JPWO2020054627A1 - Squalilium compounds, luminescent compositions and luminescent films - Google Patents

Abstract

［一般式（１）において、
環Ａ及び環Ｂは、それぞれ独立に、芳香族炭化水素環を表す。
Ｒ^１〜Ｒ^４は、それぞれ独立に、置換基を表し、Ｒ^１〜Ｒ^４のうちの少なくとも二つは芳香族炭化水素基を表す。Ｒ^１〜Ｒ^４のうちの少なくとも一つは、さらに、かさ高い置換基を有する。
Ｒ^５及びＲ^６は、それぞれ独立に、ヒドロキシ基又はアミノ基を表す。］An object of the present invention is to provide a novel squarylium compound capable of emitting near-infrared light having high luminous efficiency, particularly little decrease in luminous efficiency in a solid film, and excellent light resistance. be. Another object of the present invention is to provide a luminescent composition and a luminescent film containing the squarylium compound.
The squarylium compound of the present invention is characterized by having a structure represented by the following general formula (1).
[Chemical 1]

[In the general formula (1)
Ring A and Ring B each independently represent an aromatic hydrocarbon ring.
R ^{1 to} R ⁴ each independently represent a substituent, and at least two of ^{R 1 to} R ^{4 represent an aromatic hydrocarbon group.} At ^{least one of R 1 to} R ⁴ further has a bulky substituent.
R ⁵ and R ⁶ independently represent a hydroxy group or an amino group, respectively. ]

Description

The present invention relates to novel squarylium compounds, luminescent compositions and luminescent films. More specifically, the present invention relates to a novel squarylium compound capable of emitting near-infrared light having high luminous efficiency and excellent light resistance, a luminescent composition containing the squarylium compound, and a luminescent film. ..

In recent years, near-infrared light emitting materials have attracted a great deal of attention from the viewpoint of their use in infrared cameras, bioimaging, biosensing, infrared communication, and the like. For example, a pulse oximeter, which is one of biological sensing, uses near-infrared light to calculate the oxygen saturation in blood. It is also being studied as a sensitizer for organic solar cells. With the expansion of the fields of use of near-infrared light, the requirements for the performance required for the near-infrared light emitting material, particularly the robustness such as light emission, light resistance, and chemical resistance, are becoming stricter.

The emission wavelength suitable for each application varies, but when used for biological sensing, a material having a high brightness in a wavelength band called a "living body window" having a wavelength of 650 to 900 nm, which easily transmits a living body, is preferably used. When photoexcited from the outside, a material having a high molar extinction coefficient and excellent light resistance is required.

However, compounds that emit light in the near-near-infrared region are difficult to design and synthesize, so development has not progressed much. As an example of the compound, Non-Patent Document 1 describes a squarylium compound R-1 having the following structure.

Non-Patent Document 1 describes that the squarylium compound emits fluorescence in the near infrared region in a solution. However, when the present inventor evaluated the above squarylium compound described in Non-Patent Document 1 in a solid film, the luminous efficiency and light resistance were not sufficiently satisfactory.
Further, although a technique for suppressing concentration quenching by introducing a sterically bulky substituent into a fluorescent compound is publicly known, the light resistance is unpredictable.

S. Wang, et al. , Chem. Mater, 2011, 23, 4789-4798.

The present invention has been made in view of the above problems and situations, and the problems to be solved are near infrared rays having high luminous efficiency, particularly little decrease in luminous efficiency in a solid film, and excellent light resistance. It is to provide a novel squarylium compound capable of emitting light. Another object of the present invention is to provide a luminescent composition and a luminescent film containing the squarylium compound.

As a result of investigating the causes of the above problems in order to solve the above problems, the present inventor has high luminous efficiency by using a squarylium compound having a specific structure having a bulky substituent, and particularly emits light in a solid film. We have found a novel squarylium compound capable of emitting near-infrared light with little decrease in efficiency and excellent light resistance, and have arrived at the present invention.
That is, the above problem according to the present invention is solved by the following means.

1. 1. A squarylium compound having a structure represented by the following general formula (1).

