JP2006298776A - Quarter-pyridine derivative, complex containing the same, photoelectric converter and dye sensitization solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel quarter-pyridine derivative, a complex containing the same, a photoelectric converter, and a dye sensitization solar cell. <P>SOLUTION: The quarter-pyridine derivative is represented by formula (I) (wherein R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, and R<SP>4</SP>are each -OR', -COOR', -CONR', -CHO, -CH<SB>2</SB>OR', -CN, -COONR' or the like; R' is hydrogen or a 1-4C alkyl group; m1 and m4 are each an integer of 0-4; and m2 and m3 are each an integer of 0-3). The complex, the photoelectric converter, and the dye sensitization solar cell comprise the quarter pyridine derivative. The complex comprises the quarter pyridine, and the photoelectric converter and the dye sensitization solar cell are also disclosed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel quarterpyridine derivative, a complex containing the same, a photoelectric conversion element, and a dye-sensitized solar cell.

  Solar cells that can be used by converting solar energy into electric energy are depleted of fossil energy such as petroleum, coal, or natural gas, which is a global reserve energy of concern in the 21st century, and is due to the large consumption of fossil energy. It has become a research and development issue to deal with global warming, which is accelerating carbon emissions, and abnormal weather attributed to it. Currently, solar cells using polycrystalline or amorphous silicon are mainly used, but there are problems such as high economic cost and high energy cost in the manufacturing process. On the other hand, a dye-sensitized solar cell that replaces a polycrystalline or amorphous silicon solar cell is described in B.A. O'Regan and M.M. As described in Gratzel, Nature 353, 737 (1991) or Japanese Patent No. 2664194, it has advantages such as low cost and simple structure and easy manufacture.

This dye-sensitized solar cell includes at least a carrier transport layer including an electrode having a photoelectric conversion element including a semiconductor layer including a dye, a counter electrode, and a liquid electrolyte. A semiconductor layer such as a TiO ₂ layer used for a photoelectric conversion element has a large band gap, and can only use ultraviolet light of sunlight alone, but the visible light of sunlight is enhanced by a sensitizing action of a dye contained in the semiconductor layer. Photoelectric conversion using light can be realized. Therefore, as a property required as a dye used in a dye-sensitized solar cell, for example,
(1) being able to absorb sunlight in a wide wavelength range;
(2) Electron transfer from the excited state to the semiconductor layer effectively occurs,
(3) After electrons are transferred to the semiconductor layer to become oxidized, they are quickly regenerated to the reduced form by the reducing agent in the carrier transport layer, and (4) degradation such as decomposition occurs under sunlight irradiation. It exists stably for a long time.

So far, various compounds have been reported as dyes for dye-sensitized solar cells. Among them, the most widely used is cis-di (thiocyano) -bis (2,2'-bipyridine- 4,4′-dicarboxylic acid) ruthenium (II) complex or tri (thiocyano) -2,2 ′, 2 ″ -terpyridine-4,4 ′, 4 ″ -tricarboxylic acid) ruthenium (II) complex. However, in order to use it as a practical dye-sensitized solar cell, it is necessary to achieve higher conversion efficiency. For this purpose, a high-performance dye that can absorb sunlight in a wider wavelength range. Is essential. Therefore, for example, JP-A-2002-193935 discloses pyridine tetramer (di (thiocyano) -2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine-4,4 ', 4'',4'''-tetracarboxylic acid) ruthenium (II) derivatives are disclosed. However, the synthesis method disclosed in Japanese Patent Application Laid-Open No. 2002-193935 has a problem that only the same four substituents bonded to the pyridine ring can be synthesized. Moreover, it did not describe about the performance of the dye-sensitized solar cell using this pigment | dye.
Japanese Patent No. 2664194 JP 2002-193935 A B. O'Regan and M.M. Gratzel, Nature 353, 737 (1991)

  An object of the present invention is to provide a novel quarterpyridine derivative, a complex containing the same, a photoelectric conversion element, and a dye-sensitized solar cell.

  The present invention is represented by the following formula (I):

In formula (I), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, C 1-40 And R ′ each independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms. In the formula (I), m1 and m4 each independently represents 0 to 4; Any one of the integers, m2 and m3 each independently represents any integer of 0 to 3, and is a quarterpyridine derivative characterized in that m1 + m2 + m3 + m4> 0.

The present invention is represented by the following formula (II):
ML (X ₁ ) (X ₂ ) ---------------- (II)
In the formula (II), M represents a central atom, L represents the above-mentioned quarterpyridine derivative, and X ₁ and X ₂ each independently represent Cl, Br, CN, NCS or NCO. is there. Here, in the formula (II), M represents Ru, Fe, Os, Cu, W, Cr, Mo, Ni, Pd, Pt, Co, Ir, Rh, Re, Mn or Zn, and X ₁ and X ₂ Each preferably represents NCS.

  The present invention is represented by the following formula (III):

In the formula (III), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, C 1-40 In the formula (III), m1 and m4 each independently represent 0 to 4 or an alkyl group, halogen or —COONR ′, wherein R ′ independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms. Any one of integers, m2 and m3 each independently represents an integer of 0 to 3, m1 + m2 + m3 + m4> 0, M represents Ru, and X ₁ and X ₂ each represent NCS It is a complex characterized by this.

  In addition, the present invention is a photoelectric conversion element including a semiconductor layer, and the semiconductor layer includes any one of the above complexes. Here, the semiconductor layer is preferably made of titanium oxide or tin oxide.

  Furthermore, the present invention provides a dye sensitizing method comprising: an electrode including any one of the photoelectric conversion elements described above; a counter electrode; and a carrier transport layer disposed between the electrode including the photoelectric conversion element and the counter electrode. Type solar cell.

