JP2799101B2 - Organic nonlinear optical material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic nonlinear optical material. Specifically, it is used as a light control element in a wide field such as an optical computer and an optical communication, is stable at room temperature, has excellent light damage strength, has a large SHG (second harmonic generation) activity, and has good crystallinity. Organic non-linear optical materials.

[0002]

2. Description of the Related Art Nonlinear optical materials include optical frequency conversion elements,
It has been practically used as an optical shutter, an EO converter, and the like. At present, inorganic ferroelectric crystals such as potassium dihydrogen phosphate (KDP) and lithium niobate (LN) are used as nonlinear optical materials. Recently, attention has been paid to the magnitude of the nonlinear optical effect and the speed of the nonlinear optical response of the organic crystal, and the development of organic nonlinear optical materials has been energetically advanced.

As an organic nonlinear optical material for the secondary effect, MNA (2-methyl-4-nitroaniline, literature:
G. FIG. F. Lipscomb A. F. Garito
R. S. Narang, J .; Chem. Phys. , 7
5 (3) 1509-1516, 1981), POM (3
-Methyl-4-nitropyridine-oxide, literature:
J. Zyss D. S. Chemla, J .; Chem.
Phys. , 74 (9) 4800-4811,198.
1) has been developed, and the second-order nonlinear constant of the MNA is K
It reaches 50 times DP.

It is widely known that an organic compound having such a large nonlinear effect generally has an electron-accepting and electron-donating substituent across a π-electron conjugated chain.
It is also known that second-order nonlinear optical materials must form crystals without central symmetry.

[0005]

Since one molecule of an organic nonlinear optical material is responsible for optical non-linearity, a molecule having an asymmetric center has SHG (second harmonic generation) activity in principle. When the SHG active molecule is crystallized and used as an optical element, the crystal often loses its SHG activity. Therefore, to determine whether an organic material can be used as a nonlinear optical element, a molecular material must be actually synthesized, crystallized, and the optical nonlinearity must be evaluated.

In order to enhance the optical nonlinearity of one molecule, an electron-donating and accepting substituent may be introduced into a long conjugated system. Optical nonlinearity (supramolecular polarizability β) at the molecular level of an organic compound can be estimated from molecular orbital calculations.
According to this calculation, stilbene-based molecules are one of the typical organic nonlinear optical materials having a large β value at the molecular level, but most of them have a center of symmetry in a crystalline state and become SHG-inactive as a crystal There is a problem that.

Considering the use as a wavelength conversion element, translucency in a molecular state or a crystalline state is an important factor, but an organic material often has absorption in the visible region.
For example, a commonly known MNA is 358n
m has a maximum absorption wavelength, but in consideration of the wavelength of SH light, the transmission wavelength region needs to be extended to a shorter wavelength.

Further, in consideration of use for a nonlinear optical element, it is desirable that the melting point is high from the viewpoint of weather resistance. However, the melting point of organic materials is generally low, for example, MAP (literature; JL Oudar and R. Hierle,
J. Appl. Phys. , 48 (7) 2699-27.
04, 1977) has a low melting point of 69 ° C., which is also an important issue in this respect.

[0009]

The present invention, in order to solve the problems] The state, and are not been made in view of the above, 2-nitro-4'-bromo -α- cyano stilbene, or, 4-methoxy -
To provide an organic nonlinear optical material consisting of 4'-bromo -α- cyanostilbene Zen, it is intended to solve the above problems.

[0010]

SUMMARY OF] The onset Ming 2-nitro-4'-bromo -α- Shianosuchiru benzene, or 4-methoxy-4'-bromo -α- Shianosuchiru organic nonlinear optical material made of benzene, melting point each 16 3 ° C, 133 ° C., high thermal stability, and excellent weather resistance. Further, since the absorption edge is on the short wavelength side and shows high SHG activity, it can be used in a wide range of fields as a nonlinear optical element.

In general, a stilbene compound has a π-electron conjugate system longer than a benzene or styrene-based nonlinear optical material, and has a strong electron-accepting property (such as a nitro group) and a donating substituent (such as a dimethylamino group or an amino group). ) Is introduced at the end of the conjugated molecule, the nonlinear effect increases due to the known trade-off relationship between the nonlinear constant and the light transmission property, but the transmitted light region is narrowed. For this reason, it is necessary to introduce a substituent having an appropriate strength into an appropriate position. However, inferring from these points, in the present invention, bromine and a methoxy group act as electron donating groups, It is considered that the nitro group and the nitro group act as electron accepting groups.
In addition, it is considered that these substituents also act to prevent the crystal state from becoming centrally symmetric. Furthermore, the cyano group is introduced near the center of the stilbene conjugate as an electron-accepting substituent, weakens the strength of other electron-accepting or donating substituents, and provides both a large nonlinear effect and a wide transmitted light region. It is thought that it acts on the intramolecular conjugate system so as to satisfy the condition.

Hereinafter, the present invention will be described in detail based on embodiments.

[0013]

Example 1 1.6 g of p-nitrobenzaldehyde
(0.01 mol) was dissolved in 150 ml of ethanol, and then 2.08 g of 4-bromophenylacetonitrile was dissolved.
(0.01 mol) was added. 10 ml of an ethanol solution in which 0.7 g of sodium ethylate was dissolved was added dropwise thereto.

After stirring the solution at room temperature for 6 hours, the resulting precipitate is filtered and washed with methanol to give the desired compound 4-nitro-4'-bromo-α-cyanostilbenzene.

