JPH05241211A - Organic nonlinear optical material - Google Patents

Abstract

PURPOSE:To provide the org. nonlinear optical material which exhibits high optical nonlinearity and is usable even in a short wavelength region of visible light by constituting the material so as to have a perfluoroalkyl group as an electron-withdrawing substituent and to have the large trans-stilbene skeleton of a pi conjugation system. CONSTITUTION:This material is the trans-stilbene deriv. expressed by formula. In the formula, Rf denotes the perfluoroalkyl group; R1 denotes an alkoxy group, hydroxy group; at least one of R2 to Rs denote a halogen atom and the rest denote a hydrogen atom. Namely, the compd. of a nitroaniline system has light absorption in a visible part while exhibiting the high optical nonlinearity. The suitable electron-withdrawing substituent is required to be selected for the trans-stilbene skeleton in order to take the balance of the light absorption characteristic and the nonlinear optical characteristic. Then, the deriv. having the perfluoroalkyl group which has the relatively strong electron- withdrawing property and has no absorption in the visible light region of >=415nm as the substituent is selected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to organic nonlinear optical materials. More specifically, the present invention relates to an organic nonlinear optical material that can be used in a wide visible light region and is useful in fields such as wavelength conversion of laser light, optical communication, optical integrated circuits, and optical information processing.

[0002]

2. Description of the Related Art As a new element in the field of optoelectronics, many materials have been searched for in order to realize a nonlinear optical element.

Nonlinear optical materials are roughly classified into inorganic materials and organic materials, and conventionally, inorganic dielectrics such as KH ₂ PO ₄ and LiNbO ₃ are used. However, these inorganic non-linear optical materials have insufficient optical non-linearity, and a strong laser beam is required to exhibit a sufficient non-linear optical effect.

On the other hand, a series of organic compounds having a π-electron conjugated system has been attracting attention as a nonlinear optical material because of the magnitude of the optical nonlinearity of the molecule itself and the high-speed response. Poly
meric Materials, ACS Symposium Series 233 (198
3)).

The non-linear optical effect includes second-order, third-order, fourth-order,
········· There are n-th order effects, but of these, the ones expected to be applied are the second-order and third-order nonlinear optical effects. In order to develop a second-order nonlinear optical effect in a crystal of an organic compound, the crystal should not have a symmetry center.

As a method of removing the symmetry center of the crystal, introduction of a substituent into an asymmetric position of a molecule, use of a compound having chirality, use of an inclusion compound, selection of a counter ion in a molecular salt, intermolecular hydrogen Various methods have been proposed, such as the use of coupling and control of dipole moment.

For example, m in which a substituent is introduced at an asymmetric position
-Nitroaniline and 2-methyl-4-nitroaniline (hereinafter abbreviated as MNA) are known.
US Patent No.
4,199,698 and JP-A-55-500,960.

Many of these organic compounds have a nitro group as an electron-withdrawing substituent, and have light absorption resulting from this in the visible light region. Therefore, these organic compounds have absorption in the visible light region, particularly near 500 nm, although the optical nonlinearity is slightly excellent.

Further, since the stilbene derivative has a large π-electron conjugated system, it is known that the stilbene derivative exhibits a larger optical non-linearity per molecule as compared with a compound having a benzene ring as a π-electron conjugated system such as MNA. However, a compound having a large optical non-linearity in a crystal has been found.

While having a large optical nonlinearity, the stilbene derivative has absorption up to a considerably long wavelength side in the visible light region as compared with a compound having a benzene ring in a π-electron conjugated system.

As the organic non-linear optical material using the stilbene derivative, there are JP-A-1-207,724 and JP-A-1-173,017.

On the other hand, one of the application fields of organic nonlinear optical materials is a wavelength conversion element used for generating the second harmonic of a GaAlAs semiconductor laser.

By using the second harmonic of the GaAlAs-based semiconductor laser, the recording density of the optical disk using the conventional GaAlAs-based semiconductor laser can be quadrupled.

The characteristics required of the nonlinear optical material for the wavelength conversion element are large optical nonlinearity,
Moreover, it is a necessary condition that there is no absorption in the visible light region (415 nm or more) on the longer wavelength side than the wavelength region of the second harmonic.