  ADVANTAGE OF THE INVENTION According to this invention, a novel quarter pyridine derivative, the complex containing it, a photoelectric conversion element, and a dye-sensitized solar cell can be provided.

(Quarterpyridine derivative)
The quarterpyridine derivative of the present invention is represented by the following formula (I):

In formula (I), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, C 1-40 And R ′ each independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms. In the formula (I), m1 and m4 each independently represents 0 to 4; Any integer is represented, m2 and m3 each independently represent any integer of 0 to 3, and m1 + m2 + m3 + m4> 0.

In the formula (I), R ¹ , R ² , R ³ and R ⁴ may each represent different groups, and two or more of R ¹ , R ² , R ³ and R ⁴ represent the same group. It may be. In the formula (I), R ¹ , R ² , R ³ and R ⁴ are bonded at the positions where R ¹ is the first pyridine from the left, R ² is the second pyridine from the left, and R ³ is the second from the right. There is no particular limitation as long as the second pyridine and R ⁴ are bonded to the first pyridine from the right. “O” in the group of —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN and —COONR ′, which may be represented by R ¹ , R ² , R ³ and R ⁴ is Needless to say, oxygen represents "C" represents carbon, "N" represents nitrogen, and "H" represents hydrogen. When two or more of R ¹ , R ² , R ³ and R ⁴ represent a group containing “R ′”, each “R ′” may all represent the same, Not all may represent the same thing.

In Formula (I), m1 represents the number of R ¹ bonds, m2 represents the number of R ² bonds, m3 represents the number of R ³ bonds, and m4 represents the number of R ⁴ bonds. m1 and m4 each independently represents an integer of 0 to 4, and m2 and m3 each independently represents an integer of 0 to 3, but have a relationship of m1 + m2 + m3 + m4> 0 ( That is, m1, m2, m3 and m4 do not all represent 0 at the same time). When m1 represents an integer of 2 or more, all R ^{1 s} may be the same group or not all the same group, and R ¹ may be bonded to each other to form a ring. May be formed. Further, when m2 represents an integer of 2 or more, all R ^{2 s} may represent the same group, or may not all represent the same group, and R ² may be bonded to each other to form a ring. May be formed. Further, when m3 represents an integer of 2 or more, all R ^{3 s} may be the same group or not all the same group, and R ³ may be bonded to each other to form a ring. May be formed. When m4 represents an integer of 2 or more, all R ^{4 s} may represent the same group or may not all represent the same group, and R ⁴ may be bonded to each other to form a ring. May be formed.

(Complex)
The complex of the present invention is represented by the following formula (II):
ML (X ₁ ) (X ₂ ) ---------------- (II)
In the formula (II), M represents a central atom, L represents a quarterpyridine derivative represented by the above formula (I), and X ₁ and X ₂ each independently represents Cl, Br, CN, NCS or NCO. It is characterized by expressing. In the formula (II), the simple substance or compound represented by L, X ₁ and X ₂ is a ligand which coordinates to the central atom represented by M. Here, in the formula (II), M is Ru (ruthenium), Fe (iron), from the viewpoint of enabling coordination bonds with the ligands represented by L, X ₁ and X ₂ , respectively. Os (osmium), Cu (copper), W (tungsten), Cr (chromium), Mo (molybdenum), Ni (nickel), Pd (palladium), Pt (platinum), Co (cobalt), Ir (iridium), It preferably represents Rh (rhodium), Re (rhenium), Mn (manganese) or Zn (zinc), particularly preferably represents Ru, Fe, Os or Cu, and most preferably represents Ru. In the formula (II), X ₁ and X ₂ each preferably represent NCS. When X ₁ and X ₂ each represent NCS, a reverse current from the semiconductor layer is effectively suppressed in a dye-sensitized solar cell in which the complex represented by formula (II) is contained as a dye in the semiconductor layer. Tend to be able to.

  The complex of the present invention is represented by the following formula (III):

In the formula (III), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, C 1-40 In the formula (III), m1 and m4 each independently represent 0 to 4 or an alkyl group, halogen or —COONR ′, wherein R ′ independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms. Any integer is represented, m2 and m3 each independently represent any integer of 0 to 3, and m1 + m2 + m3 + m4> 0.

In the formula (III), R ¹ , R ² , R ³ and R ⁴ may each represent different groups, and two or more of R ¹ , R ² , R ³ and R ⁴ represent the same group. It may be. In Formula (III), R ¹ , R ² , R ^3, and R ⁴ are bonded at positions where R ¹ is the first pyridine from the left, R ² is the second pyridine from the left, and R ³ is the second from the right. There is no particular limitation as long as the second pyridine and R ⁴ are bonded to the first pyridine from the right. “O” in the group of —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN and —COONR ′, which may be represented by R ¹ , R ² , R ³ and R ⁴ is Needless to say, oxygen represents "C" represents carbon, "N" represents nitrogen, and "H" represents hydrogen. When two or more of R ¹ , R ² , R ³ and R ⁴ represent a group containing “R ′”, each “R ′” may all represent the same, Not all may represent the same thing.

In Formula (III), m1 represents the number of R ¹ bonds, m2 represents the number of R ² bonds, m3 represents the number of R ³ bonds, m4 represents the number of R ⁴ bonds, m1 and m4 each independently represents an integer of 0 to 4, and m2 and m3 each independently represents an integer of 0 to 3, but have a relationship of m1 + m2 + m3 + m4> 0 ( That is, m1, m2, m3 and m4 do not all represent 0 at the same time). When m1 represents an integer of 2 or more, all R ^{1 s} may be the same group or not all the same group, and R ¹ may be bonded to each other to form a ring. May be formed. Further, when m2 represents an integer of 2 or more, all R ^{2 s} may represent the same group, or may not all represent the same group, and R ² may be bonded to each other to form a ring. May be formed. Further, when m3 represents an integer of 2 or more, all R ^{3 s} may be the same group or not all the same group, and R ³ may be bonded to each other to form a ring. May be formed. When m4 represents an integer of 2 or more, all R ^{4 s} may represent the same group or may not all represent the same group, and R ⁴ may be bonded to each other to form a ring. May be formed. In Formula (III), M represents Ru, and X ₁ and X ₂ each represent NCS.