[In the general formula (1)
Ring A and Ring B each independently represent an aromatic hydrocarbon ring.
R ^{1 to} R ⁴ each independently represent a substituent, and at least two of ^{R 1 to} R ^{4 represent an aromatic hydrocarbon group.} At ^{least one of R 1 to} R ⁴ further has a bulky substituent.
R ⁵ and R ⁶ independently represent a hydroxy group or an amino group, respectively. ]

2. The squarylium compound according to item ^1, wherein at least two of R 1 to R ^{4 further have a bulky substituent.}

3. 3. The squarylium compound according to item 1, wherein at least one of R ¹ and R ^{2 and at least one of R 3} and R ^{4 further have a bulky substituent.}

4. R ^{1 to} R ⁴ independently represent an alkyl group or an aromatic hydrocarbon group, at least two of which represent an aromatic hydrocarbon group, and at least one of ^{R 1} and R ^2. The squarylium compound according to item 1, wherein at least one of R ³ and R ^{4 further has a bulky substituent.}

5. Rings A and B each represent a benzene ring having one or two hydroxy groups at the meta position with respect to the bond position of the nitrogen atom, and R ^{1 to} R ⁴ each represent a phenyl group, and R ¹ to R 1 to R 4 respectively. at least one of R ⁴ is, squarylium compounds described in paragraph 1, characterized in that it comprises bulky substituents in the meta or para position.

6. The squarylium compound according to item 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (2).

[In general formula (2)
Ring B represents an aromatic hydrocarbon ring.
R ³ and R ⁴ each independently represent an alkyl group or an aromatic hydrocarbon group, and at least one further has a bulky substituent.
E ¹ and E ² each independently represent a substituent, and at least one represents a bulky substituent.
R ⁶ represents a hydroxy group or an amino group. ]

7. The squarylium compound according to item 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (3).

[In general formula (3)
E ^{1 to} E ⁴ each independently represent a substituent, and at least one of ^{E 1} and E ^{2 and at least one of E 3} and E ⁴ represent a bulky substituent. ]

8. The squarylium compound according to item 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (4).

[In general formula (4)
E ^{1 to} E ⁴ each independently represent a bulky substituent. ]

9. A luminescent composition containing the squarylium compound according to any one of items 1 to 8.

10. A luminescent film containing the squarylium compound according to any one of items 1 to 8.

By the above means of the present invention, it is possible to provide a novel squarylium compound capable of emitting near-infrared light having high luminous efficiency, particularly little decrease in luminous efficiency in a solid film, and excellent light resistance. Can be done. In addition, a luminescent composition and a luminescent film containing the squarylium compound can be provided.

Although the mechanism of expression or mechanism of action of the effects of the present invention has not been clarified, it is inferred as follows.
The squarylium compound has a structure consisting of a squaric acid skeleton exhibiting strong electron acceptability and an amino group exhibiting electron donor property, and exhibits a sharp absorption / emission peak and a high molar extinction coefficient in the red to near infrared region. The typical squarylium compound R-2 and its optical characteristics (λ _max ^PL : maximum emission wavelength, Φ _f : emission quantum yield, molar absorption coefficient (logε)) are shown below.

However, the squarylium compound has a high π-planarity and a zwitterionic structure in which cations and anions coexist in the same molecule, so that it easily aggregates. As a result, it has been known that when viewed as a light emitting material, although it shows a high emission quantum yield in a solution, it aggregates in a solid film and the emission quantum yield decreases.

On the other hand, since the squarylium compound of the present invention has at least one or more bulky substituents, the interaction between molecules is sterically inhibited. That is, the interaction between the squarylium compounds and the interaction with the dispersant are suppressed. As a result, it is considered that quenching due to aggregation is unlikely to occur even in the film, and the luminescence property does not decrease.

Furthermore, it was found that the emission quantum yield was improved by the aromatic hydrocarbon ring substituted with an amino group having a strong electron donating property. This is because the squarylium compound has a structure consisting of a squaric acid skeleton exhibiting electron acceptor properties and an amino group exhibiting electron donor properties. Therefore, when a donor with strong electron donor properties is used, light emission based on the intramolecular charge transfer transition is used. It is presumed that this is because it is more likely to occur.

In addition, the squarylium compound of the present invention has an effect of being superior in light resistance to conventional squarylium compounds. Since the compound of the present invention has less heat deactivation from the excited state, decomposition due to heat is suppressed, and since aggregation is suppressed, decomposition due to aggregation is suppressed. Therefore, for example, molecules due to approaching molecules. It is presumed that this is because the reaction between them is suppressed and the absorption spectrum does not become broad like agglomerates and absorbs light in a larger wavelength range.

