JP2008274082A - Dye containing silicon-containing substituents and dye-sensitized solar cell using the dye - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel tetraphenylporphyrin derivative having a plurality of silicon-containing substituents at the phenyl groups at the meso position, to provide a porphyrin complex, and to provide dye-sensitized solar cells using them as dyes. <P>SOLUTION: The porphyrin derivative is represented by formula (1) and is synthesized by, for example, a method (the so-called Lindsey method) comprising cyclizing a silicon-containing-substituent-containing benzaldehyde derivative, a carboxylic-ester-containing benzaldehyde derivative, and pyrrole by dehydrative condensation in the presence of an acid catalyst and chemically oxidizing the product of cyclization. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel porphyrin derivative and porphyrin complex, and a dye-sensitized solar cell using these as a dye. Specifically, the present invention relates to porphyrin derivatives and porphyrin complexes used as sensitizing dyes with good photoelectric conversion efficiency in light energy conversion, particularly in dye-sensitized solar cells.

  In recent years, environmental factors such as depletion of fossil fuels and generation of global warming gas due to combustion thereof, and economic factors such as fluctuations in crude oil prices have triggered, and research on cheap and clean alternative energy has become active. Among them, many researches on solar cell technology development that promotes the effective use of sunlight have been conducted mainly on silicon solar cells. As a result, silicon solar cells are spreading all over the world, and it is predicted that the supply of high-purity silicon crystals will not be able to meet the increase in demand in the near future. Such a silicon solar cell has an advantage that it is excellent in photoelectric conversion efficiency and can use silicon dioxide present almost infinitely as a raw material. However, in reality, silicon crystals purified to high purity from silicon dioxide must be produced, and enormous power is required. In addition, the process for manufacturing the solar cell requires a high-temperature treatment and a vacuum device, and as a result, has a problem of high cost.

  Therefore, development of a solar cell that does not require these large-scale facilities and energy, has a simple element structure, and can be manufactured at low cost is promoted. In 1991, a dye-sensitized solar cell was developed by Gretzell et al. (See Non-Patent Document 1, for example). In this solar cell, a surface of a porous titanium dioxide thin film having a large surface area is filled with an electrolyte solution containing a redox system between a photoactive electrode in which a ruthenium complex dye is adsorbed and a conductive glass counter electrode in which platinum is sputtered. It is a simple structure enclosed. However, although the ruthenium complex used shows high photoelectric conversion efficiency as a dye-sensitized solar cell, the photoelectric conversion efficiency is low compared to a silicon solar cell, and ruthenium used is an expensive and rare metal, This is a cause of cost increase. Therefore, a search for a new dye that achieves both a photoelectric conversion efficiency higher than that of the ruthenium complex dye and a low cost has been actively conducted.

  Specifically, it can be broadly classified into complex dyes containing non-noble metal elements and organic dyes not containing metal elements. For organic dyes, from the viewpoint of efficiently using sunlight, it is necessary to impart long wavelength sensitivity (absorption) to the molecules, and a technique of making the conjugated system of the dye molecules as long as possible is used. However, simply increasing the length of the conjugated system causes the problem that the dye molecules themselves become larger and the solubility decreases. That is, it is preferably a dye based on a skeleton having a relatively compact molecular structure and a long conjugated system having absorption in the visible region and a moderate solubility in a solvent. In that respect, pigments having a porphyrin skeleton or a phthalocyanine skeleton are a group of compounds that relatively satisfy these conditions. Moreover, since a metal complex can be formed as necessary, the characteristics can be modified.

  Many dyes having a porphyrin as a basic skeleton have already been disclosed. Some compounds in which they are optimized for dye-sensitized solar cells are also disclosed (for example, see Patent Document 1). As an optimization method, in the tetraphenylporphyrin stabilized by replacing the meso position of the unstable porphyrin with phenyl, various substituents are further introduced into the phenyl to suppress the interaction (self-quenching) between the dyes. In many cases, the photoelectric conversion efficiency is improved by developing an effect such as expansion of the absorption range due to a change in electronic state.

