JP2003183213A - Non-resonant two-photon absorbing compound, non- resonant two-photon emission compound and non- resonant two-photon absorption inducing method and luminescent method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic material absorbing two photons in high efficiency, i.e., a material having high two-photon absorption cross-section and provide an organic material exhibiting two-photon luminescence having high luminescent intensity. <P>SOLUTION: The compound exhibiting non-resonant two-photon absorption is expressed by general formula (1): X<SP>2</SP>-(-CR<SP>4</SP>=CR<SP>3</SP>-)<SB>m</SB>-C(=O)-(-CR<SP>1</SP>=CR<SP>2</SP>-)<SB>n</SB>- X<SP>1</SP>...(1) (X<SP>1</SP>and X<SP>2</SP>are each independently a substituted or non-substituted aryl or a substituted or non-substituted heterocyclic group; R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each independently hydrogen atom or a substituent; two or more groups of R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>may be bonded together to form a ring; plural R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>groups may be the same or different when (n) or (m) is ≥2; and (n) and (m) are each independently an integer of 1-4). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material exhibiting a nonlinear optical effect, and in particular, an organic nonlinear optical having a large non-resonant two-photon absorption cross section and a large emission efficiency from an excited state generated by non-resonant two-photon absorption. It is about materials.

[0002]

2. Description of the Related Art In general, a nonlinear optical effect is a nonlinear optical response proportional to the square of the applied electric field, the cube of the electric field, or more, and is proportional to the square of the applied electric field. As the following non-linear optical effects, second harmonic generation (SHG), optical rectification, photorefractive effect, Pockels effect, parametric amplification, parametric oscillation, optical sum frequency mixing, optical difference frequency mixing, etc. are known.
As the third-order nonlinear optical effect proportional to the cube of the applied electric field, third harmonic generation (THG), optical Kerr effect,
Examples include self-induced refractive index change and two-photon absorption.

As a non-linear optical material exhibiting these non-linear optical effects, many inorganic materials have been found so far. However, it has been very difficult to put the inorganic material into practical use because it is difficult to design a desired nonlinear optical characteristic and a so-called molecular design for optimizing various physical properties required for manufacturing an element. On the other hand, organic compounds can be optimized not only for desired nonlinear optical characteristics by molecular design, but also for controlling other physical properties.
It is highly promising for practical use and is attracting attention as a promising nonlinear optical material.

In recent years, among the nonlinear optical characteristics of organic compounds, the third-order nonlinear optical effect has attracted attention, and among them, non-resonant two-photon absorption and non-resonant two-photon emission have attracted attention. Two-photon absorption is a phenomenon in which a compound is excited by absorbing two photons at the same time, and the case where two-photon absorption occurs in an energy region where the (linear) absorption band of the compound does not exist is called non-resonant two-photon absorption. . Further, non-resonant two-photon luminescence refers to luminescence emitted by an excited molecule generated by non-resonant two-photon absorption in the radiation deactivation process of the excited state. In the following description, two-photon absorption and two-photon emission refer to non-resonant two-photon absorption and non-resonant two-photon emission, unless otherwise specified. By the way, the efficiency of non-resonant two-photon absorption is proportional to the square of the applied optical field (two-photon absorption squared characteristic). Therefore, when the laser is irradiated on the two-dimensional plane, the two-photon absorption occurs only at the position where the electric field strength is high in the central portion of the laser spot, and the absorption of the two-photon is completely lost at the peripheral portion where the electric field strength is weak. It won't happen. On the other hand, in the three-dimensional space, two-photon absorption occurs only in the region where the electric field strength of the focal point where the laser light is focused by the lens is large, and in the out-of-focus area the electric field strength is weak and no two-photon absorption occurs. . Compared to the linear absorption in which excitation occurs at all positions in proportion to the applied electric field intensity, in non-resonant two-photon absorption, excitation occurs at only one point inside space due to this squared characteristic. , The spatial resolution is significantly improved. Usually, in the case of inducing non-resonant two-photon absorption, a short pulse laser in the near-infrared region, which has a longer wavelength than the wavelength region in which the (linear) absorption band of the compound exists and does not have absorption, is often used. Compound (linear)
Since so-called near-infrared light in the transparent region where no absorption band exists is used, the excitation light can reach the inside of the sample without being absorbed or scattered, and due to the square characteristic of non-resonant two-photon absorption, Since the points can be excited with extremely high spatial resolution, non-resonant two-photon absorption and non-resonant two-photon emission are two
Photon contrast and two-photon photodynamic therapy (PD
T) and other applications are expected. Further, since non-resonant two-photon absorption and two-photon emission can be used to extract photons having higher energy than the energy of incident photons, research on upconversion lasing from the viewpoint of a wavelength conversion device has also been reported.

