JP7149871B2 - Azafulvalene compound, method for producing the same, and composition for electrochemical measurement - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel azafulvalene compound that is stable against oxidation-reduction reactions and a method for producing the same. The present invention also relates to a composition for electrochemical measurements using the azafulvalene compound.

Secondary batteries are used in mobile devices and in-vehicle power sources, and the demand for them is expected to grow further in the future. On the other hand, current positive electrode materials for secondary batteries use rare metals such as cobalt, raising concerns about supply risks. Therefore, positive electrode materials for organic secondary batteries, which are free from resource constraints, have attracted attention. As an organic compound used as a positive electrode material for a secondary battery, an organic compound having bistability between an oxidized state and a reduced state and in which a redox reaction proceeds reversibly and smoothly is preferable.

Non-Patent Document 1 discloses the synthesis of azafulvalenes having a substituent on the benzo ring, but the substituent is different from the azafulvalene compound of the present invention, and its electrochemical properties are not mentioned at all. Not done.

In addition, Patent Document 1 exemplifies azafulvalenes as positive electrode materials for secondary batteries, but the substitution positions on the azafulvalene skeleton are not limited, and the substituents thereof are also different from those of the azafulvalene compound of the present invention. . Also, the compounds are not synthesized and their electrochemical properties are not described.

WO2016/102069

Journal of Heterocyclic Chemistry, 1999, 36, 1001

An object of the present invention is to provide an electrochemically stable azafulvalene compound and a composition for electrochemical measurements containing the compound.

The present inventors have made intensive studies to solve the above problems, and as a result, synthesized novel azafulvalene compounds having various substituents, and found that they have good solubility in organic solvents for electrochemical measurements. found to have In addition, it was also found by cyclic voltammetry measurement that the azafulvalene compound undergoes a reversible oxidation-reduction reaction, and that the reduction potential thereof is suitable for an organic positive electrode material for secondary batteries. Arrived.

That is, the present invention
[1]
The following general formula (1)

(In the formula, R ¹ represents an alkyl group having 7 to 20 carbon atoms. R ² , R ³ and R ⁴ each independently represent either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. ) Azafulvalene compound represented by;
[2]
R ¹ is an alkyl group having 7 to 10 carbon atoms, R ² is a hydrogen atom, and R ³ and R ⁴ are each independently either a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. The azafulvalene compound according to [1];
[3]
General formula (1a) or (1b) below

（式中、Ｒ^１及びＲ^２は前記と同じ意味を表す。）で示される、前記［１］又は［２］のいずれかに記載のアザフルバレン化合物；
に関する。

(Wherein, R ¹ and R ² have the same meanings as described above.) The azafulvalene compound according to any one of [1] or [2] above;
Regarding.

Further, the present invention
[4]
The following general formula (2)

(In the formula, R ¹ represents an alkyl group having 7 to 20 carbon atoms. R ² , R ³ and R ⁴ each independently represent either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. ) and a bisimidazole compound represented by the general formula (1), which is reacted with an oxidizing agent

(Wherein, R ¹ , R ² , R ³ and R ⁴ have the same meaning as above);
[5]
The method for producing an azafulvalene compound according to [4] above, wherein the oxidizing agent is manganese dioxide;
[6]
A composition for electrochemical measurements comprising the azafulvalene compound according to any one of [1] to [3].
Regarding.

The present invention will be described in detail below.

Definitions of R ¹ , R ² , R ³ and R ⁴ in the azafulvalene compound of the present invention are explained.

The alkyl group having 1 to 20 carbon atoms represented by R ² , R ³ and R ⁴ may be a linear, branched or cyclic alkyl group, specifically methyl group, cyclohexylmethyl group, ethyl group, 2-cyclopentylethyl group, propyl group, 2-methylpropyl group, 2,2-dimethylpropyl group, 3-cyclopropylpropyl group, isopropyl group, cyclopropyl group, butyl group, 2-methylbutyl group, 3-methylbutyl group, 1-methylpropyl group, 1,2-dimethylpropyl group, tert-butyl group, cyclobutyl group, pentyl group, 2-methylpentyl group, 3-ethylpentyl group, 2,4-dimethylpentyl group, 2-pentyl group, 2-methylpentan-2-yl group, 4,4-dimethylpentan-2-yl group, 3-pentyl group, 3-ethylpentan-3-yl group, cyclopentyl group, 2,5-dimethylcyclopentyl group, 3-ethylcyclopentyl group, hexyl group, 2-methylhexyl group, 3,3-dimethylhexyl group, 4-ethylhexyl group, 2-hexyl group, 2-methylhexane-2-yl group, 5,5-dimethylhexane- 2-yl group, 3-hexyl group, 2,4-dimethylhexan-3-yl group, cyclohexyl group, 4-ethylcyclohexyl group, 4-propylcyclohexyl group, 4,4-dimethylcyclohexyl group, heptyl group, 2- heptyl group, 3-heptyl group, 4-heptyl group, bicyclo[2.2.1]heptyl group, octyl group, 2-octyl group, 3-octyl group, 4-octyl group, cyclooctyl group, bicyclo[2. 2.2] octyl group, nonyl group, 5-nonyl group, decyl group, 2-decyl group, 5-decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, and the like. Among these, an alkyl group having 7 to 10 carbon atoms is preferable, and an octyl group is more preferable, because the azafulvalene compound of the present invention has good solubility.