[0015]

An object of the present invention is to provide an organic nonlinear optical material which exhibits a large optical nonlinearity and can be used even in a short wavelength region of visible light.

[0016]

In order to achieve the above object, the present invention has a perfluoroalkyl group having no light absorption in the visible light region as an electron-withdrawing substituent and has a large optical non-linearity. It is characterized by having a large π-conjugated transstilbene skeleton in order to have it.

That is, the following general formula

[0018]

[Chemical 2] (In the formula, R _f represents a perfluoroalkyl group, R ₁ represents an alkoxy group or a hydroxy group, and at least one of R 2, R 3, R 4 and R 5 represents a halogen atom and the other represents a hydrogen atom). It is a trans-stilbene derivative shown.

As mentioned above, p-nitroaniline, MN
Nitroaniline-based compounds such as A and m-nitroaniline show large optical nonlinearity at the molecular level due to the intramolecular charge transfer (CT) effect, while having light absorption in the visible region.

This is because the absorption due to the nitro group is in the vicinity of the visible light region, and further, the light absorption shifts to the longer wavelength side due to the bathochromic effect due to the charge transfer effect. That is, in order to obtain a compound that does not absorb in the visible light region, it is considered as one method to select a group other than the nitro group, which is a chromophore, as the electron-withdrawing substituent.

Further, by using a trans-stilbene skeleton having a large π-electron conjugated system instead of the benzene ring, the nonlinear optical characteristics can be enhanced, while the bathochromic effect of light absorption is further increased. That is, in order to balance the light absorption characteristics and the non-linear optical characteristics, it is necessary to select an appropriate electron-withdrawing substituent for the transstilbene skeleton.

In the case of the present invention, trans having a relatively strong electron-withdrawing property and a perfluoroalkyl group such as a trifluoromethyl group which does not have absorption in the visible light region as an electron-withdrawing substituent. This is achieved by selecting stilbene derivatives.

The above-mentioned perfluoroalkyl group represented by R _f is preferably a perfluoroalkyl group having 1 to 5 carbon atoms, such as trifluoromethyl group, pentafluoroethyl group, heptafluoro-n-propyl group, Heptafluoro-i-propyl group, nonafluoro-n-butyl group, nonafluoro-i-butyl group, nonafluoro-t
A butyl group and the like. More preferably, it is a trifluoromethyl group.

R ₁ is an alkoxy group or a hydroxy group, preferably an alkoxy group having 1 to 5 carbon atoms, and the alkoxy group includes a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, Examples thereof include n-butoxy group.

Further, at least one of the substituents represented by R ₂ , R ₃ , R ₄ , and R ₅ is a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), and the others are hydrogen. The atom is. The halogen atom is preferably a fluorine atom or a chlorine atom.

Specific examples of the compound in the present invention are shown below. [Compound example]

[0027]

[Chemical 3]

[0028]

[Chemical 4]

[0029]

[Chemical 5] These trans-stilbene derivatives are obtained by synthesizing a corresponding substituted benzyl halide and a substituted benzaldehyde using a Wittig reaction to obtain a trans form by isomerization, and using a corresponding substituted phenylacetic acid and a substituted benzaldehyde as a catalyst. It can be obtained by a general method for synthesizing a stilbene derivative such as the above-mentioned synthetic method.

[0030]

The present invention will be described in more detail with reference to the following examples.

[0031]

Example 1 [Synthesis of 3-fluoro-4-methoxy-4'-trifluoromethyl transstilbene (Compound 1)] 1) Synthesis of 3-fluoro-4-hydroxybenzaldehyde

[0032]

[Chemical 6] 4-fluoro-4-methoxybenzaldehyde 4 g (2
6 mmol) hydrobromic acid 6.28 g (77.6 mmo)
l) and boil for 24 hours. After that, it is washed with 2-3% caustic soda, washed with dilute hydrochloric acid, extracted with chloroform, and the solvent is distilled off. 1.87 g (yield 51.4%) of a tan solid was obtained.
2) Synthesis of 3-fluoro-4-hydroxy-4'-trifluorotransstilbene

[0033]

[Chemical 7] In a 100 ml three-necked flask equipped with a stirrer and a reflux condenser, α, α, α, trifluoro-4-toluylacetic acid 2.6 g (13 mmol), 3-fluoro-4-hydroxybenzaldehyde 1.8 g (13 mmol), Piperidine (7.7 ml) was charged, and the mixture was heated to reflux with stirring at an internal temperature of 120 ° C. for 8 hours.