A so-called stilbazolium derivative is known as an organic compound that efficiently exhibits two-photon emission and up-conversion lasing (Non-patent document 1, Non-patent document 2, Non-patent document 3, Non-patent document 4, Non-patent document). 5, Non-Patent Document 6 and Non-Patent Document 7). Further, various application examples using two-photon emission of a stilbazolium compound having a specific structure are described in Patent Document 1.

[0006]

[Non-Patent Document 1] He, G. S. et al. , App
l. Phys. Lett. 1995, 67, 3703

[Non-Patent Document 2] He, G. S. et al. , App
l. Phys. Lett. 1995, 67, 2433

[Non-Patent Document 3] He, G. S. et al. , App
l. Phys. Lett. 1996, 68, 3549

[Non-Patent Document 4] He, G. S. et al. J. A
ppl. Phys. 1997, 81, 2529

[Non-Patent Document 5] Prasad, P. et al. N. et a
l. , Nonlinear Optics 1999, 2
1,39

[Non-Patent Document 6] Ren, Y. et al. J. Ma
ter. Chem. 2000, 10, 2025

[Non-Patent Document 7] Zhou, G .; et al. , Jp
n. J. Appl. Phys. 2001,40,125
0

[Patent Document 1] International Publication (WO) 97/09043 pamphlet

In the case of applying non-resonant two-photon emission to the imaging of biological tissue, photodynamic therapy, up-conversion lasing, etc., the two-photon absorption efficiency (two-photon absorption cross section) and two-photon absorption of the organic compound used. It is necessary that the emission efficiency from the excited state generated by is high. In order to obtain double the two-photon emission intensity using the same organic compound, the four-fold excitation light intensity is required due to the square characteristic of the two-photon absorption. However, it is not desirable to irradiate an excessively strong laser beam because, for example, there is a high possibility that the biological tissue will be photodamaged and that the two-photon luminescent dye itself will be photodegraded. Therefore, in order to obtain strong two-photon emission with weak excitation light intensity, it is necessary to develop an organic compound that efficiently absorbs two-photons and emits two-photon emission. The two-photon emission efficiency of the stilbazolium derivative is not yet sufficient for practical use.

[0008]

As described above, when non-resonant two-photon absorption and non-resonant two-photon emission are utilized,
Although it can be used for various applications characterized by extremely high spatial resolution, the currently available two-photon emission compounds are
Since the photon absorption capacity is low and the two-photon emission efficiency is poor, 2
A very high power laser is required as an excitation light source for inducing photon absorption and two-photon emission.

An object of the present invention is to provide an organic material that efficiently absorbs two-photons, that is, an organic material having a large two-photon absorption cross section, and an organic material that exhibits two-photon emission with a large emission intensity. Is.

[0010]

Means for Solving the Problems The earnest efforts of the inventors of the present invention
As a result of examination, the above-mentioned object of the present invention was achieved by the following means.
Was made. (1) The following one characterized by performing non-resonant two-photon absorption
A compound represented by the general formula (1). General formula (1) X²-(-CR^Four= CR³−)_m-C (= O)-(-CR¹= CR
²−)_n-X¹ (X¹And X²Is a substituted or unsubstituted aryl group, or
Or represents a substituted or unsubstituted heterocyclic group, even if the same
Each may be different, R¹, R², R³And R^FourHaso
Each independently represents a hydrogen atom or a substituent, R¹,
R², R³And R ^Four Some of them combine with each other
A ring may be formed, and when n and m are 2 or more, a plurality of rings may be formed.
R¹, R², R³And R^FourAre the same but different
, N and m are each independently an integer of 1 to 4.
Represent )

(2) A two-photon luminescent compound having the structure of the above general formula (1).

