JPH0678301B2 - Square lilium derivative and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel squarylium derivative useful as a nonlinear optical material and a method for producing the same.

BACKGROUND ART Nonlinear optical elements play an important role in the fields of optical communication and optical information processing. The non-linear optical material used for the non-linear optical element is a light mixture that generates a sum frequency of two types of incident light having different frequencies, an optical parametric that becomes two types of light having different frequencies, and a refractive index change of an optical medium. Pockels effect, Kerr effect, or second harmonic (SHG) of incident light
Or, it is a substance that performs extremely important actions in optical communication processing, such as conversion to third harmonic (THG). Conventionally, such non-linear optical materials include inorganic ones and organic ones. Have been found.

Regarding inorganic non-linear optical materials, crystals of inorganic compounds such as KDP (KH ₂ PO ₄ ) and lithium niobate (LiNbO ₃ ) are known, but they are not sufficient to satisfy the demand. It was

On the other hand, organic non-linear optical materials have been attracting attention in recent years as materials for new optical elements in the field of optoelectronics, and research has been actively conducted each year. In particular,
With respect to organic compounds having a π-electron symmetry system, many studies have been conducted for material search because of the performance of single molecules and high-speed response.

Generally, it is known that the crystal of an organic nonlinear optical material has an SHG coefficient 10 to 100 times larger than that of an inorganic nonlinear optical material, an optical response speed of about 1000 times faster, and a large threshold against optical damage. Has been.

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 methylsulfate and 4 '
Examples include organic compounds such as -methylbenzylidene-4-nitroaniline.

The nonlinearity of organic compounds having these π-electron conjugated systems is
This is due to the interaction between the laser light as the electrode wave and the π electrons of the organic compound, and this interaction is due to the introduction of electron-withdrawing and electron-donating substituents into the π-electron conjugated system. It can be further increased.

However, in such an organic compound, generally, the dipole moment becomes large, the dipole-dipole interaction at the time of crystallization becomes strong, and the dipoles of two molecules cancel each other out. Are easily formed. There is a problem that the second-order nonlinear optical effect, which is important in application, does not appear in such a centrosymmetric crystal. In order to break the central symmetry, which is a problem in expressing nonlinearity in the crystalline state, a substituent having hydrogen bonding ability or an optically active substituent having an asymmetric carbon is added to an organic compound of π-electron conjugated system as a molecule. The idea is to introduce it at the time of design.

Problems to be Solved by the Invention Generally, the properties required as a material for a non-linear optical element are the magnitude of optical non-linearity, light transmittance, laser damage resistance, crystallinity, phase matching, processability, and mechanical properties. Strength, hygroscopicity, etc. are mentioned.

It has been extremely difficult to select a material satisfying the above-mentioned various practically required characteristics from the conventionally known materials for organic nonlinear optical elements.

The present invention has been made in view of the above-mentioned actual state of the art.

Therefore, an object of the present invention is to improve the problems in the conventionally known materials for nonlinear optical elements, to have a large nonlinear optical effect, and to be practical organic nonlinear optical with improved storage stability and processability. To provide the material.

Means for Solving the Problem Even when the compound system has a large dipole moment of the molecule and easily forms centrosymmetry at the time of crystallization, the present inventor has introduced a suitable substituent into the molecule. The present invention has been completed by finding that the following organic nonlinear optical material having a large nonlinear optical effect can be obtained.

The above object of the present invention is achieved by a novel squarylium derivative represented by the following general formula (I).

(In the formula, X represents a hydrogen atom, a methyl group, an ethyl group, or a methoxy group, and R represents -CO ₂ -tC ₄ H ₉ or -CH ₂ OH. * Represents an asymmetric carbon atom. ) The cyclobutenedione ring contained in the squarylium derivative represented by the above general formula (I) of the present invention has a strong electron absorption property similar to that of a nitro group, as can be seen from the maximum absorption wavelengths shown in Examples below. In addition to having a long π-electron conjugated system. Therefore, it becomes easy to take a structure in which the whole molecule is electronically highly polarized, which is a cause of highly nonlinear expression. Further, in the squarylium derivative represented by the general formula (I), since a substituent having an asymmetric carbon atom is introduced, even if the dipole moment of the molecule itself is large, the molecule in the bulk structure is A large optical non-linearity will be expressed by controlling the orientation of C and breaking the central symmetry.

The squarylium derivative represented by the above general formula (I) of the present invention can be easily synthesized in a high yield by the reaction formula shown below.

