JPS6352123A - Organic nonlinear optical compound - Google Patents

Abstract

PURPOSE:To obtain an optical material having large optical nonlinearity of molecules and a small dipole moment by using an org. nonlinear optical compd. represented by a prescribed general formula. CONSTITUTION:An org. nonlinear optical compd. represented by general formula I is used. Since the central symmetry of the crystal depends largely on dipole- dipole interaction between molecules, the symmetry is very effectively destroyed by reducing the dipole moment of the molecules. In case of N-(4- pyridinylmethylene)-benzenamine having a long pi-electron conjugated system, an alkyl group is used at the N-position of the pyridine ring to convert the compd. into an acceptor and a donor type substituent is introduced into the benzene ring to intensify the charge-transfer interaction, so the fluctuation of pi-electrons due to the perturbation of a photoelectric field, that is, the optical nonlinearity of the molecules is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to organic nonlinear optical materials used in optical information processing, optical communications, and the like.

(Conventional technology) Many materials exploration studies have been conducted with the aim of realizing nonlinear optical elements as new elements in the field of optoelectronics. It is attracting attention from

In particular, regarding second-order optical nonlinearity, there are a series of reports centered on benzene derivatives [Niecynis Symposium Series (AC3Symposium 5eries) 2
33 (1983)].

The optical nonlinearity of organic compounds having a π-electron conjugated system is said to be caused by the fluctuation of π-electrons upon laser beam incidence. The conventional molecular design guideline was to introduce substituents.

However, when a substituent with strong donor or acceptor properties, such as an amino group or a nitro group, is introduced, the dipole moment of the molecule increases, and the dipole-dipole interaction during crystal formation becomes stronger.

The crystal structure of organic compounds is generally determined by the structure of individual molecules and intermolecular cohesive forces such as hydrogen bonds during backing, Hund-der-Waals interactions, and dipole-dipole interactions. Conceivable.

Therefore, the compound according to the above molecular design guideline, that is,
Compounds with donor and acceptor substituents introduced into the π-electron conjugated system have stronger intermolecular dipole-dipole interactions, resulting in a centrosymmetric crystal structure in which the dipoles of two molecules cancel each other out. Easy to form.

However, such a centrosymmetric crystal does not exhibit second-order optical nonlinearity.

In conventional research, various substituents, such as optically active substituents and substituents with a large ability to form hydrogen bonds, have been added to break the central symmetry of the crystal, which is a problem in expressing optical nonlinearity in the crystal state. The idea of introducing it into a π-electron conjugated system has been taken during molecular design, and there are some success stories.

(Problem to be solved by the invention) However, these molecules have relatively small hyperpolarizability, which is an important factor in creating molecular crystals with optical nonlinearity large enough to withstand practical use. Success has only been achieved with benzene derivatives that have a relatively small dipole moment.

For example, compounds that have a long π-electron conjugated system as a parent skeleton to increase optical nonlinearity, such as 4-dimethylamino-4-m:trostilbene, which has a second-order hyperpolarizability that is more than 10 times greater than P-nitroaniline. In this case, the dipole moment increases accordingly, so there is no success example.

As explained above, when molecules are modified using conventional molecular design guidelines alone, the optical nonlinearity of the prince is large, but the dipole moment increases accordingly, so it is difficult to break the central symmetry of the crystal formed. is very difficult.

An object of the present invention is to provide an organic nonlinear optical system that produces a molecular crystal with large optical nonlinearity, and has a large molecular optical nonlinearity and a small dipole moment.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following configuration.

"The following general formula D: donor substituent R, C) -13, -02M5, etc. alkyl group R1~
R8: hydrogen or optional substituent X: CH3SO4, C2H5SO4.

CD, 04.103, NO3.

8F4, ReO2, cinnamate.

An organic nonlinear optical compound represented by Br', Cf1e.

” As mentioned above, the central symmetry of a crystal can be said to be largely due to the dipole-dipole interaction between molecules. Therefore, to break the central symmetry of the crystal, it is very effective to reduce the dipole moment of the molecule.

In the present invention, by making the N-position of the pyridine ring an alkyl salt on the N-(4-pyridinylmethylene)-benzene ring side that has a long π-electron conjugated system, it becomes an acceptor and a donor to the benzene ring. By introducing a sex-purchasing group, we strengthened the charge transfer interaction and increased the fluctuation of π electrons due to perturbation of the optical electric field, that is, the optical nonlinearity of the molecule.

