JP2927601B2 - Stimuli-responsive cholesterol compounds having a crown ring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cholesterol compound, and more particularly to a novel cholesterol compound which exhibits a unique property in response to an external stimulus such as light or the presence of various ions and can be used as a switch element or a display element. Cholesterol compounds.

[0002]

2. Description of the Related Art A large number of cholesterol compounds containing a cholesterol group in the basic structure have been known so far, but their applications are very few, and there are only a few cholesterol alkyl fatty acid esters. Only an application example of a derivative as a thermometer is known (using detection of a change in pitch that fluctuates with a change in temperature as an external stimulus as a change in color).

Recently, Lin and Weiss et al. Have found that some anthracene derivatives based on cholesterol form gels in organic solvents, reversible sol-gels resulting from temperature changes as external stimuli. It is reported that optical properties such as fluorescence and circular dichroism spectrum (CD spectrum) intensity change with the transition (J. Am. Chem.
Soc., 111 , 5542 (1989)). Such a property is conceivable for application to a switching element or a display element utilizing external responsiveness, but in fact, the sol-gel transition of the cholesterol-based compound is not sharp, but is a temperature of 10 to 20 ° C. Responsiveness such as a change in the CD spectrum intensity that occurs gradually with a width is not sufficient, and is not practical.

Further, other liquid crystal compounds such as nematic and smectic are widely used as display elements of various electric appliances and measuring instruments, but these compounds change the molecular arrangement of liquid crystal molecules exclusively by using an electric field as an external stimulus. Therefore, it cannot be applied to a display element having a large area such as a large display element or a window shutter.

[0005]

[Means for Solving the Problems and Effects of the Invention] As the inventors of the present invention have been conducting research on cholesterol compounds, they have not only properties as liquid crystals but also are not found in conventional cholesterol compounds. A cholesterol compound having a unique stimulus responsiveness was found.

That is, the present invention provides a compound represented by the following general formula:
A cholesterol compound represented by the formula:

[0007]

Embedded image R ₁ −φ−N = N−φ−R ₂ −Cho

In the above formula, Cho represents a cholesterol group, φ represents a benzene ring, and R ₁ contains a crown ring. That is, the compound of the present invention is a cholesterol derivative having a crown ether and azobenzene. R ₁ is specifically benzo-18-crown-
6, benzo-15-crown-5, benzo-12-crown-4, or benzo-13-crown-4. R ₂ represents — (CH ₂ ) _n COO—, —O (CH ₂ ) _n
COO-, n is an integer of 0 to 5, preferably 0 to 3
Is an integer. As understood from the above formula, the azobenzene moiety and the cholesterol moiety are linked via an ester bond. It is also possible to use a partially modified derivative as the cholesterol moiety represented by Cho.

One of the characteristics of the compound of the present invention is that it forms a gel reversibly or thermoreversibly in response to light or a temperature change as an external stimulus to an organic solvent, and undergoes a sol-gel transition. Along with this, the light transmittance, the CD spectrum or the absorption spectrum is significantly changed. Preferred as such a gelling compound is the above-mentioned general formula [Chemical formula 1]
In the formula, R ₁ is benzo-18-crown-6 or benzo-13-crown-4, and R ₂ is —O (C
H ₂ ) _n COO—, where n is 1 or 2.

Specific examples of such a crown ring-containing cholesterol compound of the present invention which gels an organic solvent include the following compounds.

[0011]

Embedded image B18Cr6-N = N-φ-OCH ₂ COO-
Cho

[0012]

Embedded image B13Cr4-N = N-φ-OCH ₂ COO-
Cho

In these structural formulas, B18C
r6 and B13Cr4 are each benzo-18-
Shown are crown-6 and benzo-13-crown-4. Therefore, for example, the compound of the above [Formula 2] can be expressed in detail as the following formula [Formula 4].

[0014]

Embedded image

The organic solvent that forms a gel with the crown ring-containing cholesterol compound of the above general formula [Chemical Formula 1] according to the present invention varies depending on the kind of the compound and the like, but benzene, cyclohexane, methylcyclohexane, hexane, heptane, etc. Hydrocarbons, alcohols such as propanol, butanol and dodecane, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, halogens such as carbon tetrachloride, and mixed solvents thereof are used. The mixing ratio of the compound and the solvent for forming the gel varies depending on the type of the compound or the solvent to be used, but generally, 0.5 parts by weight or more, based on 100 parts by weight of the solvent,
Preferably, 1 part by weight or more of a cholesterol compound is used.

