JPH03184024A - Organic nonlinear material - Google Patents

Abstract

PURPOSE:To develop high optical nonlinearity by introducing an acceptor type substituent into the arom. rings or hetero arom. rings at both terminals of a specific compd. system in which the bonds connecting the two arom. rings or hetero rings have a donor property. CONSTITUTION:This nonlinear material consists of the org. compd. expressed by formula. In the formula PHI<1>, PHI<2>: arom. ring or hetero ring, E<1>, E<2>: acceptor type substituent, R<1>, R<2>: hydrogen or 1 to 5C substituent, X, Y: one of X and Y is N-R<3> (R<3>: selected from hydrogen, alkyl, aryl, and aralkyl) and the other is O, S and N-R<4> (R<4>: selected from hydrogen, alkyl, aryl, and aralkyl). Where, the compd. expressed by formula 1' among the org. compds. expressed by the formula 1 is excluded). The molecular crystal having the small dipole moment and the high optical nonlinearity is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an organic nonlinear optical material made of a new substance and used particularly in optical information processing, optical communication, etc.

[Prior Art] Many materials exploration studies have been conducted with the aim of realizing nonlinear optical elements as new elements in the field of optoelectronics.In recent years, organic compounds with π-electron conjugated systems have been It is attracting attention because of its fast photoresponsiveness.

In particular, materials with second-order optical nonlinearity have been studied in various compound systems, and there are many general explanations. (1) A CS s7mposium
series 233 (1983), 2) D, J, W
illiams Angev, Chem.

lnL Ed, Engl, 23 p690 (19
84) etc. ) The optical nonlinearity of organic compounds with a π-electron conjugated system is said to be caused by the fluctuation of π-electrons when laser light is incident, and in order to increase this fluctuation, donor and acceptor properties are added to the π-electron conjugated system. The conventional molecular design guideline was to introduce substituents.

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 dipole-dipole interactions between molecules, resulting in a centrosymmetric crystal structure in which the dipoles of two molecules cancel each other out. Easy to shape.

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

In previous research, optically active substituents or substituents with high hydrogen bond-forming ability were introduced into the π-electron conjugated system in order to break the central symmetry of the crystal, which is a problem in expressing optical nonlinearity in the crystal state. This idea was taken when designing the molecule,
There are examples of relatively large optical nonlinearity.

N,N-dimethyl-2-acetylamino-4-nitroaniline (DAN), N-(4-nitrophenyl)-(L
)-Prolinol (NPP) and other benzene derivatives are typical examples.

[Problems to be Solved by the Invention] However, these do not have sufficient characteristics (optical nonlinearity, crystallinity, storage stability, etc.) necessary for practical use of nonlinear optical elements.

Therefore, the development of new compounds is expected, and material searches are currently being actively conducted.

An object of the present invention is to provide an organic nonlinear optical material comprising a novel compound capable of producing a molecular crystal with a small dipole moment and large optical nonlinearity.

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

"An organic nonlinear material comprising an organic compound represented by the following general formula [1].

R' Φ1. Φ2: aromatic ring or heteroaromatic ring E1. E2. Acceptor substituents R1, R2: hydrogen or substituents having 1 to 5 carbon atoms is selected from O9S and N-R4 (R4: selected from hydrogen, alkyl, aryl and aralkyl).

(However, among the organic compounds represented by general formula [1], the compound represented by the following general formula [1'] is excluded) (El,
(E2 near-acceptable substituent)" As mentioned above, the central symmetry of the crystal can be said to be largely due to the dipole-dipole interaction between molecules. Therefore, in order to break the central symmetry of a crystal, it is very effective to perform molecular modification on a compound system that has a basic structure that reduces the dipole moment of the molecule.

In the following compound system [2], the lone pair of electrons of the heteroatom can serve as a donor site for the aromatic ring or heteroaromatic ring at both adjacent ends.

In the present invention, the following compound system in which the bond connecting two aromatic rings or heteroaromatic rings also has donor properties [2] Acceptor substituents are introduced into the aromatic rings or heteroaromatic rings at both ends of We have discovered that large optical nonlinearity can be expressed by creating a structure in which one molecule contains two structures that are endowed with optical nonlinearity by charge transfer interactions between donors and acceptors.

