JP2020128361A - Squarilium derivative, production method thereof, organic thin film and photoelectric conversion element - Google Patents

Abstract

To provide a novel squarilium derivative having high color purity and high heat resistance and to provide an organic thin film or a photoelectric conversion element each including the squarilium derivative.SOLUTION: The squarilium derivative is represented by the following formula (1). (In the formula, Arrepresents a 6-12C monocyclic, linked or condensed ring aromatic hydrocarbon group in which the aromatic hydrocarbon group may be substituted with a halogen atom, a 1-8C alkyl group or a 1-8C haloalkyl group; R, R, R, and Reach independently represent H, a halogen atom, a 1-8C alkyl group, a 1-8C haloalkyl group, a phenyl group or a naphthyl group, or two adjacent to each other, i.e., Rand R, Rand R, and Rand R, respectively, may be combined together with each other to form an aliphatic ring or an aromatic ring including a carbon atom to which the respective ones are bonded.)SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a squarylium derivative containing an indoline structure, which is useful as a novel dye having high color purity, and a method for producing the same. The present invention also relates to an organic thin film and a photoelectric conversion element using the squarylium derivative as a dye.

Photoelectric conversion elements are used in photovoltaic devices such as optical sensors and solar cells. A photoelectric conversion element using a dye is known from Patent Document 1 and the like.

As a photoelectric conversion element, an element using a silicon semiconductor is widely used. However, since such a silicon photodiode has sensitivity in the entire visible light region, by using a color filter in which RGB is arranged in a mosaic pattern on the upper side, each pixel is distributed as a light receiving portion of each RGB, Color imaging is performed. In this method, since the utilization efficiency of incident light is low due to the loss in the color filter, there is a concern that it may be a barrier to high sensitivity. Therefore, an image pickup device in which organic photoelectric conversion layers of RGB colors are stacked (hereinafter referred to as a stacked organic image pickup device) has been proposed (for example, see Non-Patent Document 1). With this method, there is no light loss due to the color filter and the light utilization efficiency is several times higher, so it is expected as a highly sensitive device that is superior to the miniaturization of pixels accompanying the increase in the number of pixels.

As the photoelectric conversion layer of the laminated organic image pickup device, each of the RGB layers is required to have photoelectric conversion characteristics of high color purity. Non-Patent Document 1 shows the wavelength dependence of the light receiving sensitivity of each of the RGB layers, but in particular, the R layer (photoelectric conversion layer for red color) absorbs in a wide wavelength range and has low color purity. Further, Patent Document 2 describes a photoelectric conversion element for red that uses subnaphthalocyanine as a photoelectric conversion material, and exhibits maximum absorption in the red region, but exhibits absorption in all wavelength regions of visible light, There is a problem in purity. In addition, photoelectric conversion elements using a squarylium derivative as a dye having absorption in the red region have been reported (see, for example, Patent Document 3, Non-Patent Document 2 and Non-Patent Document 3).

Japanese Patent No. 4148374 JP, 2017-73426, A Japanese Patent No. 5392765

Japanese Journal of Applied Physics, 2011, 50, 024103 Laser & Photonics Reviews, 2016, 10:473. The Journal of Physical Chemistry C, 2017, 121, 15333.

However, in order to achieve further improvement in color purity, it is necessary to develop a novel derivative having a narrower half maximum width of absorption maximum peak than the reported squarylium derivative. Further, in order to mount the squarylium derivative on various electronic devices, not only optical characteristics but also stability against heat are required.

The present invention has been made in view of the above problems, has a high heat resistance, provides a squarylium derivative having a full width at half maximum narrower than existing materials, and provides an organic thin film and a photoelectric conversion element using the same And to provide a method for conveniently synthesizing the squarylium derivative.

As a result of intensive studies to solve the above problems, the present inventors have found that the novel squarylium derivative has a narrow half-value width, a high color purity, and a high decomposition temperature. Further, they have found that an organic thin film can be easily formed by using the squarylium derivative, and have completed the present invention.

That is, the present invention is
[1]
A squarylium derivative represented by the general formula (1).

(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms.
R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group, or a naphthyl group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated together to form an aliphatic ring or aromatic ring containing the carbon atoms to which they are bonded. You may form. );
[2]
The squarylium derivative according to the above [1], wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms;
[3]
The squarylium derivative according to the above [1] or [2], wherein R ³ and R ⁴ are hydrogen atoms;
[4]
R ¹ and R ² relate to the squarylium derivative according to any one of the above [1] to [3], wherein R ¹ and R ² are hydrogen atoms.
The present invention also provides
[5]
General formula (2a)

(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms.
R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group, or a naphthyl group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated together to form an aliphatic ring or aromatic ring containing the carbon atoms to which they are bonded. You may form. ) And an indoline compound represented by the formula (1) are reacted with squaric acid, the method for producing a squarylium derivative represented by the general formula (1);
[6]
A method for producing a squarylium derivative according to the above [5], wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms;
[7]
The method for producing a squarylium derivative according to the above [5] or [6], wherein R ³ and R ⁴ are hydrogen atoms;
[8]
The method for producing a squarylium derivative according to any one of [5] to [7] above, wherein R ¹ and R ² are hydrogen atoms.
The present invention also provides [9]
General formula (2b)

(In the formula, R ¹ , R ² , R ³ , and R ⁴ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group, or naphthyl. Represents a group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated together to form an aliphatic ring or aromatic ring containing the carbon atoms to which they are bonded. You may form. ) And an indoline compound represented by the general formula (3a)

(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or a haloalkyl group having 1 to 8 carbon atoms. In the formula, X ⁻ represents a counter anion), and the hypervalent iodine compound represented by the formula (2a) is reacted in the presence of a base. A method for producing a squarylium derivative represented by the general formula (1), characterized in that the indoline compound represented by the formula (1) is obtained and then reacted with squaric acid.
[10]
The method for producing a squarylium derivative according to the above [9], wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms.
[11]
The method for producing a squarylium derivative according to the above [9] or [10], wherein R ³ and R ⁴ are hydrogen atoms;
[12]
The method for producing a squarylium derivative according to any one of [9] to [11], wherein R ¹ and R ² are hydrogen atoms;
[13]
The method according to any one of [9] to [12] above, wherein X ⁻ is a trifluoromethanesulfonate ion or a hexafluorophosphate ion.
The present invention also provides
[14]
An organic thin film comprising the squarylium derivative according to any one of [1] to [4].
Further, the present invention is
[15]
The present invention relates to a photoelectric conversion element including the organic thin film according to [14].

