JP7689451B2 - Indolylmethyleneindandione derivatives, production method and photoelectric conversion element - Google Patents

Description

The present invention relates to an indolyl methylene indandione derivative and a method for producing the same.

Photoelectric conversion elements are used in sensors such as optical sensors and image sensors, and in photovoltaic devices such as solar cells. Photoelectric conversion elements using organic photoelectric conversion materials are disclosed in Patent Document 1 and elsewhere.

As photoelectric conversion elements, elements using silicon semiconductors are widely used, and silicon photodiodes are mainly used as imaging elements. Since such silicon photodiodes have sensitivity over the entire visible light range, color filters with RGB arranged in a mosaic pattern are placed on top of them, and color imaging is performed by assigning each pixel as a light receiving section for each RGB. In this method, the efficiency of light utilization is low due to the loss of incident light in the color filter, and it is feared that this will become a barrier to increasing the sensitivity of imaging elements. Therefore, imaging elements in which organic photoelectric conversion layers of each color of RGB are stacked (hereinafter referred to as stacked organic imaging elements) have been proposed (see, for example, Non-Patent Document 1). In this method, there is no light loss due to the color filter compared to when a color filter is used, and the efficiency of light utilization is several times higher, so it is expected to be used in high-sensitivity devices that have an advantage in miniaturizing pixels associated with the high pixel count of devices such as cameras.

The photoelectric conversion layer of a stacked organic imaging element is required to have high light absorption and wavelength selectivity suitable for the colors of each RGB layer. In the case of the B layer (blue photoelectric conversion layer), it is preferable that the B layer shows maximum absorption in the blue light region of 400 to 500 nm, and has small absorption in the green light region (i.e., 500 to 600 nm) and red light region (i.e., 600 to 700 nm), and a material showing such absorption characteristics is required.

Patent Document 2 describes a photoelectric conversion element containing an indolylmethylene indandione derivative, but it differs from the indolylmethylene indandione derivative of the present invention in that it has a diarylamino group on the indolyl group. It is described that the compound described in this document has a maximum absorption wavelength of 510 nm or more and 600 nm or less, and is also different from the indolylmethylene indandione derivative of the present invention in that it shows a maximum absorption in the green light region.

Patent Document 3 describes an indolyl methylene indandione derivative as a photoelectric conversion material, but it differs from the indolyl methylene indandione derivative of the present invention in that it has an acidic group.

Patent Documents 4 to 6 describe photoelectric conversion elements containing perylene derivatives, coumarin derivatives, dipyrromethene derivatives, etc., but all of these are different from the photoelectric conversion element containing the indolylmethyleneindanedione derivative of the present invention.

Patent No. 4148374 WO2014-051007A1 JP2005-19756A WO2020-195935A1 WO2020-196029A1 WO2021-029223A1

Japanese Journal of Applied Physics, 2011, Vol. 50, p. 024103

The present invention aims to provide a compound that exhibits absorption characteristics suitable for use as a blue light photoelectric conversion material, i.e., that exhibits maximum absorption in the wavelength range of 400 to 500 nm, a method for easily synthesizing the compound, and a photoelectric conversion element that contains the compound.

As a result of intensive research aimed at solving the above problems, the inventors discovered that a novel indolyl methylene indandione derivative exhibits maximum absorption in the wavelength range of 400 to 500 nm and has excellent wavelength selectivity, which led to the completion of the present invention.

That is, the present invention is
[1]
An indolylmethyleneindanedione derivative represented by formula (1):

In formula (1), R ¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a heteroaromatic group having 3 to 18 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms, and the aryl group, aralkyl group, and heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. ^R2 and ^R3 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, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. ^R2 and ^R3 may combine with each other to form an alkylene group having 2 to 6 carbon atoms. R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms and a halogen atom. R ⁷ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms and a halogen atom, provided that R ² to R ¹³ cannot all be hydrogen atoms; and n represents an integer of 0 to 3;
[2]
The indolylmethylene indanedione derivative according to the above item [1], wherein R ¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom;
[3]
The indolylmethylene indanedione derivative according to the above [1] or [2], wherein R ² and R ³ are a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and the aryl group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom;
[4]
The indolyl methylene indanedione derivative according to any one of the above [1] to [3], wherein R ⁴ , R ⁵ _, R ⁶ and R ⁷ are hydrogen atoms;
[5]
The indolylmethylene indanedione derivative according to any one of the above [1] to [4], wherein R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are hydrogen atoms, and n is 0 or 1.
[6]
Formula (2)

(In the formula, R ¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a heteroaromatic group having 3 to 18 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms, and the aryl group, aralkyl group, and heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. ^{R 2} and R ^{R 3} each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. R ² and R ³ may be bonded together to form an alkylene group having 2 to 6 carbon atoms. ^{R 4} , R ⁵ , and R ^{R 6} each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. R ⁷ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, with the proviso that R ² to R ⁷ cannot simultaneously be hydrogen atoms.

(wherein R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom; and n represents an integer of 0 to 3),

(wherein R ¹ to R ¹³ and n are as defined above);
[7]
A method for producing an indolyl methylene indandione derivative according to [6], which comprises reacting a 5-carboxyindole derivative with a 1,3-indandione derivative in the presence of an acid.
[8]
A method for producing an indolyl methylene indandione derivative according to [6], which comprises reacting a 5-carboxyindole derivative with a 1,3-indandione derivative in the presence of a base.
[9]
A photoelectric conversion element comprising the indolylmethyleneindanedione derivative according to any one of [1] to [5] above;
[10]
A photoelectric conversion element comprising the indolyl methylene indanedione derivative according to any one of [1] to [5] above in a photoelectric conversion layer;
[11]
The photoelectric conversion element according to the above [10], wherein the photoelectric conversion layer further contains a fullerene derivative;
[12]
The photoelectric conversion element according to the above [11], wherein the fullerene derivative is _C60 or _C70 .