(3) The compound represented by the general formula (1) is characterized by irradiating a laser beam having a wavelength longer than the linear absorption band of the compound to induce non-resonant two-photon absorption. Non-resonant two-photon absorption induction method.

(4) The compound represented by the general formula (1) is irradiated with laser light having a wavelength longer than the linear absorption band of the compound to induce non-resonant two-photon absorption, and the excited state generated Non-resonant 2 characterized by generating light emission from
Photon emission generation method.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The compound of the present invention represented by the following general formula (1) is described in detail below. Formula ^{(1) X 2 - (-} CR 4 = CR 3 -) m -C (= O) - (- CR 1 = CR
²⁻ ) _n —X ¹ (X ¹ and X ² represent a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, and they may be the same or different, and R ¹ , R ² , R ³ and R ^4's each independently represent a hydrogen atom or a substituent, and some of R ¹ , R ² , R ³ and R ⁴ may combine with each other to form a ring, and n and m are 2 In the above case, a plurality of R ¹ ,
R ² , R ³ and R ⁴ may be the same or different, and n and m each independently represent an integer of 1 to 4. )

In the general formula (1), X ¹ and X ² represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group.

Examples of the aryl group represented by X ¹ and X ² in the general formula (1) include phenyl, naphthyl, anthracenyl, phenanthrenyl and the like, with phenyl or naphthyl being preferable, and phenyl being particularly preferable.

The heterocyclic group represented by X ¹ and X ² in the general formula (1) is a heterocyclic group having 1 to 15 carbon atoms, more preferably a heterocyclic group having 2 to 12 carbon atoms. A preferable hetero atom is a nitrogen atom, an oxygen atom or a sulfur atom. Specific examples of the heterocycle include, for example, pyrrolidine, piperidine, piperazine, morpholine, thiophene, selenophene, furan, pyrrole, imidazole, pyrazole, pyridine, pyrazine,
Pyridazine, pyrimidine, triazole, triazine,
Indole, indazole, purine, thiazoline, thiazole, thiazizole, oxazoline, oxazole,
Oxadiazole, quinoline, isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzothiazole, benzotriazole, tetrazaindene, benzoindolenin, carbazole, When dibenzofuran, phenothiazine, julolidine and a nitrogen atom form a ring, examples thereof include a quaternary onium cation in which the nitrogen atom is quaternized.
As the hetero ring, preferably, pyridine, pyrimidine, pyrazine, indole, thiophene, thiazole, oxazole, quinoline, acridine, benzimidazole, benzoxazole, benzothiazole, benzoindolenine, carbazole, phenothiazine, julolidine and a nitrogen atom form a ring. And a quaternary onium cation in which the nitrogen atom is quaternized, and more preferably carbazole, phenothiazine, and julolidine.

X ¹ and X ^{2 in} the general formula (1) may further have a substituent, and examples of the substituent include those described below. 1 to 20 carbon atoms
A linear or cyclic alkyl group (for example, methyl, ethyl, n-propyl, isopropyl, n-butyl), a substituted or unsubstituted aryl group having 6 to 18 carbon atoms (for example,
Phenyl, chlorophenyl, anisyl, toluyl, 1-
Naphthyl), alkenyl group having 2 to 20 carbon atoms (e.g. vinyl, 2-methylvinyl), alkynyl group having 2 to 20 carbon atoms (e.g. ethynyl, 2-methylethynyl, 2-phenylethynyl), halogen atom (e.g. F, Cl,
Br, I), an amino group having 2 to 20 carbon atoms (for example, dimethylamino, diethylamino, dibutylamino, julolidino), a cyano group, a hydroxyl group, a carboxyl group,
An acyl group having 2 to 10 carbon atoms (eg, acetyl, benzoyl, salicyloyl, pivaloyl), an alkoxy group having 1 to 20 carbon atoms (eg, methoxy, butoxy, cyclohexyloxy), an aryloxy group having 6 to 18 carbon atoms (eg, , Phenoxy, 1-naphthoxy), 1 to 1 carbon atoms
20 alkylthio groups (eg, methylthio, ethylthio), arylthio groups having 6 to 18 carbon atoms (eg, phenylthio, 4-chlorophenylthio), 1 to 20 carbon atoms
An alkylsulfonyl group of (for example, methanesulfonyl,
Butanesulfonyl), an arylsulfonyl group having 6 to 18 carbon atoms (for example, benzenesulfonyl, paratoluenesulfonyl), a carbamoyl group having 1 to 10 carbon atoms,
An amide group having 1 to 10 carbon atoms, an imide group having 2 to 12 carbon atoms, an acyloxy group having 2 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, a heterocyclic group (for example, pyridyl, thienyl, Aromatic heterocycles such as furyl, thiazolyl, imidazolyl and pyrazolyl, pyrrolidine rings, piperidine rings, morpholine rings, pyran rings, thiopyran rings, dioxane rings, dithiolane rings and other aliphatic heterocycles).

