JP3316526B2 - Pyridinium derivatives and organic nonlinear optical materials using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel pyridinium derivative useful as an organic nonlinear optical material.

[0002]

2. Description of the Related Art Conventionally, nonlinear optical materials have been widely used as optical wavelength conversion elements, optical shutters and the like in laser oscillators and the like, as materials exhibiting second- and third-order nonlinear responses by an electromagnetic field. High-speed switching element,
Attention has been paid to materials that are indispensable for the realization of optical computers, such as optical logic gates and optical transistors. Development research on new materials for both inorganic and organic materials is being actively conducted.

Generally, an organic nonlinear optical material has a large nonlinear optical effect as compared with a conventional inorganic nonlinear optical material, and generates a second harmonic (SHG) and a third harmonic (THG). ) Are known to have the advantage that they have a large coefficient, have a good high-speed response, and are easy to design various molecules. Recently, urea, 4-nitroaniline, 2-methyl-
4-Nitroaniline (MNA) and the like are known, and among them, MNA which is a conventional representative organic linear optical material
Is a crystal having no center of symmetry, which is a feature of the nonlinear optical effect.
Although it has HG activity intensity, there is a problem that it is difficult to obtain a large single crystal. Therefore, among organic compounds, there is a strong demand for the development of an organic nonlinear optical material that is a single crystal having no center of symmetry, has high SHG activity, is stable at room temperature, and can grow into a large single crystal. . First,
The present inventors have proposed, as an organic nonlinear optical material having SHG several times to several tens times that of urea, p-toluenesulfonic acid.
1-methyl-4- [2- (4-hydroxyphenyl) vinyl] pyridinium and p-toluenesulfonic acid
Methyl-4- [2- (4-N, N-dimethylaminophenyl) vinyl] pyridinium (DAST) has been proposed (see JP-B-3-4547 and JP-B-4-27528).

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation in the prior art. That is, an object of the present invention is to provide a useful novel compound having excellent second-order nonlinear optical activity as compared to conventional organic nonlinear optical materials and having excellent practicability as an organic nonlinear optical material capable of forming a stable organic crystal. Is to provide.

[0005]

Means for Solving the Problems The present inventors have produced various derivatives having a stilbazolium structure as a main skeleton, and have conducted intensive studies on their nonlinear optical characteristics. As a result, the second harmonic generation (SHG) The present inventors have found a novel organic compound having good nonlinear optical characteristics such as activity, and have completed the present invention.

That is, according to the present invention, there is provided a pyridinium derivative represented by the following general formula (I).

Embedded image (Wherein, R ₁ , R ₂ , and R ₃ each represent an alkyl group or a substituted alkyl group, and X ⁻ represents an anionic group.) According to the present invention, the above general formula (I) And an organic nonlinear optical material comprising a pyridinium derivative represented by the formula:

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The pyridinium derivative of the present invention comprises
As represented by the following general formula (I), the stilbazolium skeleton has a cyano group at the 2-position of the pyrimidine ring.

Embedded image R ₁ , R ₂ and R ₃ in the general formula (I) each represent an alkyl group or a substituted alkyl group. Examples of the alkyl group include linear or branched ones having 1 to 10 carbon atoms, and specifically, a methyl group, an ethyl group,
n-, i-propyl group, n-, i-butyl group, n-, i
Examples thereof include a pentyl group and a neopentyl group, and among them, a methyl group or an ethyl group is preferable.

The substituents substituted on the alkyl group include functional groups such as a halogen atom, a hydroxyl group, an ether group, a carboxyl group, an ester group, a nitro group, an amino group and a sulfone group. X ⁻ is not particularly limited as long as it is an anionic group, but may not be present when an anionic substituent is present in the cation portion. The anionic groups include Cl, B
Examples thereof include halogen atoms such as r and I, and benzenesulfonic acids represented by the following structural formula.