The present invention is described in detail below.

The definitions of ^R1 , ^R2 , ^R3 , ^R4 , ^R5 , ^R6 , ^R7 , R8, ^R9 , ^R10 , ^R11 , ^R12 , ^R13 and n in the indolyl methylene indandione derivative (1) of the present invention will be explained ^below .

R ¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a heteroaromatic group having 3 to 18 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms, and the aryl group, aralkyl group, and heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom.

The alkyl group having 1 to 8 carbon atoms represented by ^R1 may be any of a linear, branched, or cyclic alkyl group, and specific examples thereof include a methyl group, a cyclohexylmethyl group, an ethyl group, a 2-cyclopentylethyl group, a propyl group, a 2-methylpropyl group, a 2,2-dimethylpropyl group, a 3-cyclopropylpropyl group, an isopropyl group, a cyclopropyl group, a butyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-butyl group, a 3-methylbutan-2-yl group, a tert-butyl group, a cyclobutyl group, a pentyl group, a 2-methylpentyl group, a 3-ethylpentyl group, a 2,4-dimethylpentyl group, a 2-pentyl group, a 2-methylpentan-2-yl group, a 4,4-dimethylpentan-2-yl group, a 3-pentyl group, a 3-ethylpentan-3-yl group, a cyclopentyl group, a 2,5-dimethylcyclopentyl group, a 3-ethylcyclopentyl group, a hexyl group, a 2-methylhexyl group, a 3,3-dimethylhexyl group, a 4-ethylhexyl group, a 2-hexyl group, a 2-methylhexan-2-yl group, a 5,5-dimethyl Examples of the aryl group include an arylhexyl group, an arylhexyl group, a 3-hexyl group, a 2,4-dimethylhexyl group, a cyclohexyl group, a 4-ethylcyclohexyl group, a 4,4-dimethylcyclohexyl group, a heptyl group, a 2-heptyl group, a 3-heptyl group, a 4-heptyl group, a bicyclo[2.2.1]heptyl group, an octyl group, a 2-octyl group, a 3-octyl group, a 4-octyl group, a cyclooctyl group, and a bicyclo[2.2.2]octyl group. From the viewpoint of ease of synthesis, a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group, a 2,2-dimethylpropyl group, an isopropyl group, a butyl group, a 2-butyl group, a tert-butyl group, a pentyl group, a 2-pentyl group, a 3-pentyl group, a cyclopentyl group, a hexyl group, a 2-hexyl group, a 3-hexyl group, or a cyclohexyl group is preferred, and a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group, an isopropyl group, a tert-butyl group, a cyclopentyl group, or a cyclohexyl group is more preferred.

The haloalkyl group having 1 to 4 carbon atoms represented by ^R1 may be any of a linear, branched, or cyclic haloalkyl group, and specific examples thereof include a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1-difluoroethyl group, a 2,2-difluoroethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a 2,2,3,3-tetrafluoropropyl group, a 3,3,3-trifluoropropyl group, a 1,1-difluoropropyl group, a perfluoroisopropyl group, a 2,2,2-trifluoro-1-(trifluoropropyl) group, a Examples of such a group include a fluoroalkyl group, a perfluorocyclopropyl group, a 2,2,3,3-tetrafluorocyclopropyl group, a perfluorobutyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 3,3,4,4,4-pentafluorobutyl group, a 4,4,4-trifluorobutyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, a 2-chloroethyl group, and a 3-bromopropyl group. In terms of ease of synthesis of the indolylmethyleneindanedione derivative (1), a fluoroalkyl group is preferred, and a 2,2,2-trifluoroethyl group is more preferred.

The aryl group having 6 to 14 carbon atoms represented by ^R1 is not particularly limited, and specific examples thereof include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group, a 3,5-terphenylyl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-phenanthrenyl group, a 2-phenanthrenyl group, a 3-phenanthrenyl group, a 4-phenanthrenyl group, a 9-phenanthrenyl group, a 1-fluorenyl group, a 2-fluorenyl group, a 3-fluorenyl group, a 4-fluorenyl group, a 9,9-diphenyl group, a 2-phenyl group, a 3-phenyl group, a 4- ...2-phenyl group, a 3-phenyl group, a 4-phenyl group, a 2-phenyl group, a 2-phenyl group, a 3-phenyl group, a 4-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group, a 2-phenyl group Examples of the alkyl group include methyl-9H-fluoren-1-yl, 9,9-dimethyl-9H-fluoren-2-yl, 9,9-dimethyl-9H-fluoren-3-yl, 9,9-dimethyl-9H-fluoren-4-yl, 1-pyrenyl, 2-pyrenyl, 9-pyrenyl, 1-triphenylenyl, and 2-triphenylenyl groups. Of these, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenylyl group, a 3-biphenylyl group, and a 4-biphenylyl group are preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