In the general formula (1), preferred substituents for X ¹ and X ² are a linear or cyclic alkyl group having 1 to 16 carbon atoms, an aryl group having 6 to 14 carbon atoms, and 7 to 7 carbon atoms. 15 aralkyl group, C1-16 alkoxy group, C6-14 aryloxy group, C2
To an amino group having 20 to 20 carbon atoms, a halogen atom, an alkoxycarbonyl group having 2 to 17 carbon atoms, a carbamoyl group having 1 to 10 carbon atoms, an amide group having 1 to 10 carbon atoms, and a heterocyclic group. A chain or cyclic alkyl group having 1 to 10 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, carbon Number 2 to 1
And an amino group having 0, a chlorine atom, a bromine atom, an alkoxycarbonyl group having 2 to 11 carbon atoms, a carbamoyl group having 1 to 7 carbon atoms, and an amide group having 1 to 8 carbon atoms.

In the general formula (1), more preferable substituents for X ¹ and X ² are those having a negative Hammett σ _p value. The Hammett σ _p value is, for example, C
hem. Rev. 1991, 91, 165.

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a substituent, and any ^one of R ¹ , R ² , R ³ and R ⁴ May combine with each other to form a ring.

In the general formula (1), the substituents represented by R ¹ , R ² , R ³ and R ⁴ are the above-mentioned X ¹ and X ^2.
The groups mentioned as the substituents of the group represented by can be mentioned.

Any two of the substituents mentioned for R ¹ , R ² , R ³ and R ⁴ in the general formula (1) may be bonded to each other to form a ring. Further, in the case where any two of the substituents mentioned for R ¹ , R ² , R ³ and R ⁴ are bonded to each other to form a ring, the carbonyl of the central portion represented by the general formula (1) is It is preferred that R ¹ and R ³ bonded to carbon bonded to a carbon atom be bonded to form a ring.

In the general formula (1), when R ¹ and R ³ combine to form a ring, the ring formed is preferably a 6-membered ring, a 5-membered ring or a 4-membered ring. Or 4
A member ring is more preferred.

In the general formula (1), when n and m are 2 or more, a plurality of R ¹ , R ² , R ³ and R ⁴ may be the same or different.

In the general formula (1), n and m each independently represent an integer of 1 to 5, with 2 to 4 being preferred.

The compound of the present invention was synthesized by an aldol condensation reaction between a ketone compound and an aldehyde compound. The preferred specific examples of the two-photon absorption compound and the two-photon emission compound used in the present invention are shown below, but the present invention is not limited thereto.

[0028]

[Chemical 1]

[0029]

[Chemical 2]

[0030]

[Chemical 3]

[0031]

[Chemical 4]

[0032]

[Chemical 5]

[0033]

[Chemical 6]

[0034]

[Chemical 7]

[0035]

[Chemical 8]

[0036]

[Chemical 9]

[0037]

[Chemical 10]

[0038]

[Chemical 11]

[0039]

[Chemical 12]

[0040]

[Chemical 13]

[0041]

[Chemical 14]

[0042]

[Chemical 15]

[0043]

[Chemical 16]

[0044]

[Chemical 17]

[0045]