Hydrogen atoms are preferred as R ² , R ³ and R ⁴ in terms of ease of synthesis.

The alkyl group having 7 to 20 carbon atoms represented by R ¹ may be a linear, branched or cyclic alkyl group, specifically a cyclohexylmethyl group, 2-cyclopentylethyl group, 3-ethylpentyl group, 2,4-dimethylpentyl group, 4,4-dimethylpentan-2-yl group, 3-ethylpentan-3-yl group, 2,5-dimethylcyclopentyl group, 3-ethylcyclopentyl group, 2-methylhexyl group, 3,3-dimethylhexyl group, 4-ethylhexyl group, 2-methylhexan-2-yl group, 5,5-dimethylhexan-2-yl group, 2,4-dimethylhexan-3-yl group, 4 -ethylcyclohexyl group, 4-propylcyclohexyl group, 4,4-dimethylcyclohexyl group, heptyl group, 2-heptyl group, 3-heptyl group, 4-heptyl group, bicyclo[2.2.1]heptyl group, octyl group , 2-octyl group, 3-octyl group, 4-octyl group, cyclooctyl group, bicyclo[2.2.2]octyl group, nonyl group, 5-nonyl group, decyl group, 2-decyl group, 5-decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group and the like. Among these, an alkyl group having 7 to 10 carbon atoms is preferable, and an octyl group is more preferable, because the azafulvalene compound of the present invention has good solubility.

The azafulvalene compound (1) of the present invention is not particularly limited, but can be specifically exemplified by compounds having structures shown in 1-1 to 1-42 below.

１－１から１－４２で示される化合物のうち、溶解性が良い点で、本発明のアザフルバレン化合物としては１－１、１－２、１－３で示される化合物が好ましい。

Among the compounds represented by 1-1 to 1-42, the compounds represented by 1-1, 1-2 and 1-3 are preferable as the azafulvalene compound of the present invention in terms of good solubility.

Next, the method for producing the azafulvalene compound (1) of the present invention will be described.

The azafulvalene compound (1) of the present invention can be produced by the following steps 1 to 3.

（式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は前記と同じ意味を表す。Ｒ^９及びＲ^１０は各々独立に、水素原子又は炭素数１から４のアルキル基のいずれかを表す。）
工程１は、フェニレンジアミン（３ａ）とシュウ酸化合物（４）とを反応させ、工程２で用いるベンゾイミダゾール化合物（５）を製造する工程である。

(In the formula, R ¹ , R ² , R ³ and R ⁴ have the same meanings as above. R ⁹ and R ¹⁰ each independently represent either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. )
Step 1 is a step of reacting phenylenediamine (3a) and oxalic acid compound (4) to produce benzimidazole compound (5) used in step 2.

Phenylenediamine (3a) used in step 1 can be produced, for example, by the method disclosed in Bioorganic & Medicinal Chemistry Letters, 2004, 14, 4903 pages. Moreover, you may use a commercial item.

The oxalic acid compound (4) used in step 1 can be synthesized by a known method. Moreover, you may use a commercial item.

Examples of the alkyl group having 1 to 4 carbon atoms represented by R ⁹ and R ¹⁰ in the oxalic acid compound (4) include methyl group, ethyl group and butyl group. Among these, an ethyl group is preferable in that the yield is good.

The molar ratio of the phenylenediamine (3a) and the oxalic acid compound (4) used in step 1 is not particularly limited, but it is preferably in the range of 3:1 to 1:2 from the viewpoint of good yield. More preferably in the range of 1 to 1:1.

Step 1 can be carried out in a solvent. Solvents that can be used are not particularly limited as long as they do not inhibit the reaction. Specific examples of such solvents include alcohols such as ethanol, isopropyl alcohol, butanol, ethylene glycol and glycerin, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, Ethers such as 1,4-dioxane and dimethoxyethane, and aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, and tetralin can be exemplified, and these may be mixed at any ratio and used. Among these, alcohol is preferred, and ethylene glycol is more preferred, because of good yield.