The present invention will be described in detail below.
The squarylium derivative (1) of the present invention has the resonance structures shown in 1a below, and the present patent also includes them.

The definitions of Ar ¹ , R ¹ , R ² , R ³ and R ⁴ in the squarylium derivative (1) of the present invention will be described.

Examples of the monocyclic, linked or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms represented by Ar ¹ include a phenyl group, a naphthyl group and a biphenylyl group, and the obtained squarylium derivative ( A phenyl group is preferable in that the yield of 1) is good.

The monocyclic, linked or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms represented by Ar ¹ may be substituted with a halogen atom, and the halogen atom is a fluorine atom, a chlorine atom or a bromine atom Alternatively, an iodine atom can be exemplified. A bromine atom is preferable because the yield of the obtained squarylium derivative (1) is good.

The monocyclic, linked or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms represented by Ar ¹ may be substituted with an alkyl group having 1 to 8 carbon atoms. The alkyl group having 1 to 8 carbon atoms may be a linear, branched or cyclic alkyl group, and specifically, a methyl group, a cyclohexylmethyl group, an ethyl group, a 2-cyclopentylethyl group, a propyl group, 2-methylpropyl group, 2,2-dimethylpropyl group, 3-cyclopropylpropyl group, isopropyl group, cyclopropyl group, butyl group, 2-methylbutyl group, 3-methylbutyl group, 2-butyl group, 3-methylbutane- 2-yl group, tert-butyl group, cyclobutyl group, pentyl group, 2-methylpentyl group, 3-ethylpentyl group, 2,4-dimethylpentyl group, 2-pentyl group, 2-methylpentan-2-yl group , 4,4-dimethylpentan-2-yl group, 3-pentyl group, 3-ethylpentan-3-yl group, cyclopentyl group, 2,5-dimethylcyclopentyl group, 3-ethylcyclopentyl group, hexyl group, 2- Methylhexyl group, 3,3-dimethylhexyl group, 4-ethylhexyl group, 2-hexyl group, 2-methylhexan-2-yl group, 5,5-dimethylhexan-2-yl group, 3-hexyl group, 2 , 4-dimethylhexan-3-yl group, cyclohexyl group, 4-ethylcyclohexyl group, 4,4-dimethylcyclohexyl group, heptyl group, 2-heptyl group, 3-heptyl group, 4-heptyl group, bicyclo[2. 2.1]heptyl group, octyl group, 2-octyl group, 3-octyl group, 4-octyl group, cyclooctyl group, bicyclo[2.2.2]octyl group and the like can be exemplified, and among them, From the viewpoint of good yield of the squarylium derivative (1), a methyl group, an isopropyl group or a tert-butyl group is preferable, and a tert-butyl group is particularly preferable.

The monocyclic, linked or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms represented by Ar ¹ may be substituted with a haloalkyl group having 1 to 8 carbon atoms. The haloalkyl group having 1 to 8 carbon atoms may be any of a linear, branched or cyclic haloalkyl group, and specifically, a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, 2,2,2- Trifluoroethyl group, 1,1-difluoroethyl group, 2,2-difluoroethyl group, perfluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, 2,2,3,3-tetrafluoro Propyl group, 3,3,3-trifluoropropyl group, 1,1-difluoropropyl group, perfluoroisopropyl group, 2,2,2-trifluoro-1-(trifluoromethyl)ethyl group, perfluorocyclopropyl group, 2,2,3,3-tetrafluorocyclopropyl group, perfluorobutyl group, 2,2,3,3,4,4,4-heptafluorobutyl group, 3,3,4,4,4-pentafluorobutyl group Group, 4,4,4-trifluorobutyl group, 1,2,2,3,3,3-hexafluoro-1-(trifluoromethyl)propyl group, 1-(trifluoromethyl)propyl group, 1- Methyl-3,3,3-trifluoropropyl group, perfluorocyclobutyl group, 2,2,3,3,4,4-hexafluorocyclobutyl group, perfluoropentyl group, 2,2,3,3,4 4,5,5,5-nonafluoropentyl group, 3,3,4,4,5,5,5-heptafluoropentyl group, 4,4,5,5,5-pentafluoropentyl group, 5,5 ,5-trifluoropentyl group, 1,2,2,3,3,3-hexafluoro-1-(perfluoroethyl)propyl group, 2,2,3,3,3-pentafluoro-1-(perfluoroethyl) ) Propyl group, perfluorocyclopentyl group, perfluorohexyl group, 2,2,3,3,4,4,5,5,6,6,6-undecafluorohexyl group, 3,3,4,4,5 5,6,6,6-nonafluorohexyl group, 4,4,5,5,6,6,6-heptafluorohexyl group, 5,5,6,6,6-pentafluorohexyl group, 6, A 6,6-trifluorohexyl group, a perfluorocyclohexyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, a 2-chloroethyl group or a 3-bromopropyl group can be exemplified, and among them, a squarylium derivative (1) obtained A trifluoromethyl group or a bromomethyl group is preferable in terms of good yield.

Of these, Ar ¹ is preferably a phenyl group which may be substituted with a halogen atom or an alkyl group having 1 to 8 carbon atoms, and particularly preferably a bromine atom-substituted phenyl group or a 4-tert-butylphenyl group.

Examples of the halogen atom represented by R ¹ , R ² , R ³ and R ⁴ include a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. Among them, the yield of the obtained squarylium derivative (1) is A bromine atom is preferable in terms of good points.