The aryl group having 6 to 14 carbon atoms, represented by ^R1, may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. The alkyl group having 1 to 4 carbon atoms may be any of a linear, branched, or cyclic alkyl group, and specific examples thereof include a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group, an isopropyl group, a cyclopropyl group, a butyl group, a 2-butyl group, a tert-butyl group, and a cyclobutyl group. A methyl group is preferable in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). In the dialkylamino group having 2 to 5 carbon atoms, the two alkyl groups may be either linear or branched, and the two alkyl groups may be combined together to form a ring, and specific examples thereof include a dimethylamino group, a diethylamino group, a 1-pyrrolidinyl group, and a 1-piperidinyl group, with the dimethylamino group or the 1-pyrrolidinyl group being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). In the diarylamino group having 12 to 18 carbon atoms, the two aryl groups may be bonded to form a ring, and specific examples thereof include a diphenylamino group, a 1-naphthyl(phenyl)amino group, a 2-naphthyl(phenyl)amino group, and a 9-carbazoyl group, and the like, with the diphenylamino group or the 9-carbazoyl group being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Specific examples of the aralkyl group having 7 to 12 carbon atoms represented by ^R1 include a phenylmethyl group and a phenylethyl group, and the phenylmethyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

The heteroaromatic group having 3 to 18 carbon atoms represented by ^R1 is not particularly limited, and specific examples thereof include 2-furanyl group, 3-furanyl group, 2-thienyl group, 3-thienyl group, 1-pyrrolyl group, 2-pyrrolyl group, 3-pyrrolyl group, 2-pyridyl group, 3-pyridyl group, 4-pyridyl group, 2-quinolyl group, 3-quinolyl group, 4-quinolyl group, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8-quinolyl group, 2-benzofuranyl group, 3-benzofuranyl group, 2-benzothienyl group, 3-benzothienyl group, 1-indolyl group, 2-indolyl group, 3-indolyl group, 1-carbazoyl group, 2-carbazoyl group, 3-carbazoyl group, 4-carbazoyl group, 9-phenyl-9H Examples of the aryl group include 1-carbazol-1-yl group, 9-phenyl-9H-carbazol-2-yl group, 9-phenyl-9H-carbazol-3-yl group, 9-phenyl-9H-carbazol-4-yl group, dibenzofuran-2-yl group, dibenzofuran-3-yl group, dibenzofuran-4-yl group, dibenzothiophen-2-yl group, dibenzothiophen-3-yl group, and dibenzothiophen-4-yl group. Of these, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-quinolyl group, a 3-quinolyl group, a 4-quinolyl group, a 5-quinolyl group, a 6-quinolyl group, a 7-quinolyl group, or an 8-quinolyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

The heteroaromatic group having 3 to 18 carbon atoms represented by ^R1 may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. The alkyl group having 1 to 4 carbon atoms may be any of a linear, branched, or cyclic alkyl group, and specific examples thereof include a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group, an isopropyl group, a cyclopropyl group, a butyl group, a 2-butyl group, a tert-butyl group, and a cyclobutyl group. A methyl group is preferable in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). In the dialkylamino group having 2 to 5 carbon atoms, the two alkyl groups may be either linear or branched, and the two alkyl groups may be combined together to form a ring, and specific examples thereof include a dimethylamino group, a diethylamino group, a 1-pyrrolidinyl group, and a 1-piperidinyl group, with the dimethylamino group or the 1-pyrrolidinyl group being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). In the diarylamino group having 12 to 18 carbon atoms, the two aryl groups may be bonded to form a ring, and specific examples thereof include a diphenylamino group, a 1-naphthyl(phenyl)amino group, a 2-naphthyl(phenyl)amino group, and a 9-carbazoyl group, and the like, with the diphenylamino group or the 9-carbazoyl group being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom being preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

The trialkylsilylalkyl group having 4 to 7 carbon atoms represented by ^R1 is not particularly limited, and specific examples thereof include a trimethylsilylmethyl group, a triethylsilylmethyl group, a dimethyl-tert-butylsilylmethyl group, a bis(trimethylsilyl)methyl group, and the like. In terms of ease of synthesis of the indolylmethyleneindanedione derivative (1), a trimethylsilylmethyl group is preferred.

^R1 is more preferably an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms and a halogen atom, and is most preferably an alkyl group having 1 to 8 carbon atoms.

^R2 and ^R3 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, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. ^R2 and ^R3 may combine with each other to form an alkylene group having 2 to 6 carbon atoms.

Examples of the halogen atom represented by ^R2 and ^R3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. A fluorine atom is preferred in that the indolylmethyleneindanedione derivative (1) has excellent absorption properties.

Examples of the alkyl group having 1 to 8 carbon atoms represented by ^R2 and ^R3 include the same alkyl group having 1 to 8 carbon atoms as exemplified by ^R1 , and a methyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1). ^R2 and ^R3 may be bonded together to form an alkylene group having 2 to 6 carbon atoms, and specific examples thereof include a cyclobutene ring, a cyclopentene ring, a cyclohexene ring, a cycloheptene ring, or a cyclooctene ring containing a double bond between the carbon atoms to which ^R2 and ^R3 are bonded. A cyclopentene ring or a cyclohexene ring is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

The haloalkyl group having 1 to 8 carbon atoms represented by ^R2 and ^R3 may be any of linear, branched, and cyclic haloalkyl groups, and specific examples thereof include a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1-difluoroethyl group, a 2,2-difluoroethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a 2,2,3,3-tetrafluoropropyl group, a 3,3,3-trifluoropropyl group, a 1,1-difluoropropyl group, a perfluoroisopropyl group, a 2,2,2-trifluoropropyl group, a -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-hexafluoro perfluorocyclobutyl 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-unfluoro Examples of the alkyl group include a decafluorohexyl group, a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, a 4,4,5,5,6,6,6-heptafluorohexyl group, a 5,5,6,6,6-pentafluorohexyl group, a 6,6,6-trifluorohexyl group, a perfluorocyclohexyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, a 2-chloroethyl group, and a 3-bromopropyl group. From the viewpoint of ease of synthesis of the indolylmethyleneindanedione derivative (1), a trifluoromethyl group or a 2,2,2-trifluoroethyl group is preferred.

