diglyme and polymers containing ethers (eg, polyethylene glycol octadecyl ether). One type of these may be used alone, or two or more types may be used in any ratio and combination.

Further, the electrolytic solution of this embodiment may contain any component other than the above-mentioned organic molecules, complexes, and surfactants. For example, the electrolyte may contain any metal ion that is charged and discharged by a solution deposition reaction, ie, reduced to produce a metal, eg, by accepting electrons. For example, when the active material of one of the positive and negative electrodes is the above-mentioned organic molecule or complex, metal ions can be included as the active material of the other electrode. As such metal ions, those having a large potential difference with the dissolution deposition potential of the other electrode and high dissolution and precipitation rates are preferable. Thereby, a high charge/discharge voltage can be obtained. Specifically, one or more metal ions selected from the group consisting of zinc ions, iron ions, lead ions, and manganese ions are preferred. When metal ions are included in the electrolytic solution as active materials, the electrodes are preferably made of the same type of metal as the metal ions.

[Redox capacitor]
The above-mentioned redox flow battery is a system in which an electrolytic solution containing an active material is sent to a cell using a pump, and electricity is stored or released by oxidizing and reducing the electrolytic solution in a tank during charging and discharging. On the other hand, an electric double layer capacitor is a type of electricity storage device, and although it is inferior to a normal secondary battery in terms of electricity storage capacity, its power density (instantaneous discharge ability) is superior to an electric double layer capacitor. are considered superior to secondary batteries. Although ordinary electric double layer capacitors have drawbacks such as not being able to be made large and having low energy density, they have the advantage that they can be charged and discharged for tens of thousands of cycles. The redox flow battery of the present invention described above has good cycle characteristics, low cost, and high safety even in a stationary state without flowing electrolyte, and can function similarly to an electric double layer capacitor. , it is possible to use this as a redox capacitor (redox supercapacitor). The organic molecule of the present invention may be modified or immobilized on an electrode to constitute a redox capacitor with a large surface area. Such electrodes are usually fabricated by mixing a redox active material containing organic molecules with conductive carbon particles, adding a binder if necessary, and applying the mixture to the surface of a current collector. be able to.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

(Example 1)
4,4'-bipyridyl (26.3 g) and ammonium hexafluorophosphate (4.10 g) were heated and dissolved in N,N-dimethylformamide (40 mL). After cooling this mixture to room temperature, 1,3,5-tris(bromomethyl)benzene (1.00 g) was added, and the mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (800 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (50 mL, 1/1, v/v), and ammonium hexafluorophosphate (9.60 g) was added. The mixture was poured into water (800 mL) and the resulting solid was filtered to yield 2.82 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 1." The results of ¹ H-NMR measurement of Compound 1 are shown below.

¹ H-NMR (400 MHz, CD ₃ CN): δ8.84 (6H, dd, 4.5, 1.8), 8.75 (6H, d, 7.1), 8.32 (6H, d, 7.1), 7.77 (6H, dd, 4.5, 1.8), 7.53 (3H, s), 5.74 (6H, s).

Compound 1 (30.0 g) and 1,3-propane sultone (16.2 g) were dissolved in acetonitrile (500 mL) and heated to reflux. After cooling the mixture to room temperature, water (200 mL) was added to dissolve insoluble matter. After concentrating the solvent, acetone (700 mL) was added to the residue and stirred, and the supernatant solution was removed. The obtained solid was dissolved in a mixed solvent of acetonitrile and water (300 mL, 2/1, v/v), and a solution of tetrabutylammonium chloride (123 g) in water (150 mL) was added. The solvent of this mixture was concentrated, acetone (1 L) was added and stirred, and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (100 mL), poured into acetone (800 mL), and the supernatant solution was removed to obtain 32.3 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (II). This product is referred to as "Compound 2." ¹ H-NMR of Compound 2 is shown below.

¹ H-NMR (400 MHz, D ₂ O): δ9.19 (12H, d, 6.8), 8.61-8.20 (12H, m), 6.93 (3H, s), 5.49 (6H, s). 4.92 (6H, t, 7.3), 3.05 (6H, t, 7.3), 2.59-2.52 (6H, m).

(Example 2)
4,4'-bipyridyl (16.0 g) was dissolved in diethyl 2-bromoethylphosphonate (151 g) and stirred. Toluene (100 mL) and acetone (100 mL) were added to this mixture and stirred. The resulting solid was filtered to obtain 32.2 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 3." ¹ H-NMR of Compound 3 is shown below.

