JP4604183B2 - Ruthenium complex, dye-sensitized metal oxide semiconductor electrode containing the complex, and solar cell including the semiconductor electrode - Google Patents

Description

  The present invention relates to a novel ruthenium complex, a metal oxide semiconductor electrode containing the complex, and a solar cell including the semiconductor electrode.

  The new dye-sensitized solar cell, the so-called Gretzel cell, devised by Gretzel of Lausanne University of Technology, Switzerland, is the next generation because it may realize high performance at a lower manufacturing cost than conventional solar cells. In recent years, it has attracted worldwide attention as a solar cell.

  In this type of solar cell, a ruthenium-polypyridine complex is often used as a sensitizing dye, and has a 2,2′-bipyridine derivative or a terpyridine derivative as a ligand, particularly as one having high energy conversion efficiency. Ruthenium-thiocyanate complexes are well known.

  For practical use of dye-sensitized solar cells, further improvement of battery performance such as energy conversion efficiency and improvement of battery life are extremely important research subjects. For this purpose, a compound used as a sensitizing dye such as a ruthenium complex is required to be stable over a long period even under severe conditions such as high temperature and light irradiation.

  From this point of view, the above-mentioned two most commonly used ruthenium complexes mentioned above are dissociated from some ligands and isomerized between cis and trans isomers by heat and light stimulation. The possibility of reaction has been pointed out, and it can be said that development of a more stable complex sensitizing dye is necessary.

A polydentate ligand compound having a cyclic or quasi-cyclic structure has the advantage of forming a more stable metal complex by increasing the coordination point to the central metal, and is expected to solve the above problems. Some examples of such a type of ruthenium complex have been reported (Patent Document 1, Non-Patent Document 1).
For example, Patent Document 1 is characterized by having a tetradentate ligand having a structure in which two polypyridine bidentate ligands are bonded as a complex sensitizing dye that is more stable to light and heat. A ruthenium complex, a metal oxide semiconductor electrode using the same as a sensitizing dye, and a dye-sensitized solar cell composed of the electrode have been proposed.

  This Patent Document 1 states that “this metal complex dye is selected from the group consisting of 1,10-phenanthroline, 1,10-phenanthroline derivative, 2,2′-bipyridyl and 2,2′-bipyridyl derivative. A tetradentate ligand having a structure in which two types of bidentate ligands are bonded via a divalent group is used as a ligand other than thiocyanate ion. Compared to conventional metal complex dyes in which two ligands are independently coordinated to the coordination center, the position of each ligand relative to the coordination center and the accompanying change in ligand orientation are less likely to occur. It is excellent in structural stability. Therefore, the metal complex dye of the present invention has excellent heat resistance, light resistance and chemical stability. " “In particular, complexes with two bidentate ligands coordinated to the coordination center include cis and trans isomers, and the trans form isomerizes into an unstable and stable cis form. In order to prevent isomerization and stably obtain a trans form, a method of linking two bidentate ligands as in the present invention is effective. The divalent group connecting the bidentate ligand preferably has 1 to 3 atomic chains, and in order to obtain a cis form, the divalent group connecting two bidentate ligands. It is also preferable that the group has a chain of 4 or more atoms ”.

However, the compounds specifically synthesized and mentioned for their performance are only the cis-type metal complexes described in Examples 1 to 5, and other cis-type compounds as well as trans-type metal complexes. Is not disclosed at all, and no mention is made regarding its performance.
Moreover, even in the metal complexes disclosed in Examples 1 to 5, the solar cell using this as a dye sensitizer has an energy conversion efficiency of about 2.7% at most, and its basic performance is all. It was not expensive.

JP 2003-3083 A Inorg. Chem. 2002, 41,367-378

Thus, the conventional ruthenium complex having a tetradentate ligand and having a stable structure against heat and light has a low basic performance of the battery such as energy conversion efficiency when used as a sensitizing dye of a solar battery. There was a strong demand for improvements.
An object of the present invention is to provide a ruthenium complex that has a stable structure against heat and light and can dramatically increase its energy conversion efficiency when used as a sensitizing dye for solar cells. To do.

  As a result of intensive studies on ligands of ruthenium complexes, the present inventors have devised a ruthenium complex characterized by a structure in which a bipyridine derivative of a bidentate ligand is arranged in a trans form. It has been found that the performance is remarkably improved compared to The present invention has been made based on such findings.