The reaction temperature in carrying out step 1 is not particularly limited, but it can be carried out at a temperature appropriately selected from the range of 50 ° C. to 250 ° C., and the yield is good at 120 ° C. to 200 ° C. It is preferable to carry out at a temperature appropriately selected from the range.

A benzimidazole compound (5) can be obtained by carrying out a normal treatment after the completion of the reaction in step 1. If necessary, it may be purified by recrystallization, column chromatography, sublimation, preparative HPLC, or the like, but may be subjected to step 2 without purification.

Step 2 is a step of reacting benzimidazole compound (5) with phenylenediamine (3b) to produce bisimidazole compound (2) used for producing azafulvalene compound (1) of the present invention.

Phenylenediamine (3b) used in step 2 is available in the same manner as phenylenediamine (3a) described in step 1.

The molar ratio between the benzimidazole compound (5) and the phenylenediamine (3b) used in Step 2 is not particularly limited, but it is preferably in the range of 1:1 to 1:10 in terms of good yield. More preferably in the range of 4 to 1:8.

Step 2 can be carried out in a solvent. Solvents that can be used are not particularly limited as long as they do not inhibit the reaction. As such a solvent, the same solvents as those exemplified in Step 1 can be exemplified, and alcohol is preferable, and ethylene glycol is more preferable in terms of good yield.

The reaction temperature in carrying out step 2 is not particularly limited, but it can be carried out at a temperature appropriately selected from the range of 50 ° C. to 250 ° C., and the yield is good at 180 ° C. to 200 ° C. It is preferable to carry out at a temperature appropriately selected from the range.

A bisimidazole compound (2) can be obtained by carrying out a normal treatment after completion of the reaction in step 2. If necessary, it may be purified by recrystallization, column chromatography, sublimation, preparative HPLC, or the like, but may be subjected to step 3 without purification.

Step 3 is a step of reacting the bisimidazole compound (2) with an oxidizing agent to produce the azafulvalene compound (1) of the present invention (hereinafter also referred to as the production method of the present invention).

The oxidizing agent used in the production method of the present invention is not particularly limited. Examples include organic oxidants such as 4-benzoquinone and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), oxygen, and hydrogen peroxide. Among these, the inorganic oxidizing agent is preferable, and manganese dioxide is more preferable, because the post-reaction treatment is simple.

The molar ratio of the oxidizing agent and the bisimidazole compound (2) used in the production method of the present invention is not particularly limited, but is 100:1 to 2:1 in order to produce a sufficient amount of the azafulvalene compound (1) of the present invention. A range is preferred, more preferably 30:1 to 2:1.

The production method of the present invention can be carried out in a solvent. Solvents that can be used are not particularly limited as long as they do not inhibit the reaction. Specific examples of such solvents include ethers such as diisopropyl ether, dibutyl ether, CPME, THF, 2-methyltetrahydrofuran, 1,4-dioxane and dimethoxyethane; Aromatic hydrocarbons, carbonate esters such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-fluoroethylene carbonate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, γ- Esters such as lactones, amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N,N,N',N'-tetramethylurea ( Urea such as TMU), N,N'-dimethylpropylene urea (DMPU), or dimethyl sulfoxide (DMSO) can be exemplified, and these may be mixed at any ratio and used. There are no particular restrictions on the amount of solvent used. Among these, ether is preferred, and THF is more preferred, in terms of good solubility of the starting material, bisimidazole compound (2).

Although there is no particular limitation on the reaction temperature when carrying out the production method of the present invention, the reaction can usually be carried out at a temperature appropriately selected from the range of 20°C to 200°C.

The reaction time for carrying out the production method of the present invention is not particularly limited, but the reaction time can be appropriately selected from the range of 5 to 300 hours, and the azafulvalene compound (1) of the present invention can be produced. It is preferable to react for 20 hours or more in order to produce a sufficient amount.

The azafulvalene compound (1) of the present invention can be obtained by carrying out ordinary treatments after the completion of the reaction in the production method of the present invention. If necessary, it may be purified by recrystallization, column chromatography, PTLC, or the like.

The azafulvalene compounds (1a) and (1b) contained in the azafulvalene compound (1) of the present invention (hereinafter referred to as the azafulvalene compounds (1a) and (1b) of the present invention) are represented by the following reaction schemes. It can be produced by steps 4 and 5.