The alkyl group of 1 to 8 represented by R ¹ , R ² , R ³ and R ⁴ may be a linear, branched or cyclic alkyl group, and specifically, a methyl group, a cyclohexylmethyl group, Ethyl group, 2-cyclopentylethyl group, propyl group, 2-methylpropyl group, 2,2-dimethylpropyl group, 3-cyclopropylpropyl group, isopropyl group, cyclopropyl group, butyl group, 2-methylbutyl group, 3- Methylbutyl group, 2-butyl group, 3-methylbutan-2-yl group, tert-butyl group, cyclobutyl group, pentyl group, 2-methylpentyl group, 3-ethylpentyl group, 2,4-dimethylpentyl group, 2- Pentyl group, 2-methylpentan-2-yl group, 4,4-dimethylpentan-2-yl group, 3-pentyl group, 3-ethylpentan-3-yl group, cyclopentyl group, 2,5-dimethylcyclopentyl group , 3-ethylcyclopentyl group, hexyl group, 2-methylhexyl group, 3,3-dimethylhexyl group, 4-ethylhexyl group, 2-hexyl group, 2-methylhexan-2-yl group, 5,5-dimethylhexane -2-yl group, 3-hexyl group, 2,4-dimethylhexane-3-yl group, cyclohexyl group, 4-ethylcyclohexyl group, 4,4-dimethylcyclohexyl group, heptyl group, 2-heptyl group, 3- Heptyl group, 4-heptyl group, bicyclo[2.2.1]heptyl group, octyl group, 2-octyl group, 3-octyl group, 4-octyl group, cyclooctyl group or bicyclo[2.2.2]octyl group. Examples thereof include a methyl group, and among them, a methyl group is preferable because the yield of the obtained squarylium derivative (1) is good.

The haloalkyl group having 1 to 8 carbon atoms represented by R ¹ , R ² , R ³ and R ⁴ may be a linear, branched or cyclic haloalkyl group, and specifically, a trifluoromethyl group , Difluoromethyl group, perfluoroethyl group, 2,2,2-trifluoroethyl group, 1,1-difluoroethyl group, 2,2-difluoroethyl group, perfluoropropyl group, 2,2,3,3,3- Pentafluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 3,3,3-trifluoropropyl group, 1,1-difluoropropyl group, perfluoroisopropyl group, 2,2,2-trifluoro- 1-(trifluoromethyl)ethyl group, perfluorocyclopropyl group, 2,2,3,3-tetrafluorocyclopropyl group, perfluorobutyl group, 2,2,3,3,4,4,4-heptafluorobutyl Group, 3,3,4,4,4-pentafluorobutyl group, 4,4,4-trifluorobutyl group, 1,2,2,3,3,3-hexafluoro-1-(trifluoromethyl) Propyl group, 1-(trifluoromethyl)propyl group, 1-methyl-3,3,3-trifluoropropyl group, perfluorocyclobutyl group, 2,2,3,3,4,4-hexafluorocyclobutyl group , Perfluoropentyl group, 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, 3,3,4,4,5,5,5-heptafluoropentyl group, 4,4 5,5,5-pentafluoropentyl group, 5,5,5-trifluoropentyl group, 1,2,2,3,3,3-hexafluoro-1-(perfluoroethyl)propyl group, 2,2 , 3,3,3-Pentafluoro-1-(perfluoroethyl)propyl group, perfluorocyclopentyl group, perfluorohexyl group, 2,2,3,3,4,4,5,5,6,6,6-un Decafluorohexyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, 4,4,5,5,6,6,6-heptafluorohexyl group, 5,5 , 6,6,6-pentafluorohexyl group, 6,6,6-trifluorohexyl group, perfluorocyclohexyl group, chloromethyl group, bromomethyl group, iodomethyl group, 2-chloroethyl group or 3-bromopropyl group, etc. It can be illustrated.

Two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ may be integrated with each other to form an aliphatic ring containing a carbon atom bonded to each other; Examples of the aromatic ring include a cyclopentene ring, a cyclohexene ring, a cycloheptene ring, and a benzene ring. Among them, the benzene ring is preferable because the yield of the obtained squarylium derivative (1) is good.

A hydrogen atom is particularly preferable as R ¹ and R ² , and a hydrogen atom is particularly preferable as R ³ and R ⁴ .

The squarylium derivative (1) of the present invention is not particularly limited and, for example, compounds having the structures 1-1 to 1-45 below can be specifically exemplified.

In the present specification, Me represents a methyl group.

Among the compounds represented by 1-1 to 1-45, the squarylium derivative (1) of the present invention is 1-1, 1-2, 1-4, 1-16, 1-17 in terms of easy synthesis. , 1-19, 1-31, 1-32 or 1-34 are preferable, and the compounds represented by 1-1, 1-2, 1-4 or 1-34 are particularly preferable.

Next, a method for producing the squarylium derivative (1) of the present invention (hereinafter referred to as the production method of the present invention) will be described.

The squarylium derivative (1) of the present invention can be produced by the step 1 or 2 shown in the following reaction formula.

(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms.
R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group, or a naphthyl group.
Further, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ may be integrated together to form a ring. X ⁻ represents a counter anion. )
Step 1 is a step of reacting an indoline compound (2a) with squaric acid to produce a squarylium derivative (1) of the present invention.

Specific examples of the indoline compound (2a) used in Step 1 include compounds having the structures shown in 2a-1 to 2a-45 below.

Of the compounds represented by 2a-1 to 2a-45, 2a-1, 2a-2, 2a-4, 2a-16, 2a-17, 2a-19, 2a-31, 2a- are easy to synthesize. Compounds represented by 32 or 2a-34 are preferable, and compounds represented by 2a-1 and 2a-2 are particularly preferable. The indoline compound (2a) can be produced by a general method well known to those skilled in the art or the method of step 2. Moreover, you may use a commercial item.

The molar ratio of squaric acid to the indoline compound (2a) used in step 1 is not particularly limited, and the molar ratio of the squaric acid:indoline compound (2a) is in the range of 1:1 to 1:10 in terms of good yield. It is preferable that the amount is in the range of 1:2 to 1:3 from the viewpoint of good reaction yield.

Step 1 can be carried out in a solvent. The solvent that can be used is not particularly limited, and any solvent that does not inhibit the reaction may be used. Specific examples of such a solvent include diisopropyl ether, dibutyl ether, cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane, ethers such as dimethoxyethane, benzene, and toluene. , Aromatic hydrocarbons such as xylene, mesitylene, nitrobenzene, anisole, tetralin, etc., ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, carbonates such as 4-fluoroethylene carbonate, ethyl acetate, butyl acetate, propion Methyl acid, ethyl propionate, methyl butyrate, esters such as γ-lactone, acetonitrile, propionitrile, valeronitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile and other nitriles, methanol, ethanol, propanol Alcohols such as isopropyl alcohol, butanol, isobutyl alcohol, sec-butanol, tert-butanol, and octanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), etc. , N,N,N′,N′-tetramethylurea (TMU), N,N′-dimethylpropyleneurea (DMPU) and other urea, and dimethylsulfoxide (DMSO) can be exemplified, and any of these can be used. You may mix and use at the ratio of. The amount of solvent used is not particularly limited. Of these, toluene, xylene, butanol, octanol and a mixed solvent thereof are preferably used, and a mixed solvent of toluene and butanol is more preferable, from the viewpoint that the reaction yield of the squarylium derivative (1) of the present invention is good.