¹ H-NMR (400 MHz, D ₂ O): δ9.06 (2H, d, 6.9), 8.81 (2H, dd, 4.7, 1.8), 8.50 (2H, d, 6.9), 7.95 (2H, dd, 4.7, 1.8), 5.04-4.96 (2H, m), 4.17-4.10 (4H, m), 2. 86-2.77 (2H, m), 1.25 (6H, t, 7.1).

Compound 3 (27.0 g) and ammonium hexafluorophosphate (21.9 g) were heated and dissolved in N,N-dimethylformamide (40 mL). After cooling this mixture to room temperature, 1,3,5-tris(bromomethyl)benzene (2.00 g) was added, and the mixture was heated and stirred at 110° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (800 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (100 mL, 1/1, v/v), and ammonium hexafluorophosphate (32.9 g) was added. Water (300 mL) was added to the residue after concentrating the solvent, and the resulting solid was filtered to obtain 9.46 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 4." ¹ H-NMR of Compound 4 is shown below.

^1H -NMR (400MHz, _CD3CN ): δ8.97 (12H, d, 6.7), 8.42-8.38 (12H, m), 7.69 (3H, s), 5.84 (6H, s), 4.89-4.81 (6H, m), 4.08-4.01 (12H, m), 2.58-2.50 (6H, m), 1.24 (18H , t, 7.1).

Compound 4 (15.6 g) was dissolved in acetonitrile (200 mL), bromotrimethylsilane (18.4 g) was added, and the mixture was stirred at room temperature. Isopropyl alcohol (200 mL) was added to this mixture and stirred. The resulting solid was filtered to obtain 11.8 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 5." ¹ H-NMR of Compound 5 is shown below.

¹ H-NMR (400 MHz, D ₂ O): δ9.18 (12H, d, 6.4), 8.59-8.53 (12H, m), 7.84 (3H, s), 6.03 (6H, s), 4.97-4.90 (6H, m), 2.48-2.40 (6H, m).

Compound 5 (18.2 g) was dissolved in water (100 mL), and a solution of tetrabutylammonium chloride (85.1 g) in water (400 mL) was added. The solvent of this mixture was concentrated, acetone (800 mL) was added, stirred, and filtered. The obtained solid was dissolved in water (80 mL), then poured into acetone (800 mL), and the supernatant solution was removed. The obtained viscous liquid was dissolved in water (100 mL), poured into acetone (800 mL), and the supernatant solution was removed. The residue was purified by column chromatography (SEPHADEX LH20, water) to obtain 11.1 g of product. Ta. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (III). This product is referred to as "Compound 6." ¹ H-NMR of Compound 6 is shown below.

¹ H-NMR (400 MHz, D ₂ O): δ9.19-9.17 (12H, m), 8.61-8.54 (12H, m), 7.81 (3H, s), 6.03 (6H, s), 4.98-4.91 (6H, m), 2.48-2.40 (6H, m).

(Example 3)
Compound 1 (30.0 g) and 2-bromoethanol (33.0 g) were dissolved in acetonitrile (500 mL) and heated to reflux. After cooling the mixture to room temperature, toluene (500 mL) was added and filtered. The obtained solid was dispersed in water (100 mL), and a solution of tetrabutylammonium chloride (245 g) in water (200 mL) was added. The solvent of this mixture was concentrated, acetone (800 mL) was added and stirred, and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (15 mL), poured into acetone (800 mL), and the supernatant solution was removed to yield 16.5 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (IV). This product is referred to as "Compound 7." ¹ H-NMR of Compound 7 is shown below.

¹ H-NMR (400 MHz, D ₂ O): δ9.21 (6H, d, 7.0), 9.14 (6H, d, 7.0), 8.63-8.58 (12H, m) , 7.83 (3H, s), 6.05 (6H, s), 4.87 (6H, t, 5.0), 4.15 (6H, t, 5.0).

(Example 4)
1,3,5-tris(bromomethyl)benzene (22.8 g) and 4,4'-bipyridyl (0.500 g) were dissolved in N,N-dimethylformamide (40 mL) and heated at 90°C under microwave. The mixture was heated and stirred. After cooling to room temperature, the mixture was poured into dichloromethane (500 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (30 mL, 1/1, v/v), and ammonium hexafluorophosphate (10.4 g) was added. The mixture was poured into water (500 mL) and the resulting solid was filtered to yield 3.11 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 8." ¹ H-NMR of Compound 8 is shown below.