(In the formula, R ¹ , R ² , R ⁹ and R ¹⁰ have the same meanings as above.)
Step 4 is a step of reacting phenylenediamine (3a) with oxalic acid compound (4) to produce bisimidazole compound (2a) used for producing azafulvalene compounds (1a) and (1b) of the present invention.

The molar ratio of the phenylenediamine (3a) and the oxalic acid derivative (4) used in step 4 is not particularly limited, but is preferably in the range of 2:1 to 10:1 in terms of yield. More preferably in the range of 1 to 8:1.

Step 4 can be carried out in a solvent. Solvents that can be used are not particularly limited as long as they do not inhibit the reaction. As such a solvent, the same solvents as those exemplified in Step 1 can be exemplified, and alcohol is preferable, and ethylene glycol is more preferable in terms of good yield.

The reaction temperature for carrying out step 4 is not particularly limited. It is preferable to carry out at a temperature appropriately selected from the range.

A bisimidazole compound (2a) can be obtained by performing a normal treatment after completion of the reaction in step 4. If necessary, it may be purified by recrystallization, column chromatography, sublimation, preparative HPLC, or the like, but may be subjected to step 5 without purification.

Step 5 is a step of reacting the bisimidazole compound (2a) with an oxidizing agent to produce the azafulvalene compounds (1a) and (1b) of the present invention (hereinafter also referred to as the production method of the present invention).

As the oxidizing agent used in the production method of the present invention, the same oxidizing agent as exemplified in step 3 can be exemplified, and an inorganic oxidizing agent is preferable in that the treatment after the reaction is simple, and manganese dioxide is further used. preferable.

The molar ratio between the oxidizing agent and the bisbenzimidazole compound (2) used in Step 5 is not particularly limited, but is within the range of 100:1 to 2:1 for producing a sufficient amount of the azafulvalene compound (1) of the present invention. preferably in the range of 30:1 to 2:1.

Step 5 can be carried out in a solvent. Solvents that can be used are not particularly limited as long as they do not inhibit the reaction. As such a solvent, the same solvents as those exemplified in Step 3 can be exemplified. Among these, ether is preferably used because the starting material, bisimidazole compound (2a), has a high solubility. is preferred, and THF is more preferred.

Although there is no particular restriction on the reaction temperature when carrying out step 5, it can usually be carried out at a temperature appropriately selected from 20°C to 200°C.

The azafulvalene compounds (1a) and (1b) of the present invention can be obtained by carrying out ordinary treatments after the completion of the reaction in step 5. If necessary, it may be purified by recrystallization, column chromatography, PTLC, or the like.

Next, a method for preparing a composition for electrochemical measurements containing the azafulvalene compound (1) of the present invention will be described.

The composition for electrochemical measurements can be prepared by dissolving the azafulvalene compound (1) of the present invention together with an electrolyte compound in a solvent.

As the electrolyte used for the preparation of the composition for electrochemical measurements, those commonly used in electrochemical measurements by those skilled in the art can be mentioned. Ammonium salts such as tetraethylammonium, tetrabutylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetraethylammonium tosylate, tetrabutylammonium tosylate, lithium perchlorate, tetrafluoroboric acid Lithium salts such as lithium and lithium hexafluorophosphate can be exemplified. Among these, ammonium salts are preferred because of their good solubility, and tetrabutylammonium hexafluorophosphate is more preferred. The amount of the electrolyte used is not particularly limited, and the concentration of the electrolyte is preferably selected from the range of 0.001 to 5.0M, more preferably 0.01 to 2.0M. can do.

The solvent used for preparing the electrochemical measurement composition is not particularly limited as long as it is an organic solvent having an appropriate potential window, and diethyl ether, THF, 1,4-dioxane, 1,2-dimethoxy Ethers such as ethane, esters such as ethyl acetate, butyl acetate, methyl butyrate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, halogenated hydrocarbons such as dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene, acetonitrile, valeronitrile , nitriles such as benzonitrile, nitromethane, DMF, DMSO, hexamethylphosphoric acid triamide, etc., and these may be mixed in an arbitrary ratio and used. Among these, acetonitrile, dichloromethane, and diethyl carbonate are preferred, and dichloromethane is more preferred, in terms of good solubility of the azafulvalene compound of the present invention and a suitable potential window.

The concentration of the azafulvalene compound of the present invention used for the preparation of the composition for electrochemical measurement is preferably 0.01 to 10 mM, more preferably 0.1 to 2 mM, and the concentration is appropriately selected from the range of 0.1 to 2 mM. of azafulvalene compounds can be added.