（式中、Ｒ_１、Ｒ_２、Ｒ_３は水素原子またはＣＯＯＭであり、そのうち少なくとも一つはＣＯＯＭである。Ｍは水素原子また第４級アンモニウムカチオンを、Ｒ_４は水素原子あるいは置換基を有してもよいアリール基、置換基を有してもよいアルキル基、置換基を有してもよいパーフルオロアルキル基である。）
（２）上記（１）に記載のルテニウム錯体を含む金属酸化物半導体電極。
（３）半導体電極とその対極、およびそれらの電極に接触するレドックス電解質とから構成される色素増感型太陽電池であって、半導体電極が上記（２）に記載の金属酸化物半導体電極であることを特徴とする色素増感型太陽電池。 That is, according to this application, the following invention is provided.
(1) A ruthenium complex represented by the general formula (I).

(Wherein R ₁ , R ₂ and R ₃ are a hydrogen atom or COOM, at least one of which is COOM. M is a hydrogen atom or a quaternary ammonium cation, and R ₄ is a hydrogen atom or a substituent. An aryl group that may have, an alkyl group that may have a substituent, and a perfluoroalkyl group that may have a substituent.)
(2) A metal oxide semiconductor electrode comprising the ruthenium complex according to (1).
(3) A dye-sensitized solar cell including a semiconductor electrode, a counter electrode thereof, and a redox electrolyte in contact with the electrode, wherein the semiconductor electrode is the metal oxide semiconductor electrode according to (2) above A dye-sensitized solar cell characterized by the above.

  The ruthenium complex of the present invention has a structure in which a bidentate bipyridine derivative is arranged in a trans form and a thiocyanate ligand is coordinated above and below a ruthenium atom. When used as a sensitizer for modifying a metal oxide semiconductor electrode of a battery, the energy conversion efficiency can be dramatically increased as compared with the case where a conventional ruthenium complex of the same type is used.

  The metal complex of the present invention is represented by the above general formula (I), and a bipyridine derivative of a bidentate ligand is arranged in trans with respect to a ruthenium metal atom (a bidentate ligand facing the ruthenium metal atom). And a thiocyanate ligand is arranged above and below a ruthenium atom.

In the general formula (I), R ₁ , R ₂ and R ₃ are hydrogen atoms or COOM, and at least one of them is COOM. M is a hydrogen atom or a quaternary ammonium cation, R ₄ is a hydrogen atom or an aryl group which may have a substituent, an alkyl group which may have a substituent, or a perfluoro which may have a substituent. It is an alkyl group.
In this case, at least one of R ₁ , R ₂ , and R ₃ , that is, at least two or more in the whole molecule so that the ruthenium complex represented by the general formula (I) is firmly adsorbed on the surface of the oxide semiconductor. Is preferably COOM, more preferably at least 3 or more, and more preferably 4 or more in the whole molecule.

In the ruthenium complex represented by the general formula (I), examples of the aryl group in which R ₄ may have a substituent include a phenyl group, a naphthyl group, a tolyl group, and an ethylphenyl group. Examples of the alkyl group having 1 to 30 carbon atoms that may have include a methyl group, an ethyl group, a hexyl group, an octyl group, a decyl group, a benzyl group, a phenethyl group, and a phenylbutyl group. Examples of the perfluoroalkyl group having 1 to 7 carbon atoms that may have a substituent include a perfluoromethyl group, a perfluoroethyl group, a perfluorohexyl group, and a perfluorooctyl group. .

Specific examples of the ruthenium complex represented by the general formula (I) described above include compounds represented by the following formulas (II), (III), and (IV).

（式中、Ｒ_１、Ｒ_２、Ｒ_３は水素原子またはＣＯＯＭであり、そのうち少なくとも一つはＣＯＯＭである。Ｍは水素原子また第４級アンモニウムカチオンを、Ｒ_４は水素原子あるいは置換基を有してもよいアリール基、置換基を有してもよいアルキル基、置換基を有してもよいパーフルオロアルキル基である。Ｘは塩素あるいは臭素原子である。） The ligand bis [2,2 ′] bipyridinyl-6-yl-amine derivative (general formula (V)) of the ruthenium complex represented by the general formula (I) is represented by 2 molecules represented by the general formula (VI). , 2′-bipyridine derivative and ammonia or a primary amine represented by the general formula (VII) can be produced.

(Wherein R ₁ , R ₂ and R ₃ are a hydrogen atom or COOM, at least one of which is COOM. M is a hydrogen atom or a quaternary ammonium cation, and R ₄ is a hydrogen atom or a substituent. An aryl group that may have, an alkyl group that may have a substituent, and a perfluoroalkyl group that may have a substituent, where X is a chlorine or bromine atom.)