^1H -NMR (400MHz, _CD3CN ): δ8.96 (4H, d, 6.9), 8.38 (4H, d, 6.9), 7.54 (2H, s), 7.47 (4H, d, 1.6), 5.79 (4H, s), 4.57 (8H, s).

4,4'-bipyridyl (20.0 g) and ammonium hexafluorophosphate (3.10 g) were heated and dissolved in N,N-dimethylformamide (40 mL). After cooling this mixture to room temperature, compound 8 (1.60 g) was added, and the mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (800 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (50 mL, 1/1, v/v), and ammonium hexafluorophosphate (7.30 g) was added. The mixture was poured into water (800 mL) and the resulting solid was filtered to yield 2.95 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 9." ¹ H-NMR of Compound 9 is shown below.

¹ H-NMR (400 MHz, CD ₃ CN): δ8.88 (4H, d, 7.0), 8.83 (8H, dd, 4.5, 1.7), 8.76 (8H, d, 7.0), 8.35 (4H, d, 7.0), 8.31 (8H, d, 7.0), 7.76 (8H, dd, 4.5, 1.7), 7. 59 (4H, s), 7.55 (2H, s), 5.80 (4H, s), 5.75 (8H, s).

Compound 9 (10.5 g) and 1,3-propane sultone (4.09 g) were dissolved in acetonitrile (200 mL) and heated to reflux. After cooling the mixture to room temperature, water (50 mL) was added to dissolve insoluble matter. After concentrating the solvent, acetone (300 mL) was added to the residue and stirred, and the supernatant solution was removed. The obtained solid was dissolved in a mixed solvent of acetonitrile and water (150 mL, 2/1, v/v), and a solution of tetrabutylammonium chloride (46.6 g) in water (150 mL) was added. The solvent of this mixture was concentrated, acetone (700 mL) was added and stirred, and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (50 mL), poured into acetone (700 mL), and the supernatant solution was removed to obtain 10.0 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (V). This product is referred to as "Compound 10." ¹ H-NMR of Compound 10 is shown below.

^1H -NMR (400MHz, _D2O ): δ9.21-9.15 (20H, m), 8.62-8.54 (20H, m), 7.86 (2H, s), 7.83 (4H, s), 6.06 (8H, s), 6.03 (4H, s), 4.93 (8H, t, 7.2), 3.04 (8H, t, 7.2), 2.57 (8H, m).

(Example 5)
Compound 3 (1.81 g) and ammonium hexafluorophosphate (1.48 g) were dissolved in N,N-dimethylformamide (10 mL). Compound 8 (0.282 g) was added to this mixture, and the mixture was heated and stirred at 110° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (200 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (30 mL, 1/1, v/v), and ammonium hexafluorophosphate (2.20 g) was added. Water (20 mL) was added to the residue after concentrating the solvent, and the resulting solid was filtered to obtain 0.720 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 11." ¹ H-NMR of Compound 11 is shown below.

^1H -NMR (400MHz, _CD3CN ): δ8.98-8.91 (20H, m), 8.42-8.38 (20H, m), 7.64 (6H, s), 5.82 (12H, s), 4.89-4.81 (8H, m), 4.08-4.00 (16H, m), 2.58-2.50 (8H, m), 1.24 (24H , t, 7.0).

Compound 11 (0.800 g) was dissolved in acetonitrile (15 mL), bromotrimethylsilane (0.784 g) was added, and the mixture was stirred at room temperature. Isopropyl alcohol (15 mL) was added to this mixture and stirred. The resulting solid was filtered to yield 0.627 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 12." ¹ H-NMR of Compound 12 is shown below.

^1H -NMR (400MHz, _D2O ): δ9.15 (20H, d, 6.5), 8.55-8.49 (20H, m), 7.82 (6H, s), 6.00 (12H, s), 4.95-4.88 (8H, m), 2.44-2.36 (8H, m).

Compound 12 (0.500 g) was dissolved in water (3 mL), and a solution of tetrabutylammonium chloride (2.40 g) in water (10 mL) was added. The solvent of this mixture was concentrated, acetone (50 mL) was added and stirred, and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (3 mL), then poured into acetone (50 mL), and the supernatant solution was removed to obtain 0.372 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (VI). This product is referred to as "Compound 13." ¹ H-NMR of Compound 13 is shown below.