In the preparation of the composition for electrochemical measurements, methods well known to those skilled in the art, such as stirring, shaking, and ultrasonic irradiation, can be used to dissolve the electrolyte and the like. At this time, it may be heated.

Next, a method for cyclic voltammetry measurement using the composition for electrochemical measurements will be described.

Cyclic voltammetry measurement can be performed by inserting a working electrode, a reference electrode and a counter electrode into the composition for electrochemical measurement of the present invention and using a dedicated commercial device.

The working electrode is not particularly limited, and examples thereof include a platinum electrode, a glassy carbon electrode, and the like. Among these, a platinum electrode is preferable because electron transfer proceeds smoothly, and a wire-like platinum electrode having a large surface area is more preferable.

The reference electrode is not particularly limited, and generally commercially available Ag/AgCl electrodes, Ag/Ag+ electrodes, and the like can be used.

A common platinum electrode can be used as the counter electrode. There are no particular restrictions on the shape, but examples include plate-like and wire-like shapes. Among these, a wire-shaped platinum electrode is preferable because it has a large surface area.

The azafulvalene compound of the present invention is expected to be used as a positive electrode material for secondary batteries such as lithium ion batteries, since progress of a reversible oxidation-reduction reaction was observed by cyclic voltammetry measurement.

The azafulvalene compound of the present invention has bistability between an oxidized state and a reduced state, and its reduction potential is higher than that of existing anthraquinones. can be expected to be used as

EXAMPLES The present invention will be described in more detail below with reference to examples, reference examples, and comparative examples, but the present invention should not be construed as being limited thereto.

The following analytical methods were used for identification of the azafulvalene compound and the like of the present invention. A Bruker ASCEND ^™ AVANCE III HD (400 MHz) was used for ¹ H-NMR measurements. ¹ H-NMR was measured using deuterated chloroform (CDCl ₃ ) as a measurement solvent and tetramethylsilane (TMS) as an internal standard substance. Commercially available reagents were used.

Reference example-1

Diethyl oxalate (1.02 g, 6.8 mmol) and ethylene glycol (14 mL) were added to 4-methyl-1,2-phenylenediamine (3.35 g, 27 mmol) under an argon atmosphere, and the mixture was stirred at 200° C. for 30 hours. . Distilled water was added to the reaction mixture, and the precipitated solid was collected by filtration. The resulting solid was purified by silica gel column chromatography (chloroform:ethyl acetate=20:1, 1% triethylamine added) to give the desired 5,5′-dimethyl-2,2′-bisbenzimidazole (2.95 g, 11 mmol, 82%).
¹ H-NMR (CDCl ₃ ) δ 2.44 (s, 6H), 3.78 (s, 2H), 7.12 (d, J = 8.1 Hz, 2H), 7.37-7.42 (m , 2H), 7.48-7.55 (m, 2H).
Reference example-2

Diethyl oxalate (0.55 mL, 3.9 mmol) and ethylene glycol (7.8 mL) were added to 4-hexyl-1,2-phenylenediamine (3.00 g, 13 mmol) under an argon atmosphere, and the mixture was stirred at 200°C for 35 hours. Stirred. Distilled water was added to the reaction mixture, and the precipitated solid was collected by filtration. The resulting solid was purified by silica gel column chromatography (chloroform:ethyl acetate=20:1, 1% triethylamine added) to give the desired 5,5′-dihexyl-2,2′-bisbenzimidazole (1. 23 g, 3.1 mmol, 78%).
¹ H-NMR (CDCl ₃ ) δ 0.84 (t, J = 6.6 Hz, 6H), 1.25-1.33 (m, 12H), 1.55-1.62 (m, 4H), 2 .66 (t, J=7.7 Hz, 4H), 7.12 (d, J=8.5 Hz, 2H), 7.40 (m, 2H), 7.53 (m, 2H).
Reference example - 3

Diethyl oxalate (1.00 g, 6.8 mmol) and ethylene glycol (14 mL) were added to 4-octyl-1,2-phenylenediamine (6.01 g, 27 mmol) under an argon atmosphere, and the mixture was stirred at 200°C for 37 hours. . Distilled water was added to the reaction mixture, and the precipitated solid was collected by filtration. The resulting solid was purified by silica gel column chromatography (chloroform:ethyl acetate=10:1, with 1% triethylamine added) and then washed with ethanol to give the desired 5,5'-dioctyl-2,2'-bisbenzimidazole. (2.73 g, 5.9 mmol, 88%) was obtained.
¹ H-NMR (CDCl ₃ ) δ 0.84 (t, J = 6.8 Hz, 6H), 1.22-1.30 (m, 20H), 1.55-1.62 (m, 4H), 2 .66 (t, J=7.6Hz, 4H), 7.13 (d, J=8.4Hz, 2H), 7.40 (m, 2H), 7.51-7.56 (m, 2H) .
Reference example - 4