As an example, a porphyrin dye having improved solubility while introducing two t-butyls having a large steric hindrance into phenyl and suppressing association and aggregation of the dyes is disclosed (see Patent Document 2). Moreover, the porphyrin pigment | dye which introduce | transduced trimethylsilyl on the benzene ring is disclosed (refer patent document 3). According to this document, the knowledge that the trimethylsilyl substituent is improved in the photoelectric conversion efficiency of the dye-sensitized solar cell due to its steric bulk and the electron donating property of the silicon substituent is shown. However, the silicon-containing porphyrins that are being studied are only compounds in which one trimethylsilyl is introduced for each phenyl, and are composed of molecules in which a plurality of trimethylsilyls are introduced for each phenyl, or porphyrin derivatives having silicon-containing substituents other than trimethylsilyl. The dyes to be produced have not been developed yet.
Nature, Vol 353, 737 (1991) JP 2002-63949 A JP 2006-80346 A JP 2007-55978 A

  In these porphyrin derivatives and porphyrin complexes, depending on the structure of the substituent and the substitution position, the influence of steric hindrance is reduced, and association between the dye molecules and self-quenching are induced, and the photoelectric conversion efficiency may be reduced.

  Accordingly, an object of the present invention is to provide a novel porphyrin derivative and porphyrin complex having a plurality of substituents containing a silicon atom in phenyl at the meso position, which are more affected by the steric hindrance of the substituent.

  Another object is to provide a dye-sensitized solar cell and an organic thin-film solar cell with high photoelectric conversion efficiency by using such a porphyrin derivative or a porphyrin complex as a sensitizing dye.

  The present inventors introduced a plurality of silyl substituents to phenyl located at each meso position of tetraphenylporphyrin, thereby suppressing association between dye molecules due to steric hindrance and light absorption due to the heavy atom effect of silicon. We have studied earnestly from the viewpoint of realizing a broad wavelength range. As a result, a novel porphyrin derivative and porphyrin complex having phenyls introduced with a plurality of substituents containing a silicon atom at each meso position were found.

  Furthermore, these novel porphyrin derivatives and porphyrin complexes are excellent in photoelectric conversion efficiency, solubility in solvents, etc., and are useful as sensitizing dyes for dye-sensitized solar cells or electron donors for organic thin-film solar cells. As a result, the present invention has been completed.

  The porphyrin derivative of the present invention is represented by the formula (1).

In the formula (1), R ¹ , R ² and R ³ are each independently alkyl having 1 to 20 carbons, alkoxy having 1 to 20 carbons or aryl having 6 to 20 carbons, and a, b and c Are each independently an integer of 2 to 5, and d is an integer of 1 to 5.

In the formula (1), R ¹ , R ² and R ³ are each independently methyl, ethyl, propyl,
It may be butyl or phenyl, and R ¹ , R ² and R ³ may be each independently methyl, butyl or phenyl.

Further, in the formula (1), it is desirable that a, b and c are 2 and d is 1.
The porphyrin derivative of the present invention is characterized by being represented by the formula (2).

The porphyrin complex of the present invention is characterized by comprising these porphyrin derivatives and a metal element.
The metal element is preferably zinc or copper.

The organic thin film solar cell of the present invention is characterized by using these porphyrin derivatives or porphyrin complexes as electron donors.
Furthermore, the dye-sensitized solar cell of the present invention is characterized by using these porphyrin derivatives or porphyrin complexes as sensitizing dyes.

  The porphyrin derivative of the present invention has excellent characteristics such as photoelectric conversion efficiency and solubility in an organic solvent because a plurality of silicon-containing substituents are introduced for each phenyl. Due to its excellent solubility, it is possible to prepare a high concentration dye solution with a relatively safe solvent. If the porous semiconductor electrode is immersed in the resulting high concentration dye solution, more dye can be adsorbed on the electrode in a short time. Moreover, since the porphyrin itself has the property of easily forming complexes with various metal elements, the porphyrin complex of the present invention can easily adjust the photochemical properties according to the required properties.