^1H -NMR (400MHz, _D2O ): δ9.16 (20H, d, 6.0), 8.59-8.52 (20H, m), 7.79 (6H, s), 6.01 (12H, s), 4.96-4.77 (8H, m), 2.44-2.36 (8H, m).

(Example 6)
Compound 9 (1.00 g) and 2-bromoethanol (1.32 g) were dissolved in acetonitrile (10 mL) and heated to reflux. The mixture was concentrated, acetone (30 mL) was added to the residue and stirred, and the supernatant solution was removed. The obtained solid was dissolved in a mixed solvent of acetonitrile and water (15 mL, 2/1, v/v), and tetrabutylammonium chloride (7.37 g) was dissolved in a mixed solvent of acetonitrile and water (7.5 mL, 2/1). , v/v) was added. The solvent of this mixture was concentrated, poured into acetone (100 mL), and the supernatant solution was removed to yield 0.660 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (VII). This product is referred to as "Compound 14." ¹ H-NMR of Compound 14 is shown below.

^1H -NMR (400MHz, D ₂ O): δ9.20 (12H, d, 7.0), 9.13 (8H, d, 6.7), 8.62-8.57 (20H, m) , 7.83 (4H, s), 7.81 (2H, s), 6.04 (12H, s), 4.86 (8H, t, 5.0), 4.14 (8H, t, 5 .0).

(Example 7)
1,3,5-tris(bromomethyl)benzene (21.0 g) and ammonium hexafluorophosphate (3.00 g) were dissolved in N,N-dimethylformamide (30 mL), and compound 1 (2.00 g) was added. The mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (400 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (40 mL, 1/1, v/v), and ammonium hexafluorophosphate (6.58 g) was added. The mixture was poured into water (400 mL) and the resulting solid was filtered to yield 4.36 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 15." ¹ H-NMR of Compound 15 is shown below.

¹ H-NMR (400 MHz, CD ₃ CN): δ8.95 (6H, d, 6.7), 8.90 (6H, d, 6.7), 8.39-8.36 (12H, m) , 7.64 (3H, s), 7.60 (3H, s), 7.47 (6H, s), 5.8 (6H, s), 5.79 (6H, s), 4.57 ( 12H, s).

4,4'-bipyridyl (26.3 g) and ammonium hexafluorophosphate (4.10 g) were heated and dissolved in N,N-dimethylformamide (40 mL). After cooling this mixture to room temperature, compound 15 (3.20 g) was added, and the mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (800 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (50 mL, 1/1, v/v). The above operation was repeated and the reaction and treatment were performed twice. The dispersions obtained in the two reactions were mixed, and ammonium hexafluorophosphate (19.2 g) was added. This mixture was poured into water (800 mL) and the resulting solid was filtered to yield 10.1 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 16." ¹ H-NMR of Compound 16 is shown below.

¹ H-NMR (400 MHz, CD ₃ CN): δ8.92-8.89 (12H, m), 8.81 (12H, dd, 4.7, 1.7), 8.76 (12H, d, 6.6), 8.38 (12H, d, 6.6), 8.31 (12H, d, 6.6), 7.75 (12H, dd, 4.4, 1.7), 7. 63 (3H, s), 7.59 (6H, s), 7.56 (3H, s), 5.81 (12H, s), 5.75 (12H, s).

Compound 16 (19.3 g) and 1,3-propane sultone (5.87 g) were dissolved in acetonitrile (200 mL) and heated to reflux. After cooling the mixture to room temperature, water (50 mL) was added to dissolve insoluble matter. After concentrating the solvent, acetone (300 mL) was added to the residue and stirred, and the supernatant solution was removed. The obtained solid was dissolved in a mixed solvent of acetonitrile and water (150 mL, 2/1, v/v), and tetrabutylammonium chloride (89.1 g) was dissolved in a mixed solvent of acetonitrile and water (120 mL, 3/1, v/v). v) was added to the solution. The solvent of this mixture was concentrated, poured into acetone (800 mL), and the supernatant solution was removed. The obtained viscous liquid was dissolved in water (50 mL), tetrabutylammonium chloride (17.8 g) was added, and then poured into acetone (800 mL), and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (80 mL), poured into a mixed solvent of acetonitrile and acetone (800 mL, 1/1, v/v), and the supernatant solution was removed to obtain 16.4 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (VIII). This product is referred to as "Compound 17." ¹ H-NMR of Compound 17 is shown below.