The squarylium compound of the present invention is characterized by having a structure represented by the general formula (1). This feature is a technical feature common to or corresponding to each of the following embodiments (forms).
In an embodiment of the present invention, it is preferable that at least two of the ^{above R 1 to} R ⁴ further have a bulky substituent from the viewpoint of exhibiting the effect of the present invention.
Further, it is preferable that at least one of R ¹ and R ² and at least one of R ³ and R ^{4 further have a bulky substituent.}

Further, in the present invention, the R ^{1 to} R ⁴ independently represent an alkyl group or an aromatic hydrocarbon group, at least two of which represent an aromatic hydrocarbon group, and R ¹ and R ² At least one of them, and at least one of R ³ and R ⁴ , preferably further has a bulky substituent.
Further, ring A and ring B each represent a benzene ring having one or two hydroxy groups at the meta position with respect to the bond position of the nitrogen atom, and R ^{1 to} R ⁴ each represent a phenyl group, and R At least one of the ¹ to R ⁴ preferably has a bulky substituent at the meta or para position.

It is preferable that the compound having the structure represented by the general formula (1) is a compound having the structure represented by the general formula (2) in terms of increasing the luminous efficiency.
Further, in the present invention, the compound having the structure represented by the general formula (1) is preferably a compound having the structure represented by the general formula (3). As a result, the luminous efficiency can be further increased.
As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, the compound having the structure represented by the general formula (1) is a compound having the structure represented by the general formula (4). Is preferable. This makes it possible to reduce agglutination in the solid film.
A luminescent composition or a luminescent film containing the squarylium compound of the present invention is preferable.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

Hereinafter, the squarylium compound, the luminescent composition, and the luminescent film of the present invention will be described, but the present invention is not limited thereto.
《Squarylium compound》
[Squarylium compound having a structure represented by the general formulas (1) to (4)]
The squarylium compound of the present invention receives excitation energy from the outside, transitions to a singlet excited state, and then emits fluorescence when returning to the ground state. In addition, since this compound exhibits a high molar extinction coefficient, it is excellent in light emission by photoexcitation and light emission by Felster-type energy transfer. Furthermore, it was found that it was excellent in light resistance.
The emission color of the squarylium compound of the present invention is a near-infrared light color. Specifically, the maximum emission wavelength in the fluorescence spectrum is in the range of 650 to 1000 nm.
The squarylium compound of the present invention has a structure represented by the following general formula (1).

[In the general formula (1), ring A and ring B each independently represent an aromatic hydrocarbon ring. R ^{1 to} R ⁴ each independently represent a substituent, and at least two of ^{R 1 to} R ^{4 represent an aromatic hydrocarbon ring.} At ^{least one of R 1 to} R ⁴ further has a bulky substituent. R ⁵ and R ⁶ independently represent a hydroxy group or an amino group, respectively. ]
The aromatic hydrocarbon ring represented by rings A and B (also referred to as an aromatic hydrocarbon ring group, an aromatic carbocyclic group, an aryl group, etc.) is a substituted or unsubstituted aromatic hydrocarbon having 6 to 18 carbon atoms. It is a hydrogen ring, and examples thereof include a phenyl group, a naphthyl group, an anthryl group, a fluorenyl group, a phenanthryl group, and a biphenylyl group. Preferably, a phenyl group, a naphthyl group, an anthryl group and the like can be mentioned.

