JPH04221358A - Molecular crystal - Google Patents

Abstract

PURPOSE:To obtain a molecular crystal containing an ethyl 4- nitrophenylcarbamate molecule as an active ingredient, exhibiting high efficiency in manifestation of secondary non-linear optical effect and useful as an optically functional element material. CONSTITUTION:The objective molecular crystal containing the compound expressed by the formula as an active ingredient. When the compound is irradiated with Nd-YAG laser (lambda-1064nm) in a state of powder, the compound generates the remarkably strong and green second high harmonic wave. Further, cut-off wavelength in crystal state is 410nm and use in wide wavelength area is made possible. Since the compound has high strength and is water soluble and free from sublimation and rich in processability, it can be used as an optically functional element material utilized in nonlinear optical effect such as wavelength converting element or light control element and electro-optical effect.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a molecular crystal belonging to single crystal P21 of an organic compound that is applicable to optical materials such as nonlinear optics and electro-optics and is useful for all optoelectronic devices that utilize the optical effects thereof. .

0002

[Prior Art] Conventionally, as a material that can be used in nonlinear optics, electro-optics, etc., for example, potassium dihydrogen phosphate (K
DP), lithium niobate (LiNbO3), 3-methyl-4-nitropyridine-N-oxide (POM)
, 2-methyl-4-nitroaniline (MNA), and other inorganic or organic compounds are known.

However, these materials lack the desired optical effect, are difficult to process to bring out the effect, have a large walk-off angle that prevents a sufficient effective working length, and have problems with crystal growth. There are various problems such as difficulty.

0004

[Problem to be solved by the invention] In organic compounds,
In order to enhance the second-order nonlinear optical effect, it is sufficient to increase the dipole moment of the molecule, and it is well known that introducing an electron-donating group and an electron-withdrawing group into the molecule is effective for this purpose. There is. However, important unresolved issues remain in this regard. That is, in order to produce a second-order nonlinear optical effect, the crystal must have a form without a center of inversion symmetry.

However, when organic compounds have a large dipole moment in their molecules, when they are crystallized, they are arranged so that their dipole moments cancel each other out, and as a result, the molecules have a large second-order supramolecular polarizability β. However, as a crystal or molecular assembly, it may not exhibit second-order nonlinear effects because it has a center of inversion symmetry. In fact, there are a large number of organic compounds with such properties.

[0006] Therefore, when developing organic compound materials that focus on second-order nonlinear optical effects, it is necessary to easily obtain high-quality crystals that have a large supramolecular polarizability β and have no center of inversion symmetry. An important challenge is to synthesize such compounds.

4-Nitroaniline is an aromatic compound with the simplest electron-donating group and electron-withdrawing group, and is one of the compounds with a large supramolecular polarizability β among organic compounds. Since the molecules of a crystal are arranged so that their dipole moments cancel each other out, the crystal has a center of inversion symmetry and does not exhibit second-order nonlinear optical effects. Furthermore, 4-nitroaniline is significantly colored because it exhibits large electronic transition absorption in the near ultraviolet to visible range due to intramolecular charge transfer between nitro and amino groups.

The inventors have conducted extensive studies on improving the symmetry and transparency of aromatic compounds such as 4-nitroaniline, which have an electron-withdrawing group and an electron-donating group at the para-position of the benzene ring. As a result of repeated research, we discovered that certain nitrophenylcarbamate ester derivatives do not have a center of inversion symmetry when they form crystals or molecular aggregates, and that they can effectively improve transparency in the near-ultraviolet to visible range. After confirming this, we have developed the present invention.

The objects of the present invention are to have a material with a large second-order nonlinear optical effect, a short cutoff wavelength for expanding the wavelength range of use as an optical material, and better crystal growth and processability. Our goal is to provide molecular crystals.

0010

Means for Solving the Problems The molecular crystal according to the present invention for achieving the above object is structurally characterized in that it is composed of 4-nitrophenylcarbamic acid ethyl ester molecules. The 4-nitrophenylcarbamic acid ethyl ester is represented by the chemical formula below.

[0011]

[Chemical formula 1]

The above-mentioned 4-nitrophenylcarbamic acid ethyl ester is prepared by converting 4-nitrophenyl isocyanate into an acid (BF3 .Et2O, HCl, AlCl3,
R2Sn(OAc)2 etc.) or bases (Et3
N, pyridine, AcONa, etc.) as a catalyst in an ethyl alcohol solvent. The microcrystalline aggregates of 4-nitrophenylcarbamic acid ethyl ester synthesized in this way are mixed with alcohols such as methanol and ethanol, which have high solubility.
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, chloroform,
When it is dissolved in dichloromethane, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, etc. and subjected to crystallization treatment over 4 to 5 days by solvent evaporation or solvent cooling, it grows into a good rod-shaped single crystal several millimeters square.