^1H -NMR (400MHz, _D2O ): δ9.24-9.20 (36H, m), 8.64-8.60 (36H, m), 7.92 (3H, s), 7.87 (6H, s), 7.79 (3H, s), 6.09-6.03 (24H, m), 4.94 (12H, t, 7.3), 3.05 (12H, t, 7 .3), 2.61-2.54 (12H, m).

(Example 8)
1,3,5-tris(bromomethyl)benzene (16.7 g) and ammonium hexafluorophosphate (2.28 g) were dissolved in N,N-dimethylformamide (40 mL), and compound 9 (2.2 g) was added. The mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (600 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (70 mL, 1/1, v/v), and ammonium hexafluorophosphate (5.33 g) was added. This mixture was poured into water (800 mL) and the resulting solid was filtered to yield 3.91 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 18." ¹ H-NMR of Compound 18 is shown below.

^1H -NMR (400MHz, _CD3CN ): δ8.96-8.89 (20H, m), 8.40-8.37 (20H, m), 7.63-7.60 (10H, m) , 7.47 (8H, s), 5.81 (12H, s), 5.79 (8H, s), 4.57 (16H, s).

4,4'-bipyridyl (14.0 g) and ammonium hexafluorophosphate (3.65 g) were heated and dissolved in N,N-dimethylformamide (40 mL). After cooling this mixture to room temperature, compound 18 (2.00 g) was added, and the mixture was heated and stirred at 90° C. while being exposed to microwaves. After cooling to room temperature, the mixture was poured into dichloromethane (500 mL) and filtered. The obtained solid was dispersed in a mixed solvent of acetonitrile and methanol (50 mL, 1/1, v/v), and ammonium hexafluorophosphate (3.65 g) was added. This mixture was poured into water (400 mL) and the resulting solid was filtered to yield 2.94 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula. This product is referred to as "Compound 19." ¹ H-NMR of Compound 19 is shown below.

^1H -NMR (400MHz, _CD3CN ): δ8.94-8.89 (20H, m), 8.80 (16H, dd, 4.5, 1.7), 8.76 (16H, d, 6.7), 8.42-8.37 (20H, m), 8.31 (16H, d, 6.7), 7.75 (16H, dd, 4.5, 1.7), 7. 65-7.56 (18H, m), 5.81 (20H, s), 5.75 (16H, s).

Compound 19 (20.0 g) and 1,3-propane sultone (5.49 g) were dissolved in acetonitrile (200 mL) and heated to reflux. After cooling the mixture to room temperature, water (50 mL) was added to dissolve insoluble matter. After concentrating the solvent, acetone (300 mL) was added to the residue and stirred, and the supernatant solution was removed. The obtained viscous liquid was dissolved in a mixed solvent of acetonitrile and water (150 mL, 2/1, v/v), and tetrabutylammonium chloride (93.6 g) was dissolved in a mixed solvent of acetonitrile and water (120 mL, 3/1, v/v). /v) was added. The solvent of this mixture was concentrated, poured into acetone (800 mL), and the supernatant solution was removed. The resulting viscous liquid was dissolved in water (50 mL), poured into acetone (800 mL), and the supernatant solution was removed to obtain 14.8 g of product. Analysis by ¹ H-NMR revealed that this product was represented by the following formula (IX). This product is referred to as "Compound 20." ¹ H-NMR of Compound 20 is shown below.

^1H -NMR (400MHz, D ₂ O): δ9.23-9.20 (52H, m), 8.64-8.60 (52H, m), 7.96-7.80 (18H, m) , 6.09-6.06 (36H, m), 4.94 (16H, t, 7.1), 3.05 (16H, t, 7.1), 2.59-2.55 (16H, m).

(Example 9)
A cross-over test was conducted using the apparatus shown in FIG. 3 to evaluate the mobility of the compound. Carbon felts 52 with a diameter of 1 cm are placed on both sides of the Nafion membrane 51 with a thickness of 50 μm, and a solution containing the target compound is placed in container A, and a supporting electrolyte is placed in container B. A solution containing only A was prepared, and each solution was poured into a cell at a rate of 10 mL/min, and the concentration of the compound transferred from A to B was sampled at regular time intervals and quantified using an ultraviolet-visible spectrophotometer. The test covered Compound 2 and Compound 7, as well as a comparison compound similar to Compound 7 (1,1'-bis(2-hydroxyethyl)-4,4'-bipyridinium dichloride). The concentration was adjusted so that the concentration of the viologen unit, which is a structural unit, was 0.1M, and 1M potassium chloride was used as the supporting electrolyte. The results are shown in FIG. The vertical axis of FIG. 4 shows the concentration of the compound that moved from A to B, and the larger this value is, the more crossover occurs. It can be seen that the comparative compound is the most likely to cross over, and that crossover is dramatically suppressed in Compound 2 and Compound 7. The results of calculating the permeability coefficient of each compound to the Nafion membrane from the crossover amount are shown in Table 1 below.