There is no particular limitation on the reaction temperature when carrying out step 1, and it can be carried out usually at a temperature appropriately selected from 40 to 230° C., and the reaction yield of the squarylium derivative (1) of the present invention is good. In this respect, it is preferable to carry out at a temperature appropriately selected from 120 to 180°C.

The squarylium derivative (1) of the present invention can be obtained by performing an ordinary treatment after the completion of the reaction of step 1. It may be purified by recrystallization, column chromatography, sublimation, preparative HPLC, or the like, if necessary.

In step 2, after reacting the indoline compound (2b) and the hypervalent iodine compound (3a) in the presence of a base, a step of producing the indoline compound (2a) (hereinafter referred to as step 2A) is performed. This is a step of subsequently producing the squarylium (1) of the present invention by the step 1.

As the indoline compound (2b) used in Step 2A, for example, compounds having the structures shown in 2b-1 to 2b-3 below can be specifically exemplified.

Of the compounds represented by 2b-1 to 2b-3, the compound represented by 2b-1 or 2b-3 is preferable in view of easy synthesis, and the compound represented by 2b-1 is particularly preferable. The indoline compound (2b) can be produced by a general method well known to those skilled in the art. For example, according to the method disclosed in Tetrahedron Letters, 2011, 52, 6758-6762, etc. The indoline compound (2b) can be obtained efficiently. Moreover, you may use a commercial item.

The counter anion X ⁻ in the hypervalent iodine compound (3a) used in Step 2A is a halide ion such as a fluoride ion, a chloride ion, a bromide ion or an iodide ion, an inorganic oxo such as a perchlorate ion or a nitrate ion. Examples of organic acid ions such as acid ion, trifluoromethanesulfonate ion, toluenesulfonate ion, hexafluorophosphate ion, hexafluoroarsenate ion, tetrafluoroborate ion or tetrakis(pentafluorophenyl)borate ion You can Among these, an organic acid ion or a hexafluorophosphate ion is preferable, and a trifluoromethanesulfonate ion or a hexafluorophosphate ion is more preferable, from the viewpoint of good reactivity.

Examples of the hypervalent iodine compound (3a) used in step 2A include diphenyliodonium chloride, diphenyliodonium bromide, diphenyliodonium iodide, diphenyliodonium hexafluorophosphate, diphenyliodonium perchlorate, diphenyliodonium nitrate, diphenyliodonium hexafluoro. Arsenate, diphenyliodonium trifluoromethanesulfonic acid, bis(4-tert-butylphenyl)iodonium hexafluorophosphate, bis(4-fluorophenyl)iodonium trifluoromethanesulfonate or bis(4-bromophenyl)iodonium trifluoromethanesulfonate Can be illustrated. Diphenyliodonium trifluoromethanesulfonic acid, bis(4-bromophenyl)iodonium trifluoromethanesulfonate and bis(4-tert-butylphenyl)iodonium hexafluorophosphate are preferable in that the reaction yield of the indoline compound (2a) is good. , Diphenyliodonium trifluoromethanesulfonic acid or bis(4-tert-butylphenyl)iodonium hexafluorophosphate is more preferred. The hypervalent iodide (3a) can be produced by a general method well known to those skilled in the art, and for example, the method disclosed in Chemistry-A European Journal, 2015, 21:16801-16806, etc. According to the above, the hypervalent iodide (3a) can be obtained in good yield. Moreover, you may use a commercial item.

The molar ratio of the hypervalent iodine compound (3a) and the indoline compound (2b) used in step 2A is not particularly limited, and the molar ratio of the hypervalent iodine compound (3a):indoline compound (2b) is 1:2. It is preferably in the range of 10:1, and more preferably in the range of 1:2 to 1:1 in terms of good reaction yield.

Examples of the base used in Step 2A include metal hydroxide salts such as sodium hydroxide, potassium hydroxide and calcium hydroxide, metal carbonate salts such as sodium carbonate, potassium carbonate, lithium carbonate and cesium carbonate, potassium acetate and acetic acid. Metal acetate such as sodium, potassium phosphate, metal phosphate such as sodium phosphate, metal fluoride salt such as sodium fluoride, potassium fluoride, cesium fluoride, sodium methoxide, potassium methoxide, sodium ethoxide And metal alkoxides such as potassium isopropyl oxide and potassium tert-butoxide. Of these, metal alkoxides are preferable, and potassium tert-butoxide is more preferable, from the viewpoint of good reaction yield. There is no particular limitation on the amount of base used. From the viewpoint of good reaction yield, the molar ratio of the base to the hypervalent iodine compound is preferably in the range of 1:2 to 10:1, more preferably in the range of 1:1 to 4:1. preferable.

Step 2A can be performed in a solvent. As the solvent in Step 2A, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane, ethers such as dimethoxyethane; benzene, toluene, xylene, mesitylene, Aromatic hydrocarbons such as tetralin; carbonic acid esters such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-fluoroethylene carbonate; ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate , Esters such as γ-lactone; amides such as N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); N,N,N′,N′-tetramethylurea (TMU ), N,N′-dimethylpropylene urea (DMPU) and other urea; dimethyl sulfoxide (DMSO) and the like. These may be used alone or may be mixed and used at an arbitrary ratio. The amount of solvent used is not particularly limited. Of these, aromatic hydrocarbons are preferable, and benzene or toluene is more preferable, from the viewpoint of good reaction yield.

The reaction temperature for carrying out Step 2A is not particularly limited, and it can be carried out at a temperature appropriately selected from 0 to 150°C, and a temperature appropriately selected from 20 to 80°C in terms of good yield. It is preferable to carry out.

The indoline compound (2a) can be obtained by performing a usual treatment after the completion of the reaction of step 2A. If necessary, it may be purified by recrystallization, column chromatography, sublimation, preparative HPLC or the like, or may be subjected to the step 1 without purification.