[0015]

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Was obtained. The yield was 73%. The maximum absorption wavelength was 340 nm (in 1,4-dioxane) (FIG. 1), and the melting point was 159 ° C. by DSC measurement. Next, when the obtained fine powder crystal is irradiated with a Nd: YAG laser (wavelength = 1.64 μm), a second harmonic is generated, and green light having a half wavelength (532 nm) of the incident light is observed. Was done. This SHG intensity is three times the urea ratio,
It was confirmed that the efficiency was stronger than that of urea.

Further, needle-like crystals were easily obtained by recrystallization operation from ethanol, and a single crystal could be formed as a seed crystal.

[0018]

Example 2 1.6 g of o-nitrobenzaldehyde
(0.01 mol) was dissolved in 150 ml of ethanol, and then 2.08 g of 4-bromophenylacetonitrile was dissolved.
(0.01 mol) was added. A sodium ethylethanol solution was added dropwise thereto. This solution is added at room temperature for 6 hours.
After stirring for an hour, the resulting precipitate was filtered and washed with methanol to give the desired 2-nitro-4'-bromo-α-.
Cyanostilbenzene

[0019]

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Was obtained. The yield was 74%. The maximum absorption wavelength was 274 nm (in 1,4-dioxane) (FIG. 2), and the melting point was 163 ° C. by DSC measurement. Next, when SHG was evaluated in the same manner as in Example 1, green light having a wavelength (532 nm) of half of the incident light was observed. This SHG intensity was three times the urea ratio, and it was confirmed that the SHG efficiency was stronger than that of urea.

Further, needle-like crystals were easily obtained by the recrystallization operation from ethanol, and single crystals could be formed as seed crystals.

[0022]

Example 3 1.4 g (0.01 g) of p-anisaldehyde
mol) was dissolved in 150 ml of ethanol, and 2.08 g (0.01 mol) of 4-bromophenylacetonitrile was dissolved.
l) was added. Sodium ethylate-etano-
Solution was added dropwise. After the solution was stirred at room temperature for 6 hours, the resulting precipitate was filtered and washed with methanol to give the desired 4-methoxy-4'-bromo-α-cyanostilbenzene.

[0023]

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Was obtained. The yield (FIG. 3) was 74%. The maximum absorption wavelength was 340 nm (in 1,4-dioxane), and the melting point was 133 ° C. as measured by DSC. Next, when SHG was evaluated in the same manner as in Example 1, green light having a wavelength (532 nm) of half of the incident light was observed. This SHG intensity was confirmed to be almost the same as that of urea.

Further, needle-like crystals were easily obtained by recrystallization operation from ethanol, and single crystals could be formed as seed crystals.

[0026]

COMPARATIVE EXAMPLE The inventors of the present invention carried out a comparative study on 4-cyano-4'-bromo-α-cyanostilbene having a cyano group at the 4-position of the phenyl group (β-position) of α-cyano-stilbene.

[0027]

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As for the nitro group, 3-nitro-4'-bromo-α-cyanostilbene introduced at the 3-position is used.

[0029]

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The two types of 4'-bromo-α-cyanostilbenzene were also synthesized to produce crystals. However, when these compounds were evaluated by the powder method, they were SHG-inactive.

[0031]

Effect of the Invention The present onset Akira of 2-nitro-4'-bromo--α
-Cyanostilbenzene or 4-methoxy-4'-
Organic nonlinear optical material consisting of bromo -α- Shianosuchiru benzene has a melting point of higher thermally stable with each 16 3 ° C, 133 ° C , it has excellent weather resistance. Furthermore, since the absorption edge is on the short wavelength side and shows high SHG activity,
It can be used in a wide range of fields as a nonlinear optical element.

Further, by using such an organic material having excellent optical nonlinearity, translucency and thermal stability, the characteristics of an expensive inorganic nonlinear optical material can be provided at a low price.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the wavelength and the absorbance of 4-nitro-4′-bromo-α-cyanostilbene in 1,4-dioxane.

FIG. 2 is a diagram showing the relationship between the wavelength and the absorbance of 2-nitro-4′-bromo-α-cyanostilbene in 1,4-dioxane.

FIG. 3 is a diagram showing the relationship between the wavelength and the absorbance of 4-methoxy-4′-bromo-α-cyanostilbene in 1,4-dioxane.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-32606 (JP, A) US Pat. No. 4,961,331 (US, A) CHEMICAL PHYSICS LETTERS, VOL. 148 NO. 2-3 PP. 136-141 (1988) Y. WANG ET. AL. 971 PP., SPIE PROCEEDINGS, NONLINEAR OPTICAL PROPERTIES OF ORGA NIC MATERIALS, VOL. 107-112 (1988) WIL SON TAM ET. AL. , (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/35-3/02 C07C 255/32-255/44 C07C 255/50-255/51 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. Induction of 4'-bromo-α-cyanostilbene
In an organic nonlinear optical material comprising a conductor, the 4′-bromo-α-cyanostilbene derivative has a structural formula An organic nonlinear optical material characterized by using 2-nitro-4'-bromo-α-cyanostilbenzene represented by the following formula: 2. Induction of 4'-bromo-α-cyanostilbene
In the organic nonlinear optical material comprising a conductor, the 4′-bromo-α-cyanostilbene derivative has a structural formula An organic nonlinear optical material characterized by using 4-methoxy-4'-bromo-α-cyanostilbenzene represented by the following formula: