JP2789699B2 - Materials for nonlinear optical elements - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a non-linear optical element used for optical communication and optical information processing, and more particularly to a material having an electron-withdrawing substituent and a conjugated π.
The present invention relates to a material for a nonlinear optical element comprising a cyclobutenedione ring containing an electronic molecule.

2. Description of the Related Art In the fields of optical communication and optical information processing, nonlinear optical elements play an important role. Nonlinear optical element material is light mixing that generates the sum frequency of two types of incident light with different frequencies, optical parametric that becomes two types of light with different frequencies,
The Pockels effect or Kerr effect that changes the refractive index of an optical medium electrically or optically, or the second harmonic (SHG) of incident light
Or, it has a very important effect on optical signal processing, such as conversion to third harmonics (THG).

Conventionally, KDP (KH ₂ P
Inorganic crystals such as O ₄ ) and lithium niobate (LiNbO ₃ ) have been known, but no material has been found that satisfies the requirements.

Organic nonlinear optical materials have recently attracted attention as new optical materials in the field of optoelectronics, and have been actively studied year by year. In particular, organic compounds having a π-electron conjugated system have been extensively studied for material search due to the high performance and high-speed response of the molecule itself. In general, crystals of an organic compound are better than crystals of an inorganic compound.
It is known that the coefficient of SHG is about 10 to 100 times larger, the light response speed is about 1000 times faster, and the threshold value for optical damage is large.

Conventionally known organic nonlinear optical materials include 2-
Methyl-4-nitroaniline, m-nitroaniline, N
-(4-nitrophenyl) -L-prolinol, 2-acetylamino-4-nitro-N, N-dimethylaniline,
4-dimethylamino-4'-nitrostilbene, 4'-
Dimethylamino-N-methyl-4-stilbazolium methyl sulfate and 4'-methylvindylidene-4-
Nitroaniline and the like. The optical nonlinearity of these organic compounds having a π-electron conjugate system is due to the interaction between laser light as an electromagnetic wave and π-electrons of the organic compound. The size can be further increased by introducing a substituent having an electron-donating property.

However, in such an organic compound system, the dipole moment generally increases, the dipole-dipole interaction at the time of crystallization increases, and a centrally symmetric crystal in which dipoles of two adjacent molecules cancel each other out. Easy to form. Then, there is a problem that the second-order nonlinear optical effect, which is important in application, does not appear in such a centrally symmetric crystal.
In order to break the central symmetry, which is a problem in expressing optical nonlinearity in the crystalline state, a substituent having hydrogen bonding ability or an optically active substituent having an asymmetric carbon atom is introduced into the π-electron conjugate system at the time of molecular design. The idea is to do it.

Problems to be Solved by the Invention In general, the properties required as a material for a nonlinear optical element include the magnitude of optical nonlinearity, light transmission, laser damage resistance, crystallinity, phase matching, workability, and mechanical properties. Strength, hygroscopicity and the like.

It has been difficult to select a material for a nonlinear optical element that satisfies the above-mentioned various practically required requirements from conventionally known materials for a nonlinear optical element.

The present invention has been made in order to improve the above-described problems of the conventionally known materials for a nonlinear optical element, and has an object to improve a large nonlinear optical effect, storage stability, and processability. Another object of the present invention is to provide a practical material for an organic nonlinear optical element.

Another object of the present invention is to provide a material for an organic nonlinear optical element having a large second-order nonlinear optical effect.

Means for Solving the Problems The present inventors have found that a dipole moment of a molecule is large, and by introducing an appropriate substituent into a molecule even in a compound system which easily forms central symmetry during crystallization, The present inventors have found that a material for an organic nonlinear optical element having a large second-order nonlinear optical effect can be obtained, and have completed the present invention.

That is, the above object of the present invention is achieved by using a compound represented by the following general formula (I).

The material for a nonlinear optical element of the present invention has the following general formula (I)
And a compound represented by the formula:

(Wherein, Ar represents a π-electron conjugated compound residue, and X represents an organic compound residue bonded to a cyclobutenedione ring via an amino group or an oxygen atom or a nitrogen atom). In the compound represented by the above general formula (I), the π-electron conjugated compound residue of Ar includes aromatic, polycyclic aromatic and heterocyclic compound residues.

Preferably, the compound has an electron-donating substituent at any position of the π-electron conjugated system. Here, the π-electron conjugate system means benzene, naphthalene, acetoracene,
Compounds such as pyrene, pyridine, pyrrole, indole, carbazole, stilbene, azobenzene, benzylideneaniline, diphenylacetylene and diphenyldiacetylene and derivatives thereof. Further, as the electron donating substituent, an amino group, an imino group, an alkoxy group,
Examples thereof include an alkylthio group, a hydroxyalkyl group, and an alkyl group.

In the general formula (I), the substituent X is an amino group,
Or an organic compound residue bonded to the cyclobutenedione ring via an oxygen atom or a nitrogen atom, specifically, ammonia, an aliphatic or aromatic alcohol, a low molecule in which active hydrogen is bonded to a nitrogen atom or A polymeric amine (XH) and a 3-chlorocyclobutenedione ring or 3
-Can be introduced by reaction with an alkoxycyclobutenedione ring.

Further, in order to control the orientation of molecules in a bulk state, it is desirable that these substituents X further have an asymmetric carbon atom and are optically active.

In that case, even if the dipole moment of the molecule itself is large, it controls the orientation of the molecule in the bulk structure,
By breaking the central symmetry, large optical nonlinearity can be developed.

Specific examples of the compound represented by the general formula (I) in the present invention are shown below.

4- (4'-dimethylaminophenyl) -3-isopropylaminocyclobutene-1,2-dione [compound (I
-1)] 4- (4'-dimethylaminophenyl) -3- (2 '
-Hydroxyethyl-1'-amino) cyclobutene-1,
2-dione [compound (I-2)] 4- (4'-dimethylaminophenyl) -3- (2 '
-Hydroxypropyl-1'-amino) cyclobutene-
1,2-dione [compound (I-3)] 4- (4'-dimethylaminophenyl) -3- (2 '
-Tert-butoxycarbonylpyrrolidinyl) cyclobutene-1,2-dione [compound (I-4)] 4- (4'-dimethylamino-2'-methylphenyl) -3- (2'-tert-butoxycarbonyl (Pyrrolidinyl) cyclobutene-1,2-dione [compound (I-5)] 4- (4'-dimethylamino-2'-ethylphenyl) -3- (1'-hydroxybutyl-2'-amino)
Cyclobutene-1,2-dione [compound (I-6)] 4- (4'-dimethylamino-2'-ethylphenyl) -3- (1'-hydroxypropyl-2'-amino) cyclobutene-1,2 -Dione [compound (I-7)] 4- (4'-dimethylamino-2'-ethylphenyl) -3- (2'-t-butoxycarbonylpyrrolidinyl) cyclobutene-1,2-dione [compound ( I-8)] 4- (4'-Dimethylamino-2'-methoxyphenyl) -3- (1'-hydroxypropyl-2'-amino) cyclobutene-1,2-dione [Compound (I-9)] 4- (4'-dimethylamino-2'-hydroxyphenyl) -3- (2'-tert-butoxycarbonylpyrrolidinyl) cyclobutene-1,2-dione [compound (I-1
0)] 4- (4'-dimethylaminophenyl) -3-aminocyclobutene-1,2-dione [compound (I-11)] The compound represented by the above general formula (I) in the present invention is It can be easily synthesized in good yield according to any of the reaction formulas (A) and (B) shown.

First, as a reaction of the first step, in the case of the reaction formula (A), for example, at a temperature of about 40 to 50 ° C., a compound of the formula (II), for example, about 20 to 50 mmol of dimethylaniline and the formula (II)
I) about 60 to 150 mmol of dichlorocyclobutenedione in about 10
The reaction is carried out by mixing and stirring in 0 to 1000 ml of a Friedel-Crafts solvent (for example, carbon disulfide, nitrobenzene, methylene chloride, etc.). The reaction is carried out in the presence of a catalyst, preferably, for example, about 20 to 100 mmol of aluminum chloride. The reaction is allowed to continue for about 4-8 hours, after which the Friedel-Crafts solvent is removed to give, as an intermediate, the chlorocyclobutenedione derivative of formula (IV).

Further, in the case of the reaction formula (B), about 20 to 100 mmol of the dialkyloxycyclobutenedione of the formula (V) is
The reaction is carried out at room temperature with about 50 to 200 mmol of a trialkyloxonium salt, for example triethyloxonium fluoroborate, about 50 to 250 ml of a halogenated solvent, for example methylene chloride and a compound of formula (II), for example about 20 to 200 mmol of dimethylaniline. After stirring for 6 to 12 hours, the solvent is removed under reduced pressure to obtain an alkoxycyclobutenedione derivative of the formula (VI) as an intermediate.

Next, as a second step reaction, the compound represented by the general formula (IV) or (VI) obtained as described above is reacted with the compound (XH) having active hydrogen. That is, the compound represented by the general formula (IV) or (VI) is suspended or dissolved in a solvent such as acetone, tetrahydrofuran, methanol, and ethanol. Then, to this suspension or solution, a compound (XH) having the above-mentioned active hydrogen in an equivalent amount or more to the compound represented by the general formula (IV) or (VI) is gradually added while stirring, Let react.
The reaction usually proceeds promptly, but can be heated if necessary. If the product precipitates as the reaction proceeds, the product is filtered. If the product does not precipitate, the product is concentrated or a poor solvent is added to precipitate. The obtained compound represented by the general formula (I) is, if necessary, recrystallized with a solvent such as alcohol or acetone, or purified by sublimation.

Specific examples of the compound (XH) having an active hydrogen capable of introducing the substituent X into the general formula (I) in the present invention include methanol, ethanol, propanol, isopropanol, butanol, t-butyl alcohol, and pen. Tanol, hexanol, heptanol, decanol, octadecyl alcohol, polyvinyl alcohol, active amyl alcohol, methyl S-(+)-3-hydroxy-n-butyrate (L), S-(-)-phenylethyl alcohol, S-(- ) -2-Methyl-1-octanol, S-
(-) - alcohol compound such as phenyl methyl carbinol, NH _3, methylamine, formamide, hydrazine, dimethylamine, ethylamine, diethylamine, propylamine, isopropylamine, butylamine, octadecylamine, beta-hydroxy ethylamine, aniline, p -Nitroaniline, polyamine, polyimine, S-(-)-α-methylbenzylamine, R-
(+)-Α- (1-aminoethyl) naphthalene, R-
Amino and imino compounds such as (+)-1-phenylethylamine, and S-(+)-2-amino-1-propanol, R-(-)-1-amino-2-propanol, R-(-) -2-amino-1-butanol, D-phenylalanine, L-prolinol, L-leucinol, L-methioninol, L-valinol, 2-amino-1,3-propanediol, 3-amino-1-propanol, -Amino-2-butanol, L-alanine-t
-Butyl ester, L-proline-t-butyl ester, L-alanine methyl ester, L-proline methyl ester, L-valine methyl ester, L-isoleucine methyl ester, L-leucine methyl ester, L-
Examples thereof include amino acid derivatives such as alanine ethyl ester, L-phenylalanine methyl ester, L-proline benzyl ester, L-tyrosine ethyl ester, L-noradrenaline, L-methionine ethyl ester, and D-forms thereof.

Next, a synthesis example of an example of the compound represented by the general formula (I) will be described.

Synthesis Example Synthesis of 4- (4′-dimethylaminophenyl) -3-isopropylaminocyclobutene-1,2-dione [exemplified compound (I-1)]: 4- (4′-dimethylaminophenyl) -3- 0.5 g (2.2 mmol) of methoxycyclobutene-1,2-dione is added to 20 ml of isopropylamine, and the mixture is stirred with heating and reacted for about 2 hours. After completion of the reaction, the mixture was evaporated to dryness, and the remaining residue was recrystallized from methanol to give 0.22 g (0.85 mmol) of yellow-green crystals of the exemplary compound (I-1) represented by the following formula.
l) (39% yield).

Melting point: 234 ° C. Maximum absorption wavelength: 397 nm (in C ₂ H ₅ OH) Elemental analysis C H N Calculated value 69.74 7.02 10.85 Observed value 69.52 7.22 10.72 Other compounds represented by the above general formula (I) were prepared in the same manner as in the above synthesis examples. Can be synthesized.

The compound represented by the general formula (I) in the present invention is used as a constituent material of a nonlinear optical element. Examples of the nonlinear optical element include an optical wavelength conversion element, an optical shutter, a high-speed optical switching element, an optical logic gate, and an optical transistor.

