JPH06345713A - Molecular crystal - Google Patents

Abstract

PURPOSE:To obtain a molecular crystal, composed of an isopropyl 4- ethoxycarbonylphenylcarbamate molecule, having great secondary nonlinear optical effects and changing the cutoff wavelength into a shorter one for enlarging the wavelength region used as an optical material. CONSTITUTION:This molecular crystal is composed of an isopropyl 4- ethoxycarbonylphenylcarbamate molecule, expressed by the formula and belonging to a monoclinic system space group P21. The molecular crystal is obtained by reacting, e.g. ethyl 4-aminobenzoate with isopropyl chloroformate, thereby providing the compound expressed by the formula, then dissolving the resultant compound in methanol, acetone, tetrahydrofuran, etc., having a high solubility and crystallizing the compound molecule from the prepared solution for 4-5 days according to a solvent evaporating or a solvent cooling method. The resultant molecular crystal is a large-sized platy crystal of good quality, capable of especially readily matching the phase in a natural growth face of the crystal and useful as various optical functional element materials utilizing nonlinear optical and electrooptical effects such as wavelength converting or optical controlling elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to molecular crystal belonging to 4-ethoxycarbonyl constructed from phenyl carbamic acid isopropyl ester molecule monoclinic P2 _1, which is an optical, such as non-linear optical, electro-optical It is adapted to the material. Further, it can be applied to all optoelectronic devices that can utilize these effects.

[0002]

2. Description of the Related Art Nonlinear optical effect is a phenomenon in which, when very strong light passes through an object, a substance is polarized by the electric field of the light, a harmonic wave is generated by the induced polarization, and the incident light itself is changed. Say. Although such a phenomenon has been known before the invention of the laser, much has come to the fore with the advent of laser light. In particular, the invention of the laser largely bears the clarification of phenomena such as optical harmonic generation, optical parametric oscillation / amplification, optical phase conjugation, and optical bistability, which have recently attracted attention for application to optical functional devices. These nonlinear optical effects are the conversion of infrared light into visible light and ultraviolet light,
It can be applied to optical amplification, optical switches, optical modulation, and distortion-free transmission of optical signals. Nonlinear optical effect elements are positioned as functional materials that hold the key in the fields of optical information processing and optical communication, where demand is ever increasing.

Conventionally, as a substance showing a non-linear optical effect,
For example, potassium dihydrogen phosphate (KDP), lithium niobate (LiNbO ₃ ), 3-methyl-4-nitropyridine-N-oxide (P
OM), 2-methyl-4-nitrianiline (MNA), etc., but these materials have poor effect, and it is difficult to process to bring out the effect sufficiently, and the walk-off angle is large, so they are effective. There are problems such as insufficient length and difficulty in crystal growth.

[0004]

In the organic compound,
It is well known that it is effective to introduce an electron-donating group and an electron-withdrawing group into the molecule in order to increase the dipole moment of the molecule in order to enhance the second-order nonlinear optical effect. There is. However, there remain important unsolved issues in this regard. That is, in order to develop the second-order non-linear optical effect, the crystal must have a form without the center of inversion symmetry. However, organic compounds having a large dipole moment in the molecule are arranged so as to cancel each other's dipole moments when crystallized, and as a result, the molecule has a large second-order supramolecular polarizability β.
However, a crystal or a molecular assembly may not exhibit a quadratic nonlinear optical effect due to the center of inversion symmetry. In addition, due to large intramolecular charge transfer, there is electronic transition absorption in the near-ultraviolet to visible region, which leads to a loss of transparency, which is important as an optical material. In reality, there are many such organic compounds.

Therefore, in developing an organic nonlinear optical compound mainly focusing on the second-order nonlinear optical effect, a supramolecular polarizability β which is sufficiently large as a molecule without impairing transparency is obtained.
It is an important subject to synthesize a compound which has the above-mentioned property and can easily obtain a high-quality crystal having no inversion symmetry center.

4-Nitroaniline is an aromatic compound having the simplest electron-donating group and electron-withdrawing group, and is one of the organic compounds having a large supramolecular polarizability β. The crystal has an inversion symmetry center because the molecules are arranged so as to cancel each other's dipole moments,
It does not show quadratic nonlinear optical effects. In addition, due to intramolecular charge transfer by nitro group and amino group, there is a large electronic transition absorption from near ultraviolet to visible region. For this reason, 4-nitroaniline is markedly colored.

The relationship between the secondary supramolecular polarizability β and the transparency of aromatic compounds having an electron-withdrawing group and an electron-donating group at the para-position of the benzene ring such as 4-nitroaniline, symmetry As a result of diligent studies on property modification, certain types of 4-ethoxycarbonylphenylcarbamic acid alkyl ester derivatives have a large second-order supramolecular polarizability β, and when a crystal or molecular assembly is formed, an inversion symmetry center is formed. It was clarified that it does not have, and that transparency in the near-ultraviolet to visible region can be remarkably improved, and the present invention was completed.

The object of the present invention is that the second-order non-linear optical effect is large and the cut-off wavelength is shortened in order to expand the wavelength range used as an optical material. To provide good molecular crystals.

[0009]

Means for Solving the Problems The molecular crystal of the present invention is characterized by comprising 4-ethoxycarbonylphenylcarbamic acid isopropyl ester represented by the formula (1).