This reaction is advantageously carried out in a suitable solvent in the presence of a base and a catalyst. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane, alcohols such as ethyl alcohol and t-butyl alcohol, dimethylformamide and acetamide. Acid amides, nitriles such as acetonitrile and propionitrile, and ethers such as dioxane and tetrahydrofuran, among which toluene is particularly preferable. The base is preferably a metal alkoxide such as sodium tert-butoxide or potassium tert-butoxide, or a carbonate such as cesium carbonate or potassium carbonate, and the catalyst is a mixture of a palladium salt such as divalent palladium acetate or palladium chloride and phosphine, or Zero-valent palladium phosphine complexes are preferred.

  The reaction temperature varies depending on the type of raw material used, the amount of catalyst, and the type of solvent, but is generally room temperature to 150 ° C, preferably 60 to 100 ° C. Furthermore, the reaction time varies depending on the reaction temperature and the type of raw material, and cannot be generally defined, but is usually 2 to 24 hours. The amount of the catalyst is 0.5 to 10%, preferably 2 to 5% in terms of a molar amount with respect to the bipyridine derivative represented by the general formula (VI) and the amine represented by the general formula (VII). In order to maintain the activity of the catalyst, it is desirable to use a dehydrated solvent and perform the reaction in an inert gas atmosphere such as nitrogen or argon.

In addition, the ligand bis [2,2 ′] bipyridinyl-6-yl-amine derivative (general formula (V)) of the ruthenium complex represented by the general formula (I) is represented by 2, It can also be produced by reacting a 2'-bipyridine derivative with a bipyridine derivative represented by the aforementioned general formula (VI).

（（式中、Ｒ_１、Ｒ_２、Ｒ_３は水素原子またはＣＯＯＭであり、そのうち少なくとも一つはＣＯＯＭである。Ｍは水素原子また第４級アンモニウムカチオンを、Ｒ_４は水素原子あるいは置換基を有してもよいアリール基、置換基を有してもよいアルキル基、置換基を有してもよいパーフルオロアルキル基である。Ｘは塩素あるいは臭素原子である。） The ruthenium complex represented by the general formula (I) is obtained by heating the bis [2,2 ′] bipyridinyl-6-yl-amine derivative represented by the general formula (II) and a metal compound in an appropriate solvent. Although it can manufacture via the ruthenium complex shown by general formula (IX) obtained, a metal complex etc. which have a metal salt, a substitutable ligand, etc. are mentioned as a metal compound. For example, in the general formula (IX), when X is a chlorine ion, a corresponding metal chloride is used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene and xylene, alcohols such as ethyl alcohol and t-butyl alcohol, acid amides such as dimethylformamide and acetamide, nitriles such as acetonitrile and propionitrile, and dioxane. , Tetrahydrofuran, diglyme (diethylene glycol dimethyl ether) and the like, and dimethylformamide and diglyme are particularly preferred.

(In the formula, R ₁ , R ₂ and R ₃ are a hydrogen atom or COOM, at least one of which is COOM. M is a hydrogen atom or a quaternary ammonium cation, and R ₄ is a hydrogen atom or a substituent. An aryl group that may have a substituent, an alkyl group that may have a substituent, and a perfluoroalkyl group that may have a substituent. X is a chlorine or bromine atom.)

  This reaction varies depending on the type of the solvent of the derivative or metal salt used, but is generally 50 ° C to 160 ° C, preferably 100-140 ° C. Furthermore, although reaction time changes with reaction temperature and the kind of raw material and cannot be defined unconditionally, it is 2 to 5 hours normally.

  The conversion from the ruthenium complex represented by the general formula (IX) to the ruthenium complex represented by the general formula (I) is carried out by heating the alkali metal salt or ammonium salt of the metal complex (IX) and thiocyanate in an appropriate solvent. Obtained by. Examples of the solvent include water, aromatic hydrocarbons such as benzene, toluene and xylene, alcohols such as ethyl alcohol and t-butyl alcohol, acid amides such as dimethylformamide and acetamide, and nitriles such as acetonitrile and propionitrile. , Ethers such as dioxane and tetrahydrofuran can be mentioned, and dimethylformamide is particularly preferred.

  This reaction is generally carried out in the range of 50 to 160 ° C., preferably 100 to 140 ° C., although it varies depending on the raw materials and the solvent used. Furthermore, although reaction time changes with reaction temperature and the kind of raw material and cannot be defined unconditionally, it is 2 to 5 hours normally.

