JPH06263696A - Nitrobutadiene compound and its production and non-linear optical material using same - Google Patents

Abstract

PURPOSE:To provide the subject compound useful for nonlinear optical materials exhibiting high nonlinearity, etc., by addition-reacting thiophenol, a nitroalkane, etc., to an unsaturated aldehyde, subjecting the addition product to dehydration and dehydrogenation reactions to form a butadiene structure, and respectively substituting the product with an amino structure. CONSTITUTION:An alpha, beta-unsaturated aldehyde of formula I (R<1>, R<2> are H, alkyl) or formula II (e.g. acrolein) is dissolved in tetrahydrofuran, addition-reacted to a compound of the formula Ar-ZH (Ar is aromatic; Z is S, Se, Te) (e.g. thiophenol) for 2-3hrs with cooling and stirring, and subsequently mixed with a nitroalkane (e.g. nitroethane). The reaction product is addition-reacted with the formyl group of an,-unsaturated aldehyde, and subjected to a dehydration reaction and a dehydrogenation reaction to form a butadiene structure. The Ar-Z group of the reaction product is substituted with an amino group to afford the objective nitrobutadiene compound represented by the formula III [R<1>, R<1>' are alkyl, group of formula IV (R<4>, R<5> are H, hydrocarbon, etc.,); R<3>, R<3> are alkyl, nitro, H].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel nitrobutadiene compound, a method for producing the same, and a non-linear optical material containing the same, and is particularly effective for controlling light by being used as an electro-optical light modulating element, a wavelength converting element or the like. A non-linear optical material that can be used is provided.

[0002]

2. Description of the Related Art Non-linear optical materials are widely used for conversion and control of light, particularly laser light, such as wavelength conversion of light, modulation of light by change in refractive index, switching and the like. This is understood as a phenomenon caused by the nonlinear polarization of a substance due to an electromagnetic field applied from the outside. here,
Letting E be the electric field (light or electrostatic field) applied from the outside and P being the polarization of the substance induced by it, P is expanded by E, and it can be expressed as the following formula (3).

P = P ₀ + χ ⁽¹⁾ E + χ ⁽²⁾ EE + χ ⁽³⁾ EEE + ... (3) This χ ⁽²⁾ is called the second-order and χ ⁽³⁾ is called the third-order nonlinear susceptibility, These related phenomena are described, for example, in Y. R. Sh
en "Principles of Nonline
ar Optics ”.

At present, KDP (KH ₂ PO ₄ ) and LiNbO ₃ are actually used as nonlinear optical materials.
(Lithium niobate), KTP (KTiOPO ₄ ) and other oxide single crystals, and semiconductor materials such as GaAs are mainly used.

In recent years, π-electron conjugated organic compounds have been attracting attention as this nonlinear optical material. This is because its nonlinear susceptibility is much higher than that of inorganic materials and it is derived from electronic polarization, so when it is applied to all-optical devices, it has an ultra-fast response time of picoseconds or less. It depends on what is expected. In addition, it has a low dielectric constant, is more resistant to optical damage than lithium niobate, etc., the manufacturing method is easier for polymer materials than single crystal growth, and various functions are possible due to various molecular designs. There is a possibility of adding the above-mentioned reason as another reason why the organic material is expected as a nonlinear optical material. By utilizing the features of such organic compounds, it is possible to fabricate wavelength conversion elements such as second harmonic generation for low power lasers such as semiconductor lasers, and electro-optical modulation elements that are driven at low voltage and have high speed response. It is possible.

Various forms of organic materials have been investigated as actual organic materials as nonlinear optical materials. In organic compounds, nonlinear susceptibility is discussed in terms of molecular hyperpolarizability.
Let E be the electric field acting on the molecule, and p be the dipole moment of the molecule induced by this, which can be expressed by the following equation (4).

P = μ + αE + βEE + γEEE + (4) Here, α is called a molecular polarizability, β and γ are called second-order and third-order molecular hyperpolarizabilities, respectively, and the nonlinear susceptibility of a molecular assembly is β, It is derived from γ.