  Therefore, the porphyrin derivative and the porphyrin complex of the present invention are materials for photoelectric conversion elements that are required to have excellent photoelectric conversion efficiency and wavelength absorption characteristics as compared with conventional porphyrin-based dyes, in particular, sensitizing dyes for dye-sensitized solar cells, Or it is useful as an electron donor of an organic thin-film solar cell.

  Furthermore, a dye-sensitized solar cell or an organic thin-film solar cell using these porphyrin derivatives or porphyrin complexes as a material for a photoelectric conversion element can perform good power generation.

Next, the porphyrin derivative and porphyrin complex of the present invention will be specifically described.
<Porphyrin derivative of the present invention>
The porphyrin derivative of the present invention is represented by the formula (1).

In formula (1), R ¹ , R ² and R ³ are not particularly limited as long as they are each independently alkyl having 1 to 20 carbons, alkoxy having 1 to 20 carbons or aryl having 6 to 20 carbons, These may be substituted or unsubstituted.

Specific examples of the alkyl include methyl, ethyl, propyl, butyl, pentyl, hexyl, 1,1,2-trimethylpropyl, heptyl, octyl, 2,4,4-trimethylpentyl, nonyl, decyl, undecyl, Dodecyl, tetradecyl, hexadecyl,
Alkyls such as octadecyl and eicosyl;
Cycloalkyl such as cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, decalyl;
3,3,3-trifluoropropyl, 3,3,4,4,5,5,6,6,6-nonadecafluorohexyl, tridecafluoro-1,1,2,2-tetrahydrooctyl, heptadeca Fluoroalkyl such as fluoro-1,1,2,2-tetrahydrodecyl, perfluoro-1H, 1H, 2H, 2H-dodecyl, perfluoro-1H, 1H, 2H, 2H-tetradecyl can be mentioned.

  These alkyls may be linear or branched, and may be alkyl having an unsaturated bond in the carbon chain (generally called alkenyl). Specific examples include ethenyl, 2-propenyl, 3-butenyl, 5-hexenyl, 7-octenyl, and 10-undecenyl.

Specific examples of the alkoxy include 3-methoxypropyl, methoxyethoxyundecyl, and 3-heptafluoroisopropoxypropyl.
Specific examples of the aryl include phenyl, naphthyl, anthonyl, fluoryl, pentafluorophenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 4-methylphenyl, 4-ethylphenyl, and 4-propylphenyl. 4-butylphenyl, 4-pentylphenyl, 4-heptylphenyl, 4-octylphenyl, 4-nonylphenyl, 4-decylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2,4 , 6-triethylphenyl, 4- (1-methylethyl) phenyl, 4- (1,1-dimethylethyl) phenyl, 4- (2-ethylhexyl) phenyl, 2,4,6-tris (1-methylethyl) Phenyl, 4-methoxyphenyl, 4-ethoxyphenyl, 4-propoxyphenyl 4-butoxyphenyl, 4-pentyloxyphenyl, 4-heptyloxyphenyl, 4-decyloxyphenyl, 4-octadecyloxyphenyl, 4- (1-methylethoxy) phenyl, 4- (2-methylpropoxy) phenyl, 4 -(1,1-dimethylethoxy) phenyl, 4-ethenylphenyl, 4- (1-methylethenyl) phenyl, 4- (3-butenyl) phenyl and the like can be mentioned.

  Of these, lower (C1-6) alkyl or C6-10 aryl, which are easily available, are preferable. More preferred is methyl, ethyl, propyl, butyl or phenyl, and even more preferred is methyl, butyl or phenyl.

  In formula (1), a, b and c are each independently an integer of 2 to 5, preferably an integer of 2 to 3, more preferably 2. In addition, it is desirable that the silicon-containing substituent has a highly symmetrical arrangement. Specifically, it is an embodiment of a silicon-containing substituent represented by any of the following formulas (a) to (e). In the formulas (a) to (e), the free bond on the phenyl is linked to the meso position (5-position, 10-position, 20-position) of the porphyrin skeleton.