  Further, more preferred specific examples of the complex represented by the formula (III) include compounds represented by the following formula (IV), formula (V) and formula (VI).

(Photoelectric conversion element)
The photoelectric conversion element of the present invention includes a semiconductor layer, and the semiconductor layer includes any one of the above complexes. Here, the semiconductor layer is formed on, for example, a conductive support. The method for forming this semiconductor layer is not particularly limited, and a known method can be used. For example, the following methods (i) to (iv) can be used.
(I) A method of forming a semiconductor layer on a conductive support by applying a suspension containing semiconductor fine particles constituting the semiconductor layer onto a conductive support, drying and firing.
(Ii) A method of forming a semiconductor layer on a conductive support by a CVD method using a desired source gas, an MOCVD method, or the like.
(Iii) A method of forming a semiconductor layer on a conductive support by a PVD method such as an evaporation method using a raw material solid or a sputtering method.
(Iv) A method of forming a semiconductor layer on a conductive support by a sol-gel method, a method using an electrochemical redox reaction, or the like.

Examples of the material constituting the semiconductor layer include titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, zirconium oxide, cerium oxide, silicon oxide, aluminum oxide, nickel oxide, tungsten oxide, barium titanate, One or more kinds of strontium titanate, cadmium sulfide, lead sulfide, zinc sulfide, indium phosphide or copper-indium sulfide (for example, CuInS ₂ ) can be used. Especially, it is preferable that a semiconductor layer consists of a titanium oxide or a tin oxide from a viewpoint of favorable stability and safety | security.

  The semiconductor constituting the semiconductor layer may be either single crystal or polycrystalline, but is preferably polycrystalline from the viewpoint of stability, difficulty in crystal growth, and manufacturing cost. The semiconductor layer is preferably composed of semiconductor fine particles having a particle size of 1 nm to 1000 nm. Further, two or more kinds of semiconductor fine particles having different particle diameters may be used. When two or more kinds of semiconductor fine particles having different particle diameters are used, the material of each semiconductor fine particle may be the same or different.

  The semiconductor layer contains the complex of the present invention. Here, as a method for containing the complex of the present invention in the semiconductor layer, for example, a method of immersing the semiconductor layer in an organic solvent in which the complex of the present invention is dissolved or an organic solvent in which the complex of the present invention is dissolved is applied to the semiconductor layer. There are methods. By using these methods, the complex of the present invention can be adsorbed in the semiconductor layer and contained in the semiconductor layer.

(Dye-sensitized solar cell)
The present invention provides a dye-sensitized solar comprising the electrode including the photoelectric conversion element of the present invention, a counter electrode, and a carrier transport layer disposed between the electrode including the photoelectric conversion element and the counter electrode. It is a battery. Here, the electrode including the photoelectric conversion element of the present invention can be obtained, for example, by forming the above-described photoelectric conversion element of the present invention on a conductive support. As the conductive support used in the present invention, for example, a conductive support itself having conductivity, such as a transparent conductive film made of metal, SnO ₂ (tin oxide), ITO, CuI, ZnO, or the like is used. be able to. In addition, as the conductive support used in the present invention, a support in which a conductive layer is formed on the surface of an insulating substrate made of glass, plastic, a transparent polymer sheet, or the like can be used. Here, the conductive layer can be obtained by forming a conductive material such as gold, platinum, silver, copper, aluminum, indium, conductive carbon, ITO, or SnO _{2 on} the surface of the insulating substrate by a known method. it can. As the transparent polymer sheet, for example, tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PA), polyether imide (PEI), phenoxy resin, or the like. Can be used.

The counter electrode used in the present invention is not particularly limited as long as it is conductive. Examples of the counter electrode include an n-type or p-type semiconductor, gold, platinum, silver, copper, aluminum, indium, titanium, tantalum or A metal such as tungsten or a transparent conductive film such as SnO ₂ , ITO, CuI, or ZnO can be used. Moreover, as a counter electrode used for this invention, what formed the conductive layer on the surface of the insulated substrate which consists of glass, a plastic, or a transparent polymer sheet | seat etc. can also be used. Here, the conductive layer can be obtained by forming a conductive material such as gold, platinum, silver, copper, aluminum, indium, conductive carbon, ITO, or SnO ₂ using a known method. As the transparent polymer sheet, for example, tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PA), polyether imide (PEI), phenoxy resin, or the like. Can be used. Further, a protective layer made of platinum or the like may be formed on the surface of the conductive layer of the counter electrode.

Examples of the carrier transport layer used in the present invention include a hole transport material such as polyvinyl carbazole or triphenylamine, an electron transport material such as tetranitrophlorenone, a conductive polymer such as polythiophene or polypyrrole, a liquid electrolyte, or a polymer. An ionic conductor such as an electrolyte, copper iodide, or copper thiocyanate can be used. Especially, it is preferable to use an ionic conductor as a carrier transport layer used for this invention, and it is more preferable to use the liquid electrolyte containing a redox electrolyte. Here, as the redox electrolyte, for example, a redox species such as I ⁻ / I ³⁻ , Br ²⁻ / Br ³⁻ , Fe ²⁺ / Fe ^3+, or quinone / hydroquinone is included. Things can be used. Examples of the redox species include a combination of metal iodide such as lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), or calcium iodide (CaI ₂ ) and iodine (I ₂ ). A combination of tetraalkylammonium salts such as tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI) or tetrahexylammonium iodide (THAI) with iodine, or bromide lithium (LiBr), sodium bromide (NaBr), a combination of a metal bromide and bromine such as potassium bromide (KBr) or calcium bromide (CaBr ₂₎ are preferred, the combination of LiI and I ₂ among these Preferred. The electrolyte concentration in the liquid electrolyte is preferably in the range of 0.1 to 1.5 mol / liter, particularly preferably in the range of 0.1 to 0.7 mol / liter.