In the general formula (1), the ^{substituents represented by R 1 to} R ⁴ and the substituents that the rings A and B may have include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, etc.). Isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, cyclopentyl group, cyclohexyl group, etc.) Vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (eg, phenyl group, p-chlorophenyl group, mesityl group, trill group, xsilyl group, naphthyl group, anthryl group Group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc., aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group) , Pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1,2,3-triazole-1-yl group, etc.), pyrazolotriazolyl group, oxazolyl group, Benzoxazolyl group, thiazolyl group, isooxazolyl group, isothiazolyl group, frazayl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carborinyl group, diaza Carbazolyl group (indicating one in which one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced with a nitrogen atom), quinoxalinyl group, pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group ( For example, pyrrolidyl group, imidazolidyl group, morpholic group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cyclo Alkoxy groups (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy groups (eg, phenoxy group, naphthyloxy group, etc.), alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, etc. Octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (For example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (for example, , Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group Group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octyl) Carbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc., acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group) , Dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (eg, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2- Ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group) , Pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example) , Methyl ureido group, ethyl ureido group, pentyl ureido group, cyclohexyl ureido group, octyl ureido group, dodecyl ureido group, phenyl ureido group, naphthyl ureido group, 2-pi Lysylaminoureid group, etc.), sulfinyl group (eg, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group Groups, etc.), alkylsulfonyl groups (eg, methylsulfonyl groups, ethylsulfonyl groups, butylsulfonyl groups, cyclohexylsulfonyl groups, 2-ethylhexylsulfonyl groups, dodecylsulfonyl groups, etc.), arylsulfonyl groups or heteroarylsulfonyl groups (eg, phenyl). Sulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamino group, diisopropylamino group, ditatebutyl group, cyclohexylamino group, butylamino group, Cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon group (eg, fluorine atom, chlorine atom, bromine atom, etc.) For example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenyl). Cyril group, phenyldiethylsilyl group, etc.), phosphono group and the like. Preferred examples include an alkyl group, an aromatic hydrocarbon group, an amino group, a hydroxy group and a silyl group.
Further, these substituents may be further substituted by the above-mentioned substituents.

Of these, the ^{substituent represented by R 1 to} R ⁴ is preferably an alkyl group or an aromatic hydrocarbon group.

As the ^{alkyl group represented by R 1 to} R ⁴ , a substituted or unsubstituted alkyl group having 6 to 10 carbon atoms is preferable. Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a cyclopentyl group and a cyclohexyl group.

As the ^{aromatic hydrocarbon group represented by R 1 to} R ⁴ , a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms is preferable. For example, an aromatic hydrocarbon group (phenyl group, naphthyl group, anthryl group, fluorenyl group, phenanthryl group, biphenylyl group, etc.) can be mentioned. Preferably, a phenyl group and a naphthyl group can be mentioned.

In the general formula (1), the ^{"bulky substituent" possessed by at least one of R 1 to} R ⁴ means a substituent having a Taft steric parameter value (Es value) smaller than -1.6. .. Here, the Es value is a steric parameter derived from chemical reactivity, and the smaller this value is, the more sterically bulky the substituent can be said.
Regarding the Es value, for example, "Structural-activity relationship of drugs" (Chemistry Area Special Edition No. 122, Nankodo) p. 124-126, "American Chemical Society Professional Reference Book,'Exploring QSAR' p.81 Table 3-3". Some of them are shown in the table.

Further, as a substituent not shown in the above table, for example, when the bulky substituent bonded to the aromatic hydrocarbon group is an aromatic ring, it further has a group having an Es value smaller than −1.6 as a substituent. Alternatively, it must be twisted and bonded to the aromatic hydrocarbon group so as to increase the steric hindrance (for example, vinaphthalene).
This is because, in the case of an unsubstituted aromatic ring bonded to the meta-position or the para-position, the highly planar π-conjugated surface spreads, so that the aggregation tends to be promoted more (the aromatic ring has a high tendency to promote aggregation). Both aromatic hydrocarbon rings and aromatic heterocycles are included).

Examples of the substituent having a steric parameter Es value smaller than -1.6 include a branched alkyl group having 3 to 20 carbon atoms, a linear alkyl group having 4 to 20 carbon atoms, and a cycloalkyl group having 3 or more carbon atoms. These include, but are not limited to. Further, these substituents may further have a substituent, or the carbon atom may be replaced with an O, S, N, Si atom, a halogen atom, or the like).
More preferably, an alkyl group containing a secondary or higher carbon (for example, a secondary carbon: isopropyl group, an isobutyl group, a tertiary carbon: a tert-butyl group, an adamantyl group), or a tertiary amino group (for example, a dimethylamino group, Diethylamino group, diphenylamino group), tertiary silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.).

The number of substituents in the general formula (1) is not particularly limited. When there are two or more substituents, the substituents may be the same or different from each other. Adjacent substituents may be bonded to each other to form a cyclic structure.

