JP2896604B2 - Materials for nonlinear optical elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a material for a nonlinear optical element used for optical communication, optical information processing and the like. More specifically, the present invention relates to a material for a nonlinear optical element, wherein the conjugated π-electron system having an electron-donating substituent contains a cyclobutenedione ring as an electron-withdrawing substituent.

(Prior 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 a sum and difference frequency of two types of incident light having different frequencies, optical parametric that becomes two types of light having different frequencies,
In addition, the Pockels effect or Kerr effect, which electrically and optically changes the refractive index of an optical medium, or the exchange of incident light with a second harmonic (SHG) or third harmonic (THG), such as optical signal processing. It has a very important effect on the above.

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 element materials in the field of optoelectronics,
The research is growing every 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, it is known that an organic compound crystal has an SHG coefficient about 10 to 100 times larger, a photoresponse speed about 1000 times faster than an inorganic compound crystal, and a larger threshold value for optical damage.

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'-methylbenzylidene-4-nitroaniline. The optical non-linearity of these organic compounds having a π-electron conjugate system is due to the interaction between laser light as an electromagnetic wave and the 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, the dipole moment generally increases, the interaction between dipoles and dipoles during crystallization increases, and a crystal having a central symmetry 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.
Therefore, in order to break down 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 molecularly designed into a π electron conjugate system. The idea of introducing it at times is made. The present inventors have introduced such an optically active substituent having an asymmetric carbon atom into a π-electron conjugated system, and disclosed a specific example of a material exhibiting a larger nonlinear effect than the conventional one in Japanese Patent Application No. 1-248108. However, it is desired to further improve the nonlinear effect.

(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, and workability. , Mechanical strength, hygroscopicity and hardness.

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 introduce a suitable substituent into a molecule even in a compound system having a large dipole moment in the ground state of the molecule and easily forming central symmetry during crystallization. As a result, it has been found that a material for an organic nonlinear optical element having a large secondary nonlinear optical effect can be obtained, and the present invention has been completed. 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 X is an amino acid derivative having an asymmetric carbon atom. Yn is n electron-donating substituents represented by the following chemical formula bonded to a phenyl group, where n is 1 to 5) In the formula, R _{1 to} R ₅ represent a substituted or unsubstituted aryl group, and R ₁ and R ₂ may be the same or different from each other.) In the above general formula (I), the substituent X is an organic compound residue in which an amino acid derivative having an asymmetric carbon is bonded to a cyclobutenedione ring via a nitrogen atom. The amino acid derivative can be introduced by a reaction between the amino acid derivative and a 2-chlorocyclobutenedione ring or a 2-alkoxycyclobutenedione ring.

In order to control the molecular orientation in a bulk state or a thin film state, these substituents X have an asymmetric carbon atom, and are an optically active and hydrogen bonding substituent, such as a hydroxyl group or an amino group. It is important to include such things.

In that case, even when the dipole moment of the molecule itself is large, large optical nonlinearity can be exhibited by controlling the orientation of the molecule in the bulk or thin film structure and breaking the central symmetry.

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

1- (4'-N, N-diethylaminophenyl) -2-
(2'-hydroxypropylamino) -cyclobutene-
3,4-dione, [Compound (I-1)] 1- (4′-N, N-diethylaminophenyl) -2-
(1'-hydroxymethyl-2'-phenylethylamino) -cyclobutene-3,4-dione, [Compound (I-
2)] 1- (4'-N-methyl, N-ethylaminophenyl)-
2- (1'-hydroxymethyl-2'-phenylethylamino) -cyclobutene-3,4-dione, [Compound (I
-3)] 1- (4'-N-methyl, N methoxyethylaminophenyl) -2- (2'-hydroxypropylamino) -cyclobutene-3,4-dione, [Compound (I-4)] 1 -(4'-methoxyphenyl) -2- (2'-hydroxypropylamino) -cyclobutene-3,4-dione,
[Compound (I-5)] 1- (4′-methoxyphenyl) -2- (1′-hydroxymethylpropylamino) -cyclobutene-3,4-dione, [Compound (I-6)] 1- ( 4'-methylthiophenyl) -2- (1'-hydroxymethyl-2'-phenylethylamino) -cyclobutene-3,4-dione, [Compound (I-7)] 1- (3 ', 4' -Dimethoxyphenyl) -2- (2'-
(Hydroxymethylethylamino) -cyclobutene-3,4
-Dione, [compound (I-8)] 1- (3 ', 4'-dimethoxyphenyl) -2- (2'-
(Hydroxypropylamino) -cyclobutene-3,4-dione, [Compound (I-9)] 1- (3 ′, 4′-dimethoxyphenyl) -2- (1′-
(Hydroxymethylpropylamino) -cyclobutene-3,
4-dione, [compound (I-10)] 1- (3 ', 4'-dimethoxyphenyl) -2- (1'-
(Hydroxymethyl-2'-phenylethylamino) -cyclobutene-3,4-dione [Compound (I-11)] The compound represented by the above general formula (I) in the present invention is obtained by the reaction shown in FIG. According to any one of (A) and (B), it can be easily synthesized in good yield.

First, as the reaction of the first step, in the case of the reaction formula (A), for example, at a temperature of about 5 to 50 ° C.,
About 20 to 50 mmol of diethylaniline and about 20 to 150 mmol of dichlorocyclobutenedione of the formula (VIII)
About 100-1000 ml of Friedel Crafts solvent (for example, 2
The reaction is carried out by mixing and stirring in carbon sulfide, nitrobenzene, methylene chloride, etc.). The reaction is carried out in the presence of a catalyst, preferably, for example, about 20-500 mmol of aluminum chloride. The reaction is allowed to continue for about 2-8 hours, after which the Friedel-Crafts solvent is removed to give, as an intermediate, the chlorocyclobutenedione derivative of formula (IX).