The ruthenium complex according to the present invention is useful as a sensitizer for oxide semiconductor electrodes. Examples of the oxide semiconductor include porous TiO ₂ , ZnO, SnO ₂ , and WO _3, and TiO ₂ is particularly preferable. A method for manufacturing an oxide semiconductor electrode using the ruthenium metal complex of the present invention is not particularly limited. For example, an oxide semiconductor film formed on a substrate such as conductive glass is immersed in a ruthenium complex solution. It is produced by. As the solvent, alcohols, nitriles, amides or mixtures thereof are used, and methanol, ethanol, butyronitrile and the like are particularly preferable. The concentration of the solution and the immersion time vary depending on the temperature of the solution, the solvent, the type of the oxide semiconductor film, and the metal complex, and cannot be generally defined, but are usually 0.2 mM and about 24 hours at room temperature.

The oxide semiconductor electrode sensitized with the ruthenium complex represented by the general formula (I) thus prepared is composed of a semiconductor electrode, a counter electrode thereof, and a redox electrolyte in contact with the electrode. It can be used as a semiconductor electrode in a solar cell.
A well-known redox electrolyte can be used. For example, acetonitrile is used as a solvent, a mixture of iodine and lithium iodide is used as a redox couple, and an imidazole salt is used as an electrolyte. Further, 4-tert-butylpyridine or deoxycholic acid may be added as an additive.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1
[(Synthesis of (bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (formula (II))]
The synthesis route of this ruthenium complex is shown below.

(1) Synthesis of 6′-bromo-4-methyl- [2,2 ′] bipyridinyl (iii) Under an argon atmosphere, 3.96 g (16.7 mmol) of 2,6-dibromopyridine (ii) and tetrakis (triphenyl) To a 30 ml THF solution containing 579 mg (0.501 mmol) of phosphine) palladium, 50 ml (25 mmol) of a 0.5 M THF solution of 4-methyl-2-pyridylzinc bromide (i) is added at room temperature with stirring. The reaction mixture is stirred overnight and then poured into about 100 ml of water. The zinc salt that forms a complex with the product is dissolved by adding EDTA and sodium carbonate. The product is separated by extraction with methylene chloride. After drying, methylene chloride is distilled off, and the remaining residue is subjected to column chromatography on alumina to separate an oily product using a mixed solvent of methylene chloride and hexane as an eluent. Yield 2.05 g (49.3%)

(2) Synthesis of 6'-bromo- [2,2 '] bipyridinyl-4-carboxylic acid ethyl ester (iv) 6'-bromo-4- [2,2'] bipyridinyl (iii) 1.95 g (7. 83 mmol) is suspended in 50 ml of water. To the suspension under reflux, 3.71 g (23.5 mmol) of potassium permanganate is added in several portions with stirring. Further, heating and stirring are continued for 3 hours. The manganese dioxide produced after cooling is filtered, and the filtrate is washed several times with hot water. The filtrate and washings were combined and concentrated to a total of about 20 ml, adjusted to pH 3 with 3N hydrochloric acid, and the precipitated white solid product (6′-bromo- [2,2 ′] bipyridinyl-4-carboxylic acid) was obtained. Filter and dry. Yield 300 mg (yield%) Manganese dioxide residue was washed with methylene chloride to recover 950 mg of unreacted raw material.
622 mg (2.23 mmol) of 6′-bromo- [2,2 ′] bipyridinyl-4-carboxylic acid obtained is dissolved in 30 ml of ethyl alcohol, 0.5 ml of concentrated sulfuric acid is added, and the mixture is heated to reflux for 24 hours. After cooling, ethyl alcohol is removed, ice is added to the residue, neutralized with an aqueous sodium hydroxide solution, and the product is extracted with methylene chloride. After drying, the methyl chloride was distilled off and the product was purified by recrystallization from ethyl alcohol. Yield 489 mg (Yield 71.3%)