The cyclic structure formed by adjacent substituents may be an aromatic ring or an alicyclic ring, or may contain a hetero atom, and the cyclic structure is a fused ring having two or more rings. You may. The hetero atom referred to here is preferably one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom. Examples of the cyclic structure formed include a benzene ring, a naphthalene ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a pyrrol ring, an imidazole ring, a pyrazole ring, a triazole ring, an imidazoline ring, an oxazole ring, an isooxazole ring, and a thiazole. Examples thereof include a ring, an isothiazole ring, a cyclohexadiene ring, a cyclohexene ring, a cyclopentaene ring, a cycloheptatriene ring, a cycloheptadiene ring, a cycloheptaene ring, a carbazole ring, and a dibenzofuran ring.

The ^{amino group represented by R 5} and R ⁶ is a substituted or unsubstituted amino group, preferably an unsubstituted amino group.

The squarylium compound having the structure represented by the general formula (1) is described in the following general formula (2).
It is preferable that the compound has a structure represented by.

[In the general formula (2), ring B represents an aromatic hydrocarbon ring. R ³ and R ⁴ each independently represent an alkyl group or an aromatic hydrocarbon group, and at least one further has a bulky substituent. E ¹ and E ² each independently represent a substituent, and at least one represents a bulky substituent. R ⁶ represents a hydroxy group or an amino group. ]
Ring B represents an aromatic hydrocarbon ring, similarly to ring B of the general formula (1).
E ¹ and E ² represent substituents. The structure of the substituent is synonymous with the substituent of the general formula (1).
At ^{least one of E 1} and E ² represents a bulky substituent. The structure of the bulky substituent is synonymous with the bulky substituent represented by the general formula (1).
R ³ and R ⁴ independently represent an alkyl group or an aromatic hydrocarbon group, respectively, and are synonymous with the alkyl group or the aromatic hydrocarbon group listed as preferable substituents in ^{R 1 to} R ^4.

At ^{least one of R 3} and R ⁴ further has a bulky substituent. The structure of the bulky substituent is synonymous with the bulky substituent represented by the general formula (1).

Further, it is preferable that the compound having the structure represented by the general formula (1) is a compound having the structure represented by the following general formula (3).

[In general formula (3), E ^{1 to} E ⁴ each independently represent a substituent, and at least one of ^{E 1} and E ^{2 and at least one of E 3} and E ⁴ are Represents a bulky substituent. ]
E ^{1 to} E ⁴ each independently represent a substituent, and the structure of the substituent is synonymous with the substituent of the general formula (1).
At ^{least one of E 1} and E ² and at least one of E ³ and E ⁴ represent bulky substituents, and the structure of the bulky substituents is bulky as represented by the general formula (1). Synonymous with substituent.

Further, it is preferable that the compound having the structure represented by the general formula (1) is a compound having the structure represented by the following general formula (4).

[In the general formula (4), E ^{1 to} E ⁴ each independently represent a bulky substituent. ]
In the general formula (4), the structure of the bulky ^{substituent represented by E 1 to E 4} is synonymous with the bulky substituent represented by the general formula (1).
The following is an example of a squarylium compound having a structure represented by the general formulas (1), (2), (3) and (4) of the present invention, but the present invention is not limited thereto.

<Synthesis method>
The squarylium compound of the present invention is, for example, the method described in Chemistry of Materials, Vol. 23, p. 4789 (2011), The Journal of Physical Chemistry, Vol. 91, p. 5184 (1987), or these. It can be synthesized by referring to the method described in the reference document described in the document. As an example, a synthesis example of the exemplary compound D-1 is shown below.

<Synthesis of Exemplified Compound D-1>
It was synthesized by the following scheme.

Toluene 3,4-dihydroxy-3-cyclobutene-1,2-dione (1.14 g, 10.0 mol) and 3- (bis (4-tartbutylphenyl)) aminophenol (7.47 g, 20.0 mol) It was dissolved in a mixed solution of (80 ml) and normal butanol (80 ml), and the mixture was heated with reflux for 12 hours. The product was purified by column chromatography and recrystallized from a mixed solution of methanol and dichloromethane to obtain 3.30 g of the desired exemplary compound (D-1).