  In Formula (1), d is an integer of 1-5, Preferably it is an integer of 1-2, More preferably, it is 1. In the porphyrin derivative of the present invention, the carboxyl in the formula (1) is an essential substituent for fixing the porphyrin derivative serving as a dye on the titanium oxide surface and imparting the function as a photoactive electrode to the porphyrin derivative. . The substitution position is preferably para to the meso position (15th position) of the porphyrin skeleton.

As a preferred embodiment of these porphyrin derivatives of the present invention, a porphyrin derivative in which R ¹ , R ² and R ³ in formula (1) are methyl, a, b and c are 2, and d is 1 That is, the porphyrin derivative represented by Formula (2) is mentioned.

  The porphyrin derivative of the present invention can be produced by various organic chemical techniques. Among them, a method of synthesizing a benzaldehyde derivative having a silicon substituent, a benzaldehyde derivative having a carboxylic acid ester, and pyrrole by dehydration condensation in the presence of an acid catalyst, followed by chemical oxidation (commonly known as Lindsey). Law) is the most common.

  Further, a benzaldehyde derivative having a silicon substituent, a benzaldehyde derivative having a carboxylic acid ester, and pyrrole may be reacted in an organic acid solution such as propionic acid at a high temperature. Subsequently, if the carboxylic acid ester is deprotected by hydrolysis or the like, the target porphyrin derivative can be obtained.

  As an example of these, a synthesis method (Lindsey method) of a porphyrin derivative represented by the formula (2) is shown in the following reaction formula.

  As shown in the above reaction formula, a benzaldehyde derivative having a silicon substituent, a benzaldehyde derivative having a carboxylic acid ester, and pyrrole are cyclized by dehydration condensation in the presence of an acid catalyst. Subsequently, the obtained cyclized product is chemically oxidized to form a conjugated system, thereby obtaining a carboxylic acid ester which is a precursor of the porphyrin derivative of the present invention. Then, the porphyrin derivative of this invention is obtained by deprotecting the obtained carboxylic acid ester.

  Examples of the solvent include halogen-containing solvents such as dichloromethane, chloroform, carbon tetrachloride, and 1,2-dichloroethane, ethers such as diethyl ether, tetrahydrofuran (hereinafter referred to as THF), dioxane, benzene, toluene, xylene, chlorobenzene, and dioxane. Aromatic hydrocarbons such as chlorobenzene and halogen-substituted products thereof can be used. Of these, chloroform or THF is preferable.

The acid catalyst is preferably a strongly acidic organic compound such as boron trifluoride diethyl ether complex, p-toluenesulfonic acid, trifluoroacetic acid or the like.
A dehydrogenating agent is used to oxidize the cyclized product. As this dehydrogenating agent, parachloranil and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone are preferable.

  Generally, these dehydration condensation reaction and oxidation reaction are carried out stepwise. At this time, it is preferable to first add an acid catalyst and react for 30 minutes to 24 hours, and then add a dehydrogenating agent and stir for 30 minutes to 24 hours. The reaction temperature may normally be −20 to 120 ° C., preferably 20 (room temperature) to 60 ° C.

The conditions for deprotecting the carboxylic acid ester vary depending on the type of the ester, but are preferably esters substituted with a group that can be deprotected by alkaline hydrolysis, specifically, methyl, ethyl, benzyl, phenyl Examples include esters substituted with groups such as esters. Examples of the alkali hydrolysis solvent include methanol, ethanol, 2-propanol, THF, dioxane, and mixed solvents thereof. Among them, 2-propanol,
THF is preferred. As the base, an aqueous solution of lithium hydroxide, sodium hydroxide, or potassium hydroxide is preferable. The reaction temperature may usually be 20 (room temperature) to 100 ° C. Moreover, reaction time should just be normally 1 to 12 hours, Preferably it is 3 to 6 hours.

  Further, the carboxylic acid ester may be an ester substituted with a group that is deprotected under conditions other than alkaline hydrolysis. Specifically, benzyl ester that can be removed by catalytic reduction, acid-cleavable t-butyl Examples include esters.

<Porphyrin Complex of the Present Invention>
The porphyrin complex of the present invention is characterized by comprising the porphyrin derivative of the present invention and a metal element. In the porphyrin complex of the present invention, the metal element coordinated at the center is not particularly limited as long as it has a complex forming ability with known porphyrins.