EXAMPLES Specific examples of the present invention will be described below based on experimental results. [Synthesis of compound]

Synthesis Example 1 Synthesis of Compound (1) p- (Dimethylamino) cinnamaldehyde (17.5)
g, 0.1 mol) and cyclopentanone (4.2 g, 0.05
mol) in isopropyl alcohol (2.4 L) and sodium methoxide in methanol (1 ml)
Was added and the mixture was stirred at 40 ° C. for 1 hour. The crystals precipitated as the reaction proceeded were filtered, the crystals separated by filtration were dissolved in chloroform, methanol was added, and the precipitated crystals were filtered. Dark red crystals 11.0 g (yield 55%).
The structure of the obtained compound was confirmed by ¹ H NMR. 1H NMR (CDCl ₃ −d ₁ ) δ = 2.86 (2,4
H, cyclopentane ring), 3.01 (s, 12H, dimethylamino group), 6.67 (d, 4H, benzene ring),
7.39 (d, 4H, benzene ring), 6.76 (t, 2
H, methine chain), 6.90 (d, 2H, methine chain), 7.
24 (d, 2H, methine chain) Synthesis Example 2 Synthesis of compound (17) In the same manner as in Synthesis Example 1 except that acetone (2.9 g, 0.05 mol) was used instead of cyclopentanone shown in Synthesis Example 1. To synthesize the compound (17). Dark red crystals 3.8
g (yield 20%). The structure of the obtained compound was confirmed by ¹ H NMR. 1H NMR (CDCl ₃ −d ₁ ) δ = 3.01 (s, 1
2H, dimethylamino group), 6.67 (d, 4H, benzene ring), 7.38 (d, 4H, benzene ring), 6.46
(D, 2H, methine chain), 6.76 (m, 2H, methine chain), 6.90 (d, 2H, methine chain), 7.48 (m,
2H, methine chain) Synthesis Example 3 Synthesis of compound (31) Compound (31) was prepared in the same manner as in Synthesis Example 1 except that cyclohexanone (4.9 g, 0.05 mol) was used instead of the cyclopentanone shown in Synthesis Example 1. 31) was synthesized. 7.2 g of dark red crystals (yield 35%). The obtained compound is ¹ H NM
The structure was confirmed by R. 1H NMR (DMSO-d ₆ ) δ = 1.85 (m, 2
H, cyclohexane ring), 2.75 (t, 4H, cyclohexane ring), 3.00 (s, 12H, dimethylamino group), 6.66 (d, 4H, benzene ring), 7.39
(D, 4H, benzene ring), 6.89 (m, 4H, methine chain), 7.50 (d, 2H, methine chain) Other compounds of the present invention can also be easily synthesized according to the method of the above synthesis example. it can.

[Method for evaluating two-photon absorption cross section] The two-photon absorption cross section of the compound of the present invention is evaluated by MA Albota et.
The method described in al., Appl. Opt. 1998, 37, 7352. was used as a reference. The light source for measuring the two-photon absorption cross section is Ti: sapphir.
e-pulse laser (pulse width: 100fs, repetition: 80MH
z, average output: 1W, peak power: 100kW), 700n
The two-photon absorption cross section was measured in the wavelength range from m to 1000 nm. In addition, rhodamine B and fluorescein were measured as reference substances, and the obtained measured values were used as C. Xu et al., J. O.
The two-photon absorption cross section of each compound was obtained by correcting the two-photon absorption cross section values of rhodamine B and fluorescein described in pt. Soc. Am. B 1996, 13, 481. Two
A solution in which a compound was dissolved at a concentration of 1 × 10 ⁻² to 1 × 10 ⁻⁴ M was used as a sample for measuring photon absorption.

Example 1 The two-photon absorption cross section of the compound of the present invention was measured by the above method, and the obtained results are shown in Table 1 in GM units (1GM = 1 × 10 ⁻⁵⁰ cm ⁴ s). / photon).
The values shown in the table are the maximum values of the two-photon absorption cross section within the measurement wavelength range.

[Comparative Example 1] Two-photon absorption cross sections of Comparative Compound 1 and Comparative Compound 2 having the structures shown below were measured by the above method, and the results are shown in Table 1.