Diethyl oxalate (1.00 g, 6.8 mmol) and ethylene glycol (14 mL) were added to 4-octyl-1,2-phenylenediamine (1.52 g, 6.8 mmol) under an argon atmosphere, and the mixture was stirred at 200°C for 25 hours. Stirred. Distilled water was added to the reaction mixture, and the precipitated solid was collected by filtration. The resulting solid was purified by washing with ethanol to give the desired 5-octyl-benzimidazole-2-carboxylic acid (1.29 g, 4.7 mmol, 69%).
¹ H-NMR (DMSO-d6) δ 0.85 (t, J = 6.8 Hz, 3H), 1.24-1.29 (m, 10H), 1, 49-1.55 (m, 2H), 2.52 (t, J=7.5Hz, 2H) 6.90-6.92 (m, 2H), 7.02 (d, J=8.8Hz, 1H), 11.8 (m, 2H)
Reference example-5

Under an argon atmosphere, 1,2-phenylenediamine (2.63 g, 24 mmol) and ethylene glycol (7.5 mL) were added to 5-octyl-benzimidazole-2-carboxylic acid (1.00 g, 3.6 mmol). C. for 27 hours. Distilled water was added to the reaction mixture, and the precipitated solid was collected by filtration. The resulting solid was purified by washing with ethanol to give the desired 5-octyl-2,2'-bisbenzimidazole (279 mg, 0.81 mmol, 22%).
¹ H-NMR (CDCl ₃ ) δ 0.84 (t, J = 6.9 Hz, 3H), 1.22-1.30 (m, 10H), 1.55-1.62 (m, 2H), 2 .66 (t, J = 7.6 Hz, 2H), 7.15 (d, J = 8.9 Hz, 1H), 7.29-7.33 (m, 2H), 7.40-7.44 ( m, 1H), 7.55-7.57 (m, 1H), 7.60-7.75 (m, 2H)
Reference example-6

アルゴン雰囲気下、参考例－１で得られた５，５’－ジメチル－２，２’－ビスベンゾイミダゾール（３００ｍｇ，１．１ｍｍｏｌ）に二酸化マンガン（２．０１ｇ，２３ｍｍｏｌ）及びテトラヒドロフラン（１２ｍＬ）を加え、室温で４８時間攪拌した。この反応混合物をセライトろ過し、ろ液を減圧乾固した。得られた固体をＰＴＬＣ（クロロホルム：酢酸エチル＝５：１）によって精製し、目的の２－（５’－メチル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－メチル－２Ｈ－ベンゾイミダゾールと２－（６’－メチル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－メチル－２Ｈ－ベンゾイミダゾールを混合物として得た（４７ｍｇ，０．１８ｍｍｏｌ，１４％）。
^１Ｈ―ＮＭＲ（ＣＤＣｌ_３）δ２．７１（ｓ，３．１８Ｈ），２．７２（ｓ，２．８２Ｈ），７．７８（ｄｄ，Ｊ＝１．９，９．１Ｈｚ，１．０６Ｈ），７．７９（ｄｄ，Ｊ＝１．９，９．１Ｈｚ，０．９４Ｈ），８．１２－８．１４（ｍ，２Ｈ）８．２９（ｄ，Ｊ＝９．１Ｈｚ，２Ｈ）．
参考例－７

Under an argon atmosphere, manganese dioxide (2.01 g, 23 mmol) and tetrahydrofuran (12 mL) were added to 5,5′-dimethyl-2,2′-bisbenzimidazole (300 mg, 1.1 mmol) obtained in Reference Example-1. The mixture was added and stirred at room temperature for 48 hours. The reaction mixture was filtered through celite, and the filtrate was dried under reduced pressure. The resulting solid was purified by PTLC (chloroform:ethyl acetate=5:1) to give the desired 2-(5′-methyl-2H-benzimidazolo-2′-ylidene)-5-methyl-2H-benzimidazole. and 2-(6′-methyl-2H-benzimidazolo-2′-ylidene)-5-methyl-2H-benzimidazole as a mixture (47 mg, 0.18 mmol, 14%).
¹ H-NMR (CDCl ₃ ) δ 2.71 (s, 3.18H), 2.72 (s, 2.82H), 7.78 (dd, J = 1.9, 9.1Hz, 1.06H) , 7.79 (dd, J=1.9, 9.1 Hz, 0.94 H), 8.12-8.14 (m, 2 H) 8.29 (d, J=9.1 Hz, 2 H).
Reference example - 7