After completion of the reaction, piperidine was distilled off, the residue was dissolved in chloroform, washed with 6% HCl, and the chloroform was concentrated. Then, crude purification solid was obtained by column chromatography using chloroform as a developing solvent. By recrystallizing the crude product with hexane, 1.65 g of white plate crystals (yield 4
4.8%). 3) Synthesis of compound 1

[0035]

[Chemical 8] 100m equipped with stirrer, reflux condenser and dropping funnel
1.5 g of 3-fluoro-4-hydroxy-4'-trifluoromethylstilbene described above in a 4-necked 4-neck flask.
(5.3 mmol) was dissolved in methanol and added. 0.4g (3mmol) of dimethylsulfate with continuous stirring at room temperature
Added.

While cooling the outside of the flask with ice water and stirring, 0.6 g (5.2 mmo) of 35% sodium hydroxide was added.
1) is added dropwise over 15 to 30 minutes, and then lightly boiled for 2 hours.

After the reaction, the mixture was sufficiently cooled, washed with water, and then extracted twice with chloroform. The precipitated crude purified product was filtered and recrystallized with hexane to give 0.8 to 0.5 white granular crystals.
0.9 g (yield 57.2%) was obtained.

Identification was carried out by ¹ HNMR (FIG. 1) and IR (FIG. 2) in deuterated acetone, and 3-fluoro-4-
It was confirmed to be methoxy-4′-trifluoromethyl transstilbene (Compound 1).

[0039]

Example 2 [Synthesis of 2-chloro-4-methoxy-4'-trifluoromethyl transstilbene (Compound 2)]

[0040]

[Chemical 9] 2-Chloro-4-hydroxy-similar to 3) of Example 1
4'-trifluoromethylstilbene 4.0 g (13 m
mol) and 1.01 g (8 mmol) of dimethylsulfate into 1.53 g (13 mmo) of 35% sodium hydroxide.
l) is added dropwise.

After completion of the reaction, post-treatment is carried out and the crudely purified product is filtered to obtain a white-yellow solid. The residue was dissolved in hexane and evaporated to give 1.17 g (yield 28.7%) of a white solid. White crystals were obtained by recrystallizing this with a polar solvent. It was confirmed to be compound 2 in the same manner as in Example 1.

[0042]

Example 3 [Synthesis of 2-chloro-4-hydroxy-4′-trifluoromethyltransstilbene (Compound 14)]

[0043]

[Chemical 10] As in 3) of Example 1, α, α, α, trifluoro-4
-Toluyl acetic acid 10.2 g (50 mmol), 2-chloro-4-hydroxybenzaldehyde 7.88 g (50
mmol), 30 ml of piperidine were charged, and the internal temperature was 115 ° C.
The mixture was reacted for 8 hours and separated by column chromatography to obtain about 10 g of a light green-yellow solid.

Recrystallization from hexane gave 3.12 g (yield 20.8%) of white yellow plate crystals. By recrystallizing this with a polar solvent, white yellow crystals were obtained. It was confirmed to be compound 14 as in Example 1.

[0045]

[Test Example] [Evaluation of second-order nonlinear optical characteristics and light absorption characteristics at the molecular level] 2 of the compounds obtained in Examples 1 to 3
In order to investigate the following non-linear optical characteristics, the EFISH method of Levine et al. (BF Lenine et al,
J. Appl. Phys. , 50 , 2543 (197)
The second-order nonlinear hyperpolarizability β was measured according to 9)).

The sample was dissolved in 1,4-dioxane to obtain N
Using the fundamental wave (wavelength 1064 nm) of the d: YAG laser, the second harmonic (532n) generated while applying an electric field
m) was observed, and the second-order nonlinear susceptibility β, which is a measure of the magnitude of the second-order nonlinearity at the molecular level, was determined using nitrobenzene as a reference sample.