(3) Synthesis of bis- (4′-ethoxycarbonyl- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (v) 2,2′-bis (diphenylphosphino) -1 under an argon atmosphere , 1'-binaphthyl is dissolved in about 0.7 ml of dehydrated toluene in a Schlenk tube. To this is added 18.7 mg (0.0835 mmol) of palladium acetate along with about 0.7 ml of toluene. After stirring the solution for about 10 minutes, 513 mg (1.67 mmol) of 6′-bromo- [2,2 ′] bipyridinyl-4-carboxylic acid ethyl ester (iv) is added together with about 3 ml of toluene. Further, 258 mg (2.00 mmol) of n-octylamine and 1.52 g (4.68 mmol) of cesium carbonate are added together with about 3 ml of toluene. The reaction mixture is stirred for 24 hours at 100 ° C. under an argon atmosphere. After completion of the reaction, toluene is distilled off, and the remaining residue is subjected to alumina column chromatography to separate the product using a mixed solvent of methylene chloride and hexane as an eluent. The separated product was further purified by recrystallization from ethyl alcohol. As a result, 219 mg of the target product is obtained (yield 50%). Furthermore, 1: 1 adduct 6'-octylamino- [2,2 '] bipyridinyl-4-carboxylic acid ethyl ester (vi) with amine as a by-product is obtained in a yield of 80.1 mg (15% yield). ). The structure and purity of the product were confirmed by NMR.
1H NMR (CDCl3): δ8.91 (2H, dd, J = 1.0, 1.0); 8.80 (2H, d, J = 5.0); 8.03 (2H, d, J = 8.0); 7.85 (2H, dd, J = 1.0, 5.0); 7.58 (1H, t, J = 8.0); 7.31 (1H, dd, J = 0.8, 8.0); 4.43 (4H, q, J = 7.2); 4.43 (2H, t, J = 8.0 ); 1.92 (2H, quint, J = 8.0); 1.51 (2H, t, J = 8.0); 1.42 (6H, t, J = 7.2); 1.41-1.19 (8H, multi); 0.81 (3H, t, J = 6.8)
6'-octylamino- [2,2 '] bipyridinyl-4-carboxylic acid ethyl ester (vi)
1H NMR (CDCl3): δ 8.83 (1H, dd, J = 0.8, 1.6); 8.78 (1H, dd, J = 0.8, 5.2); 7.81 (1H, dd, J = 1.6, 5.2); 7.67 (1H , dd, J = 0.8, 7.6); 7.58 (1H, t, J = 7.6); 6.45 (1H, dd, J = 0.8, 7.6); 4.67 (1H, bs); 4.45 (2H, q, J = 7.2 ); 3.35 (2H, dt, J = 4.4, 6.8); 1.68 (2H, quint, J = 7.2); 1.44 (3H, t, J = 7.2); 1.40-1.23 (10H, multi); 0.88 (3H, t, J = 6.8)

  By-products 6'-octylamino- [2,2 '] bipyridinyl-4-carboxylic acid ethyl ester (vi) and 6'-bromo- [2,2'] bipyridinyl-4-carboxylic acid ethyl ester (iv ), The target bis- (4′-ethoxycarbonyl- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (v) is obtained under similar reaction conditions. That is, 67.6-octylamino- [2,2 ′] bipyridinyl-4-carboxylic acid ethyl ester (vi) 97.6 mg (0.275 mmol) and 6′-bromo- [2,2 ′] bipyridinyl-4-carboxylic acid Acid ethyl ester (vi) 82.9 mg (0.270 mmol) in the presence of palladium acetate 2.42 mg (0.0108 mmol), triphenylphosphine 5.66 mg (0.0216 mmol), cesium carbonate 100 mg (0.307 mmol) in toluene In the reaction, 76.0 mg of the desired product was obtained (yield 49%).

(4) Synthesis of bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (vii) under nitrogen atmosphere, bis- (4′-ethoxycarbonyl- [2,2 ′) 215 mg (0.369 mmol) of bipyridinyl-6-yl) -octyl-amine (v) are dissolved in 40 ml of a mixed solvent of ethyl alcohol and water in a volume ratio of 4: 1. To this was added 34.1 mg (0.812 mmol) of lithium hydroxide monohydrate, and the mixture was stirred and refluxed overnight. After cooling the reaction mixture, the ethyl alcohol is distilled off. Ice water is added to the residue (about 100 ml), and the solution is acidified (pH 3) with 1N hydrochloric acid. The purified precipitate is filtered, washed with water and dried. 172 mg of the desired product is obtained (yield 89%).