Next, an organic thin film containing the squarylium derivative (1) of the present invention as a dye (hereinafter referred to as “organic thin film of the present invention”) will be described.

The organic thin film of the present invention can be produced by forming the squarylium derivative (1) of the present invention into a film. The method for forming the film is not particularly limited, and for example, a known method commonly used by those skilled in the art such as a vacuum vapor deposition method, a spin coating method, an inkjet method, a casting method, and an LB (Langmuir-Blodgett) method can be used. .. In order to produce the organic thin film of the present invention, the squarylium derivative (1) of the present invention may be used alone to form a film, and if necessary, a film is formed by using a material such as a doping agent or a binder resin, and a solvent. You may.

The thickness of the organic thin film is not particularly limited and can be appropriately selected depending on the situation, and is usually in the range of 5 nm to 5 μm.

Further, a photoelectric conversion element containing the squarylium derivative (1) of the present invention (hereinafter, referred to as “photoelectric conversion element of the present invention”) will be described. The photoelectric conversion element of the present invention includes a substrate, a negative electrode layer, a photoelectric conversion layer, and a positive electrode layer. If necessary, a hole transport layer and/or an electron injection blocking layer may be provided between the negative electrode layer and the photoelectric conversion layer, and an electron transport layer and/or a hole injection blocking layer may be provided between the positive electrode layer and the photoelectric conversion layer. May be provided.

The organic thin film of the present invention is used as the photoelectric conversion layer of the photoelectric conversion element of the present invention. The photoelectric conversion layer may contain a doping agent, and examples of the doping agent include [60]fullerene, [70]fullerene, phenyl-C ₆₁ -methyl methyl butyrate ([60]PCBM), and phenyl-C _71. - methyl butyric acid ([70] PCBM), phenyl _{-C 85} - can be exemplified butyrate ([84] PCBM) fullerene derivative, and the like.

The positive electrode layer and the negative electrode layer of the photoelectric conversion element of the present invention are connected to a power source via an electrical conductor such as a lead wire. Either the positive electrode layer or the negative electrode layer can be in contact with the substrate of the photoelectric conversion element of the present invention. The electrode that contacts the substrate is conveniently referred to as the lower electrode. In the photoelectric conversion element of the present invention, either the positive electrode layer or the negative electrode layer may serve as the lower electrode.

At least one of the positive electrode layer and the negative electrode layer (hereinafter, referred to as “electrode”) of the photoelectric conversion element of the present invention, which is a light receiving surface, is preferably light transmissive. As the light-transmissive electrode, a general transparent electrode material can be used, and indium-tin oxide (ITO), indium-zinc oxide (IZO), tin oxide, aluminum or indium-doped tin oxide, Examples thereof include metal oxides such as magnesium-indium oxide and nickel-tungsten oxide, metal nitrides such as gallium nitride, metal selenides such as zinc selenide, and metal sulfides such as zinc sulfide. Metal oxides are preferable, and ITO, IZO, and tin oxide are more preferable, in terms of good light transmittance and conductivity. Also, the electrodes can be modified with plasma-deposited fluorocarbons.

For the other electrode that is not the light-receiving surface, an opaque or reflective electrode material can be used in addition to the transparent electrode material exemplified above. Examples of the opaque or reflective electrode material include gold, iridium, molybdenum, palladium, platinum, sodium, sodium-potassium alloy, magnesium, lithium, magnesium/copper mixture, magnesium/silver mixture, magnesium/aluminum mixture, magnesium/indium. Examples thereof include a mixture, aluminum, an aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, indium, a lithium/aluminum mixture, and a rare earth metal.

The photoelectric conversion element of the present invention is formed on a substrate. The substrate may be light transmissive or opaque, depending on the intended light receiving direction. Light transparency is preferable for receiving light through a substrate, and examples of the substrate include transparent glass, quartz, plastic, and the like. Examples of the opaque substrate include silicon and silicon oxide. Also, the substrate may be a composite structure including multiple layers of material.

In the photoelectric conversion element of the present invention, a hole transport layer may be provided between the negative electrode and the photoelectric conversion layer, and an electron transport layer may be provided between the positive electrode and the photoelectric conversion layer for the purpose of improving carrier transportability. The hole-transporting layer is one having any of hole injection or transport and electron barrier properties, and may be either an organic substance or an inorganic substance. Specifically, a triazole derivative, an oxadiazole derivative, Imidazole derivative, polyarylalkane derivative, pyrazoline derivative and pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, oxazole derivative, styrylanthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative, silazane derivative, aniline-based copolymer Examples of the polymer include a polymer and a conductive polymer oligomer, and poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) can be given as an example. The electron transporting layer is not particularly limited, and it is preferable that the electron injecting efficiency is high and the injected electrons are efficiently transported. Specifically, the nitro-substituted fluorene derivative, the diphenylquinone derivative, and the thiopyran dioxide are preferable. Examples thereof include derivatives, carbodiimides, fluorenylidene methane derivatives, anthraquinodimethane and anthrone derivatives, or oxadiazole derivatives. Further, for the purpose of suppressing the generation of dark current, an electron injection blocking layer may be provided between the negative electrode and the photoelectric conversion layer, and a hole injection blocking layer may be provided between the positive electrode and the photoelectric conversion layer. Examples of the electron injection blocking layer include triarylamines such as 2,7-bis(9-carbazolyl)-9,9-spirobifluorene (Spiro-2CBP). Examples of the hole injection blocking layer include tris(8-quinolinolato)aluminum (Alq ₃ ).

Since the squarylium derivative (1) of the present invention has a narrow half width and high heat resistance, it can be expected to be applied as an organic electronic material represented by an organic photoelectric conversion element.