The molecular design guidelines that should be emphasized for the above compounds are -N=
The N atom of the C-bond is on the side of the benzene ring into which the donor substituent is introduced. Only in this case, the electronegativity of the N atom suppresses the polarization caused by the π electrons in the ground state, reducing the dipole moment of the molecule.

For compound t of the present invention, the alkyl salt of γ-picoline and substituted aniline are mixed and stirred in alcohol in the presence of Lewis acid as a catalyst, and if necessary, heated slightly to condense. Obtained by the method of synthesizing aromatic imine derivatives ( )1. M., Sprung, Che.
m,, Rev 26 297 (1940)).

Examples of donor substituents in the present invention include amino,
Monomethylamino, dimethylamino, diethylamino,
Amino groups such as n-butylamino and t-butylamino,
L-[(2-hydroxymethyl)-pyrrolidinyl], L
- Various optically active amino groups such as alaninyl, L-serinyl, and L-tyrosinyl, alkoxy groups such as hydroxy, methoxy, ethoxy, n-7toxy, and t-butoxy, methyl, ethyl, n-propyl, n-butyl, t-
Examples include chain or branched alkyl groups such as butyl, n-pentyl, and n-octadecyl, hydroxyalkyl groups such as bitroxymethyl and hydroxyethyl, and halogens.Also, examples of the alkyl group at the acceptor site include methyl, ethyl, Examples include n-butyl and t-butyl.

It is particularly preferable to introduce a donor exchange group at the 4-position in order to improve the optical nonlinearity of the compound, and
Methosulfate ion and ethosulfate ion are particularly effective as anions that form salts to disrupt the central symmetry of the crystal.

Examples of compounds include N-(4-pyridinylmethylene)
-4-dimethylaminobenzenamine dimethyl sulfate, N-(4-pyridinylmethylene)-4-dimethylaminobenzenamine diethyl sulfate, N-(4
-pyridinylmethylene)-4-monomethylaminobenzenamine dimethylsulfate, N-(4-pyridinylmethylene)-4-diethylaminobenzenamine ethiodite, N-(4-pyridinylmethylene)-4- (L)
-[(2-hydroxymethyl)-pyrrolidinyl]penzenamine dimethylsulfate, N-(4-pyridinylmethylene)-4-(L)-[(2-hydroxymethyl)
-pyrrolidinyl]penzenamine distylsulfate, N-(4-pyridinylmethylene)-4-(L)-7 raninylbenzenamine dimethylsulfate, N-(4-pyridinylmethylene)-4-(L)-7
-pyridinylmethylene)-4-(L)-serinylbenzenamine diethyl sulfate.

Although the substituents R1 to R8 in the general formula are not particularly limited, it is necessary that they do not significantly affect the π-electron conjugated system of the parent skeleton.

Preferably, Hammett's substituent constant σ.

So, it is a substituent of about 1σl)+<0.4.

Furthermore, preferred substituents include hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, which can form hydrogen bonds, and acetamide groups.

These compounds include N-(4-pyridinylmethylene)-4-dimethylamino-3-hydroxymethylbenzenamine distylsulfate, N-(4-pyridinylmethylene)-4-dimethylamino- 3-acetaminobenpinamine dimethyl sulfate, N-(4-pyridinylmethylene)-4-(L)-[(2-hydroxymethyl)-pyrrolidinyl]-3-acetaminobenzenamine diethyl sulfate, N-[4-(2-acetaminopyridinyl)methylene]-4-dimedylamino-3
- Examples include acetaminobenpinamine dimethyl sulfate.

In addition, although the optical nonlinearity of the molecule itself is slightly reduced, it also makes the crystal formed by the compound more likely to become non-centrosymmetric, and shifts the absorption of the compound to shorter wavelengths, reducing the expression of nonlinear optical effects due to absorption. In order to prevent this, it is preferable to weaken the electron donating property of the donor co-substituent group.

Such a donor substitution group is defined by Hammett's substituent constant σ. Using -0,4<σ.

Examples of substituents and halogens include alkyl groups such as methyl, ethyl, n-butyl, and t-butyl, hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, and alkoxy groups such as hydroxy, methoxy, and ethoxy. Can be mentioned.