As the second-order nonlinear optical material, an intramolecular charge transfer material containing an electron-donating group and an electron-withdrawing group in the molecule, which are linked by a π-electron conjugated system,
It has been shown that the second-order molecular hyperpolarizability (β) becomes large, and the organic compounds showing a large χ ⁽²⁾ known so far are typified by methylnitroaniline (MNA). , Most are molecules of this type.

However, the second-order nonlinear optical material has a limitation that its structure has no macroscopic inversion symmetry. That is, since χ ⁽²⁾ is the third-order tensor, β
Χ ⁽²⁾ is 0 when the aggregate has a crystal structure with inversion symmetry or is amorphous even if is large. Therefore, how to orient a molecule having a large β in a polar structure is a major issue in material search.

In this organic nonlinear optical material, it is the most common practice to utilize the crystal structure,
The powder SHG method is a method for easily screening such materials.

Conventionally, in order to obtain a crystal in which molecules have an optimal arrangement, some ideas for molecular design such as introduction of an optically active group, a skeleton having a small dipole moment in the ground state, and use of hydrogen bond have been proposed. Was done.

However, the effect is not clear unless the crystal is finally obtained. Further, the crystal of the organic compound is a molecular crystal and is soft and poor in processability. Furthermore, it is often desirable to process into a waveguide structure when it is put to practical use as a nonlinear optical element, but the thin film forming method, control of crystal orientation, and method of partially changing the refractive index are very necessary for this. It's difficult. From such a fact, although the possibility of a large number of organic crystals as a nonlinear optical material has been investigated, it is the present situation that only a few examples are processed into elements.

Another secondary organic non-linear optical material is a polymer material. This is an acrylic polymer with Disperse Red 1 (N-ethyl-
N-hydroxylethyl-4-amino-4′-nitroazobenzene: represented by Comparative Example 1), which is typified by doping with a molecule having a large β, or binding to a side chain of a polymer. . It is known that a polymer material can be easily formed into a thin film by coating and becomes an optically excellent optical waveguide material, but a film just coated is generally amorphous and χ ⁽²⁾ is 0. As a method for showing χ ⁽²⁾ , β is heated to a temperature not lower than the glass transition temperature Tg while applying an electric field to the polymer film, and β
The operation called boring in which a unit having a large size is oriented and then cooled to room temperature to fix the orientation is most often used, and a material exhibiting an electro-optical effect comparable to that of lithium niobate is obtained. However, the biggest drawback of this procedure is that its orientation is thermally relaxed and χ ⁽²⁾ is gradually attenuated.

In addition, as a method of obtaining a structure in which a unit having a large β is oriented, it has been attempted to use an oriented film such as a Langmuir-Blodgett film.

In any of the nonlinear optical materials, a material having a large χ ⁽²⁾ has many advantages for making the device highly efficient. For example, in an optical switch element utilizing the electro-optical effect, if a material having a large electro-optical effect is used, a low voltage drive type can be obtained and the length of the element can be shortened, which is advantageous for integration.

[0016]

As described above, in order to obtain a material having a large nonlinear optical effect, it is necessary to utilize a molecule showing a large β. Most of the compounds that have been mainly studied so far have the aromatic ring substituted with an electron-withdrawing group represented by a nitro group and an electron-donating group represented by an amino group. Methylnitroaniline and Disperse Red 1 mentioned above are typical examples, but according to theoretical calculations such as the molecular orbital method, linear polyene is superior as a conjugated system, and the same degree of conjugation is obtained. Comparing the lengths of the systems, polyene has a larger β
Is proposed to have.

However, it is difficult to introduce a nitro group having an excellent electron-withdrawing property to the end of polyene, and there have been few examples synthesized so far. Although there is an example in which an aromatic aldehyde such as benzaldehyde is reacted with nitromethane to synthesize a nitroethylene compound, it is difficult to further extend the conjugation with a carbon = carbon double bond by this method.