  As the solvent for the liquid electrolyte, carbonate compounds such as propylene carbonate, nitrile compounds such as acetonitrile, alcohols such as ethanol, water, or aprotic polar substances can be used. Among these, carbonate compounds and / or Or it is especially preferable to use a nitrile compound. These solvents can also be used as a mixture of two or more.

  Further, an additive may be added to the liquid electrolyte. Here, examples of the additive include nitrogen-containing aromatic compounds such as t-butylpyridine (TBP), dimethylpropylimidazole iodide (DMPII), methylpropylimidazole iodide (MPII), and ethylmethylimidazole iodide (EMII). ), Imidazole salts such as ethylimidazole iodide (EII) or hexylmethylimidazole iodide (HMII) can be used.

  Examples of the polymer electrolyte include polymer compounds such as polyethylene oxide, polypropylene oxide, polyethylene succinate, poly-β-propiolactone, polyethyleneimine, polyalkylene sulfide, and cross-linked products thereof, polyphosphazene, polysiloxane. , Polyvinyl alcohol, polyacrylic acid, polyalkylene oxide, and the like, which are obtained by adding a polyether segment or an oligoalkylene oxide structure as a side chain to a functional group of a polymer, or a copolymer thereof. Those having a structure as a side chain and those having a polyether segment as a side chain are preferred.

  In FIG. 1, the typical expanded sectional view of a preferable example of the dye-sensitized solar cell of this invention is shown. The dye-sensitized solar cell of the present invention is adsorbed on the surface of the semiconductor particle 6, the conductive support 9 in which the transparent conductive film 7 is formed on the insulating substrate 8, the semiconductor layer composed of a plurality of semiconductor particles 6. The complex 5 of the present invention, the carrier transport layer 4, and the counter electrode 12 in which the transparent conductive film 2 and the platinum layer 3 are sequentially formed on the insulating substrate 1 are included. Here, the photoelectric conversion element 10 of the present invention is formed from the complex 5 of the present invention and a semiconductor layer composed of a plurality of semiconductor particles 6, and the photoelectric conversion element is formed from the photoelectric conversion element 10 and the conductive support 9. An electrode 11 is formed.

  When sunlight enters the dye-sensitized solar cell of the present invention having such a configuration, the complex 5 absorbs sunlight and is excited. Electrons generated by this excitation move to the semiconductor particles 6, and then move from the transparent conductive film 7 to the transparent conductive film 2 of the counter electrode 12 through an external circuit. Then, the electrons reduce the redox system in the carrier transport layer 4 from the transparent conductive film 2 through the platinum layer 3. On the other hand, the complex 5 in which electrons are transferred to the semiconductor particles 6 is in an oxidant state, but this oxidant is reduced by the redox system in the carrier transport layer 4 and returns to the original state. . Through the flow of electrons in such a process, light energy is continuously converted into electrical energy.

Example 1
(1) Synthesis of complex (a) Synthesis of 2-tributylstannyl-4-picoline

To a solution of 2-bromopicoline (20.0 g, 116.3 mmol) in anhydrous THF (200 mL, −78 ° C.), 1.6M n-butyllithium in hexane (72.6 mL, 116.3 mmol) was added dropwise. And added. The reaction was stirred at −78 ° C. for 30 minutes, then tributyltin chloride (31.6 mL, 116.3 mmol) was added and stirred for an additional 60 minutes before warming to room temperature. NH ₄ Cl saturated aqueous solution (100 mL) was added to the reaction system, and the phases were separated. The aqueous phase was extracted 3 times with diethyl ether (200 mL). The combined organic phases were dried over sodium sulfate and the solvent was removed under reduced pressure. The resulting oil was purified by alumina column chromatography (ethyl acetate / hexane = 1/20 (V / V)). Yield: 83%. The analysis results are as follows. C ₁₈ H ₃₃ NSn: Calculated: C, 56.57; H, 8.70; N, 3.67; Found: C, 56.42; H, 8.72; N, 3.44. MS (ESIMS): m / z: 383.

  (B) Synthesis of 6-bromo-4'-methyl-2,2'-bipyridine

2-Tributylstannyl-4-picoline (6.23 g, 16.3 mmol), 2,6-dibromopyridine (9.08 g, 38.7 mmol) and Pd (PPh ₃ ) ₄ (0.613 g, 0. 003 equivalents) was refluxed in toluene (150 mL) under an argon atmosphere for 72 hours. Upon cooling to room temperature, the reaction system is concentrated, and 6M HCl (50 mL) is added and extracted three times with methylene chloride (100 mL), whereby components such as raw material 2,6-dibromopyridine and subcomponent terpyridine are removed. Removed. The combined aqueous phases were neutralized by adding aqueous ammonia (28%). Subsequently, an excess amount of NiCl ₂ .6H ₂ O was added, and extraction with methylene chloride (100 mL) three times gave a brown solution. The brown solution was dried over Na ₂ SO ₄ and the solvent was removed under reduced pressure to give a brown oil. The brown oil was purified by silica gel column chromatography (ethyl acetate / hexane = 1/4 (V / V)). Yield: 69%. C ₁₁ H ₉ N ₂ Br: Calculated: C, 53.04; H, 3.64 ; N, 11.25; Found: C, 53.12; H, 3.62 ; N, 11.21. MS (ESIMS): m / z: 250.