This molecular crystal is monoclinic and has space group P21.
belongs to (0,0,1), (0,0,-1), (0
,1,3) ,(0,1,-3),(0,-1,3),
(0,-1,-3), (0,1,4), (0,1,
-4), (0, -1, 4), (0, -1, -4), (
1,0,1), (1,0,-1), (-1,0,1)
, (-1,0,-1) , (1,0,2) , (1,0
,-2), (-1,0,2), (-1,0,-2),
(1,0,3), (1,0,-3), (-1,0,3
), (-1,0,-3), (1,1,0), (1,
-1,0), (-1,1,0), (-1,-1,0)
, (1,1,2) , (1,1,-2), (1,-1,
2), (1,-1,-2), (-1,1,2), (-
1,1,-2), (-1,-1,2), (-1,-
1,-2), (1,1,3), (1,1,-3), (
1,-1,3), (1,-1,-3), (-1,1,
3), (-1,1,-3), (-1,-1,3),
(-1,-1,-3), (2,0,1), (-2,0
,1), (-2,0,-1), (2,1,3), (
2,1,-3),(2,-1,3),(2,-1,-3
) , (-2,1,3), (-2,1,-3) , (-
2, -1, 3) and (-2, -1, -3), and a hexahedron to 18-hedron formed from these.

[0014]

[Function] The 4-nitrophenylcarbamic acid ethyl ester according to the present invention can be used in powder form by Nd:YAG laser.
When irradiated with λ=1064 nm), a significantly strong green second harmonic is generated. In addition, it is milky white in powder form, colorless and transparent even as a single crystal, and its cutoff wavelength has been significantly shifted to the shorter wavelength side.

In the case where the fundamental wave is infrared light having a wavelength of 1 to 1.2 μm, the fundamental wave may be absorbed by overtone absorption of the stretching vibration of C-H and converted into thermal vibration. Therefore, when the intensity of the fundamental wave is strong, phenomena such as an increase in the temperature of the crystal and a fluctuation in the angle of the emitted light occur. If this is adopted, the absorption region shifts to the longer wavelength side, and this phenomenon can be effectively prevented.

[0016]

[Example] Example 1 4-nitrophenyl isocyanate 80g (600mm
ol) and a catalytic amount of triethylamine (20 mmol
) was dissolved in a 1:1 mixed solvent of ethyl alcohol and tetrahydrofuran, and stirred and reacted in a 50°C water bath for about 4 hours. After the reaction was completed, the concentrated and precipitated reaction product was washed with alcohol and dried under reduced pressure at a temperature of 50° C. to obtain 4-nitrophenylcarbamic acid ethyl ester. Then, the obtained 4-nitrophenylcarbamic acid ethyl ester was recrystallized from a tetrahydrofuran solution, and was converted into rod-shaped or plate-shaped crystals exhibiting a pale yellow and transparent color. The melting point of this molecular crystal was 131±1° C. at its peak, the production yield was 80%, and the purity was 99%.

A sample of the above-mentioned 4-nitrophenylcarbamic acid ethyl ester prepared into a fine powder with a particle size of 60 to 100 μm was sandwiched between slide glasses, and irradiated with a 10 nsec pulse using a Q-switched Nd:YAG laser. Then, the intensity of the second harmonic generated from the sample was measured. As a result, it showed 50 times more second harmonics than urea of the same size.

Example 2 4-nitrophenylcarbamic acid ethyl ester 100
Dissolve g in a saturated solution of tetrahydrofuran and raise the temperature to 25
Crystal growth was performed for 5 days using a solvent evaporation method while keeping the temperature constant. The obtained crystals are (0,0,1), (0,0
,-1), (1,0,1,), (1,0,-1),(-
1,0,1), (-1,0,-1), (1,1,
2), (1, -1, 2), (1, -1, 2), (-1,
It was a 2 x 3 x 20 mm rod-shaped crystal composed of (-1, -2) and (-1, -1, -2) planes, and the cutoff wavelength in this crystal state was 410 nm.

Example 3 0.1×0.1 composed of the same crystal planes as Example 2
Crystal structure analysis was performed on a 4-nitrophenylcarbamic acid ethyl ester crystal of x0.5 mm using an X-ray 4-axis automatic diffractometer. As a result, this single crystal belongs to the monoclinic system, space group P21, and has a lattice constant of a=6.
133, b=5.031, c=15.884 (A)
, β=91.03, two molecules existed in the unit cell, and the density was 1.42.

[0020]

[Effects of the Invention] As described above, the molecular crystal of the present invention consisting of 4-nitrophenylcarbamic acid ethyl ester is
It exhibits high efficiency in producing second-order nonlinear optical effects. In addition, in general, nonlinear materials that have large nonlinear optical effects have a cutoff wavelength in the long wavelength range (MNA: 480 nm).
However, the 4-nitrophenylcarbamic acid ethyl ester according to the present invention has a cutoff wavelength of 410 nm in a crystalline state, and is suitable for use in a wide wavelength range. Usage becomes possible.

Furthermore, the crystals have higher strength than other organic crystals, are not soluble in water, have no sublimation property, and are highly processable. Therefore, it is expected to be widely used as a material for various optical functional elements that utilize nonlinear optical effects and electro-optic effects, such as wavelength conversion elements and light control elements.

Claims (1)

[Claims] 1. A molecular crystal comprising 4-nitrophenylcarbamic acid ethyl ester molecules.