[0009]

Embedded image

The pyridinium derivative represented by the general formula (I) according to the present invention can be obtained, for example, by the following reaction formula:
Starting from 4-methylpyridine N-oxide (1) as a starting material, 2-cyano-1,4-dimethylpyridinium iodide obtained through four steps of sequentially synthesizing compounds (2), (3) and (4) ( 5) is reacted with 4-dimethylaminobenzaldehyde in the presence of acetic anhydride to give the desired 2-cyano-1-methyl-4-iodide
(2- (4- (dimethylamino) phenyl) ethenyl)
Pyridinium (6a) can be produced.

[0011]

Embedded image

Other pyridinium derivatives included in the general formula (I) can be synthesized in the same manner as in the above method. The pyridinium derivative represented by the general formula (I) of the present invention is extremely useful as an organic nonlinear optical material. For example, as described above, the present inventors have previously proposed 1-methyl-p-toluenesulfonic acid / 1-methyl- as an organic nonlinear optical material having good second-order nonlinear optical activity.
Compared with 4- [2- (N, N-dimethylaminophenyl) vinyl] pyridinium (DAST), the hyperpolarizability β of the cation portion of DAST is 241 × 10 ⁻³⁰ eau (half) Calculated by the empirical molecular orbital method, the MOPAC / PM3 method), whereas the iodide 2-
In the cation portion of cyano-1-methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium (6a), the hyperpolarizability β is 297 × 10 ⁻³⁰ ea
u.

From this, the pyridinium derivative having a cyano group at the 2-position of the pyridine ring (cyano-substituted product) in the present invention has a hyperpolarizability β of 20% larger than that of a conventional good organic nonlinear optical material, It can be understood that this is a very useful electro-optical material. In addition, the maximum absorption spectrum (λmax) of those compounds is 476 in the case where the anion group of the conventional DAST is replaced with iodine (7a).
In contrast to (6a), it was 534 nm. FIG. 1 shows these absorption spectrum diagrams.

[0014]

EXAMPLES The present invention will be described below in more detail with reference to examples and the like, but the present invention is not limited to these examples. Example 1 [Synthesis Example] (a) Synthesis of 1-methoxy-4-methylpyridinium iodide (first step) In a 300 ml four-necked flask equipped with a magnetic stirrer,
25 g of -methylpyridine N-oxide was added, 50 ml of methyl iodide was added, and the mixture was allowed to stand at room temperature for 1 day. Thereafter, 100 ml of water was added, and the mixture was washed three times with 100 ml of ethyl acetate. Then, the solvent was distilled off from the aqueous layer and dried to obtain a yellow-white solid of 1-methoxy-4-methylpyridinium iodide which was extremely hygroscopic. Was. The physical properties of the obtained solid are shown below. ¹ H NMR (CDCl ₃ , δ) 2.71 (s, 3
H), 4.45 (s, 3H), 8.03 (d, J = 6.
8 Hz, 2H), 9.14 (d, J = 6.8 Hz, 2
H)

(B) Synthesis of 2-cyano-4-methylpyridine (Second Step) In a 300 ml four-necked flask equipped with a magnetic stirrer, all of the 1-methoxy-4 iodide obtained by the above reaction are placed. -Methylpyridinium was added, and 40 ml of water and 100 ml of 1,4-dioxane were added. Then, under ice-cooling, an aqueous solution in which 23 g of potassium cyanide was dissolved was added little by little, and the mixture was stirred for 30 minutes. After returning to room temperature and stirring for 2 hours, the solution turned brown. The solvent in the solution was distilled off, purified by a short column (hexane: ethyl acetate = 5: 1), and then recrystallized from hexane and ethyl acetate to give 2
8.7 g of transparent plate-like crystals of -cyano-4-methylpyridine with a brownish tinge were obtained. The yield from the starting material 4-methylpyridine iodide N-methoxide was 32%. The physical properties of the obtained crystal are shown below. mp: 85-86 ° C; ¹ H NMR (CDCl ₃ , δ) 2.44 (s, 3
H), 7.34 (dq, J = 5.0 Hz, J = 0.7H)
z, 1H), 7.53 (q, J = 0.7 Hz, 1H),
8.57 (d, J = 5.0 Hz, 1H); Found: C, 71.03; H, 5.16;
N, 23.44%. Calcd for C ₇ H ₆ N ₂ : C, 71.1
7; H, 5.12; N, 23.71%