The present invention has been made in view of the above conventional circumstances, and has been difficult to manufacture until now.
An object of the present invention is to provide a butadiene compound having a nitro group at the terminal and a method for producing the same. Further, it is an object of the present invention to provide a non-linear optical material using the compound having the large β and having a large non-linear susceptibility and capable of producing an element exhibiting higher performance than the conventional element.

[0019]

The nitrobutadiene compound according to claim 1 is characterized by being represented by the following general formula (1).

[0020]

[Chemical 3]

In the method for producing a nitrobutadiene compound according to claim 2, the nitrobutadiene compound according to claim 1 is converted into an α, β unsaturated aldehyde represented by the following general formula (2a) or (2b) and represented by the general formula Ar- After adding a compound represented by ZH (where Ar represents an aromatic ring and Z represents an S, Se or Te atom), a nitroalkane is further added to the formyl group of the α, β unsaturated aldehyde, and then , Butadiene structure is formed by dehydration and dehydrogenation, and then Ar
It is characterized in that it is produced by substituting the -Z group with an amino group.

[0022]

[Chemical 4]

A non-linear optical material according to a third aspect uses the nitrobutadiene compound according to the first aspect.

The present invention will be described in detail below.

In the nitrobutadiene compound of the present invention represented by the general formula (1), R ¹ and R ¹ 'are each independently an alkyl group and an amino group having substituents R ⁴ and R ⁵ (here, R ⁴ and R ⁵ represent a hydrocarbon which may form a ring between the two, an aromatic ring which may be substituted, or a hydrogen atom) or a hydrogen atom, and R ² represents an alkyl group or represents a hydrogen atom, R ³ and R ³ 'represents an alkyl group, a nitro group or a hydrogen atom, R ³ or R ^3' is either at a minimum of a nitro group.

Such a nitrobutadiene compound is easily produced by the method of the present invention. A specific synthetic method of the present invention is shown by the following reaction formula.

[0027]

[Chemical 5]

In order to use the nitrobutadiene compound of the present invention thus obtained as a second-order nonlinear optical material, it is necessary to orient the molecules in a polar structure. For this purpose, it is dispersed in a polymer in a molecular form, or is bonded to a side chain or a main chain of the polymer by utilizing the substituents of R ¹ "to R ^{5 and} the glass transition temperature Tg is around while applying an electric field. A method called so-called poling, in which the material is oriented by heating up to, can be used.

Further, a long-chain alkyl group or the like is introduced as a substituent of R ¹ "to R ⁵ , and both a hydrophilic group and a hydrophobic group are provided to form a monomolecular film on the water surface. The Langmuir-Blodgett method can be used to obtain the oriented film by transferring the compound to a substrate.Further, if a crystal having no inversion symmetry of the nitrobutadiene compound of the present invention can be obtained, it can be used as a material exhibiting extremely high nonlinearity. Become.

The thus obtained non-linear optical material containing the present compound can be used as a material for producing an optical modulator or an optical switch element by utilizing its electro-optical effect. Further, if an appropriate wavelength is selected, it can be applied to a wavelength conversion element such as sum, difference frequency generation, parametric amplification and oscillation including second harmonic generation.

[0031]

The present inventors have studied various methods for producing a compound having an amino group and a nitro group at both ends of a polyene, and as a result, found a method of introducing an amino group and a nitro group by conjugating both ends of a butadiene structure. It has become possible to synthesize the nitrobutadiene compound represented by the general formula (1).

Although the nitrobutadiene compound of the present invention is a relatively short conjugated system having only two carbon = carbon double bonds, it has a large β and a large nonlinear optical coefficient per molecular weight. It is a particularly useful molecule for

Such a nitrobutadiene compound of the present invention can be effectively used as a second-order nonlinear optical material by orienting it in a polar structure. Further, a crystal having no inversion symmetry obtained from such a nitrobutadiene compound provides a nonlinear optical material exhibiting extremely high nonlinearity.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 Synthesis of γ-phenylthiopropanal Acrolein (1 equivalent, several g) was dissolved in 20 ml of THF (tetrahydrofuran), thiophenol (1 equivalent) was added dropwise while cooling, and the mixture was stirred for 2-3 hours. did. The product was extracted with ether, dried over anhydrous sodium sulfate, and then the solvent was removed. When the obtained product was purified by column chromatography, γ-phenylthiopropanal was obtained in a yield of 90% or more.