Examples of the aryl group having 6 to 14 carbon atoms represented by ^R2 and ^R3 include the same aryl groups having 6 to 14 carbon atoms as exemplified by ^R1 , and a phenyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the heteroaromatic group having 3 to 18 carbon atoms represented by ^R2 and ^R3 include the same heteroaromatic groups having 3 to 18 carbon atoms as exemplified by ^R1 , and a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

^R2 and ^R3 are more preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and the aryl group may be substituted with one or more of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom, and are most preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom.

Examples of the alkyl group having 1 to 8 carbon atoms represented by R ⁴ , R ⁵ , and R ⁶ include the same alkyl groups having 1 to 8 carbon atoms as exemplified by R ¹ , and a methyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the aryl group having 6 to 14 carbon atoms represented by R ⁴ , R ⁵ , and R ⁶ include the same aryl groups having 6 to 14 carbon atoms as exemplified for R ¹ , and a phenyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the heteroaromatic groups having 3 to 18 carbon atoms represented by R ⁴ , R ⁵ and R ⁶ include the same heteroaromatic groups having 3 to 18 carbon atoms as exemplified for R ¹ , and among these, a 2-pyridyl group, a 3-pyridyl group or a 4-pyridyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

R ⁴ , R ⁵ and R ⁶ are more preferably hydrogen atoms in terms of ease of synthesis.

^R7 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

Examples of the alkyl group having 1 to 8 carbon atoms represented by ^R7 include the same alkyl groups having 1 to 8 carbon atoms as exemplified for ^R1 , and a methyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the aryl group having 6 to 14 carbon atoms represented by ^R7 include the same aryl groups having 6 to 14 carbon atoms as exemplified by ^R1 , and a phenyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

^R7 is more preferably a hydrogen atom in terms of ease of synthesis.

R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group are optionally substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom.

Examples of the halogen atom represented ^by R8, ^R9 , ^R10 , ^R11 , ^R12 , and ^R13 include the same halogen atoms as those exemplified for ^R2 and ^R3 , and a fluorine atom or a chlorine atom is preferred in terms of facilitating the synthesis of the indolylmethyleneindanedione derivative (1).

The alkyl group having 1 to 4 carbon atoms represented by R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ may be any of linear, branched or cyclic alkyl groups. Specific examples thereof include a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group, an isopropyl group, a cyclopropyl group, a butyl group, a 2-butyl group, a tert-butyl group and a cyclobutyl group. A methyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the aryl group having 6 to 14 carbon atoms represented by R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ include the same aryl groups having 6 to 14 carbon atoms as exemplified for R ¹ , and a phenyl group is preferred in terms of ease of synthesis of the indolylmethyleneindanedione derivative (1).

Examples of the heteroaromatic groups having 3 to 18 carbon atoms represented by R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ include the same heteroaromatic groups having 3 to 18 carbon atoms as exemplified for R ^1. In terms of excellent absorption properties of the indolylmethyleneindanedione derivative (1), a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-quinolyl group, a 3-quinolyl group, a 4-quinolyl group, a 5-quinolyl group, a 6-quinolyl group, a 7-quinolyl group or an 8-quinolyl group is preferred.

R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are more preferably a hydrogen atom.

Although specific examples of R ² to R ¹³ are given above, R ² to R ¹³ cannot simultaneously be hydrogen atoms.

n represents an integer of 0 to 3. In terms of ease of synthesis of the indolyl methylene indandione derivative (1), n is preferably an integer of 0 to 2, and more preferably 0 or 1.

The indolyl methylene indandione derivative (1) of the present invention is not particularly limited, and specific examples include compounds having the structures shown in 1-1 to 1-74 below.

In this specification, Me represents a methyl group.

Among the compounds represented by 1-1 to 1-74, the indolyl methylene indandione derivative (1) of the present invention is preferably a compound represented by 1-1, 1-2, 1-3, 1-4, 1-5, 1-8, 1-9, 1-10, 1-11, 1-13, 1-31, 1-37, 1-38, 1-47, 1-48 or 1-60 in terms of ease of synthesis, and more preferably a compound represented by 1-1 or 1-2.

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

The indolyl methylene indandione derivative (1) of the present invention can be produced by step 1 shown in the following reaction scheme.

(In the formula, R ¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a heteroaromatic group having 3 to 18 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms, and the aryl group, aralkyl group, and heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. ^{R 2} and R ^{R 3} each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. R ² and R ³ may be bonded together to form an alkylene group having 2 to 6 carbon atoms. ^{R 4} , R ⁵ , and R ^{R 6} each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. R ⁷ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms. R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , and R ¹³ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms and a halogen atom. However, R ² to R ¹³ cannot all be hydrogen atoms. n represents an integer of 0 to 3.
Step 1 is a step for producing the indolylmethyleneindandione derivative (1) of the present invention by reacting a 5-carboxyindole derivative (2) with a 1,3-indandione derivative (3).