  Specific examples of these metal elements include magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprodium, holmium, tin, ytterbium, titanium, Zirconium, hafnium, vanadium, niobium, tantalum, thorium, uranium, manganese, chromium, iron, cobalt, zinc, molybdenum, nickel, rhodium, and the like can be given. Among these, copper, titanium, nickel, iron, and zinc are preferable, and copper or zinc is more preferable.

The porphyrin complex of the present invention can be easily prepared by mixing the porphyrin derivative of the present invention and metal hydrochloride or metal acetate in an appropriate solvent. As an example, a reaction formula between the porphyrin derivative represented by the formula (2) and zinc acetate is shown below. In the following formula, TMS represents —Si (CH ₃ ) ₃ .

<Dye-sensitized solar cell and organic thin-film solar cell of the present invention>
The dye-sensitized solar cell of the present invention comprises a porphyrin derivative or a porphyrin complex of the present invention (hereinafter also referred to as a sensitizing dye of the present invention) between a transparent substrate having a transparent conductive film and another conductive substrate as its counter electrode. It is characterized by a structure in which a photo-active electrode carrying a redox system is provided and an electrolyte layer containing a redox system is enclosed therein.

  In the dye-sensitized solar cell of the present invention, the semiconductor layer used as the photoactive electrode is a porphyrin derivative represented by the formula (1) or (2), or one type of porphyrin complex composed of the derivative and a metal element, Alternatively, two or more kinds are supported simultaneously. These sensitizing dyes of the present invention may be used in combination with known sensitizing dyes, specifically, ruthenium-bipyridine complexes, coumarins, methine organic dyes, phthalocyanine derivatives, and the like.

Such a semiconductor layer is preferably an oxide semiconductor carrying the sensitizing dye.
Specific examples of the oxide semiconductor include metal oxides such as titanium oxide, zinc oxide, tin oxide, and zirconium oxide, and perovskite oxides such as strontium titanate and calcium titanate.

  Furthermore, the semiconductor layer is preferably in a porous state. Many methods for making a semiconductor layer porous have already been disclosed. For example, titanium isopropoxide is hydrothermally reacted in an acidic solution to form a colloidal solution of titanium oxide, and then the solution and a binder are mixed, and then made uniform with a ball mill or the like. A method of obtaining a porous semiconductor thin film by forming a film on a substrate by screen printing or the like and then sintering it at a high temperature can be mentioned.

  The porous semiconductor thin film thus obtained is preferably loaded with a larger amount of the sensitizing dye of the present invention. For this purpose, these sensitizing dyes may be dissolved in a suitable organic solvent, and the semiconductor thin film may be immersed in this solution. A method in which the sensitizing dye is left until it is sufficiently adsorbed, taken out and dried is more preferable.

  As a transparent substrate having a transparent conductive film, on a heat resistant substrate such as glass, polyethylene terephthalate, polyethylene naphthalate, polysilsesquioxane, tin oxide-indium alloy (ITO), tin oxide, or indium oxide. Examples thereof include a substrate on which a transparent electrode thin film is formed, or a conductive glass doped with fluorine.

  As the conductive substrate serving as the counter electrode, a known material such as aluminum, silver, tin, or indium may be arbitrarily used. Among these, a material having a property of promoting the reduction reaction of oxidized redox ions is preferable, and specific examples thereof include platinum, rhodium, ruthenium, ruthenium oxide, and carbon.

  As an electrolyte sealed between both electrodes, a well-known thing can be arbitrarily employ | adopted as an electrolyte solution of a solar cell. Specific examples of the electrolyte that is often used include an electrolyte in which iodine and potassium iodide are dissolved in a carbonate-based solvent. In recent years, examples in which a so-called ionic liquid represented by tetrafluoroborate of imidazole is used as an electrolyte have been disclosed, and any of these may be used.

  Moreover, since the porphyrin derivative or porphyrin complex of the present invention has excellent performance as an electron donor, an organic thin film can be obtained by using these to form an organic thin film by the same method as described above.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.
In addition, the physical property of each compound was measured with the following method.