In the case of the reaction formula (B), about 20 to 100 mmol of diethoxycyclobutenedione of the formula (X) is added to about 50 to 200 mmol of triethyloxonium fluoroborate, about 50 to 250 ml of a halogenated solvent such as methylene chloride and Compounds of formula (VII), for example diethylaniline about 20-200 mm
Reaction with ol at room temperature. After stirring for 6 to 12 hours, the solvent is removed under reduced pressure to obtain an alkoxycyclobutenedione derivative of the formula (XI) as an intermediate.

Next, as a second step reaction, the compound represented by the general formula (IX) or (XI) obtained as described above is reacted with an amino acid derivative having an asymmetric carbon. That is, the compound represented by the general formula (IX) or (XI) is suspended or dissolved in a solvent such as acetone, tetrahydrofuran, methanol, and ethanol. Next, to this suspension or solution, the above-mentioned amino acid derivative having an asymmetric carbon in an equivalent amount or more is gradually added with stirring to the compound represented by the general formula (IX) or (XI) to cause a reaction. . The reaction usually proceeds rapidly, but it is also possible to heat it 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 amino acid derivative having an asymmetric carbon into which the substituent X can be introduced in the general formula (I) of the present invention include S-(+)-2-amino-1-propanol, R-
(-)-1-amino-2-propanol, R-(-)-
2-amino-1-butanol, D-phenylalaninol, L-prolinol, L-leucinol, L-methioninol, L-valinol, L-alanine-t-butyl ester, L-proline-t-butyl ester, L-prolinol -Alanine methyl ester, L-proline methyl ester,
L-valine methyl ester, L-isoleucine methyl ester, L-leucine methyl ester, L-alanine ethyl ester, L-phenylalanine methyl ester,
Examples include amino acid derivatives such as L-proline benzyl ester, L-tyrosine ethyl ester, L-noradrenaline, L-methionine ethyl ester and the like, and optical isomers thereof.

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

(Synthesis example) 1- (4'-N, N-diethylaminophenyl) -2-
(2'-hydroxypropylamino) cyclobutene-3,
Synthesis of 4-dione [Exemplified Compound (I-1)]: 15 ml of 0.8 g (3.0 mmol) of 1- (4'-diethylaminophenyl) -2-chlorocyclobutene-3,4-dione
In a solution obtained by adding R-(-)-1-
Add 1 ml of amino-2-propanol and, with stirring,
Incubate for about 2 hours. The product precipitated during the reaction is filtered to obtain 0.42 g (1.4 mmol) of yellow microcrystals (47% yield).

Melting point: 226 ° C Maximum absorption wavelength: 406 nm (in CH ₂ Cl ₂ ) Elemental analysis CHN Calculated value 67.52 7.34 9.27 Measured value 67.63 7.22 9.15 Other compounds represented by the above general formula (I) can be prepared in the same manner as in the above synthesis example. Can be synthesized.

The compound represented by the above 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.

(Function) The compound represented by the above general formula (I) in the present invention has a cyclobutenedione ring having a strong electron-withdrawing property like a nitro group and a long π-electron conjugated system. Therefore, it is easy to take a structure in which the whole molecule is electrically largely polarized, and has high optical nonlinearity.

Further, since an amino acid derivative having an asymmetric carbon atom is introduced as X in the above general formula (I), even when a π-electron conjugated system having a large dipole moment in the ground state is included. Has high optical nonlinearity.

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

(Example 1) 1- (4'-N, N-diethylaminophenyl) -2-
(2'-hydroxypropylamino) -cyclobutene-
A powder of 3,4-dione (Exemplified Compound I-1 below) was filled in a glass cell, and Nd: YAG laser (wavelength 1.064 μm) was added thereto.
m, output 180mJ / pulse), the SHG 5
32 nm green scattered light was generated. When the strength was measured, it was 16 times the value measured for the urea powder under the same conditions.

FIG. 2 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 a 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 SHG intensity was measured by measuring, using a photomultiplier tube 16, green scattered light having a wavelength of 532 nm generated from the sample.

(Example 2) The following 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, and the results of measuring the SHG intensity of the sample in the same manner as in Example 1 are shown in Table 1.

The structural formula of the exemplified compound is as follows.

(Wherein ^* C represents an asymmetric carbon atom) (Effect of the Invention) The material for a nonlinear optical element of the present invention has high SHG strength, excellent heat resistance, light resistance, and transparency, good stability and workability, and is easy to obtain a large single crystal. Therefore,
The material for a non-linear optical element of the present invention is very excellent as a constituent material for 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 shows an example of a chemical formula for synthesizing the nonlinear optical material of the present invention. FIG. 2 is a block diagram of an optical system used for evaluating SHG intensity by a powder method. 11 ... Nd: YAG laser, 12 ... sample, 14 ... filter, 15 ... monochromator, 16 ... photomultiplier tube,
17 ... Box car integrator, 18 ... Oscilloscope.

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, X is an amino acid derivative having an asymmetric carbon, and Yn represents n (n represents a number from 1 to 5) electron donating substituents bonded to a phenyl group.) 2. In the above general formula (I), Y represents the following chemical formula (I
The material for a nonlinear optical element according to claim 1, which is an electron-donating substituent represented by any one of (I) to (VI) and a combination thereof. (Wherein R _{1 to} R ₅ represent a substituted or unsubstituted aryl group;
R ₁ and R ₂ may be the same or different. )