(Measurement of fluorescence spectrum)
The emission color of the squarylium compound of the present invention can be confirmed by the following method.
The squarylium compound of the present invention ^{is adjusted to 10-6} M in a toluene solution, and the fluorescence spectrum of this sample is measured at room temperature (300 K). A spectrofluorometer (F7000, manufactured by Hitachi High-Technos Co., Ltd.) is used for measuring the emission spectrum. Then, when the maximum emission wavelength (wavelength at which the emission intensity is maximum; also referred to as “emission peak wavelength”) is within the range of 650 to 1000 nm, it is determined to be a near-infrared color.

<< Luminous composition and luminescent film >>
The luminescent composition of the present invention is characterized by containing the squarylium compound of the present invention. The luminescent composition of the present invention is preferably used as a composition in which a dispersant is added to a squarylium compound for film formation stability and the like, or a composition in which a solvent is further added. Furthermore, the luminescent film of the present invention is characterized by containing the squarylium compound of the present invention. Specifically, it can be produced by forming the luminescent composition of the present invention in the form of a film.

Dispersants include (meth) acrylate-based resins, polyester-based resins, polyamide-based resins, polyimide-based resins, polystyrene-based resins, polyepoxy-based resins, polyester-based resins, amino-based resins, fluorine-based resins, phenol-based resins, and polyurethanes. Examples thereof include based resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, polyvinyl alcohol resins, polyether resins, polyether ketone resins, polyphenylene sulfide resins, polycarbonate resins, aramid resins and the like, but are preferable. Is a polystyrene-based resin, a polyethylene-based resin, a polypropylene-based resin, a polyvinyl chloride-based resin, or the like. Moreover, these copolymers are also preferable.

The (meth) acrylate-based resin is synthesized by homopolymerizing or copolymerizing various methacrylate-based monomers or acrylate-based monomers, and by changing the monomer species and the monomer composition ratio in various ways, the desired (meth) acrylate is used. A based resin can be obtained. Further, in the present invention, it can be used by copolymerizing with a (meth) acrylate-based monomer together with a copolymerizable monomer having an unsaturated double bond other than the (meth) acrylate-based monomer, and further in the present invention. Can also be used by mixing a plurality of other resins together with the poly (meth) acrylate-based resin.

Examples of the monomer component forming the (meth) acrylate-based resin used in the present invention include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. , Isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, dimethylaminoethyl (meth) Acrylate, 2-hydroxypropyl (meth) acrylate, di (ethylene glycol) ethyl ether (meth) acrylate, ethylene glycol methyl ether (meth) acrylate, isobonyl (meth) acrylate, ethyltrimethylammonium chloride (meth) acrylate, trifluoroethyl (Meta) acrylate, octafluoropentyl (meth) acrylate, 2-acetamidomethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, 3-trimethoxysilanepropyl (meth) Acrylate, benzyl (meth) acrylate, tridecyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, 2-diethylaminoethyl (meth) Examples thereof include acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and glycidyl (meth) acrylate, but (meth) acrylic acid, methyl (meth) acrylate, and ethyl (meth) acrylate are preferable. ) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, benzyl (meth) acrylate, tridecyl (meth) acrylate, Dodecyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

The polystyrene-based resin is a homopolymer of a styrene monomer, or a random copolymer, a block copolymer, or a graft copolymer obtained by copolymerizing another monomer having an unsaturated double bond copolymerizable with the styrene monomer. Can be mentioned. Further included are blends and polymer alloys in which such polymers are blended with other polymers. Examples of the styrene monomer include nuclear alkyl substitutions such as styrene, α-methylstyrene, α-ethylstyrene, α-methylstyrene-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, etc. Examples thereof include nuclear halide styrenes such as styrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, dichlorostyrene, dibromostyrene, trichlorostyrene and tribromostyrene. Styrene and α-methylstyrene are preferable.

The resin used in the present invention by homopolymerizing or copolymerizing these is, for example, a copolymer resin such as benzyl methacrylate / ethyl acrylate or butyl acrylate, or a copolymer resin such as methyl methacrylate / 2-ethylhexyl methacrylate. Also, a copolymer resin of methyl methacrylate / methacrylic acid / stearyl methacrylate / acetoacetoxyethyl methacrylate, a copolymer resin of styrene / acetoacetoxyethyl methacrylate / stearyl methacrylate, and styrene / 2-hydroxyethyl methacrylate / stearyl methacrylate. Examples thereof include copolymers and copolymer resins such as 2-ethylhexyl methacrylate / 2-hydroxyethyl methacrylate.