  (C) Synthesis of 6-bromo-4'-carboxy-2,2'-bipyridine

To concentrated sulfuric acid (30 mL), 6-bromo-4′-methyl-2,2′-bipyridine (13.5 g, 40.1 mmol) was added and stirred well and the solution was cooled to 0 ° C. Subsequently, potassium dichromate (41.6 g, 120.3 mmol) was added to the solution in small portions. Then, it maintained at 70-80 degreeC for 4 hours. After cooling to room temperature, the mixture was further reacted for 10 hours. After the reaction, the reaction system was poured into ice water (1 L) to precipitate a white solid. The suspension was filtered and washed with water to give a pale yellow solid. This pale yellow solid was added to water and solid potassium hydroxide was added to the suspension with vigorous stirring until the solution was completely basic. This suspension was filtered, and the filtrate was oxidized with concentrated hydrochloric acid to precipitate a white solid again. The suspension was filtered through a membrane and washed with water, methanol and ether. Yield: 90.6%. _{C 13 H 7 N 2 BrO 2} : Calculated: C, 47.34; H, 2.53 ; N, 11.47; Found: C, 47.44; H, 2.47 ; N, 11.23 . MS (ESIMS): m / z: 279.

  (D) Synthesis of 6-bromo-4'-ethoxycarbonyl-2,2'-bipyridine

To a suspension of 6-bromo-4′-carboxy-2,2′-bipyridine (8.8 g, 31.5 mmol) in absolute ethanol solution (200 mL) was added 20 mL concentrated sulfuric acid. The mixture was refluxed for 4 hours to obtain a clear solution and then cooled to room temperature. Then 25% aqueous ammonia was added until pH> 7. Subsequently, an excess amount of NiCl ₂ .6H ₂ O was added, and extraction with methylene chloride (100 mL) three times gave a light brown solution. The pale brown solution was dried over Na ₂ SO ₄ , filtered through filter paper, and the filtrate was concentrated under reduced pressure to obtain a pale brown solid. Furthermore, it refine | purified by recrystallizing with ethanol. Yield: 90%. The analysis results are as follows. _{C 13 H 11 BrN 2 O 2} : Calculated: C, 50.84; H, 3.61 ; N, 9.12; Found: C, 50.65; H, 3.92 ; N, 9.33 . MS (ESIMS): m / z: 307.0.

  (E) Synthesis of 4,4 ""-diethoxycarbonyl-2,2 ': 6', 2 ": 6", 2 ""-quaterpyridine

To a mixture of NiBr ₂ (PPh ₃ ) ₂ (100 mg, 0.144 mmol), Zn (120 mg, 1.89 mmol) and n-Bu ₄ NI (86 mg, 0.233 mmol) was added 20 mL of THF solution and green color was added. When the solution turned into a black solution, 6-bromo-4′-ethoxycarbonyl-2,2′-bipyridine (70 mg, 0.229 mmol) and THF solution (20 mL) were added and reacted at 50 ° C. for 16 hours. It was. As soon as 25% aqueous ammonia (60 mL) was added, it became a colorless solution. The combined organic phases were washed 3 times with water (100 mL) and 1 time with saturated aqueous NaCl (100 mL). The organic phase was further dried over Na ₂ SO ₄ and concentrated. The residual liquid was dissolved with concentrated hydrochloric acid (20 mL) and extracted with methylene chloride (50 mL) to remove unreacted raw materials. The aqueous phase combined with concentrated hydrochloric acid after removal of unreacted raw materials was neutralized with Na ₂ CO ₃ and extracted with methylene chloride (100 mL). Subsequently, the organic phase was dried over Na ₂ SO ₄ and concentrated to give a white solid. Further purification by column chromatography on silica using hexane / ethyl acetate (4/1, v / v). Yield: 38.6%. The analysis results are as follows. _{C 26 H 22 N 4 O 4} : Calculated: C, 68.71; H, 4.88 ; N, 12.33; Found: C, 68.67; H, 4.70 ; N, 12.33 . MS (FABMS): m / z: 454.5.

(F) Synthesis of Ru (4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ″ ′-quarterpyridine) Cl ₂

[Ru (p-cymene) Cl ₂ ] ₂ (21.6 mg, 0.035 mmol) was dissolved while heating an ethanol solution (20 mL) under an argon atmosphere, and then 4,4 ′ ″-diethoxycarbonyl- 2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-Quotapyridine (32 mg, 0.070 mmol) was added and the reaction was refluxed for 6 hours to give a black suspension. Got. This was cooled to room temperature, filtered, and purified by washing with ethanol. Yield: 98%. The analysis results are as follows. C ₂₆ H ₂₂ N ₄ Cl ₂ O ₄ Ru: Calculated: C, 49.85; H, 3.54; N, 8.94; Cl, 11.32; Found: C, 49.84; H, 3.70; N, 8.93; Cl, 11.50. MS (ESIMS): m / z: 626.5.

(G) Synthesis of Ru (2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine-4,4 ′ ″-dicarboxylic acid) (NCS) ₂

Ru (4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) Cl ₂ (43.2 mg, 0.069 mmol) and Excess NH ₄ SCN (350 mg, 4.6 mmol) was refluxed in a mixed solvent of DMF (35 mL) and water (15 mL) for 3 hours, triethylamine (10 mL) was added, and the reaction system was further refluxed for 24 hours. It was. Upon cooling to room temperature, the reaction was concentrated and purified by reprecipitation with 0.5M hydrochloric acid. Yield: 85%. The analysis results are as follows. _{C 24 H 14 N 6 O 4} RuS 2: Calculated: C, 46.82; H, 2.29 ; N, 13.65; Found: C, 46.67; H, 2.35 ; N, 13 .33. MS (ESIMS): m / z: 615.6.