It is a figure of the normalized absorption spectrum of the organic thin film obtained in Example-1 and Comparative Example-1. It is a cross-sectional schematic diagram of the photoelectric conversion element obtained in Example-5. It is a figure of the measurement result of the external quantum efficiency of the photoelectric conversion element obtained in Example-5.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention should not be construed as being limited thereto.
[ ¹ H-NMR measurement]
Bruker ASCEND 400 (400 MHz; manufactured by BRUKER) was used for ¹ H-NMR measurement. ¹ H-NMR was measured using deuterated chloroform (CDCl ₃ ) as a measurement solvent and tetramethylsilane (TMS) as an internal standard substance. The identification of the compound was performed with reference to The Journal of Organic Chemistry, 2017, 82, 5819-5825 and Journal of American Chemical Society, 1995, 117, 2214-2225.
[TG/DTA measurement]
EXSTAR TG/DTA6200 (product name, manufactured by SII Nanotechnology Inc.) was used to measure the 5% weight loss temperature and the decomposition temperature. The measurement was performed under a nitrogen gas stream (50 mL/min) while raising the temperature at a rate of 10° C./min.
[Thin film production and film thickness measurement]
The thin film was formed by a spin coat method, and a spin coater MS-A100 (manufactured by Mikasa) was used. The substrate used was one that had been cleaned with isopropyl alcohol in advance and then cleaned with oxygen plasma. A stylus type film thickness meter DektakXT (manufactured by BRUKER) was used for film thickness measurement.
[Measurement of absorption spectrum]
For the absorption spectrum measurement, Hitachi spectrophotometer U-4100 (manufactured by Hitachi High-Tech Science) was used. The measurement was performed at a scan speed of 750 nm/min.
[External quantum efficiency measurement]
A solar cell spectral sensitivity measuring device (Soma Optical Co., Ltd.) was used for measuring the external quantum efficiency. The measurement was performed with an irradiation light intensity of 100 μW/cm ² .
As the reagents, commercially available products were used.

Example-1

2,3-Dimethyl-3-phenylindolenine (1.20 g, 5.4 mmol) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (300 mg, 2.6 mmol) were added to toluene (under an argon atmosphere). It was dissolved in a mixed solvent of 50 mL) and butanol (50 mL) and stirred at 130° C. for 14 hours. After allowing to cool to room temperature, the precipitated solid was collected by filtration. This solid was purified by recrystallization from methanol and silica gel column chromatography (chloroform/methanol) to give 2-[{3-[(1,3-dihydro-3-methyl-3-phenyl- 2H-indole-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobutene-1-ylidene}methyl]-3-methyl-3-phenyl-3H-indole (Z,Z-form and Z, A mixture of E-forms (2:1) and Exemplified compound 1-1) were obtained (840 mg, 61%).
¹ H-NMR (CDCl ₃ ): δ 12.92 (s, 1.3H), 12.67 (s, 0.7H), 7.23-7.34 (m, 7.3H), 7.13-. 7.18 (m, 6H), 7.00-7.08 (m, 4.7H), 5.25 (s, 0.7H), 5.20 (s, 1.3H), 1.82 ( s, 6H).

As a result of measuring TG/DTA of the obtained squarylium derivative (1-1), the decomposition temperature was 305°C.

An organic thin film of the obtained squarylium derivative (1-1) was prepared and its absorption characteristics were evaluated. An organic thin film was prepared by preparing a chlorobenzene solution (concentration: 0.5 wt%) of the obtained squarylium derivative (1-1), applying it on a quartz substrate by a spin coating method, and then drying it at 100° C. for 45 minutes under argon. Got The rotation conditions of the spin coating method are 1500 rpm and 30 seconds. The film thickness of the organic thin film was 12 nm. The normalized absorption spectrum of the organic thin film is shown in FIG. The maximum absorption wavelength was 695 nm and the full width at half maximum was 87 nm. In addition, the full width at half maximum in this specification shall represent full width at half maximum (full width at half maximum, FWHM).

Example-2

Under an argon atmosphere, 2,3-dimethylindole (620 mg, 4.3 mmol) and potassium-tert-butoxide (954 mg, 8.5 mmol) were stirred in toluene (20 mL) at 50°C for 10 minutes. After stirring, bis(4-bromophenyl)iodonium triflate (2.50 g, 4.3 mmol) was added, and the mixture was stirred at 50° C. for 18 hours again. After allowing to cool to room temperature, chloroform was added to the reaction mixture to extract an organic layer, the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, the low-boiling fraction was distilled off, and the obtained oily substance was purified by silica gel column chromatography (hexane/ethyl acetate) to give a yellow oily 2,3-dimethyl-3-( 4-Bromophenyl)indolenine was obtained (250 mg, yield 20%).
¹ H-NMR (CDCl ₃ ): δ 7.60 (d, J=7.7 Hz, 1 H), 7.39 (brd, J=8.6 Hz, 2 H), 7.34 (ddd, J=6.4). , 6.4, 1.2 Hz, 1H), 7.16 (ddd, J=6.5, 6.4, 1.0 Hz, 1H), 7.06 (d, J=7.0 Hz, 1H), 6.89 (brd, J=8.6 Hz, 2H), 2.11 (s, 3H), 1.66 (s, 3H).

The resulting 2,3-dimethyl-3-(4-bromophenyl)indolenine (260 mg, 0.87 mmol) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (50 mg, 0 under an argon atmosphere. 0.43 mmol) was dissolved in a mixed solvent of toluene (4.0 mL) and butanol (4.0 mL), and the mixture was stirred at 130° C. for 14 hours. After allowing to cool to room temperature, chloroform was added to the reaction mixture to extract an organic layer, the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, and the low boiling point was distilled off. The obtained solid was purified by silica gel column chromatography (hexane/ethyl acetate), recrystallization from methanol, and then recycle HPLC to give 2-[3-{[1,3-dihydro-3-methyl as a blue solid. -3-(4-Bromophenyl)-2H-indole-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobutene-1-ylidene}methyl]-3-methyl-3-(4-bromo Phenyl)-3H-indole (mixture of Z,Z-form and Z,E-form (2:1), exemplified compound 1-2) was obtained (47 mg, 16%).
¹ H-NMR (CDCl ₃ ): δ 12.93 (s, 1.3H), 12.67 (s, 0.7H), 7.40-7.44 (m, 4H), 7.25-7. 35 (m, 2.7H), 7.16 (d, J=7.8Hz, 1.3H), 7.00-7.07 (m, 8H), 5.23 (s, 0.7H), 5.17 (s, 1.3H), 1.80 (s, 6H).
As a result of measuring TG/DTA of the obtained squarylium derivative (1-2), the decomposition temperature was 298°C.