(In the formula, Y represents a chlorine atom, a bromine atom, a methoxy group, or an ethoxy group, and X, R, and * have the same meanings as defined above.) That is, the squarylium represented by the general formula (II) The derivative is suspended or dissolved in a solvent such as acetone, tetrahydrofuran, methanol, ethanol or the like, and then, in the obtained suspension or solution, the compound represented by the general formula (III) is equivalent to or more than the above-mentioned squarylium derivative. The pyrrolidine compound is gradually added to react with stirring. The reaction usually proceeds rapidly, but heating can be performed if necessary. If a product begins to precipitate as the reaction progresses, it may be filtered, and if a product does not precipitate, the product may be concentrated, or a suitable poor solvent may be added for precipitation. If necessary, the obtained crystals are recrystallized with a solvent such as alcohol or acetone, or purified by sublimation.

Instead of the pyrrolidine compound represented by the general formula (III), an acid addition salt thereof, for example, hydrochloride, bromate, p-
It is also possible to use toluenesulfonic acid salt or the like as a raw material and react it with a squarylium derivative represented by the general formula (II) in the same manner as above in the presence of a basic compound such as triethylamine or N-methylmorpholine. it can.

The squarylyl derivative represented by the general formula (II) is obtained by, for example, adding a dimethylaniline compound and dichlorocyclobutenedione to a Friedel-Crafts solvent (for example, carbon disulfide, nitrobenzene,
Chlorocyclobutenedione derivative by mixing and stirring in methylene chloride or the like, or by reacting dialkoxycyclobutenedione with a dimethylaniline compound together with a trialkyloxonium salt and a halogenated solvent. It can be produced by a method of obtaining a cyclobutenedione derivative, or the like.

Examples Hereinafter, the present invention will be described with reference to Examples.

Example 1 4- (4'-Dimethylaminophenyl) -3- (2'-t-butoxycarbonylpyrrolidinyl) -cyclobutene-1,2-
Synthesis of dione In 50 ml of an acetone solution of 1 g (4.2 mmol) of a compound represented by the following structural formula (II ′), 1.5 ml of L-proline-t-butyl ester was added with stirring to react. After reacting for 2 hours, the solvent was distilled off, and the residue was recrystallized from methanol to give 4- (4'-dimethylaminophenyl) -3- (2'- represented by the following structural formula (I '). 1.3 g (3.5 mmol) of t-butoxycarbonylpyrrolidinyl) -cyclobutene-1,2-dione were obtained as yellow crystals.

Yield 83% Melting point: 115 ° C Maximum absorption wavelength λmax: 399nm (in CH ₂ Cl ₂ ) Elemental analysis CHN Calculated value 68.08 7.08 7.56 Measured value 67.63 7.53 7.50 Examples 2 to 6 Example 1 was repeated except that the squarylyl derivative described in the column of the general formula (II) and the pyrrolidine compound described in the column of the general formula (III) in Table 1 were used as the raw material. The target product described in the column of the general formula (I) in Table 1 was synthesized in the same manner as described.

About the obtained product, elemental analysis value, maximum absorption wavelength λ
The max and melting point were measured. The results are shown in Table 2.

Application Example A compound of the above-mentioned structural formula (I ′) described in Example 1 was added to a powder sample filled in a glass cell with Nd: YAG.
When a laser (wavelength 1.064 μm, output 180 mJ / pulse) was irradiated, green scattered light of 532 nm due to SHG was generated. When the strength was measured, it was 8 times the value measured for the urea powder under the same conditions.

EFFECTS OF THE INVENTION The squarylium derivative represented by the above general formula (I) of the present invention is a novel compound, exhibits high non-linearity, and is excellent in heat resistance, light resistance, storage stability and processability. Since it is a substance, it can be used for manufacturing non-linear optical elements such as optical wavelength conversion elements, optical shutters, high-speed optical switching elements, optical logic gates, and optical transistors.

Claims (3)

[Claims] 1. A squarylium derivative represented by the following general formula (I). (In the formula, X represents a hydrogen atom, a methyl group, an ethyl group, or a methoxy group, and R represents -CO ₂ -tC ₄ H ₉ or -CH ₂ OH. * Represents an asymmetric carbon atom. ) 2. The following general formula (II) (In the formula, Y represents a chlorine atom, a bromine atom, a methoxy group or an ethoxy group), and a general formula (II
I) (Wherein, R represents a -CO ₂ -tC ₄ H ₉ or -CH ₂ OH. In addition, * denotes an asymmetric carbon atom.) Patents comprises reacting a pyrrolidine compound represented by A method for producing a squarylium derivative according to claim 1. 3. A squarylium derivative represented by the general formula (II) is reacted with an acid addition salt of a pyrrolidine compound represented by the general formula (III) in the presence of a basic compound. A method for producing a squarylium derivative according to claim 1.