For example, the compound represented by the above formula [Formula 2] forms a gel with cyclohexane, methylcyclohexane, heptane, propanol, butanol, a mixed solvent of cyclohexane / benzene and the like.

As described above, the crown-ring-containing cholesterol compound represented by the general formula [Formula 1] forms a photoreversible and thermoreversible gel with an organic solvent. The optical properties change significantly. Thus,
The present invention provides, as another aspect, a gelling composition comprising the cholesterol-based compound represented by the general formula [Chemical Formula 1] and an organic solvent in the above-described ratio. Since the gelling composition has unique properties, it can be used as various functional elements.

In particular, the gelling composition can be obtained by appropriately selecting the concentration of the gelling agent so that visible light-ultraviolet light-
By alternating the light irradiation like visible light,
The gel-sol-gel structural change occurs reversibly even in the room temperature range, and accordingly, the light transmittance, absorption coefficient and CD
It exhibits a unique property that the intensity and shape of the spectrum change significantly. Such a feature suggests that the gelling composition according to the present invention can be suitably used as a new optical switching device or display device. The expression of such properties in the compound or the gelling composition of the present invention is caused by the fact that the azobenzene unit contained in the cholesterol-based compound represented by the general formula [Chemical Formula 1] undergoes cis-trans change, and accordingly, -Presumed to be caused by a change in gel structure.

The concentration of the cholesterol compound exhibiting photoreversibility varies depending on the type of the compound and the solvent used, but is generally from 1 to 3 per 100 parts by weight of the solvent.
0 parts by weight, preferably 2 to 25 parts by weight of a cholesterol compound is used. However, even if a gel is formed in the cis structure, the CD spectrum has a significantly different spectrum intensity between the cis state and the trans state.
It can be used as a photoreversible switch system even in a range exceeding the weight part.

These cholesterol compounds may be used in combination with other cholesterol-based compounds or other liquid crystal compounds as long as the effects of the present invention are not impaired.

The gel-sol change in the gelling composition according to the present invention is characteristically caused by irradiation with visible light-ultraviolet light, but the gel-sol can also be changed by changing the temperature or the concentration. Can be changed. It can be used for a switching element or a display element based on a change in light transmittance or CD spectrum caused by a change in the state of the gel-sol corresponding to such an external stimulus.

Further, another feature of the gelling composition comprising the crown-ring-containing cholesterol compound of the present invention is that its gelling properties are changed by the presence of various ions such as metal ions and ammonium ions. . For example, the gel formation temperature and the gel collapse temperature differ depending on the presence of alkali ions.

The compound of the present invention is not only used as a gelling composition together with an organic solvent, but also exhibits a cholesteric liquid crystal structure in a specific temperature range corresponding to each compound. This compound exhibits different light transmittance and CD spectrum characteristics depending on the liquid crystal phase-crystal phase-isotropic phase. In particular, the CD spectrum of the liquid crystal phase forms a large excitation CD spectrum and exhibits a remarkably large spectral intensity different from the crystal phase and the isotropic phase. Therefore, when a phase change is caused by an appropriate external stimulus, it is suitably used as an optical switch element or the like. As the external stimulus, in addition to an electric field and a thermal stimulus (temperature change) which are generally performed with liquid crystal, ultraviolet light-visible light irradiation is also performed. Such light irradiation causes a cis-trans change between the liquid crystal structures, and the CD spectrum intensity is higher in the trans state than in the cis state. Thus, the liquid crystal compound of the present invention can provide a new switch system for detecting a state change between a liquid crystal phase, a crystal phase, and an isotropic phase or a state change between liquid crystal phases by a signal called a CD spectrum. The temperature range in which the state change (phase transition) occurs varies depending on each compound, but generally, the transition temperature from the crystal to the liquid crystal is 0 to 300 ° C, and the transition from the liquid crystal to the isotropic phase is 20 to 300 ° C. Occurs at 320 ° C.