(C) 2-cyano-1, borate tetrafluoride,
Synthesis of 4-dimethylpyridinium (third step) After replacing a 100 ml three-necked flask equipped with a magnetic stir bar with nitrogen gas, 2-cyano-4-methylpyridine 6 was added.
30 mg, 30 ml of dehydrated methylene chloride and 500 mg of trimethyloxonium tetrafluoroborate were added. After stirring at room temperature for 20 hours, 30 ml of dehydrated ether was added, and the precipitate was separated by filtration. The solvent was distilled off from the filtrate, and the obtained solid was dissolved in a small amount of acetonitrile.
0 ml was added little by little to allow crystallization. The crystallized product was separated by filtration and dried to obtain 1.0 g of white powder of 2-cyano-1,4-dimethylpyridinium tetrafluoroborate (88% yield). The physical properties of the obtained powder are shown below. mp: 143-146 ° C .; ¹ H NMR (CD ₃ OD, δ) 2.73 (s, 3
H), 4.50 (s, 3H), 8.17 (d, J =
6.0 Hz, 1H), 8.53 (s, 1H), 9.
02 (d, J = 6.0 Hz, 1H); Found: C, 43.52; H, 4.37;
N, 12.70%. _{Calcd for C 8 H 9 N 2} F 4 B: C, 43.
68; H, 4.12; N, 12.73%

(D) Synthesis of 2-cyano-1,4-dimethylpyridinium iodide (fourth step) In a 500 ml eggplant-shaped flask equipped with a magnetic stirrer,
Add 6.4 g of 2-cyano-1,4-dimethylpyridinium tetrafluoroborate, and further add 15 ml of acetonitrile
And melted. To this was added a solution of 4.9 g of potassium iodide in acetonitrile, and the mixture was stirred at room temperature for 16 hours. The solution turned yellow as soon as the acetonitrile solution was added. The solvent in the reaction solution was distilled off to about 100 ml, and the deposited precipitate was separated by filtration, crystallized by adding ethyl acetate, filtered, and dried to obtain 2-iodide.
4. Yellow crystals of cyano-1,4-dimethylpyridinium
8 g was obtained (yield 77%). The physical properties of the obtained crystal are shown below. mp: 176-177 ° C; ¹ H NMR (CD ₃ OD, δ) 2.73 (s, 3
H), 4.51 (s, 3H), 8.20 (d, J = 5.
7 Hz, 1H), 8.56 (s, 1H), 9.07
(D, J = 5.7 Hz, 1H); Found: C, 36.89; H, 3.51;
N, 10.71%. _{Calcd for C 8 H 9 N 2} I: C, 36.9
6; H, 3.49; N, 10.77%

(E) Synthesis of 2-cyano-1-methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium iodide (fifth step) 500 ml of 4 with a magnetic stirrer 2-cyano-1,4-dimethylpyridinium iodide in a one-necked flask.
5 g, 200 ml of acetic anhydride and 1.81 g of 4-dimethylaminobenzaldehyde were added, and the mixture was stirred at 70 ° C. for 1 day. A few hours after stirring, the color of the solution turned purple. After cooling to room temperature, the mixture was transferred to a separating funnel, and 200 ml of water was added thereto and washed with hexane. The solvent was distilled off, toluene was added and distilled off again, and this operation was repeated several times to completely distill off the solvent. Then, by recrystallization with methanol,
2.1 g of a black-purple crystal powder of 2-cyano-1-methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium iodide was obtained (yield: 40%). The physical properties of the obtained crystalline powder of the target compound are shown below. ¹ H NMR (CD ₃ OD, δ) 3.12 (s, 6
H), 4.32 (s, 3H), 6.81 (d, J = 9.
0 Hz, 2H), 7.10 (d, J = 15.9 Hz,
1H), 7.66 (d, J = 9.0 Hz, 2H),
8.00 (d, J = 15.9 Hz, 1H), 8.0
5 (dd, J = 6.8 Hz, J = 2.2 1H),
8.57 (d, J = 2.2 Hz, 1H), 8.6
6 (d, J = 6.8 Hz, 1H); Found: C, 51.83; H, 4.63; N, 9.
66%. _{Calcd for C 17 H 18 N 3} I: C, 52.
19; H, 4.64; N, 10.74%