Example-3

Under an argon atmosphere, 2,3-dimethylindole (0.27 mg, 1.9 mmol) and potassium-tert-butoxide (206 mg, 3.7 mmol) were stirred in toluene (10 mL) at 50° C. for 10 minutes. After stirring, bis(4-tert-butylphenyl)iodonium hexafluorophosphate (1.00 g, 1.9 mmol) was added, and the mixture was stirred again at 50° C. for 18 hours. After allowing to cool to room temperature, chloroform was added to the reaction mixture to extract an organic layer, the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, the low-boiling fraction was distilled off, and the obtained oily substance was purified by silica gel column chromatography (hexane/ethyl acetate) to give a yellow oily 2,3-dimethyl-3-( 4-tert-Butylphenyl)indolenine was obtained (170 mg, 33% yield).
¹ H-NMR (CDCl ₃ ): δ 7.60 (d, J=7.7 Hz, 1 H), 7.31 (brdd, J=7.7, 7.4 Hz, 1 H), 7.28 (brd, J =8.5 Hz, 2 H), 7.14 (brdd, J=7.4, 7.3 Hz, 1 H), 7.10 (brd, J=7.3 Hz, 1 H), 6.97 (brd, J= 8.5 Hz, 2H), 2.14 (s, 3H), 1.67 (s, 3H), 1.28 (brs, 9H).

The obtained 2,3-dimethyl-3-(4-tert-butylphenyl)indolenine (170 mg, 0.60 mmol) and 3,4-dihydroxycyclobut-3-ene-1,2-dione under an argon atmosphere. (30 mg, 0.30 mmol) was dissolved in a mixed solvent of toluene (4 mL) and butanol (4 mL), and the mixture was stirred at 130° C. for 14 hours. After allowing to cool to room temperature, chloroform was added to the reaction mixture to extract an organic layer, the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, and the low boiling point was distilled off. The obtained solid was recrystallized from methanol and then purified by recycling HPLC to give 2-[3-{[1,3-dihydro-3-methyl-3-(4-tert-butylphenyl)) as a blue solid. -2H-indole-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobutene-1-ylidene}methyl]-3-methyl-3-(4-tert-butylphenyl)-3H-indole ( A mixture (2:1) of Z,Z-form and Z,E-form, and Exemplified Compound 1-4) was obtained (96 mg, 51%).
¹ H-NMR (CDCl ₃ ): δ 12.88 (s, 1.3H), 12.62 (s, 0.7H), 7.24-7.33 (m, 6.7H), 7.14 ( d, J=7.9 Hz, 1.3 H), 6.99-7.11 (m, 8 H), 5.25 (d, J=1.4 Hz, 0.7 H), 5.21 (d, J =2.5 Hz, 1.3 H), 1.81 (brs, 6 H), 1.27-1.28 (m, 18 H).
As a result of measuring TG/DTA of the obtained squarylium derivative (1-4), the decomposition temperature was 302°C.

Example-4

1,2-Dimethyl-3H-benzo[e]indole (195 mg, 1.0 mmol), potassium-tert-butoxide (224 mg, 2.0 mmol) and bis(4-tert-butylphenyl)iodonium hexafluoro under an argon atmosphere. Phosphate (538 mg, 1.0 mmol) was stirred in toluene (5 mL) at 50° C. for 18 hours. After allowing to cool to room temperature, water and diethyl ether were added to the reaction mixture to extract an organic layer, and the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, the low-boiling fraction was distilled off, and the obtained oily substance was purified by silica gel column chromatography (hexane/ethyl acetate) to give a yellow oily 1,2-dimethyl-1-( 4-tert-butylphenyl)-1H-benzo[e]indole was obtained (148 mg, yield 45%).
¹ H-NMR (CDCl ₃ ): δ 7.90 (brd, J=8.7 Hz, 1 H), 7.89 (brd, J=8.5 Hz, 1 H), 7.83 (brd, J=8.5 Hz). , 1H), 7.48 (brd, J=8.1 Hz, 1H), 7.30-7.39 (m, 2H), 7.26 (brd, J=8.7 Hz, 2H), 6.98. (Brd, J=8.4 Hz, 2H), 2.17 (s, 3H), 1.84 (s, 3H), 1.28 (brs, 9H).

The obtained 1,2-dimethyl-1-(4-tert-butylphenyl)-1H-benzo[e]indole (148 mg, 0.5 mmol) and 3,4-dihydroxycyclobut-3-ene under an argon atmosphere. -1,2-dione (26 mg, 0.2 mmol) was dissolved in a mixed solvent of toluene (4 mL) and butanol (4 mL), and the mixture was stirred at 130°C for 14 hours. After allowing to cool to room temperature, chloroform was added to the reaction mixture to extract an organic layer, the organic layer was washed with water and then with saturated saline, sodium sulfate was added, and the mixture was stirred at room temperature. The desiccant was filtered off, and the low boiling point was distilled off. The obtained solid was recrystallized from methanol and then purified by recycling HPLC to give 2-[3-{[1,3-dihydro-1-methyl-1-(4-tert-butylphenyl)) as a purple solid. -2H-benzo[e]indole-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobutene-1-ylidene}methyl]-1-methyl-1-(4-tert-butylphenyl)- 1H-benzo[e]indole (mixture of Z,Z-form and Z,E-form (2:1), exemplified compound 1-34) was obtained (125 mg, 59%).
¹ H-NMR (CDCl ₃ ): δ13.07 (s, 1.3H), 12.82 (s, 0.7H), 7.91 (d, J=8.7Hz, 0.7H), 7. 82-7.88 (m, 3.3H), 7.55 (d, J=8.6Hz, 0.7H), 7.42 (dd, J=8.6, 1.5Hz, 1.3H) , 7.26-7.37 (m, 10H), 7.08-7.13 (m, 4H), 5.29 (d, J=2.7 Hz, 0.7H), 5.24 (d, J=3.8 Hz, 1.3 H), 2.00 (d, J=5.3 Hz, 6 H), 1.26-1.28 (m, 18 H).
As a result of measuring TG/DTA of the obtained squarylium derivative (1-34), the decomposition temperature was 294°C.

Comparative Example-1
2-[{3-[(1,3-dihydro-3,3-dimethyl-2H-indole-2-ylidene according to the method disclosed in European Journal of Medicinal Chemistry, 2016, 113, 187-197. ) Methyl]-2-hydroxy-4-oxo-2-cyclobutene-1-ylidene}methyl]-3,3-dimethyl-3H-indole (SQ-1 below) was synthesized and its TG/DTA was measured. The decomposition temperature was 270°C.