2-nitro-5-phenylthio-3-
Γ-Phenylthiopropanal obtained by the synthesis of pentanol (1 equivalent)
And nitroethane (1 equivalent) were dissolved in 20 ml of acetonitrile. A catalytic amount of base was added thereto, and the mixture was stirred at room temperature for 30 hours. Then, 10 ml of 5% hydrochloric acid was added, and the product was extracted with ether and washed with water. After drying over anhydrous sodium sulfate, the solvent was removed. The obtained product was purified by column chromatography to give 2-nitro-5-
Phenylthio-3-pentanol was obtained with a yield of 90%.

2-nitro-5-phenylthio-2-
2-Nitro-5-phenylthio-3-pentanol obtained in the synthesis of pentene was dissolved in 30 ml of dry dichloromethane. 1 basic activated alumina to 5 mmol substrate
The mixture was added at a rate of g and heated under reflux for 30 hours with stirring.
Then, the alumina was filtered off, washed with water, dried over anhydrous sodium sulfate, and then the solvent was removed. The obtained product was purified by column chromatography to give 2-nitro-5
-Phenylthio-2-pentene was obtained in a yield of 50-60%.

2-nitro-5-phenylthio-2,
2-Nitro-5-phenylthio-2-pentene (1 equivalent) obtained in the synthesis of 4-pentadiene was dissolved in dry dichloromethane and cooled to 0 ° C with ice water. Sulfuryl chloride (1.2 equivalents) was added dropwise thereto while adjusting the speed so that the temperature did not rise too high, and the mixture was stirred at 0 ° C. for 2 hours. After removing the solvent under reduced pressure, 20 ml of dry dichloromethane was added again, and the mixture was cooled to 0 ° C with ice water. Triethylamine (1.2 equivalents) was added dropwise while adjusting the speed so that the temperature did not rise too high, and the mixture was stirred at 0 ° C for 2 hours. 10 ml of 5% hydrochloric acid
After the addition, the solvent was removed under reduced pressure. The product was purified by column chromatography to give 2-nitro-5
50-60% of -phenylthio-2,4-pentadiene
It was obtained with a yield of. The melting point of this product was 88 to 90 ° C, and the NMR spectrum was as shown in Fig. 1.

Synthesis of 1- (1-pyrrolidino) -4-nitro-1,3, pentadiene 2-nitro-5-phenylthio-2,4-
Pentadiene (1 equivalent) was dissolved in 10 ml of methanol. Pyrrolidine (2 equivalents) was added dropwise thereto, and the mixture was stirred at room temperature. After confirming the completion of the reaction by thin layer chromatography, water was added and the purified product was extracted with dichloromethane. After drying it over anhydrous sodium sulfate,
The solvent was removed. The obtained product was purified by column chromatography to find that the desired 1- (1-pyrrolidino) -4-nitro-1,3, pentadiene was 50-6.
Obtained in a yield of 5%. This product has a melting point of 122-12
It was 3 ° C., and the NMR spectrum of this compound was as shown in FIG.

Examples 2 to 5 Using the corresponding aldehydes as raw materials, nitrobutadiene compounds having each substituent shown in Table 1 were synthesized in the same manner as in Example 1. The product was identified by NMR, IR, mass spectrum and the like.

[0041]

[Table 1]

Example 6 The powder of the compound obtained in Example 2 was sandwiched between slide glasses, and Q-switch pulse N was applied using the apparatus shown in FIG.
Generated by radiating pulsed light of d: YAG laser 5
The second harmonic of 32 nm was detected. The intensity of this second harmonic was 2.3 times that of urea.