Examples of compounds include he(4-pyridinylmethylene)
-4-Methylbenzenamine dimethyl sulfate, N
-(4-pyridinylmethylene)-4-hydroxybenzenamine dimethylsulfate, N-(4-pyridinylmethylene)-4-methoxybenzenamine dimethylsulfate, N-(4-pyridinylmethylene) )-4-chloro-3-acetaminobenzenamine diethyl sulfate, N-(4-pyridinylmethylene)-4-hydroxy-3-acetaminobenzenamine diethyl sulfate, and the like.

Note that although deuteration of a compound has a near-infrared absorption shift effect, it has the same nonlinear optical effect as a non-deuterated compound. Therefore, part or all of the nonlinear optical compound may be substituted with deuterium.

[Example] N-(4-pyridinylmethylene)-4-hydroxybenzenamine dimethyl sulfate 4.34 CI (20 mmol) of 4-pyridine aldehyde was placed in a 200 mQ three-turn flask equipped with a reflux condenser and a magnetic stirrer.・Dimethyl sulfate and 2.180 (20mm
ol) P-aminophenol was added, about 50 ml of ethanol was used as a reaction solvent, and the mixture was stirred at room temperature for about 10 minutes.

Next, about 34 mQ (2 mmol) of P-toluenesulfonic acid was added as a catalyst, and the mixture was allowed to react at room temperature for about 2 hours.

At this time, the yellow target product produced by the condensation reaction began to crystallize.

After confirming the completion of the reaction by thin layer chromatography using a mixed solvent of chloroform/acetone (9/1) as a developing solvent, stirring was stopped and the mixture was allowed to cool naturally. Further yellow crude crystals precipitated, which were removed and washed with cold ethanol.

After recrystallizing the yellow crude crystals obtained here with ethanol,
Vacuum dried.

The target product was produced in a maximum of 4.52 (11 (yield 73.4%)), and identification was performed by IR and elemental analysis.

Melting point>202.0~203.0℃ <IR>3300o++-" (-OH)1650
cm' (-CH=N-) 1600 Rho 1 (Benzene ring ~ 1500 cm-1 and pyridine ring) Elemental analysis (CHN) as shown in spectrum chart drawing In order to investigate the second harmonic, the powder method (S, Kurtz
, Ding 9, Perry, J, Apl) 1. Phys.
, 39, 3798 (1968)). The light i used in the measurement is Nd:YAGL/
−'fr, wavelength $t1.06 μm. The sample was ground in a mortar to a particle size of 10 μm or less.

The measurement results were compared to conventional typical optical nonlinear compounds such as urea, m-nitroaniline (m-NA), and 2-methyl-4.
-Nitroaniline (MNA>, 4-dimethylamino-
Shown together with 4'-nitrostilbene (DANS) (Table 1
).

N-(4-pyridinylmethylene)-4-hydroxybenzenamine dimethyl sulfate according to the present invention exhibited submerged tip nonlinearity that was 20 times the optical nonlinearity of urea.

[Effects of the Invention] According to the present invention, by introducing a donor-based buy-back into benzenamine in the pyridinium salt of N-(4-pyridinylmethylene)-benzenamine, the dipole moment is small, but the molecule has a small dipole moment. Compounds with large optical nonlinearity can be obtained. In this case, since the double-dipole-dipole action can be weakened, molecular modifications such as blue change bases are also effective.
It is possible to break the central symmetry in the bulk state, for example, in the fine state, and produce a large nonlinear optical effect.

[Brief explanation of the drawing]

The drawing shows an infrared absorption spectrum chart of a compound of an example of the present invention.

Claims (5)

[Claims] (1) General formula below▲ Numerical formula, chemical formula, table, etc.▼ D: Donor substituent R: Alkyl group such as -CH_3, -C_2H_5 R_1 to R_8: Hydrogen or any substituent X: CH_3SO_4, C_2H_5SO_4ClO_
4, IO_3, NO_3 BF_4, ReO_4, cinnamate, Br^■
, an organic nonlinear optical compound represented by Cl^■. (2) The organic nonlinear optical compound according to claim (1), which has a donor substituent at the para position. (3) X^■ in the general formula is CH_3SO_4^■,
The organic nonlinear optical compound according to claim (1) or (2), which is C_2H_5SO_4^■. (4) The organic nonlinear optical compound according to claim 1, 2, or 3, characterized in that the donor property of the substituent is weak. (5) The organic nonlinear optical compound according to claim (1), wherein some or all of the hydrogens in the compound are deuterated.