2 Φ1 Φ2: aromatic ring or heteroaromatic ring R', R2: hydrogen or a substituent having 1 to 5 carbon atoms X, Y: one of X or Y is N-R3 (R3: hydrogen, alkyl and aryl, (Chosen from Aralquil)
In this case, where the other is selected from O9S and N-R4 (R4: selected from hydrogen, alkyl, aryl and aralkyl), the compound has a symmetric or quasi-symmetric structure, so
Since it is possible to suppress the increase in dipole moment due to the lengthening of absorption and the introduction of acceptor substituents, it is effective in the following points.

A) Decrease in optical nonlinearity and compound deterioration due to absorption of harmonics can be suppressed.

B) Since the dipole moment is small, backing control of the bulk state formed by molecules, that is, molecular orientation becomes easy.

That is, the compound used in the material of the present invention easily loses its central symmetry in a bulk state, for example, in a crystalline state, due to intermolecular cohesive forces such as hydrogen bonds, and exhibits optical nonlinearity.

Optical nonlinearity is particularly likely to occur when a hydrogen bonding or sterically hindering substituent is introduced into an aromatic ring or a heteroaromatic ring.

When an acceptor substituent is introduced into a site with a large resonance effect, it is effective because it can strengthen the charge transfer interaction and increase the optical nonlinearity of the compound.

The sites with a large resonance effect here include, for example, the following sites. In a 6-membered ring, the 4th position (the 1st position is X or Y in formula [1]) is common.

Furthermore, the acceptor substituent EI E of formula [1]
If 2 are the same, the structure of the compound will be symmetrical, and the above advantages A) and B) will be even more pronounced and effective.

Furthermore, the optical nonlinearity of molecular crystals is proportional to the molecular density. Therefore, as R1 and R2 in the general formula [1], a relatively small substituent that does not significantly reduce the molecular density in a crystalline state, ie, hydrogen or a substituent having 1 to 5 carbon atoms, is effective. Hydrogen is preferred, and in this case, synthesis is also relatively easy.

In addition, when R1 to R4 in the general formula [1] are hydrogen, the compound of the present invention can be prepared by hydrogenation of a Lewis acid using glyoxal and an aromatic amine having a hydroxyl group, mercapto group, or amino group at the 2-position as a catalyst. Below is a general synthesis method for imine compounds (MM, Sprung, Chem, R
ev 26297 (1940)). In particular, benzene derivatives can be easily synthesized.

Examples of the acceptor substituent in the present invention include alkyl esters such as nitro, cyano, isocyanate, aldehyde, methyl carboxylate, and ethyl carboxylate, sulfonyl, and halogen.

It is particularly preferable to introduce a nitro group as an acceptor substituent in order to improve the optical nonlinearity of the compound.

There are no particular restrictions on the introduction of substituents to positions other than those at which acceptor substituents are introduced in the aromatic ring or heteroaromatic ring at both ends, but if introduced, it will not have a major effect on the π-electron conjugated system of the parent skeleton. It is important that it is a substituent.

For example, Hammett's substituent constant σ is -0,4
<σ<0.4 or so. Preferred are hydrogen-bonding hydroxyl groups, alkoxy groups such as methoxy and ethoxy, alkanoylamino groups such as acetylamino and ethylcarbonylamino, and carbamoylamino groups.

However, in the present invention, among the organic compounds represented by the general formula [1], the organic compounds represented by the following general formula [1' (El, E2
(near accelerating substituent) In addition, deuteration of the compound is
Although it has a near-infrared absorption shift effect, it has the same nonlinear optical effect as a non-deuterated compound. Therefore,
In the nonlinear optical compound, some or all of the hydrogens may be substituted with deuterium.

[Example] a. Synthesis of 1-acetamino-2-acetoxy-naphthalene In a 1000 ml Erlenmeyer flask equipped with a magnetic stirrer, approximately 500 ml of ethanol and 15.9 g (0.1 mol) of 1-amino-2-hydroxynaphthalene were added. )
was added and stirred at room temperature.

Next, when 100 ml of acetic anhydride/acetic acid (1:1) solution was gradually added to the above reaction solution, light brown crystals were precipitated, which were collected by filtration and vacuum-dried (target object 21.
6g, yield 88.7%).

b. Synthesis of 1-acetamino-2-acetoxy-4-nitronaphthalene 10 ml of glacial acetic acid and 18 g (74 mmol) of 1-acetamino-2-acetoxynaphthalene were added to a 300 ml Erlenmeyer flask equipped with a magnetic stirrer and stirred.

The reaction solution was cooled with ice water, 20 ml of concentrated sulfuric acid was gradually added while keeping the temperature at about 5°C, and then 4 cC of fuming nitric acid was added dropwise while being careful not to let the reaction temperature rise above 20°C. At this time, the reaction solution turned yellow.

Thereafter, the solution turned yellow-orange when left at room temperature (approximately 25° C.) for 30 hours. When this solution was added to approximately 10,100 O of ice water, yellow-brown crude crystals were precipitated, which were collected by filtration, washed with cold water, and then dried under vacuum heat.

Next, the obtained crude crystals were separated using a column chromatograph packed with silica gel. As the developing solvent, a mixed solvent of acetone/chloroform (2:1) was used. The main product (second layer) upon development was separated and the solvent was evaporated to obtain yellow crystals. Identification was performed by IR and NMR.

(Target product 12.4 g, yield 58.6%) Synthesis of c, 1-amino-2-hydroxy-4-nitro-naphthalene 300 m equipped with a reflux condenser and a magnetic stirrer
150ml of ethanol, 50ml in Mitsuro flask
1 dimethyl sulfoxide, and 1-acetamino-
2-acetoxy-4-nitronaphthalene Log (35 mmol) was added and stirred at 50°C.

Next, 30ml of 3Qwt% sodium hydroxide aqueous solution
was added and then refluxed for 10 hours.

When the red reaction solution was added to 5QQml of water, orange crystals precipitated, which were collected by filtration and dried under vacuum heating at 80°C.

(5.61 g of target product, 78.5% yield) 5.0 g (24 mmol) of 1-amino-2-
Hydroxy-4-nitronaphthalene and about 20 mg (1,
2 mmol) of p-toluenesulfonic acid and about 1
Using 00111 ethanol as the reaction solvent, 1
Stirred for 0 minutes.

Next, 1.74 g (12 mmol) of glyoxal aqueous solution (40 wt%) was gradually added dropwise to the orange-red reaction solution.

Thereafter, the reaction temperature was maintained at 50° C. and stirring was continued for about 3 hours, and an orange target product crystallized.

After the completion of the reaction was confirmed by thin layer chromatography using ethanol/chloroform (1:1) as a developing solvent, stirring was stopped.

The precipitated crude crystals were collected by filtration and washed with cold ethanol.

The orange crude crystals obtained here were mixed with acetone/chloroform (3
Recrystallization with a mixed solvent of /1) gave yellow-orange crystals, which were collected by filtration and dried in vacuum.

(2.73 g (yield 52.8%) of target product, identified by IR,
This was done by NMR.

Next, in order to investigate the optical nonlinearity of this compound, the second harmonic was measured using the powder method (S, Kutt!, T, T, Peru
, J. Appl, Ph7s 393798 (19
66)). The light source used for the measurement was Nd:
Using the YAG laser, the sample was ground to 10 μm or less in a mortar.

The measurement results are shown in Table 1. The compound according to the invention exhibited optical nonlinearity 10 times greater than that of the standard known compound urea.

Table 1゜ Organic nonlinear optical material powder S HG (λ=1 06μm)

Claims (1)

[Scope of Claims] (1) An organic nonlinear material comprising an organic compound represented by the following general formula [1]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [1] Φ^1, Φ^2: Aromatic ring or heteroaromatic ring E^1, E
2: Acceptor substituent R^1, R^2: Hydrogen or substituent having 1 to 5 carbon atoms X, Y: One of X and Y is N-R^3 (R^3:
selected from hydrogen, alkyl, aryl and aralkyl), the other being O, S and N
-R^4 (R^4: selected from hydrogen, alkyl, aryl and aralkyl). (However, among the organic compounds represented by general formula [1], the compound represented by general formula [1'] below is excluded) ▲ Numerical formula,
There are chemical formulas, tables, etc. ▼ [1'] (E^1, E^2: acceptor substituent) (2) Formula [
Claim 1, characterized in that E^1 and E^2 of [1] are substituted with sites with a large resonance effect.
) The organic nonlinear material described in section 2. (3) The organic nonlinear material according to claim (1), wherein E^1 and E^2 in formula [1] are the same substituent. (4) The organic nonlinear material according to claim (1), wherein E^1 and E^2 in formula [1] are nitro groups. (5) The organic nonlinear material according to claim (1), wherein R^1 and R^2 in formula [1] are hydrogen. (6) The organic nonlinear material according to claim (1), wherein Φ^1 and Φ^2 in formula [1] are benzene rings. (7) The organic nonlinear material according to claim (1), wherein formula [1] is ▲a mathematical formula, a chemical formula, a table, etc.▼. (8) Claim No. (1) characterized in that some or all of the hydrogens in compound formula [1] are deuterated.
Organic compounds described in Section.