As shown in Table 1, it was found that the permeability coefficients of Compound 2 and Compound 7 were more than 100 times smaller than those of the comparative compounds. Note that the permeability coefficient of vanadium oxide sulfate (VOSO ₄ ) used in vanadium redox flow batteries through the Nafion membrane is 7.95×10 ⁻⁹ cm ² /s, and compared to this, compounds 2 and 7 are practically It is considered to be extremely promising.

From the above results, it was found that when the compound of the present invention is used as an active material in a redox flow battery, crossover, which causes performance deterioration, can be significantly reduced. Furthermore, regarding Compound 10, Compound 13, Compound 14, Compound 17, and Compound 20, which have larger molecular sizes than Compounds 2 and 7, the molecular size is larger than the pore size of commonly used diaphragms. It is thought that it is possible to achieve a significant reduction in crossover due to the increased size.

(Example 10)
Using a glassy carbon electrode as a working electrode, a platinum wire as a counter electrode, and a silver-silver chloride electrode as a reference electrode, the concentration of the compound was adjusted to 10 mM in constituent units, and a 1M KCl aqueous solution was used as a supporting electrolyte at a sweep rate of 0. The redox potential was examined by cyclic voltammetry at .1 V/sec. The results are shown in Table 2 below. As shown in Table 2, it was found that the synthesized compound exhibited a reversible redox response. In addition, the redox potential is around -0.4V to -0.5V, which is approximately the same as the redox potential of the negative electrode electrolyte used in vanadium redox flow batteries, so it is considered an alternative material to vanadium redox flow batteries. This shows that it is applicable as

According to the present invention, it is possible to obtain a compound that can reduce crossover, which causes a decrease in the performance of a redox flow battery. The compound of the present invention can be used as an electrochemical device and the like. Further, the electrochemical device of the present invention is useful as a redox flow battery, a redox capacitor, and the like.

1, 30 Negative electrode 2 Negative electrode cell 3, 31 Positive electrode 4 Positive electrode cell 5, 32 Diaphragm 6 Test cell 7 Tank for negative electrode electrolyte 8 Tank for positive electrode electrolyte 9, 10 Pump 11 Redox flow battery 21 Small test cell 33, 34 Graphite composite current collector plates 35, 36 Gasket 37 Negative terminal 38 Positive terminal 39, 40 Back plate 41 to 44 Tube 51 Nafion membrane 52 Carbon felt

Claims (8)

General formula (I)
(wherein, Ar is a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a bipyridinium group, a is an integer of 0 or 1, b is an integer of 0 to 5, c is an integer of 1 to 6, d is an integer of 1 to 5, e is an integer of 1 to 6, n is an integer necessary to maintain the electrical neutrality of the molecule, and X is an integer of 1 to 6. , halogen anion, BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , N(CF ₃ SO ₂ ) ₂ ⁻ , CF ₃ SO ₃ ⁻ , and CF ₃ CO ₂ ⁻ Y is a counter anion selected from the group consisting of a hydroxy group, an alkylammonium group, a sulfonic acid group, a phosphonic acid group, a phosphoric acid group, a carboxy group, a boric acid group, and a group corresponding to a salt thereof. A viologen derivative represented by a selected hydrophilic substituent. The substituent of the aryl group or heteroaryl group is an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxy group, a haloalkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, Selected from the group consisting of acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen atom, cyano group, and heterocyclic group The viologen derivative according to claim 1, which is a group that is The viologen derivative according to claim 1, wherein the Ar is an unsubstituted aryl group, an unsubstituted heteroaryl group, or a bipyridinium group. The viologen derivative according to claim 1, wherein the Ar is a phenyl group, a bipyridinium group, a pyrazinium group, or a triazinium group. The viologen derivative according to claim 1, which is a compound represented by the following formulas (II) to (IX).
An electrochemical device comprising the viologen derivative according to any one of claims 1 to 5. The electrochemical device according to claim 6, wherein the electrochemical device is a redox flow battery. The electrochemical device according to claim 6, wherein the electrochemical device is a redox capacitor.