In FIG. 3, 1 is a Nd: YAG laser, 2 is a half mirror, 3 is a quartz plate (reference), 4 is an infrared light cut filter, 5 is a photomultiplier tube, 6 is a sample, and 7 is a sample. It is a spectroscope.

Example 7 A film of polymethylmethacrylate in which 5% of the compound obtained in Example 2 was dissolved was formed on the transparent electrode to a thickness of 3 μm. Gold is vapor-deposited on this to form a sandwich type sample, which is subjected to 110 V with 100 V DC electric field applied.
After heating to 0 ° C. and holding for 10 minutes, it was cooled to room temperature.

Using the device shown in FIG. 4, an AC voltage of 20 Vrms was superposed while applying the DC voltage, and
When the semiconductor laser light of 1.3 μm polarized at 5 ° C. is irradiated from the transparent electrode side, the phase difference of the light reflected by the gold electrode is
The electro-optic coefficient was measured by measuring the change in this AC electric field.

In FIG. 4, 11 is a laser and 1
Reference numeral 2 is a polarizer, 13 is a papine soleil compensator, 14 is an analyzer, 15 is a photodiode, 16 is a lock-in amplifier, 17 is a power supply, 18 is a sample, 19 is a heater, 2
Reference numeral 0 is an electrode (ITO and gold), and 21 is a temperature controller.

The obtained electro-optic coefficient is 1.2 pm / V
Met. From this, assuming that the dipoles in the polymer are independently oriented, the product μβ of the dipole moment μ of the molecule and the second-order molecular hyperpolarizability β is calculated to be 120
It was requested to be 0x10 ^-48 esu.

[0048]

As described above in detail, according to the nitrobutadiene compound and the method for producing the same of the present invention, a novel compound having an amino group and a nitro group at both ends of a polyene, which has been difficult to produce, can be easily prepared. Provided to.

The nitrobutadiene compound of the present invention is
The non-linear optical material of the present invention having a large second-order molecular hyperpolarizability β and thus using such a nitrobutadiene compound provides an extremely high-performance non-linear optical material having a remarkably good non-linear susceptibility. To be done.

The non-linear optical material of the present invention as described above is industrially very useful as a non-linear optical material for controlling light when used in an electro-optical light modulator, a wavelength converter, and the like.

[Brief description of drawings]

1 is an intermediate of the synthesis in Example 1 (2-nitro-
5 is a NMR spectrum of (5-phenylthio-2,4-pentadiene).

FIG. 2 1- (1-pyrrolidino) synthesized in Example 1
4 is an NMR spectrum of 4-nitro-1,3, pentadiene.

FIG. 3 is a configuration diagram showing a nonlinear effect measurement device used in a sixth embodiment.

FIG. 4 is a configuration diagram showing an electro-optical effect measuring device used in Example 7.

[Explanation of symbols]

 1 Nd: YAG laser 2 Half mirror 3 Quartz plate (reference) 4 Infrared light cut filter 5 Photomultiplier tube 6 Sample 7 Spectrometer 11 Laser 12 Polarizer 13 Papinesoleil compensator 14 Analyzer 15 Photodiode 16 Lock-in amplifier 17 Power supply 18 Sample 19 Heater 20 Electrode (ITO and gold) 21 Temperature controller

Claims (3)

[Claims] 1. A nitrobutadiene compound represented by the following general formula (1). [Chemical 1] 2. An α, β unsaturated aldehyde represented by the following general formula (2a) or (2b) is added to the general formula Ar-ZH (wherein Ar represents an aromatic ring and Z represents an S, Se or Te atom). ), A nitroalkane is further added to the formyl group of the α, β-unsaturated aldehyde, and then a butadiene structure is formed by dehydration and dehydrogenation, and then the Ar-Z group is amino-substituted. The method for producing a nitrobutadiene compound according to claim 1, wherein the nitrobutadiene compound is substituted with a group. [Chemical 2] 3. A non-linear optical material comprising the nitrobutadiene compound according to claim 1.