(5) Synthesis of (bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dichlororuthenium (II) (viii) dichloro (p-cumene) ruthenium under argon atmosphere 30.6 mg (0.05 mmol) of the dimer is dissolved in 10 ml of dehydrated diglyme. To this is slowly added 5 ml of a diglyme solution of 52.5 mg (0.100 mmol) of bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (vii). The reaction solution is stirred at reflux for 150 minutes. The product precipitated after cooling is filtered, washed with water and ether and dried. 57.2 mg of the desired green complex is obtained. The structure was confirmed by mass spectrometry.
MS (ESIMS): m / z: 348.4 (M-2H) ^2- , 696.0 (MH) ^- ; MW: 697 calcd.for C ₃₀ H ₃₁ N ₅ O ₄ RuCl ₂

(6) Synthesis of (bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (II) under an argon atmosphere (bis- (4 '-Carboxy- [2,2'] bipyridinyl-6-yl) -octyl-amine) dichlororuthenium (viii) 57.7 mg (0.0828 mmol) is dissolved in 15 ml of dehydrated dimethylformamide. To this is slowly added 5 ml of an aqueous solution of 377 mg (4.97 mmol) of ammonium thiocyanate. The reaction solution is stirred and refluxed for 4 hours. After cooling, dimethylformamide is removed and about 10 ml of water is added. The insoluble material is filtered, washed with water and ether and then dried. This is purified by a gel filtration column (LH20) using a mixed solvent of methyl alcohol-chloroform 1: 1 as an eluent. 32.5 mg of the desired purple complex is obtained. The structure was confirmed by mass spectrometry.
MS (ESIMS): m / z: 370.3 (M-2H) ^2- , 742.0 (MH) ^- ; MW: 743 calcd. For C ₃₂ H ₃₁ N ₇ O ₄ RuS ₂
In addition, (bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) has a trans structure, which is a basic skeleton structure around ruthenium. Is confirmed by the results of crystal structure analysis of a ruthenium complex of bis (1,10-phenanthrolin-2-yl) amine, which is exactly the same as this complex (Inorg. Chem. 2002, 41, 5937-5939).

Preparation of Solar Cell A 0.2 mM methyl alcohol solution of ruthenium complex (bis- (4′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (II) A visible light-responsive electrode is prepared by immersing a 30-μm thick titanium oxide porous film prepared on the conductive glass surface for 20 hours. An electrolyte solution is sandwiched between a counter electrode in which platinum is vapor-deposited on the surface of conductive glass to constitute a solar cell. As the electrolyte solution, an acetonitrile solution containing lithium iodide (0.1 M), iodine (0.05 M), dimethyl imidazolium iodide (0.6 M), and 4-tert-butylpyridine (0.5 M) was used. As a result, a photocurrent having a short-circuit current of 11.8 mA / cm ² , an open-circuit voltage of 0.58 V, an FF of 63%, and an energy conversion efficiency of η4.3% can be extracted under irradiation of pseudo sunlight of AM1 and 5.

Example 2
[(Synthesis of (bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (formula (III))]
The synthesis route of this ruthenium complex is shown below.

(1) Synthesis of 6′-bromo-5-methyl- [2,2 ′] bipyridinyl (x) Under an argon atmosphere, 3.96 g (16.7 mmol) of 2,6-dibromopyridine (ii) and tetrakis (triphenyl) To 30 ml of THF solution containing 579 mg (0.501 mmol) of phosphine) palladium, 50 ml (25 mmol) of 0.5 M THF solution of 5-methyl-2-pyridylzinc bromide (ix) is added at room temperature with stirring. The reaction mixture is stirred overnight and then poured into about 100 ml of water. The zinc salt that forms a complex with the product is dissolved by adding EDTA and sodium carbonate. The product is separated by extraction with methylene chloride. After drying, methylene chloride is distilled off, and the remaining residue is subjected to column chromatography on alumina to separate an oily product using a mixed solvent of methylene chloride and hexane as an eluent. Yield 2.23 g (54.0%)

(2) Synthesis of 6'-bromo- [2,2 '] bipyridinyl-5-carboxylic acid ethyl ester (xi) 6'-bromo-5-methyl- [2,2'] bipyridinyl (x) 1.37 g ( 5.5 mmol) is suspended in 50 ml of water. To the suspension under reflux, 2.60 g (16.5 mmol) of potassium permanganate is added in several portions with stirring. After heating and stirring for 3 hours, 0.5 g of potassium permanganate is further added. The manganese dioxide produced after cooling is filtered, and the filtrate is washed several times with hot water. The filtrate and washings were combined and concentrated to a total of about 20 ml, adjusted to pH 3 with 3N hydrochloric acid, and the precipitated white solid product (6′-bromo- [2,2 ′] bipyridinyl-5-carboxylic acid) was obtained. Filter and dry. Yield 454 mg (yield%) Manganese dioxide residue was washed with methylene chloride to recover 340 mg of unreacted raw material.
450 mg (1.61 mmol) of 6′-bromo- [2,2 ′] bipyridinyl-5-carboxylic acid obtained is dissolved in 30 ml of ethyl alcohol, 0.5 ml of concentrated sulfuric acid is added, and the mixture is heated to reflux overnight. After cooling, ethyl alcohol is removed, ice is added to the residue, neutralized with an aqueous sodium hydroxide solution, and the product is extracted with methylene chloride. After drying, the methyl chloride was distilled off and the product was purified by recrystallization from ethyl alcohol. Yield 405 mg (Yield 82.0%)