(2) Manufacture of an electrode including a photoelectric conversion element and a dye-sensitized solar cell First, a commercially available titanium oxide paste (manufactured by Solaronix, trade name: Ti-Nanoxide D, average particle size: 13 nm) is transparent by a doctor blade method. From a titanium oxide film having a film thickness of 16 μm, it was applied to the surface of a glass substrate (manufactured by Nippon Sheet Glass Co., Ltd.) on which an SnO ₂ film as a conductive film was deposited, pre-dried at 100 ° C. for 10 minutes and then baked at 500 ° C. for 30 minutes A semiconductor layer was formed.

Next, the complex obtained in Example 1 (complex represented by the above formula (IV)) was dissolved in ethanol so as to have a concentration of 5 × 10 ⁻⁴ mol / L to prepare a solution. Next, the glass plate on which the above titanium oxide film is formed is immersed in this solution for 5 hours, and the complex obtained in Example 1 is adsorbed on the titanium oxide film as a dye, so that the photoelectric conversion element having the configuration shown in FIG. The electrode containing was produced.

A counter electrode was formed by depositing a platinum film of 300 nm on a glass substrate on which a SnO ₂ film having the same structure as described above was deposited. A liquid electrolyte was injected between the counter electrode and the electrode including the photoelectric conversion element, and the side surfaces thereof were sealed with resin. Liquid electrolyte in acetonitrile (Aldrich), (Aldrich) 0.1 M of LiI, I ₂ (Aldrich) in 0.05 M, 0.5M of t- butylpyridine (Aldrich) and 0 A solution in which 6 M dimethylpropylimidazolium iodide (manufactured by Shikoku Kasei Co., Ltd.) was dissolved was used. Thereafter, a lead wire was attached to each electrode to obtain a dye-sensitized solar cell having the configuration shown in FIG.

(Example 2)
(1) Synthesis of complex (a) Synthesis of 2,6-dihydroxy-4-methyl-pyridine

A mixture of 2,6-dihydroxy-4-methyl-3-pyridinecarbonitrile (8.65 g, 57.6 mmol), concentrated H ₂ SO ₄ (24 mL) and water (20 mL) was heated at reflux for 5 hours. . The mixture was cooled with ice and neutralized with solid NaHCO ₃ . The precipitate was filtered, washed with water and Et ₂ O, and dried under vacuum, 2,6-dihydroxy-4-methyl - give mixture and the free acid of pyridine (not decarboxylated). This mixture was used without further purification for the next reaction step. Yield: 85%. The analysis results are as follows. C ₂₁ H ₃₇ NO _2: Calculated: C, 75.17; H, 11.12 ; N, 4.17; O, 9.54; Found: C, 75.03; H, 11.09 ; N 4.25; O, 9.38. MS (ESIMS): m / z: 335.3.

  (B) Synthesis of 2,6-dibromo-4-methyl-pyridine

2,6-Dihydroxy-4-methyl-pyridine (2.48 g, 20.0 mmol) and POBr ₃ (8.60 g, 30.0 mmol) are powdered and autoclaved at a temperature of 180-190 ° C. for 5 hours. Melted together. After cooling, the mixture was quenched with water and filtered. The combined filtrate was extracted 3 times with methylene chloride (100 mL). Extraction with a Soxhlet extractor in methylene chloride was performed for 24 hours to obtain a yellow solution. The yellow solution was dried over Na ₂ SO ₄ and the solvent was removed under reduced pressure. The residue was purified by column chromatography on silica using hexane / EtOAc (4/1, v / v). Yield: 76.7%. The analysis results are as follows. C ₆ H ₅ Br ₂ N: Calculated: C, 28.72; H, 2.01; Br, 63.69; N, 5.58; Found: C, 28.84; H, 2.00; Br, 69.50; N, 5.70. MS (ESIMS): m / z: 251.2.

  (C) Synthesis of 6-bromo-4,4'-dimethyl-2,2'-bipyridine

The title compound was synthesized by the same procedure as in Step (b) described in Example 1, except that 2,6-dibromopyridine was changed to 2,6-dibromo-4-methyl-pyridine. Yield: 60%. C ₁₂ H ₁₁ N ₂ Br: Calculated: C, 54.77; H, 4.21 ; N, 10.65; Found: C, 54.80; H, 3.92 ; N, 11.00. MS (ESIMS): m / z: 263.1.

  (D) Synthesis of 6-bromo-2,2'-bipyridine-4,4'-dicarboxylic acid

Step (c) described in Example 1 except that 6-bromo-4′-methyl-2,2′-bipyridine was changed to 6-bromo-4,4′-dimethyl-2,2′-bipyridine. The title compound was synthesized by a procedure similar to that described above. Yield: 85%. _{C 12 H 7 N 2 BrO 4} : Calculated: C, 44.61; H, 2.18 ; N, 8.67; Found: C, 44.44; H, 2.18 ; N, 8.57 . MS (FABMS): m / z: 323.1.

  (E) Synthesis of 6-bromo-4,4'-diethoxycarbonyl-2,2'-bipyridine

Step (d) described in Example 1 except that 6-bromo-4′-carboxy-2,2′-bipyridine was changed to 6-bromo-2,2′-bipyridine-4,4′-dicarboxylic acid. The title compound was synthesized according to the same procedure as for). Yield: 95%. The analysis results are as follows. _{C 16 H 15 BrN 2 O 4} : Calculated: C, 50.68; H, 3.99 ; N, 7.39; Found: C, 50.65; H, 3.89 ; N, 7.33 . MS (FABMS): m / z: 379.0.