Further, when the squarylium compound of the present invention is used as a light emitting material for an organic EL device, a known host compound can be used as a dispersant. Specific examples thereof include compounds described in the following documents, but the present invention is not limited thereto. JP 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002. 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003 -3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002- 302516, 2002-305083, 2002-305084, 2002-308837, US Patent Application Publication No. 2003/01755553, US Patent Application Publication No. 2006/0280965, US Patent Application Publication No. 302 2005/0112407, US Patent Application Publication No. 2009/0017330, US Patent Application Publication No. 2009/0030202, US Patent Application Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126 , International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/0637996, International Publication No. 2007/0637554, International Publication No. 2004/107822, International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012/0293947, Japanese Patent Application Laid-Open No. 2008-074939, Japanese Patent Application Laid-Open No. 2007 −254297A, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853, Japanese Patent Application Laid-Open No. 2015-38941, and the like.

Regarding the content of the light emitting material in the light emitting composition and the light emitting film of the present invention, the preferable lower limit is 0.001 part by mass and the preferable upper limit is 50 parts by mass with respect to 100 parts by mass of the dispersant. When the content of the luminescent material is within this range, it has high transparency and can display a high-luminance image by being irradiated with light rays. A more preferable lower limit of the content of the luminescent material is 0.01 parts by mass, a more preferable upper limit is 10 parts by mass, a further preferable lower limit is 0.05 parts by mass, a further preferable upper limit is 8 parts by mass, and a particularly preferable lower limit is 0.1. Parts by mass, particularly preferably the upper limit is 5 parts by mass.

[Emission quantum yield]
The emission quantum yield is expressed as the ratio of the number of absorbed photons to the number of emitted photons. If all the excited molecules return to the ground state by fluorescence, the emission quantum yield will be 1, but in reality it will not be 1 due to non-radiative deactivation.

Non-radiative deactivation is a transition that returns to the ground state without emitting fluorescence. In addition to relaxation to the triplet state due to intersystem crossing, the energy of the electronic state is converted to vibration energy and finally becomes thermal energy. There are internal conversions and energy transfers that transfer energy to other molecules.

Assuming that the rate constants of the fluorescence transition and the non-radiation transition of the excited molecule are Kf and Knr, respectively, the emission quantum yield Φ (%) is
Φ (%) = (Kf / (Kf + Knr)) × 100
It is represented by.
Therefore, in order to improve the emission quantum yield, it is necessary to suppress the non-radiative deactivation of the excited molecule.

The present invention is characterized by a structure in which a bulky substituent is introduced in order to suppress non-radiative deactivation. Aggregation between molecules can be suppressed by three-dimensionally shielding the molecules with bulky substituents. As a result, it is presumed that the quenching caused by aggregation becomes smaller and the luminescence is improved.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the indication of "parts" or "%" is used, but unless otherwise specified, it indicates "parts by mass" or "% by mass".

[Example 1]
The compounds used in the comparative examples are shown below.

<Measurement of emission quantum yield>
Comparison of the squarylium compounds D-1, D-7, D-11, D-16, D-17, D-21, D-22, D-23, D-35, D-47 and D-55 of the present invention. For each of the compounds R-1 to R-4, the emission quantum yields in the solution and in the film were measured by the following methods, respectively.

(1) Evaluation of Emission Quantum Yield in Solution The squarylium compound or comparative compound of the present invention was dissolved in toluene so as to have a concentration of ^{10-6 M.} The emission quantum yield of the obtained solution was measured using an absolute PL quantum yield measuring device (manufactured by Hamamatsu Photonics Co., Ltd .: C11347).

(2) Evaluation of Emission Quantum Yield in Film The ratio of CBP (4,4'-N, N'-dicarbazolebiphenyl) to the squarylium compound or comparative compound of the present invention is 99 in chloroform. It was dissolved so as to be 5.5% by mass and 0.5% by mass. The obtained solution was applied onto a quartz substrate by a spin coating method at 500 rpm for 30 seconds to form a thin film, and then dried at 50 ° C. for 30 minutes. The absolute PL quantum yield of the obtained thin film was measured using an absolute PL quantum yield measuring device (manufactured by Hamamatsu Photonics Co., Ltd .: C11347) and used as the emission quantum yield in the film. In Table I, the luminescence quantum yield of D-1 in the solution is shown as a relative value of 100.