Example 2 General Procedure for Anion Exchange Reaction of 2-Cyano-1-methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium Iodide In an Erlenmeyer flask equipped with a magnetic stirrer And 1 mmol of 2-cyano-1-methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium iodide was heated and dissolved in methanol. Thereafter, a methanol solution of 1 mmol of a silver salt of an anion was added to this solution with stirring. After stirring for a while, a precipitate of silver iodide was formed. This precipitate was filtered using celite, and the methanol in the filtrate was distilled off, followed by recrystallization from methanol to give 2-cyano-1 having the target anion as a counter anion.
-Methyl-4- (2- (4- (dimethylamino) phenyl) ethenyl) pyridinium compound was obtained (yield 80
%).

Example 3 In the same manner as in Example 2, p-
2-cyano-1-methyl-4 nitrobenzenesulfonate
-(2- (4- (Dimethylamino) phenyl) ethenyl) pyridinium was obtained. The physical properties of this compound are shown below. ¹ H NMR (CD ₃ OD, δ) 3.10 (s, 6
H), 4.32 (s, 3H), 6.80 (d, J =
9.0 Hz, 2H), 7.09 (d, J = 15.9)
Hz, 1H), 7.65 (d, J = 9.0 Hz,
2H), 7.97-8.05 (m, 4H), 8.2
9 (d, J = 9.0 Hz, 2H), 8.56 (d,
J = 2.4 Hz, 1H), 8.65 (d, J = 6.
8 Hz, 1H); Found: C, 57.42; H, 4.84; N, 1
1.67%. _{Calcd for C 23 H 22 N 4} O 5 S: C, 5
9.22; H, 4.75; N, 2.01%

[SHG activity of microcrystalline powder]
2-cyano-1-methyl-4 nitrobenzenesulfonate
A crystal powder of-(2- (4- (dimethylamino) phenyl) ethenyl) pyridinium is filled in a glass plate having a thickness of 3 mm and a hole having a diameter of about 4 mm in the center, and Nd: YAG laser (1064 nm , An output of 1 mJ / pulse) resulted in 532 nm due to SHG.
Green light emission was observed. The strength was about 30 times the SHG strength similarly generated from the urea microcrystalline powder.

[0022]

Since the pyridinium derivative according to the present invention has a high second-order nonlinear optical activity, it is extremely useful as an organic nonlinear optical material. Therefore, a light wavelength conversion element, an optical shutter, a high-speed optical switching element, It can be suitably used as a material for materials such as optical logic gates and optical transistors.

[Brief description of the drawings]

FIG. 1 shows a compound (6a) of the present invention and a conventional compound (7)
It is an absorption spectrum figure of a).

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-337459 (JP, A) CARICIFCI, N.I. S. , Et al. , Synth. Metals, 41-43 pp. 2339-2402 (1991) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 213/00-213/90 G02F 1/00-1/361 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. A compound represented by the following general formula (I) (Wherein, R ₁ , R ₂ , and R ₃ each represent an alkyl group or a substituted alkyl group, and X ⁻ represents an anionic group). 2. An organic nonlinear optical material comprising a pyridinium derivative represented by the general formula (I). 3. An organic nonlinear optical material, wherein the pyridinium derivative is represented by the following formula (II). Embedded image