  (F) Synthesis of 6-tributylstannyl-4,4'-dimethyl-2,2'-bipyridine

The title compound was synthesized by the same procedure as in step (a) described in Example 1, except that 2-bromopicoline was changed to 6-bromo-4,4′-dimethyl-2,2′-bipyridine. . Yield: 78%. The analysis results are as follows. C ₂₄ H ₃₈ N ₂ Sn: Calculated: C, 60.91; H, 8.09 ; N, 5.92; Found: C, 60.88; H, 8.02 ; N, 5.95. MS (FABMS): m / z: 473.4.

  (G) Synthesis of 4,4'-diethoxycarbonyl-4 ", 4" "-dimethyl-2,2 ': 6', 2": 6 ", 2" "-quarterpyridine

The steps described in Example 1 except that 6-bromo-4′-ethoxycarbonyl-2,2′-bipyridine was changed to 6-bromo-4,4′-diethoxycarbonyl-2,2′-bipyridine. The title compound was synthesized by the same procedure as (e). Yield: 54%. The analysis results are as follows. _{C 28 H 26 N 4 O 4} : Calculated: C, 69.69; H, 5.43 ; N, 11.61; Found: C, 69.71; H, 5.62 ; N, 11.21 . MS (FABMS): m / z: 483.5.

(H) Ru (4,4′-diethoxycarbonyl-4 ″, 4 ′ ″-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) Cl Synthesis of ₂

4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quaterpyridine is converted to 4,4′-diethoxycarbonyl-4 ″, 4 ′ ″ -Dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-The procedure was similar to step (f) described in Example 1 except that it was changed to quarterpyridine. The title compound was synthesized. Yield: 96%. The analysis results are as follows. C ₂₈ H ₂₆ N ₄ Cl ₂ O ₄ Ru: Calculated: C, 51.38; H, 4.00; N, 8.56; Cl, 10.83; Found: C, 51.84; H, 3.90; N, 8.53; Cl, 10.70. MS (ESIMS): m / z: 654.7.

(I) Ru (4 ″, 4 ′ ″-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine-4,4′-dicarboxylic acid) (NCS ₂ ) Synthesis of ₂

Ru (4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) Cl ₂ is replaced with Ru (4,4′-diethoxycarbonyl). -4 ″, 4 ′ ″-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) described in Example 1 except that it was changed to Cl _2. The title compound was synthesized by the same procedure as in step (g). Yield: 88%. The analysis results are as follows. C ₂₆ H ₁₈ N ₆ O ₄ RuS ₂ : Calculated value: C, 48.52; H, 2.82; N, 13.06; Found: C, 48.48; H, 2.85; N, 13 .00. MS (ESIMS): m / z: 644.0.

(2) Production of an electrode including a photoelectric conversion element and a dye-sensitized solar cell The complex obtained in Example 2 (represented by the above formula (V)) instead of the complex represented by the above formula (IV) Except for using the complex), an electrode including a photoelectric conversion element and a dye-sensitized solar cell were produced in the same procedure as in Example 1.

(Example 3)
(1) Synthesis of complex (a) Synthesis of 2,6-dibromo-4-pyridine-carboxylic acid

The title compound was prepared by a procedure similar to step (b) described in Example 2, except that 2,6-dihydroxy-4-methyl-pyridine was changed to 2,6-dihydroxy-4-pyridine-carboxylic acid. Synthesized. Yield: 64%. The analysis results are as follows. _{C 6 H 3 Br 2 NO 2} : Calculated: C, 25.65; H, 1.08 ; Br, 56.89; N, 4.99; O, 11.39; Found: C, 25.58 H, 1.11; Br, 56.87; N, 5.98; O, 11.35. MS (ESIMS): m / z: 280.7.

  (B) Synthesis of 2,6-dibromo-4-ethoxycarbonyl-pyridine

According to the same procedure as in step (d) described in Example 1, except that 6-bromo-4′-carboxy-2,2′-bipyridine was changed to 2,6-dibromo-4-pyridine-carboxylic acid. The title compound was synthesized. Yield: 84%. The analysis results are as follows. _{C 8 H 7 Br 2 NO 2} : Calculated: C, 31.10; H, 2.28 ; Br, 51.73; N, 4.53; O, 10.36; Found: C, 31.30 H, 2.29; Br, 51.87; N, 4.40; O, 10.39. MS (ESIMS): m / z: 309.1.

  (C) Synthesis of 6-bromo-4'-methyl-4-ethoxycarbonyl-2,2'-bipyridine

The title compound was synthesized by the same procedure as in Step (b) described in Example 1, except that 2,6-dibromopyridine was changed to 2,6-dibromo-4-ethoxycarbonyl-pyridine. Yield: 60%. The analysis results are as follows. _{C 14 H 13 N 2 BrO 2} : Calculated: C, 52.36; H, 4.08 ; Br, 24.88; N, 8.72; O, 9.96; Found: C, 52.40 H, 3.98; Br, 25.00; N, 8.70; O, 10.00. MS (ESIMS): m / z: 321.2.

  (D) Synthesis of 4 ", 4" "-diethoxycarbonyl-4,4'-dimethyl-2, 2": 6 ', 2 ": 6", 2 ""-quarterpyridine

As described in Example 1, except that 6-bromo-4′-ethoxycarbonyl-2,2′-bipyridine was changed to 6-bromo-4′-methyl-4-ethoxycarbonyl-2,2′-bipyridine. The title compound was synthesized by the same procedure as in step (e). Yield: 62%. The analysis results are as follows. _{C 28 H 26 N 4 O 4} : Calculated: C, 69.69; H, 5.43 ; N, 11.61; Found: C, 69.69; H, 5.52 ; N, 11.51 . MS (FABMS): m / z: 483.0.