Melting point: A polarizing microscope was equipped with a hot stage (FP-82 manufactured by METTLER) and measured at a rate of temperature increase of 5 ° C. per minute.
Proton NMR spectrum ( ¹ H-NMR): JNM-GSX4 manufactured by JEOL Ltd.
00, using chloroform-d as a solvent at 400 MHz and tetramethylsilane as an internal standard substance, and measuring at room temperature.

[Example 1]: Synthesis of 5- (4-carboxyphenyl) -10,15,20-tris (3,5-ditrimethylsilyl) porphyrin (porphyrin derivative represented by the formula (2)) Detailed explanation will be given.

1) Synthesis of 3,5-bis (trimethylsilyl) bromobenzene (compound A) (according to D. Wrobel et al, J. Organomet. Chem, 225 , 203 (1982))
In a 500 ml three-necked flask equipped with a thermometer, a condenser tube and a dropping funnel, magnesium (7.7 g, 0.32 mol) and THF (tetrahydrofuran) soaked in magnesium were taken and stirred at room temperature in a nitrogen atmosphere. . A small amount of a solution of 1,3,5-tribromobenzene (50 g, 0.16 mol) dissolved in 160 ml of THF was first dropped into the three-necked flask. After the start of the reaction, the remainder was added dropwise at a temperature of 60 ° C. or lower, followed by stirring at room temperature for 2 hours. Next, trimethylsilyl chloride (34.8 g, 0.32 mol) was added dropwise at room temperature, and the mixture was refluxed for about 1 hour after the completion of the addition. After returning the reaction solution to room temperature, the reaction solution was poured into a large amount of ammonium chloride solution to stop the reaction, and extracted twice with ethyl acetate. The organic layer was washed with pure water and dried over magnesium sulfate, and then the desiccant was filtered off and concentrated under reduced pressure. The obtained residue was distilled under reduced pressure to obtain a fraction of 69 to 75 ° C./0.2 kPa, thereby obtaining 16.1 g (0.054 mol, yield 33.7%) of Compound A as a colorless liquid.

The obtained compound was confirmed by ¹ H-NMR;
¹ H-NMR (400 MHz, CDCl ₃ ) δ 0.29 (s, 18H), 7.42 (t, 1H), 7.49 (d, 2H).

2): Synthesis of 3,5-bis (trimethylsilyl) benzaldehyde (Compound B) Into a 200 ml three-necked flask equipped with a thermometer, a condenser tube, and a dropping funnel, magnesium (1.4 g, 0.058 mol) and magnesium Was taken up at a room temperature under a nitrogen atmosphere. A small amount of a solution obtained by dissolving compound A (15.9 g, 0.053 mol) obtained in 1) in 30 ml of THF was dropped into the three-necked flask. After the start of the reaction, the remainder was added dropwise at a temperature of 50 ° C. or lower, followed by stirring at room temperature for 2 hours. Then, a THF solution of dimethylformamide (4.64 g, 0.064 mol) was added dropwise at room temperature, and the mixture was stirred overnight at room temperature. The reaction solution was poured into a large amount of ammonium chloride solution to stop the reaction, and extracted twice with ethyl acetate. The organic layer was washed with pure water and dried over magnesium sulfate, and then the desiccant was filtered off and concentrated under reduced pressure. The obtained residue was distilled under reduced pressure to obtain a fraction of 79 to 85 ° C./0.2 kPa. This liquid was stored in a refrigerator to obtain 3.81 g (0.015 mol, yield 28.6%, melting point: 64.3 to 65.4 ° C.) of white solid compound B.

The obtained compound was confirmed by ¹ H-NMR;
¹ H-NMR (400 MHz, CDCl ₃ ) δ 0.33 (s, 18H), 7.79 (t, 1H), 7.89 (d, 2H), 10.01 (s, 1H).