Substituents in the 5-carboxyindole derivative (2) used in step 1 can be the same as those in the indolylmethyleneindanedione derivative represented by formula (1), and in terms of ease of synthesis, R ¹ , R ² , R ³ , R 4, R ⁵ , R ^{6 ,} and R ⁷ are preferably an alkyl group having 1 to 8 carbon atoms, ^an aryl group having 6 to 14 carbon atoms, or a heteroaromatic group having 3 to 18 carbon atoms, and the aryl group and the heteroaromatic group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a dialkylamino group having 2 to 5 carbon atoms, a diarylamino group having 12 to 18 carbon atoms, and a halogen atom. In terms of ease of synthesis, R ² and R ³ are preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and the aryl group may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms and a halogen atom. From the viewpoint of ease of synthesis, R ⁴ , R ⁵ _, R ⁶ and R ⁷ are preferably hydrogen atoms.

Specific examples of the 5-carboxyindole derivative (2) used in step 1 include compounds having structures shown in the following structures 2-1 to 2-66.

Among the compounds represented by 2-1 to 2-66, compounds represented by 2-1, 2-2, 2-3, 2-4, 2-7, 2-8, 2-9, 2-10, 2-12, 2-30, 2-37, 2-38, 2-47, 2-48, 2-49, 2-50, 2-51 or 2-52 are preferred in terms of ease of synthesis, and compounds represented by 2-1, 2-2, 2-7, 2-8, 2-9, 2-10, 2-37, 2-38, 2-47, 2-48, 2-51 or 2-52 are more preferred. The 5-carboxyindole derivative (2) can be produced by a general method well known to those skilled in the art, for example, according to the method disclosed in Journal of the American Chemical Society, 2008, Vol. 130, pp. 2926-2927 or Chemistry - A European Journal, 2013, Vol. 19, pp. 15093-15096. Commercially available products may also be used.

Examples of the substituent in the 1,3-indandione derivative (3) used in step 1 include the same as the substituent in the indolylmethyleneindandione derivative represented by formula (1). In terms of ease of synthesis, R ⁸ , ^{R 9} , R 10 , R ¹¹ , R ¹² and R ¹³ are preferably a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a phenyl group, more preferably a hydrogen atom; and n is preferably 0 to 2, more preferably 0 or 1.

Specific examples of the 1,3-indandione derivative (3) used in step 1 include compounds having structures shown in the following structures 3-1 to 3-21.

Among the compounds represented by 3-1 to 3-21, the compounds represented by 3-1, 3-2, 3-3, 3-4, 3-7, or 3-13 are preferred in terms of ease of synthesis, and the compounds represented by 3-1 or 3-2 are more preferred. The 1,3-indanedione derivative (3) can be produced by a general method well known to those skilled in the art, for example, according to the method disclosed in Helvetica Chimica Acta, 2019, Vol. 102, p. e1900229 or Dyes and Pigments, 2020, Vol. 175, p. 108182. Commercially available products may also be used.

There is no particular restriction on the molar ratio of the 5-carboxyindole derivative (2) to the 1,3-indandione derivative (3) used in step 1. In terms of good yield, the molar ratio of the 5-carboxyindole derivative (2):1,3-indandione derivative (3) is preferably in the range of 10:1 to 1:10, and in terms of good reaction yield, it is even more preferable that it is in the range of 2:1 to 1:2.

Step 1 can be carried out in a solvent. There are no particular limitations on the solvent that can be used, and any solvent that does not inhibit the reaction may be used. Specific examples of such solvents include ethers such as diisopropyl ether, dibutyl ether, cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane, and dimethoxyethane; aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, and tetralin; aliphatic hydrocarbons such as pentane, hexane, heptane, octane, and cyclohexane; carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and 4-fluoroethylene carbonate; ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate. Examples of the solvent include esters such as methyl butyrate, methyl butyrate, and γ-lactone; amides such as N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); ureas such as N,N,N',N'-tetramethylurea (TMU), N,N'-dimethylpropyleneurea (DMPU), and dimethylsulfoxide (DMSO); and alcohols such as methanol, ethanol, isopropyl alcohol, butanol, octanol, benzyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and 2,2,2-trifluoroethanol; and the like, which may be mixed in any ratio. There is no particular limit to the amount of the solvent used. In terms of the good reaction yield of the indolyl methylene indandione derivative (1) of the present invention, aliphatic hydrocarbons or alcohols are preferred, and octane or ethanol is more preferred.

The reaction in step 1 can be promoted by carrying out the reaction in the presence of an acid. The acid used is not particularly limited, and may be either an inorganic acid or an organic acid. Examples of inorganic acids include hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, etc., and examples of organic acids include carboxylic acids such as acetic acid, propionic acid, benzoic acid, etc., and sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc. Hydrochloric acid, sulfuric acid, or p-toluenesulfonic acid is preferred, and p-toluenesulfonic acid is more preferred, in terms of the good reaction yield of the indolylmethyleneindanedione derivative (1) of the present invention.

There are no particular limitations on the molar equivalent of the acid used in step 1, but in terms of good yield, the molar ratio of the 1,3-indandione derivative (3) to the acid is preferably in the range of 100:1 to 1:100, and in terms of good reaction yield, it is even more preferable that it is in the range of 10:1 to 1:10. The reaction can be promoted by carrying out step 1 in the presence of a base. The base used is not particularly limited, and may be either an inorganic base or an organic base. Examples of the inorganic base include metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; metal carbonates such as sodium carbonate, potassium carbonate, lithium carbonate, and cesium carbonate; metal acetates such as potassium acetate and sodium acetate; metal phosphates such as potassium phosphate and sodium phosphate; metal hydrides such as sodium hydride, potassium hydride, and calcium hydride; metal alkyl oxides such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium isopropyl oxide, and potassium tert-butoxide; and examples of the organic base include tertiary alkyl amines such as trimethylamine, triethylamine, diisopropylethylamine, and tributylamine; cyclic azines such as pyridine, pyrazine, and quinoline; and secondary cyclic amines such as pyrrolidine, piperidine, piperazine, N-methylpiperazine, and morpholine. In terms of the good reaction yield of the indolylmethyleneindanedione derivative (1) of the present invention, organic bases such as triethylamine, piperidine, piperazine, and N-methylpiperazine are preferred, and piperidine or N-methylpiperazine is more preferred.