Also, using ethanol as a solvent, 10 ⁻⁴ mo
A 1 / l solution was prepared and the absorption spectrum was measured with an ultraviolet / visible spectrophotometer to examine its visible light transmission characteristics. Where λ
_max is the maximum wavelength of light absorption on the longest wavelength side. λ _cut-off is the absorption edge on the short wavelength side. The measurement results are summarized in Table 1.

[Evaluation of Second-order Nonlinear Optical Properties of Crystal] Ku
Powder method proposed by rtz et al. (SKKurtz, TTPerry, J.A.
ppl. Phys., 39, 3798 (1968)) and the presence of optical nonlinearity was investigated by observing the second harmonic.

The compounds of Examples 1 to 3 were mixed with an average particle size of 100 μm.
Adjusted to the fundamental wave of the Nd: YAG laser (wavelength 1064n
second harmonic (wavelength 532
nm) was observed. As a result, the second harmonic green light was confirmed.

[0050]

Comparative Example As a comparative example, the second-order nonlinearity of 2-methyl-4-nitroaniline, which is a typical organic nonlinear optical material, and 4-hydroxy-4′-nitrotransstilbene, which is a transstilbene derivative having a nitro group. The susceptibility β and visible light transmittance were measured in the same manner as in Test Examples. The results are shown in Table 1 together with the examples.

As is clear from these results, the compound of the present invention is transparent to the short wavelength region of the visible light region and exhibits a large optical nonlinearity as compared with the conventional compounds.

The compound of the present invention can be used not only in the crystalline form, but also in the form of being complexed with a polymer medium, introduced into a polymer side chain, or the like.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

As described above, according to the compound of the present invention, the fact that the compound of the present invention is transparent to the short wavelength side of the visible light region as compared with the conventional materials is utilized, and it is used in the field of wavelength conversion and various information processing. In, it can be used in combination with a short wavelength light source. Further, it is particularly applicable to the generation of harmonics of short wavelength light sources such as GaAlAs semiconductor lasers.

[Brief description of drawings]

FIG. 1 is an example of a nonlinear optical material according to the present invention 3
-Fluoro-4-hydroxy-4'-trifluoromethyl transstilbene (Compound 1) in heavy acetone
It is a figure which shows a ¹ H NMR spectrum.

FIG. 2 is a view showing an IR spectrum of the same compound.

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[Procedure amendment]

[Submission date] November 27, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

After completion of the reaction, piperidine was distilled off, the residue was dissolved in chloroform, washed with 6% HCl, and the chloroform solution was concentrated. Then, crude purification solid was obtained by column chromatography using chloroform as a developing solvent. The crude product was recrystallized from hexane to obtain 1.65 g of white plate crystals (yield 44.8%). 3) Synthesis of compound 1

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043]

[Chemical 10] As in 3) of Example 1, α, α, α, trifluoro-4
-Toluyl acetic acid 10.2 g (50 mmol), 2-chloro-4-hydroxybenzaldehyde 7.88 g (50
mmol), 30 ml of piperidine were charged, and the internal temperature was 115 ° C.
After reacting for 8 hours and separating by column chromatography , about 10 g of a light green-yellow solid was obtained.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Suzuki 1618 Ida, Nakahara-ku, Kawasaki-shi In the Advanced Technology Research Laboratory, Nippon Steel Corporation (72) Inventor Tatsuo Nishiyama 3-6 Ibaraki, Akita City Co., Ltd. In Tochem Products (72) Inventor Tomomi Takezono 3-6 Ibaraki, Akita City In Tochem Products Co., Ltd.

Claims (1)

[Claims] 1. A general formula: (In the formula, R _f represents a perfluoroalkyl group, R ₁ represents an alkoxy group or a hydroxy group, and at least one of R ₂ , R ₃ , R ₄ and R ₅ is a halogen atom and the other is a hydrogen atom. An organic nonlinear optical material characterized by being a transstilbene derivative represented by the formula (1) and having no absorption in the visible light region of 415 nm or longer.