3): Synthesis of 5- (4-methoxycarbonylphenyl) -10,15,20-tris (3,5-ditrimethylsilyl) porphyrin (Compound C) To a 1 L three-necked flask equipped with a nitrogen inlet tube and a thermometer 2) Compound B (3.76 g, 15.0 mmol), methyl 4-formylbenzoate (0.82 g, 5.0 mmol), pyrrole (1.34 g, 20.0 mmol), and dehydrated chloroform 500 ml Was bubbled with nitrogen at room temperature for 30 minutes. Boron trifluoride-diethyl ether complex (0.25 ml) was added thereto, and the mixture was stirred at room temperature for 2 hours under a nitrogen atmosphere. Then, chloranil (4.42 g, 18 mmol) was added at once and stirred overnight. The reaction was stopped by adding 5 ml of triethylamine, and the reaction solution was filtered through Celite and concentrated under reduced pressure. The residue was applied to a flash column with chloroform, and the resulting crude crystals were purified again with a silica gel column (volume ratio: hexane: chloroform = 2: 1), and Rf = 0.48 (volume ratio: hexane: chloroform = 1: The target product of 1) was isolated. The crystals were filtered and washed with methanol to obtain 0.79 g (0.71 mmol, yield 14.2%) of a purple solid compound C.

The obtained compound was confirmed by ¹ H-NMR;
¹ H-NMR (400 MHz, CDCl ₃ ) δ -2.70 (s, 2H), 0.41 (s, 54H), 4.11 (s, 3H), 8.02 (s, 3H), 8. 33 (q, 8H), 8.44 (d, 2H), 8.80 (d, 2H), 8.87 (d, 6H).

4): Synthesis of Porphyrin Derivative of the Present Invention Represented by Formula (2) Into a 500 mL three-necked flask equipped with a condenser and a thermometer, compound C (0.79 g)
, 0.71 mmol), 200 ml of isopropyl alcohol, and 20 ml of aqueous potassium hydroxide solution were added, and the mixture was stirred at 70 ° C. for 4 hours under a nitrogen atmosphere. The reaction solution was returned to room temperature, 6M hydrochloric acid was added to adjust the pH to 3, and the mixture was extracted twice with chloroform. The organic layer was washed with pure water, dried and concentrated under reduced pressure. The residue was purified with a silica gel column (chloroform → volume ratio: chloroform: methanol = 9: 1) to obtain 0.47 g (0.43 mmol, yield 61.8%) of the porphyrin derivative of the present invention as a purple solid.

The obtained porphyrin derivative was confirmed by ¹ H-NMR;
¹ H-NMR (400 MHz, CDCl ₃ ) δ -2.68 (s, 2H), 0.42 (s, 54H), 8.04 (s, 3H), 8.36 (d, 6H), 8. 40 (d, 2H), 8.57 (d, 2H), 8.84 (d, 2H), 8.89 (s, 6H), 8.90 (bs, 1H).

[Solubility evaluation test]
The solubility in organic solvents was compared using the porphyrin derivative obtained in Example 1 and the silicon-containing porphyrin derivative described in Patent Document 3 represented by the following formula. As a result, the porphyrin derivative of the present invention was easily dissolved in hexane, chloroform, acetone, methanol, toluene, THF, dimethyl sulfoxide (DMSO) at 5 to 10% by weight at room temperature (25 ° C.). On the other hand, the porphyrin derivative represented by the following formula is insoluble in hexane in the above solvent, and heating (50 to 80 ° C.) is required when 5 to 10% by weight is dissolved in chloroform, toluene and DMSO. From these results, it was found that the porphyrin derivative of the present invention is excellent in solubility in an organic solvent.

[Example 2]: Synthesis of porphyrin complex (complex composed of porphyrin derivative and zinc) 5- (4-carboxyphenyl) -10,15,20-tris (3,3) synthesized in Example 1 in a 200 ml eggplant flask. 5-Ditrimethylsilyl) porphyrin (0.20 g, 0.18 mmol) and 80 ml of chloroform were taken and stirred at room temperature under a nitrogen atmosphere. Next, 12 ml of a saturated methanol solution of zinc acetate was added at once, and the mixture was stirred as it was for 1 hour. The reaction solution was concentrated under reduced pressure, and the residue was purified by a silica gel column (volume ratio of chloroform: methanol = 96: 4) to quantitatively obtain a purple solid zinc complex (0.21 g, 0.18 mmol).