(3) Synthesis of bis- (5′-ethoxycarbonyl- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (xii) 2,2′-bis (diphenylphosphino) -1 under an argon atmosphere , 1′-binaphthyl (76.0 mg, 0.122 mmol) is dissolved in about 0.7 ml of dehydrated toluene in a Schlenk tube. To this is added 18.0 mg (0.0815 mmol) of palladium acetate along with about 0.5 ml of toluene. After stirring the solution for about 10 minutes, 500 mg (1.96 mmol) of 6-bromo- [2,2 ′] bipyridinyl-5-carboxylic acid ethyl ester (xi) is added along with about 3 ml of toluene. Further, 252 mg (2.00 mmol) of n-octylamine and 1.28 g (3.92 mmol) of cesium carbonate are added together with about 3 ml of toluene. The reaction mixture is stirred for 24 hours at 100 ° C. under an argon atmosphere. After completion of the reaction, toluene is distilled off, and the remaining residue is subjected to alumina column chromatography to separate the product using a mixed solvent of methylene chloride and hexane as an eluent. The separated product was further purified by recrystallization from ethyl alcohol. As a result, 219 mg of the target product is obtained (yield 50% (conversion 92%)). Furthermore, 1: 1 adduct 6′-octylamino- [2,2 ′] bipyridinyl-5-carboxylic acid ethyl ester (xiii) with amine is obtained as a by-product in a yield of 140 mg (yield 26%). The structure and purity of the product were confirmed by NMR.
1H NMR (CDCl3) δ: 9.27 (2H, dd, J = 0.6, 2.2); 8.44 (2H, dd, J = 0.6, 8.2); 8.39 (2H, dd, J = 2.2, 8.2); 8.10 (2H, d, J = 7.2); 7.71 (2H, t, J = 8); 7.28 (2H, d, J = 8.4); 4.44 (4H, q, J = 7.2); 4.39 (2H, t, J = 8.0) 1.79 (2H, quint, J = 8.0); 1.43 (6H, t, J = 7.2); 1.93-1.25 (10H, multi); 0.86 (3H, t, J = 6.8)
6'-octylamino- [2,2 '] bipyridinyl-5-carboxylic acid ethyl ester (xiii)
1H NMR (CDCl3): δ 9.24 (1H, dd, J = 0.8, 2.0); 8.41 (1H, dd, J = 0.8, 8.0); 8.36 (1H, dd, J = 2.0, 8.4); 7.74 (1H , d, J = 7.2); 7.58 (1H, t, J = 8.0); 6.47 (1H, d, J = 8.0); 4.60 (1H, t,); 4.43 (2H, q, J = 7.2); 3.36 (2H, dt, J = 6.0, 6.8); 1.67 (2H, quint, J = 7.2); 1.43 (3H, t, J = 7.2); 1.38-1.24 (10H, multi); 0.89 (3H, t, J = 6.8)

  By-products 6′-octylamino- [2,2 ′] bipyridinyl-5-carboxylic acid ethyl ester (xiii) and 6′-bromo- [2,2 ′] bipyridinyl-5-carboxylic acid ethyl ester (xi ), Bis- (5′-ethoxycarbonyl- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (xii), which is the target product, is obtained under similar reaction conditions. That is, 6'-octylamino- [2,2 '] bipyridinyl-5-carboxylic acid ethyl ester 100 mg (0.282 mmol) (xiii) and 6'-bromo- [2,2'] bipyridinyl-5-carboxylic acid ethyl Ester (xi) 82.0 mg (0.268 mmol) in toluene in the presence of palladium acetate 2.40 mg (0.0107 mmol), triphenylphosphine 5.61 mg (0.0214 mmol), cesium carbonate 100 mg (0.307 mmol) The reaction yielded 136 mg (0.234 mmol) of the desired product (yield 87%).