アルゴン雰囲気下、参考例－２で得られた５，５’－ジへキシル－２，２’－ビスベンゾイミダゾール（３００ｍｇ，０．７３ｍｍｏｌ）に二酸化マンガン（１．２８ｇ，１５ｍｍｏｌ）及びテトラヒドロフラン（７．５ｍＬ）を加え、室温で５１時間攪拌した。この反応混合物をセライトろ過し、ろ液を減圧乾固した。得られた固体をＰＴＬＣ（ヘキサン：クロロホルム＝２：１）によって精製し、目的の２－（５’－ヘキシル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－ヘキシル－２Ｈ－ベンゾイミダゾールと２－（６’－ヘキシル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－ヘキシル－２Ｈ－ベンゾイミダゾールを混合物として得た（１５ｍｇ，０．０４０ｍｍｏｌ，５％）。
^１Ｈ―ＮＭＲ（ＣＤＣｌ_３）δ０．９１（ｔ，Ｊ＝７．０Ｈｚ，６Ｈ），１．３０－１．４１（ｍ，８Ｈ），１．４３－１．５０（ｍ，４Ｈ），１．７９－１．８７（ｍ，４Ｈ），２．９４－２．９８（ｍ，４Ｈ），７．８０（ｄｄ，Ｊ＝１．９，９．１Ｈｚ，０．７Ｈ），７．８１（ｄｄ，Ｊ＝１．９，９．１Ｈｚ，１．３Ｈ），８．１１－８．１２（ｍ，２Ｈ）８．３０（ｄ，Ｊ＝９．１Ｈｚ，２Ｈ）．
実施例－１

Under an argon atmosphere, manganese dioxide (1.28 g, 15 mmol) and tetrahydrofuran (7 .5 mL) was added and stirred at room temperature for 51 hours. The reaction mixture was filtered through celite, and the filtrate was dried under reduced pressure. The resulting solid was purified by PTLC (hexane:chloroform=2:1) to give the desired 2-(5′-hexyl-2H-benzimidazolo-2′-ylidene)-5-hexyl-2H-benzimidazole and 2-(6'-hexyl-2H-benzimidazolo-2'-ylidene)-5-hexyl-2H-benzimidazole was obtained as a mixture (15 mg, 0.040 mmol, 5%).
¹ H-NMR (CDCl ₃ ) δ 0.91 (t, J = 7.0 Hz, 6H), 1.30-1.41 (m, 8H), 1.43-1.50 (m, 4H), 1 .79-1.87 (m, 4H), 2.94-2.98 (m, 4H), 7.80 (dd, J = 1.9, 9.1Hz, 0.7H), 7.81 ( dd, J=1.9, 9.1 Hz, 1.3 H), 8.11-8.12 (m, 2 H) 8.30 (d, J=9.1 Hz, 2 H).
Example-1

アルゴン雰囲気下、参考例－３で得られた５，５’－ジオクチル－２，２’－ビスベンゾイミダゾール（１００ｍｇ，０．２２ｍｍｏｌ）に二酸化マンガン（３９０ｍｇ，４．４ｍｍｏｌ）及びテトラヒドロフラン（２．０ｍＬ）を加え、室温で６７時間攪拌した。この反応混合物をセライトろ過し、ろ液を減圧乾固した。得られた固体をＰＴＬＣ（ヘキサン：クロロホルム＝３；１）によって精製し、目的の２－（５’－オクチル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－オクチル－２Ｈ－ベンゾイミダゾールと２－（６’－オクチル－２Ｈ－ベンゾイミダゾロ－２’－イリデン）－５－オクチル－２Ｈ－ベンゾイミダゾールを混合物として得た（５ｍｇ，０．０１０ｍｍｏｌ，５％）。
^１Ｈ―ＮＭＲ（ＣＤＣｌ_３）δ０．８８（ｔ，Ｊ＝７．０Ｈｚ，６Ｈ），１．２２－１．４８（ｍ，２０Ｈ），１．７９－１．８８（ｍ，４Ｈ），２．９４－２．９８（ｍ，４Ｈ），７．８０（ｄｄ，Ｊ＝１．９，９．０Ｈｚ，０．３８Ｈ），７．８１（ｄｄ，Ｊ＝１．９，９．０Ｈｚ，１．６２Ｈ），８．１２－８．１３（ｍ，２Ｈ）８．３１（ｄ，Ｊ＝９．０Ｈｚ，２Ｈ）．
実施例－２