[0050]

[Chemical 18]

[0051]

[Table 1]

[Method for evaluating two-photon emission intensity] The compound of the present invention was dissolved in chloroform and 1064 of Nd: YAG laser was used.
The emission spectrum obtained by irradiating a laser pulse of nm is measured, and the non-resonance 2
The photon emission intensity was determined.

[Example 2] Sample 1: 100 mL of 0.40 g of the compound (1) according to the present invention
Was dissolved in chloroform to prepare a 1 × 10 ⁻² M solution.

Sample 2: the compound (31) according to the present invention
0.41 g was dissolved in 100 ml of chloroform to prepare a 1 × 10 ⁻² M solution.

Comparative sample 1: As a compound emitting strong two-photon emission, 0.59 g of the compound described in International Publication (WO) 9709043 (the following compound) was dissolved in 100 mL of acetonitrile to obtain a 1 × 10 ^-2 M solution. Prepared.

[0056]

[Chemical 19]

Sample 1, Sample 2 and Comparative Sample 1 were each irradiated with a 1064 nm laser pulse of Nd: YAG laser under the same conditions, and the non-resonant two-photon emission spectrum was measured. Area of emission spectrum obtained (non-resonant two-photon emission intensity)
Is shown in Table 2 as a relative ratio when the value of Comparative Sample 1 is 1.

[0058]

[Table 2]

As shown in Table 1, good characteristics far superior to those of conventional materials were obtained.

[Example 3] Sample 3: 0.37 g of the compound (17) of the present invention according to the present invention was added to 100 m.
1 × 10 ⁻² M solution was prepared by dissolving in 1 l of chloroform.

Comparative Sample 2: ASPT used in Comparative Sample 1 above
0.59 g was dissolved in 100 mL of THF to prepare a 1 × 10 ⁻² M solution.

The samples 1 and 2 and the sample 3 and the comparative sample 2 shown in Example 1 were each manufactured by using an Nd: YAG laser of 10%.
A nonresonant two-photon emission spectrum was measured by irradiating a laser pulse of 64 nm. The area of the obtained emission spectrum is
The relative ratio is shown in Table 3 when the value of Comparative Sample 2 is 1.

[0063]

[Table 3]

As shown in Table 3, good characteristics far superior to those of conventional materials were obtained.

[0065]

INDUSTRIAL APPLICABILITY By using the compound of the present invention, a non-resonant two-photon light emitting material exhibiting much stronger non-resonant two-photon emission than ever before can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeharu Tani             798 Miyadai, Kaisei-cho, Ashigarakami-gun, Kanagawa Prefecture             Shishi Film Co., Ltd. (72) Inventor Jun Kawamata             2-5-15, Kita 25, Kita-ku, Sapporo-shi, Hokkaido             701 F term (reference) 2K002 AB12 BA01 CA05 HA13                 4H006 AA01 AB92 BJ20 BJ50 BR70                       BU46

Claims (4)

[Claims] 1. A compound represented by the following general formula (1), which exhibits non-resonant two-photon absorption. Formula ^{(1) X 2 - (-} CR 4 = CR 3 -) m -C (= O) - (- CR 1 = CR
²⁻ ) _n —X ¹ (X ¹ and X ² represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group, which may be the same or different, and are R ¹ , R ² and R ^3; And R ⁴ each independently represent a hydrogen atom or a substituent, R ¹ ,
Some of R ² , R ³ and R ⁴ may combine with each other to form a ring, and when n and m are 2 or more, a plurality of R ¹ , R ² , R ³ and R ⁴ are They may be the same or different, and n and m each independently represent an integer of 1 to 4. ) 2. A two-photon light emitting compound represented by the general formula (1) according to claim 1. 3. A compound represented by the general formula (1) according to claim 1 is irradiated with laser light having a wavelength longer than a linear absorption band of the compound to induce two-photon absorption. And a non-resonant two-photon absorption induction method. 4. A compound represented by the general formula (1) according to claim 1 is irradiated with laser light having a wavelength longer than a linear absorption band of the compound to induce non-resonant two-photon absorption, A method for generating non-resonant two-photon emission, which comprises emitting light.