(E) Ru (4 ″, 4 ′ ″-diethoxycarbonyl-4,4′-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) Cl Synthesis of ₂

4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quaterpyridine is converted to 4 ″, 4 ′ ″-diethoxycarbonyl-4, 4′-Dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-According to the procedure similar to step (f) described in Example 1 except that it is changed to quarterpyridine. The title compound was synthesized. Yield: 94%. The analysis results are as follows. C ₂₈ H ₂₆ N ₄ Cl ₂ O ₄ Ru: Calculated: C, 51.38; H, 4.00; N, 8.56; Cl, 10.83; Found: C, 51.54; H, 3.95; N, 8.53; Cl, 10.73. MS (ESIMS): m / z: 654.5.

(F) Ru (4,4 ′ ″-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine-4,4 ″ -dicarboxylic acid) (NCS) Synthesis of ₂

Ru (4,4 ′ ″-diethoxycarbonyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) Cl ₂ is replaced with Ru (4 ″, 4 ′ ″. -Diethoxycarbonyl-4,4′-dimethyl-2,2 ′: 6 ′, 2 ″: 6 ″, 2 ′ ″-quarterpyridine) as described in Example 1 except that it was changed to Cl _2. The title compound was synthesized by the same procedure as in step (g). Yield: 67%. The analysis results are as follows. C ₂₆ H ₁₈ N ₆ O ₄ RuS ₂ : Calculated value: C, 48.52; H, 2.82; N, 13.06; Found: C, 48.50; H, 2.85; N, 13 .04. MS (ESIMS): m / z: 644.0.

(2) Production of an electrode including a photoelectric conversion element and a dye-sensitized solar cell The complex obtained in Example 3 (represented by the above formula (VI)) instead of the complex represented by the above formula (IV) Except for using the complex), an electrode including a photoelectric conversion element and a dye-sensitized solar cell were produced in the same procedure as in Example 1.

(Comparative Example 1)
An electrode including a photoelectric conversion element and a dye-sensitized solar cell in the same procedure as in Example 1 except that the complex represented by the following formula (VII) described in JP-A-2002-193935 is used as a dye. Was made.

(Battery characteristics test)
A battery characteristic test was conducted to measure the conversion efficiency η of the dye-sensitized solar cells of Examples 1 to 3 and Comparative Example 1. The battery characteristic test was performed by using a solar simulator (manufactured by Wacom) and irradiating 100 mV / cm ² of artificial sunlight from a xenon lamp through an AM filter (AM-1.5). The current-voltage characteristics were measured using an IV tester, the open circuit voltage Voc (V), the short circuit current Jsc (mA / cm ² ), the fill factor F.V. F. The conversion efficiency η (%) immediately after the start of startup was obtained. The results are shown in Table 1.

  As is clear from Table 1, the conversion efficiency η of the dye-sensitized solar cells of Examples 1 to 3 was higher than that of Comparative Example 1. Further, in the dye-sensitized solar cells of Examples 2 to 3 in which the complexes in which two carboxylic acid groups of the complex of Comparative Example 1 were substituted with methyl groups were used as the dyes, the conversion efficiency η was further increased.

  It should be understood that the embodiments, synthesis examples and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  When the ruthenium complex of the present invention formed using the quarterpyridine derivative of the present invention is used as a dye of a dye-sensitized solar cell, the dye sensitization has a higher conversion efficiency than a conventionally known ruthenium complex. Type solar cell can be produced.

It is a typical expanded sectional view of a preferable example of the dye-sensitized solar cell of the present invention.

Explanation of symbols

  1,8 Insulating substrate, 2,7 Transparent conductive film, 3 Platinum layer, 4 Carrier transport layer, 5 Complex, 6 Semiconductor particles, 9 Conductive support, 10 Photoelectric conversion element, 11 Electrode including photoelectric conversion element, 12 pairs electrode.

Claims (7)

Represented by the following formula (I):

In the formula (I), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, carbon number 1 to Represents 40 alkyl groups, halogen or -COONR ';
Each R ′ independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms;
In the formula (I), m1 and m4 each independently represent an integer of 0 to 4, m2 and m3 each independently represent an integer of 0 to 3, and m1 + m2 + m3 + m4> 0. A quarterpyridine derivative, characterized in that Represented by the following formula (II):
ML (X ₁ ) (X ₂ ) ---------------- (II)
In the formula (II), M represents a central atom, L represents a quarterpyridine derivative according to claim 1, and X ₁ and X ₂ each independently represent Cl, Br, CN, NCS or NCO. Characteristic complex. M represents Ru, Fe, Os, Cu, W, Cr, Mo, Ni, Pd, Pt, Co, Ir, Rh, Re, Mn, or Zn, and X ₁ and X ₂ each represent NCS. The complex according to claim 2, wherein Represented by the following formula (III):

In the formula (III), R ¹ , R ² , R ³ and R ⁴ are each independently —OR ′, —COOR ′, —CONR ′, —CHO, —CH ₂ OR ′, —CN, carbon number 1 to Represents 40 alkyl groups, halogen or -COONR ';
Each R ′ independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms;
In the formula (III), m1 and m4 each independently represents an integer of 0 to 4, m2 and m3 each independently represents an integer of 0 to 3, and m1 + m2 + m3 + m4> 0. Wherein M represents Ru and X ₁ and X ₂ each represent NCS.   A photoelectric conversion element comprising a semiconductor layer, wherein the semiconductor layer contains the complex according to claim 2.   The photoelectric conversion element according to claim 5, wherein the semiconductor layer is made of titanium oxide or tin oxide.   A dye-sensitized type, comprising: an electrode comprising the photoelectric conversion element according to claim 5 or 6; a counter electrode; and an electrode comprising the photoelectric conversion element and a carrier transport layer disposed between the counter electrode. Solar cell.

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