[Chemical 1]

4-Ethoxycarbonylphenylcarbamic acid isopropyl ester is obtained, for example, by reacting ethyl 4-aminobenzoate with isopropyl chloroformate. This 4-ethoxycarbonylphenylcarbamic acid isopropyl ester is highly soluble in alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, tetrahydrofuran, chloroform, dichloromethane, dimethyl sulfoxide, dimethylformamide, dimethylacetamide. Etc., and crystallized in 4 to 5 days by a solvent evaporation method or a solvent cooling method to obtain a large-sized plate crystal of good quality.

[0011] belongs to this molecular crystal is monoclinic, space group P2 _1,

[Chemical 2] It will be a 6- to 18-sided structure composed of faces. Obtained 4
-Ethoxycarbonylphenylcarbamic acid isopropyl ester is powdered in Nd: YAG laser (λ = 1064n
Irradiation of m) produces a significantly stronger second harmonic of green. Further, in the single crystal state, phase matching is possible over a wide range, and a second harmonic wave having an intensity far exceeding that of powder is generated.

Generally, since the propagation constants of the fundamental wave and the harmonics in the crystal do not match, it is difficult to generate the harmonics in the crystal state,
This matching is called phase matching, and if this phase matching is not achieved, the generation of harmonics cannot be observed. There are very few organic crystals that can be phase-matched, but the molecular crystal according to the present invention generates high-strength phase-matched second harmonics as described above, and is capable of phase-matching in a wide wavelength region on the crystal natural growth plane. Also in this respect, the molecular crystal of the present invention has superior physical properties to conventional substances.

Further, it is milky white in a powder state and colorless and transparent in a single crystal state, and the cut-off wavelength is significantly shifted by a short wavelength. If the fundamental wave is 1 to 1.2 μm infrared light, C-H
The fundamental wave may be absorbed by the overtone absorption of the stretching vibration, and may be converted into thermal vibration. Therefore, when the intensity of the fundamental wave is strong, the temperature of the crystal rises, the phase matching condition changes, and the angle of the emitted light changes. In the present invention, it is preferable to adopt a compound form in which hydrogen of an alkyl group having a large overtone absorption is replaced with deuterium, because the absorption region shifts to the long wavelength side and this phenomenon can be effectively prevented.

[0014]

EXAMPLES The present invention will be described below based on examples. (Example 1) 8.3 g (50 mmol) of ethyl 4-aminobenzoate was dissolved in benzene, kept at 50 ° C in an oil bath, and 7.4 g (60 mmol) of isopropyl chloroformate was added dropwise, followed by stirring and reaction for about 4 hours. . After completion of the reaction, the reaction solution was washed with water, and the concentrated and precipitated reaction product was dried under reduced pressure at 50 ° C. to obtain 4-ethoxycarbonylphenylcarbamic acid isopropyl ester. After drying under reduced pressure, recrystallization was performed with a tetrahydrofuran solution to obtain colorless transparent rod-shaped or plate-shaped crystals of 4-ethoxycarbonylphenylcarbamic acid isopropyl ester.
The yield was 85% and the purity was 99.5%. 100 g of the obtained 4-ethoxycarbonylphenylcarbamic acid isopropyl ester was used as a saturated solution of tetrahydrofuran and the temperature was adjusted to 25
The temperature was kept constant at 0 ° C. and the crystals were grown for 10 days by the solvent evaporation method to obtain plate crystals of 80 * 25 * 6 mm.

(Example 2) 4-obtained in the same manner as in Example 1
Crystal structure analysis of a 0.50 * 0.20 * 0.10 mm crystal of isopropyl ethoxycarbonylphenylcarbamic acid was carried out using an x-ray four-axis automatic diffractometer. As a result, the single crystal belongs monoclinic, space group P2 _1, the lattice constants a = 1
2.824, b = 8.081, c = 6.874 (A), β = 105.55 °, two molecules were present in the unit cell, and the density was 1.22.

(Example 3) Using the crystal obtained in Example 1,
With this Nd: YAG laser with Q switch (λ = 1064nm)
A pulse of 10 nsec was irradiated. As a result, phase matching is possible by injecting the fundamental wave on the crystal natural growth surface,
The second harmonic generation efficiency was 500 times or more of KDP, and the second harmonic was obtained as transmitted light.

Example 4 Using the crystal obtained in Example 2,
Tunable Ti / Sapphire laser (λ = 960-700n
m) pulsed for 10 nsec. As a result, phase matching was possible in all wavelength regions, and the second harmonic was obtained as transmitted light from blue to ultraviolet region.

[0018]

INDUSTRIAL APPLICABILITY As described above, the molecular crystal of 4-ethoxycarbonylphenylcarbamic acid isopropyl ester of the present invention exhibits high efficiency in expressing the second-order nonlinear optical effect. Furthermore, while it is difficult to obtain the second-order nonlinear optical effect in the crystalline state, that is, phase matching with existing nonlinear materials such as MNA, it is possible to easily phase match with the natural growth surface of the crystal. Is remarkable. In addition, in a non-linear material having a large non-linear optical effect, the cutoff wavelength is generally in the long wavelength range.
It extends to (MNA: 480nm) and narrows the range of use as nonlinear optical materials, especially wavelength conversion materials. The 4-ethoxycarbonylphenylcarbamic acid isopropyl ester according to the present invention has a cut-off wavelength of 300 nm, and thus can be used in a wide wavelength range. Therefore, various applications can be expected in a wide wavelength range as various optical functional element materials that utilize nonlinear optical effects and electro-optical effects such as wavelength conversion elements and light control elements.

Claims (1)

[Claims] 1. A molecular crystal comprising 4-ethoxycarbonylphenylcarbamic acid isopropyl ester molecule.