There is no particular restriction on the molar equivalent of the base used in step 1, and in terms of good yield, the molar ratio of the 1,3-indandione derivative (3) to the base is preferably in the range of 500:1 to 1:100, and in terms of good reaction yield, it is more preferably in the range of 100:1 to 1:10. There is no particular restriction on the reaction temperature when carrying out step 1, and it can usually be carried out at a temperature appropriately selected from -80 to 200°C, and in terms of good reaction yield of the indolyl methylene indandione derivative (1) of the present invention, it is preferably carried out at a temperature appropriately selected from 0°C to 150°C, and more preferably carried out at a temperature appropriately selected from 10°C to 140°C.

The indolyl methylene indandione derivative (1) of the present invention can be obtained by carrying out a normal treatment after the completion of the reaction in step 1. If necessary, it may be purified by recrystallization, column chromatography, sublimation, preparative HPLC, or the like.

Furthermore, a photoelectric conversion element containing the indolyl methylene indandione derivative (1) of the present invention (hereinafter referred to as the "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. In addition, 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.

In the photoelectric conversion element of the present invention, the indolyl methylene indanedione derivative (1) of the present invention may be used in any layer, but is preferably used in the photoelectric conversion layer.
The photoelectric conversion layer may contain a dopant. Examples of the dopant include fullerene derivatives such as [60]fullerene (C ₆₀ ), [70]fullerene (C ₇₀ ), phenyl-C ₆₁ -methyl butyrate ([60]PCBM), phenyl-C ₇₁ -methyl butyrate ([70]PCBM), and phenyl-C ₈₅ -methyl butyrate ([84]PCBM), among which [60]fullerene (C ₆₀ ) or [70]fullerene (C ₇₀ ) is preferred.

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 transport. The hole transport layer has either hole injection or transport, or electron barrier properties, and may be either an organic or inorganic material. Specifically, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers can be mentioned, and in particular poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) can be exemplified. The electron transport layer is not particularly limited, and preferably has high electron injection efficiency and efficiently transports injected electrons. Specific examples include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidene methane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. In addition, for the purpose of suppressing dark current generation, 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 naphthalene tetracarboxylic acid diimides such as N,N'-di(4-pyridyl)-1,4,5,8-naphthalene tetracarboxylic acid diimide, tris(8-quinolinolato)aluminum (Alq ₃ ), and the like. The hole transport layer may also function as an electron injection blocking layer, and the electron transport layer may also function as a hole injection blocking layer.

The photoelectric conversion layer, hole transport layer, electron transport layer, hole injection blocking layer, and electron injection blocking layer (hereinafter referred to as "organic layer") of the photoelectric conversion element of the present invention may be produced by any method, but may be formed by vacuum deposition. Film formation by vacuum deposition may be performed by using a general-purpose vacuum deposition apparatus. In consideration of the production takt time and production cost of the organic electroluminescent device, the degree of vacuum in the vacuum chamber when forming a film by vacuum deposition is preferably about 1×10 ⁻² to 1×10 ⁻⁵ Pa, which can be achieved by a commonly used diffusion pump, turbomolecular pump, cryopump, or the like. The deposition rate depends on the thickness of the film to be formed, but is preferably 0.005 to 1.0 nm/sec. In addition, film formation by a spin coat method, inkjet method, cast method, dip method, or the like using a general-purpose apparatus is also possible.

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. For convenience, the electrode in contact with the substrate is called the lower electrode. In the photoelectric conversion element of the present invention, either the positive electrode layer or the negative electrode layer may be the lower electrode.

As for the positive electrode layer and the negative electrode layer (hereinafter referred to as "electrode") of the photoelectric conversion element of the present invention, at least one of them, which is the light receiving surface, is preferably optically transparent. As the optically transparent electrode, a general transparent electrode material can be used, and examples thereof include metal oxides such as indium-tin oxide (ITO), indium-zinc oxide (IZO), tin oxide, aluminum or indium-doped tin oxide, magnesium-indium oxide, or nickel-tungsten oxide, metal nitrides such as gallium nitride, metal selenides such as zinc selenide, or metal sulfides such as zinc sulfide. Metal oxides are preferred in terms of good optical transparency and electrical conductivity, and ITO, IZO, and tin oxide are more preferred. In addition, the electrode can be modified with plasma-deposited fluorocarbon.

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

There are no particular limitations on the manufacturing method of the electrodes of the photoelectric conversion element of the present invention, but film formation can be achieved by vacuum deposition, sputtering, electron beam deposition, chemical reaction methods (such as the sol-gel method), coating methods, etc.

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

There is no particular limitation on the method for producing the photoelectric conversion element of the present invention, but it can be produced by sequentially depositing an electrode layer, an organic layer, and an electrode layer on a substrate. Note that a substrate on which an electrode layer has already been deposited may be used, and an organic layer and an electrode layer may be sequentially deposited on the substrate.

The indolyl methylene indandione derivative (1) of the present invention has a maximum absorption in the blue light region and has photoelectric conversion ability, and therefore is expected to be used as an organic electronic material, such as a blue light organic photoelectric conversion element.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to these.
[ ¹ H-NMR measurement]
For ¹ H-NMR measurement, a Bruker ASCEND 400 (400 MHz; manufactured by BRUKER) was used. ¹ H-NMR was measured using deuterated chloroform (CDCl ₃ ) as a measurement solvent and tetramethylsilane (TMS) as an internal standard substance [Thin film preparation, photoelectric conversion element preparation, and film thickness measurement]
The thin film and the photoelectric conversion element were prepared by vacuum deposition using EROLA-500 (manufactured by ULVAC KIKO Co., Ltd.). The substrate was previously washed with a neutral detergent and pure water, dried, and then washed with oxygen plasma. A stylus-type film thickness gauge DektakXT (manufactured by BRUKER) was used to measure the film thickness.
[Absorption spectrum measurement]
The absorption spectrum was measured using a spectrophotometer V-750 (manufactured by JASCO Corporation) at a scan speed of 400 nm/min. A thin film prepared on a quartz substrate by vacuum deposition was used as the measurement sample.
[External quantum efficiency measurement]
The external quantum efficiency was measured using a solar cell spectral response measurement device (manufactured by Soma Optical Co., Ltd.) at an irradiation light intensity of 50 μW/cm ² .

Commercially available reagents were used.

Synthesis example 1

5-Bromo-3-methyl-1H-indole (5.0 g, 24 mmol) was dissolved in dimethylformamide (100 mL), sodium hydride (1.4 g, 36 mmol) was added in an ice bath, and the mixture was stirred for 30 minutes. After that, isobutyl bromide (3.9 g, 29 mmol) was added and the mixture was stirred at room temperature for 16 hours. Water was added to this solution to stop the reaction, and the mixture was extracted with hexane. The extract was dried over magnesium sulfate, and low boiling points were distilled off under reduced pressure to obtain 5-bromo-1-isobutyl-3-methyl-1H-indole (5.3 g, 83%).
¹ H-NMR (CDCl ₃ ): δ7.67 (d, J=2.0Hz, 1H), 7.24 (dd, J=8.8, 2.0Hz, 1H), 7.14 (d, J=8.8Hz, 1H), 6.84 (d, J=1 .2Hz, 1H), 3.81 (d, J = 7.2Hz, 2H), 2.28 (d, J = 1.2Hz, 3H), 2.14 (m, 1H) 0.90 (d, J = 7.2Hz, 6H).

Synthesis example 2

5-Bromo-1-isobutyl-3-methyl-1H-indole (3.0 g, 11 mmol) obtained in Synthesis Example-1 was dissolved in THF (50 mL), and 1.55 M n-butyllithium/hexane solution (14 mL, 22 mmol) was added at -78°C and stirred for 1 hour, after which dimethylformamide (4.3 mL, 55 mmol) was added and stirred for 2 hours while warming to room temperature. Water was added to this solution to stop the reaction, and the mixture was extracted with hexane. The resulting extract was dried over magnesium sulfate, and low boiling points were distilled off under reduced pressure to obtain 1-isobutyl-3-methyl-1H-indole-5-carbaldehyde (2.3 g, 96%).
¹ H-NMR (CDCl ₃ ): δ10.03 (s, 1H), 8.81 (d, J = 1.6Hz, 1H), 7.75 (dd, J = 8.8, 1.6Hz, 1H), 7.35 (d, J = 8.8Hz, 1H), 6.93 (d, J = 0.8 Hz, 1 H), 3.88 (d, J = 7.2 Hz, 2 H), 2.37 (d, J = 0.8 Hz, 3 H), 2.17 (m, 1 H) 0.93 (d, J = 7.2 Hz, 6 H).

Synthesis Example 1

1-Isobutyl-3-methyl-1H-indole-5-carbaldehyde (2.3 g, 11 mmol) and 1,3-indandione (1.6 g, 11 mmol) obtained in Synthesis Example 2 were suspended in ethanol (50 mL) and stirred at room temperature for 16 hours. The precipitated solid was collected by filtration and washed with ethanol and hexane to obtain 2-[(1-isobutyl-3-methyl-1H-indol-5-yl)methylene]-1,3-indandione as a yellow solid (0.96 g, 25%).
¹ H-NMR (CDCl ₃ ): δ8.94 (d, J=1.6Hz, 1H), 8.47 (dd, J=8.8, 1.6Hz, 1H), 8.10 (s, 1H), 8.03-7.95 (m, 2H), 7.80-7.74 (m, 2H), 7.36 (d, J = 8.8Hz, 1H), 6.91 (d, J = 1.2Hz, 1H), 3.89 (d, J = 7.2Hz, 2H), 2.42 (d, J = 1.2Hz, 3H), 2.19 (m, 1H) 0.94 (d, J = 7.2Hz, 6H).

Synthesis Example 2

1-Isobutyl-3-methyl-1H-indole-5-carbaldehyde (1.9 g, 8.6 mmol) and 1,3-benzoindandione (1.7 g, 8.6 mmol) obtained in Synthesis Example 2 were suspended in ethanol (50 mL) and stirred at room temperature for 72 hours. The precipitated solid was collected by filtration, washed with ethanol and hexane, extracted with chloroform, and washed with 1N-NaOH solution. The resulting extract was dried over magnesium sulfate, and the low boiling points were distilled off under reduced pressure to obtain a solid, which was dissolved in hot ethanol and allowed to stand at room temperature to obtain 2-[(1-isobutyl-3-methyl-1H-indol-5-yl)methylene]-1,3-benzoindandione as an orange solid (1.2 g, 35%).
¹ H-NMR (CDCl ₃ ): δ9.06 (d, J=1.6Hz, 1H), 8.55 (dd, J=8.8, 1.6Hz, 1H), 8.50 (s, 1H), 8.49 (s, 1H), 8.20 (s, 1H), 8.12-8.06 (m, 2H), 7.71-7.65 (m, 2 H), 7.38 (d, J = 8.8 Hz, 1H), 6.92 (d, J = 0.8 Hz, 1H), 3.90 (d, J = 7.2H z, 2H), 2.44 (d, J = 0.8Hz, 3H), 2.20 (m, 1H) 0.95 (d, J = 7.2Hz, 6H).

Evaluation examples 1 to 2
A thin film of the indolyl methylene indandione derivative of the present invention was prepared on a quartz substrate by vacuum deposition, and the absorption spectrum of the thin film was measured. The maximum absorption wavelength, the absorption coefficient at the maximum absorption wavelength, and the half width are shown in Table 1. In this specification, the half width means the full width at half maximum.

Comparative Example 1
A thin film of Coumarin 6 described in Patent Document 4 was prepared on a quartz substrate by vacuum deposition, and the absorption spectrum of the thin film was measured. The maximum absorption wavelength, the absorption coefficient at the maximum absorption wavelength, and the half-width are shown in Table 1.

From Evaluation Examples 1 and 2, it was found that the indolyl methylene indandione derivative of the present invention exhibits a maximum absorption wavelength in the range of 400 to 500 nm, which is the blue light region, and exhibits an absorption coefficient and a narrow half-width equivalent to that of Coumarin 6 shown in Comparative Example 1. The fact that it exhibits a narrow half-width is advantageous in terms of improving wavelength selectivity when applied to a stacked organic imaging element.

Evaluation Examples 1 to 2
A photoelectric conversion element containing the indolyl methylene indandione derivative of the present invention as a constituent component was produced, and its performance was evaluated.

The substrate used was a glass substrate with an ITO transparent electrode on which an ITO film having a width of 2 mm was patterned in a stripe shape. This substrate was washed with a neutral detergent and pure water, dried, and then washed with oxygen plasma. On the washed substrate, 2,7-bis(carbazol-9-yl)-9,9-spirobifluorene (Spiro-2CBP, film thickness 30 nm) was formed as a hole transport layer, a co-evaporation film (film thickness 100 nm) of the indolyl methylene indandione derivative of the present invention and [60]fullerene (C ₆₀ ) was formed as a photoelectric conversion layer, and N,N'-di(4-pyridyl)-1,4,5,8-naphthalene tetracarboxylic diimide (film thickness 30 nm) was formed as an electron transport layer in this order by a vacuum deposition method. Next, a metal mask was placed on the film-formed substrate so as to be perpendicular to the ITO stripe, and aluminum was vacuum-deposited as a positive electrode layer at a film formation speed of 0.3 nm/sec. After the film formation, the multilayer film was sealed in a nitrogen atmosphere glove box with oxygen and moisture concentrations of 1 ppm or less to prepare a photoelectric conversion element with a light receiving area of 4 ^mm2 . For sealing, a glass sealing cap and an epoxy type ultraviolet curing resin (manufactured by Nagase Chemtex Corporation) were used.

The measurement results of the external quantum efficiency when the photoelectric conversion element was irradiated with light having a wavelength of 450 nm are shown in Table 2. From this, it was found that the photoelectric conversion element of the present invention operates as a photoelectric conversion element having sensitivity in the blue light region.

The indolyl methylene indandione derivative (1) of the present invention can be used in electronic materials such as organic photodiode materials, organic thin-film solar cell materials, organic semiconductor laser materials, organic EL display materials, and photonic crystal materials.

Claims (11)

An indolylmethyleneindanedione derivative represented by formula (1):

In formula (1),
^R1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms .
R ² , R ³ , R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
^R7 represents a hydrogen atom .
R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that R ² to R ¹³ cannot simultaneously be hydrogen atoms.
n represents an integer of 0 or 1 . The indolylmethyleneindanedione derivative according to claim 1, wherein R ¹ is an alkyl group having 1 to 8 carbon atoms . The indolylmethyleneindanedione derivative according to any one of claims 1 to 2 , wherein R ⁴ , R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. The indolylmethylene indanedione derivative according to any one of claims 1 to 3 , wherein ^R8 , ^R9 , ^R10 , ^R11 , ^R12 and ^R13 are hydrogen atoms. Formula (2)

(wherein R1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, or a trialkylsilylalkyl group having 4 to 7 carbon atoms; ^R2 , R3 ^, R4 ^, R5, ^and R6 ^each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; and ^R7 represents a hydrogen atom , provided that ^R2 to ^R7 cannot simultaneously be hydrogen atoms), and a 5-carboxyindole derivative represented by formula (3):

(wherein R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and n represents an integer of 0 or 1 ),

(wherein R ¹ to R ¹³ and n are as defined above). 6. The method for producing an indolyl methylene indandione derivative according to claim 5 , which comprises reacting a 5-carboxyindole derivative with a 1,3-indandione derivative in the presence of an acid. 6. The method for producing an indolyl methylene indandione derivative according to claim 5 , which comprises reacting a 5-carboxyindole derivative with a 1,3-indandione derivative in the presence of a base. A photoelectric conversion element comprising the indolylmethyleneindanedione derivative according to claim 1 . A photoelectric conversion element comprising the indolyl methylene indanedione derivative according to claim 1 in a photoelectric conversion layer. The photoelectric conversion element according to claim 9 , wherein the photoelectric conversion layer further contains a fullerene derivative. The photoelectric conversion element according to claim 10 , wherein the fullerene derivative is _C60 or _C70 .