The obtained compound was confirmed by ¹ H-NMR;
¹ H-NMR (400 MHz, CDCl ₃ ) δ 0.41 (s, 54H), 8.01 (s
, 3H), 8.33 (d, 8H), 8.46 (d, 2H), 8.86 (d, 2H), 8.91 (d, 6H).

[Example 3]: Preparation of dye-sensitized solar cell and measurement of photoelectric conversion efficiency A titanium dioxide sintered glass substrate prepared by a known method was cut into a size of 20 mm x 15 mm, and a titanium oxide film on the surface Was cut into an octagon with a width of 6 mm. The substrate was refired at 450 ° C. for 10 minutes and allowed to cool to 80 ° C. Next, the substrate was immersed in a 5 × 10 ⁻³ M ethanol solution of 5- (4-carboxyphenyl) -10,15,20-tris (3,5-ditrimethylsilyl) porphyrin synthesized in Example 1 for 24 hours. Thereafter, it was washed with ethanol in an argon atmosphere and dried to form a photoworking electrode.

  As the counter electrode, a glass substrate with FTO (fluorinated tin oxide) provided with a platinum film having a thickness of 1 μm by a sputtering method was used. A spacer was thermocompression-bonded on this so as to have a thickness of 25 μm. As the electrolyte solution, a methoxyacetonitrile solution of iodine, lithium iodide, and t-butylpyridine was used. The concentration of each component was adjusted to be 0.05M, 0.5M, and 0.5M, respectively. An electrolyte was dropped on the counter electrode and sandwiched between dye adsorption substrates (photoworking electrodes) to prepare a dye-sensitized solar cell. A 5.5 mmφ mask was placed on this to form a measurement cell.

As a light source for operating this cell, artificial sunlight (100 mW / cm ² , AM (air
Mass) 1.5) was used. Then, the photocurrent density-voltage and the action spectrum (spectral sensitivity characteristics) were measured, and the short circuit current and the release voltage were obtained. In addition, a short circuit current means the electric current measured by short-circuiting between counter electrodes, and an open circuit voltage means the voltage which generate | occur | produced between the counter electrodes open. The photoelectric conversion efficiency calculated from these results was 3.1%.

[Comparative Example 1]
A porphyrin complex was synthesized by the same method as in Example 1 except that a porphyrin derivative represented by the following formula was used as a sensitizing dye, and a dye-sensitized solar cell was prepared by the same method as in Example 3 to produce photoelectric Conversion efficiency was measured. As a result, the photoelectric conversion efficiency was 1.4%.

Claims (9)

A porphyrin derivative represented by the formula (1);

(In the formula ^{(1), R 1, R} 2 and R ³ are each independently alkyl having 1 to 20 carbon atoms, alkoxy or aryl having 6 to 20 carbon atoms having 1 to 20 carbon atoms, a, b and c is an integer of 2-5 each independently, and d is an integer of 1-5.) In the formula (1), R ¹ , R ² and R ³ are each independently methyl, ethyl, propyl,
The porphyrin derivative according to claim 1, which is butyl or phenyl. The porphyrin derivative according to claim ¹ , wherein R ¹ , R ² and R ^{3 in the} formula (1) are each independently methyl, butyl or phenyl.   In the said Formula (1), a, b, and c are 2, d is 1, The porphyrin derivative in any one of Claims 1-3 characterized by the above-mentioned. A porphyrin derivative represented by the formula (2):

  A porphyrin complex comprising the porphyrin derivative according to any one of claims 1 to 5 and a metal element.   The porphyrin complex according to claim 6, wherein the metal element is zinc or copper.   An organic thin film solar cell using the porphyrin derivative according to any one of claims 1 to 5 or the porphyrin complex according to claim 6 or 7 as an electron donor.   A dye-sensitized solar cell using the porphyrin derivative according to any one of claims 1 to 5 or the porphyrin complex according to claim 6 or 7 as a sensitizing dye.