(4) Synthesis of bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (xiv) under nitrogen atmosphere, bis- (5′-ethoxycarbonyl- [2,2 ′) 213 mg (0.366 mmol) of bipyridinyl-6-yl) -octyl-amine (xii) are dissolved in 40 ml of a mixed solvent of ethyl alcohol and water in a volume ratio of 4: 1. To this was added 33.8 mg (0.805 mmol) of lithium hydroxide monohydrate, and the mixture was stirred and refluxed overnight. After cooling the reaction mixture, the ethyl alcohol is distilled off. Ice water is added to the residue (about 100 ml), and the solution is acidified (pH 3) with 1N hydrochloric acid. The purified precipitate is filtered, washed with water and dried. 193 mg of the desired product is obtained (yield 100%).

(5) Synthesis of (bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dichlororuthenium (II) (xv) dichloro (p-cumene) ruthenium under argon atmosphere (II) 30.6 mg (0.05 mmol) of the dimer is dissolved in 10 ml of dehydrated diglyme. To this is slowly added 5 ml of a diglyme solution of 52.5 mg (0.100 mmol) of bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine (xiv). The reaction solution is stirred at reflux for 150 minutes. The product precipitated after cooling is filtered, washed with water and ether and dried. 61.8 mg of the target green complex is obtained. The structure was confirmed by mass spectrometry.
MS (ESIMS): m / z: 348.4 (M-2H) ^2- , 696.0 (MH) ^- ; MW: 697 calcd.for C ₃₀ H ₃₁ N ₅ O ₄ RuCl ₂

(6) Synthesis of (bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (III) under an argon atmosphere, (bis- (5 61.8 mg (0.0887 mmol) of '-carboxy- [2,2'] bipyridinyl-6-yl) -octyl-amine) dichlororuthenium (II) (xv) are dissolved in 15 ml of dehydrated dimethylformamide. To this is slowly added 5 ml of an aqueous solution of 404 mg (5.32 mmol) of ammonium thiocyanate. The reaction solution is stirred and refluxed for 4 hours. After cooling, dimethylformamide is removed and about 10 ml of water is added. The insoluble material is filtered, washed with water and ether and then dried. 57.0 mg of the desired blue complex is obtained. The structure was confirmed by mass spectrometry.
MS (ESIMS): m / z: 369.9 (M-2H) ^2- , 742.0 (MH) ^- ; MW: 743 calcd. For C ₃₂ H ₃₁ N ₇ O ₄ RuS ₂
In addition, (bis- (5′-carboxy- [2,2 ′] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) has a trans structure, which is a basic skeleton structure around ruthenium. Of the crystal structure of a ruthenium complex of bis (1,10-phenanthrolin-2-yl) amine, which is exactly the same as the complex (Inorg. Chem. 2002, 41,
5937-5939).

Preparation of solar cell of ruthenium complex (bis- (5'-carboxy- [2,2 '] bipyridinyl-6-yl) -octyl-amine) dithiocyanate toruthenium (II) (III) as in (II) A 0.2 mM methyl alcohol solution is prepared, and a titanium oxide porous film having a film thickness of 30 μm prepared on the surface of the conductive glass is immersed in the solution for 20 hours to produce a visible light responsive electrode. An electrolyte solution is sandwiched between a counter electrode in which platinum is vapor-deposited on the surface of conductive glass to constitute a solar cell. As the electrolyte solution, an acetonitrile solution containing lithium iodide (0.1 M), iodine (0.05 M), dimethyl imidazolium iodide (0.6 M), and 4-tert-butylpyridine (0.5 M) was used. As a result, a photocurrent having a short-circuit current of 8.9 mA / cm ² , an open-circuit voltage of 0.56 V, an FF of 72%, and an energy conversion efficiency of η3.6% could be extracted under irradiation of simulated sunlight of AM1 and 5.

As is clear from the above results, the ruthenium complex according to the present invention has a dye sensitizing action significantly superior to that substantially disclosed in JP-A-2003-3083. It can be seen that the energy conversion efficiency of a solar cell using a dye sensitizer increases dramatically.

Claims (3)

A ruthenium complex represented by the general formula (I).

(Wherein R ₁ , R ₂ and R ₃ are a hydrogen atom or COOM, at least one of which is COOM. M is a hydrogen atom or a quaternary ammonium cation, and R ₄ is a hydrogen atom or a substituent. It may have an aryl group, an optionally substituted alkyl group, a path perfluoroalkyl group.)   A metal oxide semiconductor electrode comprising the ruthenium complex according to claim 1.   A dye-sensitized solar cell comprising a semiconductor electrode, a counter electrode thereof, and a redox electrolyte in contact with the electrode, wherein the semiconductor electrode is the metal oxide semiconductor electrode according to claim 2. Dye-sensitized solar cell.