Under an argon atmosphere, manganese dioxide (390 mg, 4.4 mmol) and tetrahydrofuran (2.0 mL) were added to 5,5'-dioctyl-2,2'-bisbenzimidazole (100 mg, 0.22 mmol) obtained in Reference Example-3. ) was added and stirred at room temperature for 67 hours. The reaction mixture was filtered through celite, and the filtrate was dried under reduced pressure. The resulting solid was purified by PTLC (hexane:chloroform=3:1) to give the desired 2-(5′-octyl-2H-benzimidazolo-2′-ylidene)-5-octyl-2H-benzimidazole and 2-(6'-Octyl-2H-benzimidazolo-2'-ylidene)-5-octyl-2H-benzimidazole was obtained as a mixture (5 mg, 0.010 mmol, 5%).
¹ H-NMR (CDCl ₃ ) δ 0.88 (t, J = 7.0 Hz, 6H), 1.22-1.48 (m, 20H), 1.79-1.88 (m, 4H), 2 .94-2.98 (m, 4H), 7.80 (dd, J = 1.9, 9.0Hz, 0.38H), 7.81 (dd, J = 1.9, 9.0Hz, 1 .62H), 8.12-8.13 (m, 2H) 8.31 (d, J=9.0Hz, 2H).
Example-2

Under an argon atmosphere, manganese dioxide (546 mg, 6.29 mmol) and tetrahydrofuran (3.1 mL) were added to 5-octyl-2,2'-bisbenzimidazole (100 mg, 0.314 mmol), and the mixture was stirred at room temperature for 50 hours. The reaction mixture was filtered through celite, and the filtrate was dried under reduced pressure. The resulting solid was purified by PTLC (chloroform:ethyl acetate=10:1) to give the desired 2-(2H-benzimidazolo-2'-ylidene)-5-octyl-2H-benzimidazole (2 mg, 0.5 mg). 0060 mmol, 2%).
¹ H-NMR (CDCl ₃ ) δ 0.88 (t, J = 7.0 Hz, 3H), 1.25-1.40 (m, 10H), 1.79-1.87 (m, 2H), 2 .96 (t, J = 7.6Hz, 2H), 7.82 (dd, J = 1.8, 9.2Hz, 1H), 7.94-7.99 (m, 2H), 8.12- 8.13 (m, 1H), 8.31 (d, J=9.2Hz, 1H), 8.39-8.44 (m, 2H).
Test example-1
(Preparation of electrochemical measurement composition)
The azafulvalene compound (4.0 mg, 0.0087 mmol) obtained in Example-1 and tetrabutylammonium hexafluorophosphate (3.37 g, 8.7 mmol) were placed in a 20 mL volumetric flask under air, and diluted with dichloromethane. up. After allowing to stand at room temperature for 1 hour, it was confirmed that a solid was not precipitated and the solution state was maintained.

Test example-2
(Cyclic voltammetry measurement)
Argon gas was bubbled through the composition for electrochemical measurement prepared in Example-3 for 10 minutes to remove dissolved oxygen. A platinum electrode as a working electrode, an Ag/AgCl electrode with a saturated KCl aqueous solution as a reference electrode, and a platinum electrode as a counter electrode were inserted thereinto and connected to a measuring device. HSV-110 (Hokuto Denko Co., Ltd.) was used as a measuring device.

Measurement conditions were as follows: initial potential application time: 1 s; potential window: -1.5 to 0.4 V; number of repetitions: 5; Slope Range: 10 mV/s; As a result, a voltammogram showing reversible two-electron oxidation and reduction was obtained, confirming that the azafulvalene compound has oxidation/reduction state bistability.

The reduction potential of the azafulvalene compound was −0.47 V vs Ag/AgCl, which was calculated as 2.78 V vs Li/Li+.

Claims (6)

General formula (1)

(In the formula, R ¹ represents an alkyl group having 7 to 20 carbon atoms, and R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.) azafulvalene compound. R ¹ is an alkyl group having 7 to 10 carbon atoms, R ² is a hydrogen atom, and R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Azafulvalene compound as described. general formula (1a) or (1b)

3. The azafulvalene compound according to claim 1 or 2, represented by (wherein R ¹ and R ² have the same meanings as defined above). general formula (2)

(In the formula, R ¹ represents an alkyl group having 7 to 20 carbon atoms, and R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.) The general formula (1) is reacted with a bisimidazole compound and an oxidizing agent

(Wherein, R ¹ , R ² , R ³ and R ⁴ have the same meanings as defined above). 5. The production method according to claim 4, wherein the oxidizing agent is manganese dioxide. A composition for electrochemical measurements, comprising the azafulvalene compound according to any one of claims 1 to 3.