For example, in the case of the crown ring-containing cholesterol compound according to the present invention represented by the above formula [Formula 5], the transition from crystal to liquid crystal is about 125 ° C., the transition from liquid crystal to isotropic liquid is about 135 ° C. A phase → liquid crystal A transition occurs at about 140 ° C., and a liquid crystal A → liquid crystal B transition occurs at about 126 ° C.

[0025]

Embedded image B15Cr5-N = N-φ-OCH ₂ COO-
Cho (B15Cr5 represents benzo-15-crown-5.)

The compound of the present invention is synthesized by devising various conventionally known reactions. Basically, the compound of the present invention is a compound represented by the formula [R ₁ -N
= N-φ-R ₂ -H] (abbreviated as compound a) and [C
[Ho-OH]. For example, a method in which thionyl chloride is added dropwise to compound a and dehydrated pyridine and acid-chlorinated, and then cholesterol is added and esterified, or compound a and cholesterol and triphenylphosphine are stirred with a solvent such as tetrahydrofuran to give diethyl azodiamine Drop the carboxylate,
A reaction method and the like can be mentioned. The compound a can be obtained by, for example, nitrating the benzocrown ring, diazo-coupling with phenol, and then carboxylating.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

[0028]

EXAMPLES Example 1 : Synthesis of 4 '-(cholesteryloxycarbonylmethoxyazo) -benzo-18-crown-6 (compound represented by the above formula [Chemical Formula 2]: hereinafter abbreviated as compound f) Benzo 18 crown 6; 5 g, chloroform 70 ml,
60 ml of acetic acid and 18 ml of 60% nitric acid were stirred at room temperature for 24 hours, and 4-nitrobenzo 18 crown 6 (compound a)
I got 0.8 g of palladium carbon is compound a4 g,
It was put in a solution of 180 ml of ethanol and reduced under a hydrogen atmosphere to obtain a compound b. 3 g of the compound c and 3 g of sodium nitrite are placed in 100 ml of an 8% aqueous hydrochloric acid solution and stirred under ice-cooling.
1 and a solution of 3 g of phenol were added dropwise and stirred for 2 hours to obtain a compound c. Compound c (4 g), (DMF) 80 ml, potassium carbonate 8.5 g and ethyl bromoacetate 3.8 g
Stirring at 4 ° C. for 4 hours gave compound d. Compound d4g, potassium hydroxide 1.6g, water 200ml, ethanol 15
0 ml was stirred at room temperature for 5 hours to obtain compound e. Furthermore,
After stirring 3 g of the compound e, 1.7 g of thionyl chloride, 180 ml of dry benzene and 0.7 ml of pyridine at 80 ° C. for 4 hours, a solution of 3.7 g of cholesterol, 250 ml of dry benzene and 0.7 ml of pyridine was added dropwise to the mixture.
The mixture was further stirred at 15 ° C. for 15 hours to obtain the desired compound f.

Nuclear magnetic resonance absorption (NMR) was performed to confirm that the target compound was obtained. Chemical shift based on tetramethylsilane, the cholesterol moiety is 0.3 to
At 2.7 ppm, the azobenzene moiety was observed at 6.5 to 8.5 and 5.0 to 5.5 ppm, and the crown ring and methyl moiety were observed at 3.5 to 5.0 ppm. In addition, in the infrared absorption spectrum, a vibration spectrum of C ＝ O attributed to an ester bond was observed at 1755 cm ⁻¹ . In the elemental analysis, H was 8.63%, whereas the measured value was 8.72%.
% And C are 71.30% of calculated value and 70.2% of measured value.
0%, N was 3.13% with respect to the calculated value of 3.26%. The crystallization temperature obtained by a differential scanning calorimeter (DSC) was 120 ° C, and the liquid crystallinity temperature was 125 ° C. .

The properties of this compound were evaluated as shown in the following examples, and its suitability as a switching element was confirmed.