(Light resistance)
The film prepared under the same conditions as the measurement of emission quantum yield was covered with glass, and the decrease in absorption intensity at the maximum absorption wavelength from the sample after exposure to sunlight for 1 week and the unexposed sample was calculated by the residual rate. However, it was evaluated according to the following criteria. A spectrophotometer (U-3300, manufactured by Hitachi High-Technos Co., Ltd.) was used to measure the absorption intensity at the maximum absorption wavelength.

Residual rate (%) = (maximum absorption wavelength intensity of exposed sample / maximum absorption wavelength intensity of unexposed sample) × 100
⊚: Residual rate is 95% or more 〇: Residual rate is 90% or more and less than 95% Δ: Residual rate is 80% or more and less than 90% ×: Residual rate is less than 80%
Practically, a residual rate of 90% or more is preferable.
The above results are shown in Table I.

Exemplified compounds D-1, D-7, D-11, D-16, D-17, D-21, D-22, D-23, D-35, D-47, which are the squarylium compounds of the present invention. It was confirmed that D-55 and D-55 each had a maximum emission wavelength in the near infrared region of 650 to 850 nm in toluene. For the measurement, the above-mentioned spectrofluorometer (manufactured by Hitachi High-Technos Co., Ltd., F7000) was used.

From Table II, it can be seen that the squarylium compound of the present invention has high luminous efficiency and excellent light resistance.

The squarylium compound of the present invention can emit near-infrared light having high luminous efficiency, particularly little decrease in luminous efficiency in a solid film, and excellent light resistance. It can be used for infrared cameras, bioimaging, biosensing, infrared communication, and the like.

Claims (10)

A squarylium compound having a structure represented by the following general formula (1).

[In the general formula (1)
Ring A and Ring B each independently represent an aromatic hydrocarbon ring.
R ^{1 to} R ⁴ each independently represent a substituent, and at least two of ^{R 1 to} R ^{4 represent an aromatic hydrocarbon group.} At ^{least one of R 1 to} R ⁴ further has a bulky substituent.
R ⁵ and R ⁶ independently represent a hydroxy group or an amino group, respectively. ] The squarylium compound according to claim 1, wherein ^{at least two of R 1 to} R ^{4 further have a bulky substituent.} The squarylium compound according to claim 1, wherein at least one of R ¹ and R ² and at least one of R ³ and R ^{4 further have a bulky substituent.} R ^{1 to} R ⁴ independently represent an alkyl group or an aromatic hydrocarbon group, at least two of which represent an aromatic hydrocarbon group, and at least one of ^{R 1} and R ^2. The squarylium compound according to claim 1, wherein at least one of R ³ and R ^{4 further has a bulky substituent.} Rings A and B each represent a benzene ring having one or two hydroxy groups at the meta position with respect to the bond position of the nitrogen atom, and R ^{1 to} R ⁴ each represent a phenyl group, and R ¹ to R 1 to R 4 respectively. at least one of R ⁴ are squarylium compound according to claim 1, characterized in that it comprises bulky substituents in the meta or para position. The squarylium compound according to claim 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (2).

[In general formula (2)
Ring B represents an aromatic hydrocarbon ring.
R ³ and R ⁴ each independently represent an alkyl group or an aromatic hydrocarbon group, and at least one further has a bulky substituent.
E ¹ and E ² each independently represent a substituent, and at least one represents a bulky substituent.
R ⁶ represents a hydroxy group or an amino group. ] The squarylium compound according to claim 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (3).

[In general formula (3)
E ^{1 to} E ⁴ each independently represent a substituent, and at least one of ^{E 1} and E ^{2 and at least one of E 3} and E ⁴ represent a bulky substituent. ] The squarylium compound according to claim 1, wherein the compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (4).

[In general formula (4)
E ^{1 to} E ⁴ each independently represent a bulky substituent. ] A luminescent composition comprising the squarylium compound according to any one of claims 1 to 8. A luminescent film containing the squarylium compound according to any one of claims 1 to 8.