Action In the present invention, the compound represented by the general formula (I) has a cyclobutenedione ring having a strong electron-withdrawing property like a nitro group and a long π-electron conjugated system. In addition, the whole molecule can easily take a structure that is greatly polarized electronically, and has high optical nonlinearity.

Further, since a substituent having an asymmetric carbon atom is introduced as X in the general formula (I), even when a π-electron conjugated system having a large dipole moment is included,
It has high optical nonlinearity.

Further, the compound represented by the general formula (I) has excellent heat resistance and light resistance, and has good stability and workability, and thus can be used as a material for a nonlinear optical element.

Examples The present invention will be described in detail with reference to examples.

Example 1 4- (4'dimethylaminophenyl) -3-isopropylaminocyclobutene-1,2-dione (Exemplified Compound I
-1) was added to a sample of the powder filled in a glass cell.
When irradiated with a d: YAG laser (wavelength 1.064 μm, output 180 mJ / pulse), 532 nm green scattered light due to SHG was generated. When the strength was measured, it was 0.5 times the value measured for the urea powder under the same conditions.

FIG. 1 is a block diagram of an optical system used to evaluate the SHG intensity of the above sample by a powder method. In the figure, 11
Is an Nd: YAG laser, 12 is a powder sample filled in a glass cell, 13 is a lens, 14 is a filter, 15 is a monochromator, 16 is a photomultiplier, 17 is a box car integrator, and 18 is an oscilloscope. Nd: YAG laser
The sample 12 was irradiated with light having a wavelength of 1.064 μm from 11 and the green light scattered at 532 nm generated from the sample was measured using a photomultiplier tube 16 to measure the SHG intensity.

Example 2 The above exemplified compounds (I-2), (I-3), and (I-
4), (I-5), (I-6), (I-7), (I-
8), (I-9), (I-10) and (I-11) were used to measure the SHG intensity of the sample in the same manner as in Example 1.

In addition, the structural formula of the above exemplified compound is as follows.
(* Represents an asymmetric carbon atom) The results are shown in the table below.

Example 3 A 1,4-dioxane saturated solution of the exemplified compound (I-3) was placed in a solution cell shown in FIG. 2, and the SHG intensity was measured. FIG. 2 is a perspective view of a solution cell in which two transparent conductive glass sheets (tin oxide or indium tin oxide) are arranged to face each other. Reference numeral 21 denotes a solution holder, 22 and 2
2 'is a conductive glass plate, and 23 and 23' are electrodes. The measurement was performed by applying an electrostatic field of 5 KV directly to the sample solution via the conductive film, applying a Nd: YAG laser to the solution cell, and observing the green light generated as electrostatic field-induced second harmonic (dcSHG). By doing that. As a result, the second-order nonlinear susceptibility is 2
Almost the same as -methyl-4-nitroaniline.

Effect of the Invention The nonlinear optical element material of the present invention has a very high SHG intensity, is stable at room temperature, and can easily obtain a large single crystal, and exhibits excellent nonlinear effects. In addition, the single crystal has a large SHG because it has no center of symmetry.
Have activity. Therefore, the material for a non-linear optical element of the present invention is very excellent as a constituent material of, for example, an optical wavelength conversion element, an optical shutter, a high-speed optical switching element, an optical logic gate, an optical transistor, and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical system used for evaluating SHG intensity by a powder method, and FIG. 2 is a perspective view of a solution cell used in Example 7. 11 ... Nd: YAG laser, 12 ... sample, 14 ... filter, 15 ... monochromator, 16 ... photomultiplier tube,
17: Box car integrator, 18: Oscilloscope, 21: Solution holder, 22, 22 ': Conductive glass plate, 23, 23': Electrode.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-259735 (JP, A) JP-A-1-204031 (JP, A) Phys. Lett. A, Vol. 70 No. 2 PP. 153-154 (1979) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/35-3/02 C09B 23/00 C07C 225/20 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A material for a nonlinear optical element comprising a compound represented by the following general formula (I). (In the formula, Ar represents a π-electron conjugated compound residue, and X represents an organic compound residue bonded to a cyclobutenedione ring via an amino group or an oxygen or nitrogen atom.) 2. The material for a nonlinear optical element according to claim 1, wherein in the general formula (I), X is a residue of an organic compound having an asymmetric carbon atom.