Example 2 A gelation test of the compound f obtained in Example 1 was performed. Cyclohexane, methylcyclohexane, cyclohexane / benzene (4: 1) mixed solvent, propanol,
Gelled with butanol, hexane and heptane. The gel concentration was 5% by weight in the case of the mixed solvent, and 2% by weight in the other cases. When these gels were irradiated with ultraviolet light (UV) using a color filter, the gels collapsed,
The solution became an isotropic (isotropic) solution. Further, upon irradiation with visible light (VIS), a gel was formed again and a sol-gel transition occurred reversibly. The light source used was a 400 W high-pressure mercury lamp, and the color filters used were D-35 (manufactured by Toshiba) for UV and L-42 (manufactured by Toshiba) for VIS.

Example 3 The light transmittance was examined using an f-methylcyclohexane / benzene (4: 1) gel. Gel concentration is 3.5
% By weight. The measurement is performed in the wavelength range of 700 nm,
And VIS were alternately irradiated, and the change in light transmittance was examined. U
The transmission coefficient of the gel before V irradiation was 75%. The gel disappears by UV irradiation and becomes liquid, almost 95%
Was obtained. Further, the gel was formed by the VIS irradiation, and the transmittance became 75% again. UV-VIS
The irradiation test was repeated 10 times, but there was almost no variation, and almost constant transmittance was obtained. The light transmittance changed with the photoreversible sol-gel transition. In addition, visible-
As an ultraviolet absorption spectrometer, UV-2200 manufactured by Shimadzu Corporation was used.

Example 4 The same light transmittance test as in Example 3 was carried out at different temperatures.
The transmittance, which was 75% in the gel state, changed to 95% in a temperature range around 40 to 50 ° C.

Example 5 A circular dichroism spectrum was measured using an f-methylcyclohexane / benzene (4: 1) gel. The gel concentration was 4% by weight. In addition, the spectrum was also measured when UV and VIS were alternately irradiated. UV
The spectrum before irradiation showed a split-type Cotton effect in which the sign was reversed at 365 nm. Note that 365 nm corresponds to the peak wavelength of the absorption spectrum. The first Cotton effect was positive and the second Cotton effect was negative, indicating a positive chirality. The maximum value and the minimum value (molecular ellipticity) of the spectrum are about 1.5 × 10 ⁴ and about −8 × 10 ³ (deg.
cm ² · dmol ^-1 ). By irradiating UV light,
The spectral intensity was significantly reduced to less than 10 ² and no split-type or even single cotton effect was observed. Further, by continuously irradiating VIS light, UV light is again emitted.
Almost the same spectrum as before irradiation was obtained. The UV and VIS light irradiation experiments were repeated 5 times on the same sample.
Repeated times gave almost the same results. The circular dichroism spectrum used was J-720 manufactured by JASCO Corporation.

Example 6 A 10-mol% lithium ion based on the compound f was added to an f-methylcyclohexane / benzene (4: 1) gel.
Rubidium ions and ammonium ions were added. The gel concentration was 4.8% by weight. When no alkali ions were added, no gel was formed in the room temperature range, but a gel was formed by adding the alkali ions. When the gel concentration was 4% by weight, the gel collapsed at about 60 ° C. in the case where no alkali ion was added, but up to 72 ° C. in the case of adding lithium and ammonium ions, and up to 80 ° C. in the case of rubidium ion, respectively. The gel did not disintegrate. As a counter anion, perchloric acid was used for lithium and rubidium, and acetic acid was used for ammonium ions.

Example 7 In the case where cesium ions were used as the alkali ions, the same examination as in Example 5 was conducted. Gel concentration is 4
% By weight. When 8 mol% was added, a gel was formed, but at 15 mol%, no gel was formed. Also, 8
The gel disintegrated at 40 ° C. in the case of mol% addition. In addition, perchloric acid was used as a counter anion.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07J 41/00

Claims (1)

(57) [Claims] 1. A cholesterol compound represented by the structural formula [Chemical Formula 1]. Embedded image R ₁ -N = N-φ-R ₂ -Cho (wherein, R ₁ is benzo-18-crown-6,
Benzo-15-crown-5, benzo-12-crown-4, or benzo-13-crown-4, R ₂ is-
_{(CH 2) n COO -,} - O (CH 2) n COO-, n is 0
Cho represents an integer of 5, Cho represents a cholesterol group, and φ represents a benzene ring. )