An organic thin film of SQ-1 was prepared and its absorption characteristics were evaluated. The film thickness of the organic thin film was 26 nm. The organic thin film was manufactured under the same conditions as in Example-1 in the present specification. The normalized absorption spectrum of the thin film is shown in FIG. The maximum absorption wavelength was 690 nm, and the full width at half maximum was 111 nm.

From the above results, the squarylium derivative (1-1) obtained in Example-1 has a higher 5% weight loss temperature and a higher 5% weight loss temperature than the conventionally known squarylium derivative (SQ-1) obtained in Comparative Example-1. It was found to have a decomposition temperature. Further, since the squarylium derivative (1-1) has a narrower half-width than the conventionally known squarylium derivative, it can be said to have high color purity.

Example-5
A photoelectric conversion element having the squarylium derivative (1-1) of the present invention as a constituent component was produced and its performance was evaluated.

As the substrate, a glass substrate with an ITO transparent electrode in which a 2 mm wide ITO film was patterned in a stripe shape was used. This substrate was washed with isopropyl alcohol and then oxygen plasma washed. A hole transport layer, a photoelectric conversion layer, and a positive electrode layer were sequentially formed on the washed substrate to manufacture a photoelectric conversion element having a light receiving area of 4 mm ² . A schematic sectional view of the photoelectric conversion element is shown in FIG.

As a hole transport layer, a thin film of PEDOT:PSS was prepared by spin coating. PEDOT:PSS was applied by using a commercially available solution (CLEVIOSPCH 8000 manufactured by Heraeus) under the conditions of 3000 rpm and 60 seconds, and dried under air at 200° C. for 15 minutes.

Then, an organic thin film of the squarylium derivative (1-1) of the present invention was formed on the hole transport layer as a photoelectric conversion layer by spin coating. A chlorobenzene solution (concentration: 0.5 wt%) of the squarylium derivative (1-1) of the present invention was prepared, applied under the conditions of 1500 rpm for 30 seconds, and dried under argon at 100°C for 45 minutes.

A metal mask was arranged on the film-forming substrate so as to be perpendicular to the ITO stripe, and aluminum was vacuum-deposited as a positive electrode layer at a film-forming rate of 0.1 nm/sec. After the film formation, this multilayer film was sealed in a nitrogen atmosphere glove box having an oxygen and water concentration of 1 ppm or less to obtain a photoelectric conversion element of the present invention. For sealing, a glass sealing cap and an epoxy type UV curable resin (manufactured by Nagase Chemtex) were used.

The thicknesses of the hole transport layer, the photoelectric conversion layer, and the positive electrode layer were 35 nm, 13 nm, and 50 nm, respectively.

The measurement result of the external quantum efficiency of the photoelectric conversion element is shown in FIG. When the applied voltage was 0.2 V, it had a maximum peak at a wavelength of 690 nm, and the external quantum efficiency at that wavelength was 0.22%. Moreover, when the applied voltage was 0.2 V, the dark current density was 5.3×10 ⁻⁷ A/cm ² . From this, it was found that the photoelectric conversion element of the present invention was driven as a photoelectric conversion element having sensitivity in the red light region.

The squarylium derivative (1) of the present invention can be used as an electronic material such as an organic photodiode material, an organic thin film solar cell material, an organic semiconductor laser material, an organic EL display material, and a photonic crystal material.

1: Glass substrate with ITO transparent electrode 2: Hole transport layer 3: Photoelectric conversion layer 4: Positive electrode layer

Claims (15)

A squarylium derivative represented by the general formula (1).
(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms.
R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group or a naphthyl group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated with each other to form an aliphatic ring or aromatic ring containing the carbon atom to which they are bonded. You may form. ) The squarylium derivative according to claim 1, wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms. The squarylium derivative according to claim 1, wherein R ³ and R ⁴ are hydrogen atoms. The squarylium derivative according to claim 1, wherein R ¹ and R ² are hydrogen atoms. General formula (2a)
(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms.
R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group or a naphthyl group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated together to form an aliphatic ring or aromatic ring containing the carbon atoms to which they are bonded. You may form. ) Indoline compound represented by the formula (1) is reacted with squaric acid.
(In the formula, Ar ¹ , R ¹ , R ² , R ³ and R ⁴ have the same meanings as described above.) A method for producing a squarylium derivative. The method for producing a squarylium derivative according to claim 5, wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms. The method for producing a squarylium derivative according to claim 5, wherein R ³ and R ⁴ are hydrogen atoms. The method for producing a squarylium derivative according to claim 5, wherein R ¹ and R ² are hydrogen atoms. General formula (2b)
(In the formula, R ¹ , R ² , R ^3, and R ⁴ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, a phenyl group, or naphthyl. Represents a group.
In addition, two adjacent R ¹ and R ² , R ² and R ³ , and R ³ and R ⁴ are integrated together to form an aliphatic ring or aromatic ring containing the carbon atoms to which they are bonded. You may form. ) And an indoline compound represented by the general formula (3a)
(In the formula, Ar ¹ represents a monocyclic, linked, or condensed aromatic hydrocarbon group having 6 to 12 carbon atoms, and the aromatic hydrocarbon group is a halogen atom or an alkyl group having 1 to 8 carbon atoms. Or may be substituted with a haloalkyl group having 1 to 8 carbon atoms. X ⁻ represents a counter anion) and is reacted in the presence of a base to give a hypervalent iodine compound represented by the general formula (2a)
(Wherein Ar ¹ , R ¹ , R ² , R ^3, and R ⁴ have the same meanings as described above), and the indoline compound is then reacted with squaric acid. Formula (1)
(In the formula, Ar ¹ , R ¹ , R ² , R ³ and R ⁴ have the same meanings as described above.) A method for producing a squarylium derivative. The method for producing a squarylium derivative according to claim 9, wherein Ar ¹ is a halogen atom or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms. The method for producing a squarylium derivative according to claim 9 or 10, wherein R ³ and R ⁴ are hydrogen atoms. The method for producing a squarylium derivative according to claim 9, wherein R ¹ and R ³ are hydrogen atoms. 13. The method for producing a squarylium derivative according to claim 9, wherein X ⁻ is a trifluoromethanesulfonate ion or a hexafluorophosphate ion. An organic thin film comprising the squarylium derivative according to any one of claims 1 to 4. A photoelectric conversion element comprising the organic thin film according to claim 14.