JPH05202011A - Oxadiazole derivative - Google Patents

Abstract

PURPOSE:To obtain a new oxadiazole derivative which can readily form a thin organic amorphous film which is suitable for an organic electroluminescence element or an electrophotographic organic photoreceptor with high stability and heat resistance. CONSTITUTION:An oxadiazole derivative of formula I (R1 through R3 are H, halogen and monovalent group), for example a compound of formula II. The compound is synthesized by reaction between 1,3,5-benzenetricarboxylic acid trichloride and the atoms or groups represented by R1 through R3 followed by dehydration of the resultant tris(dihydrazide) with phosphorus oxychloride. The thin organic film of the compound which can be suitably used in a variety of thin organic film elements is formed by a customary film-forming process. The vaporization process is particularly preferred because it is simple and the lamination of thin films can be also done through this process. The film thickness of the organic layer can be suitably selected in the range of from 100 to 1,000 angstroms.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel oxadiazole derivative suitably used for various organic thin film devices.

[0002]

2. Description of the Related Art In recent years, attempts have been actively made to realize new functional devices by thinning organic molecules. For example, organic EL (electroluminescence) devices using organic thin films formed by a vapor deposition method and others. The research on optical elements and the like has been activated. Among the organic molecules used for such an organic thin film element, the oxadiazole derivative emits strong fluorescence even in a solid state and has an excellent charge transporting ability, and therefore, an organic EL element or an organic photoconductor for electrophotography. It has been widely used in, for example, and specifically, an organic EL device using an oxadiazole derivative represented by the following general formula [2], an organic photoconductor for electrophotography, and the like have been reported.

[0003]

[Chemical 2]

In the organic thin film element as described above, it is known that it is advantageous to use an organic thin film in an amorphous state in terms of film uniformity, stability and light transmission. For example, in an organic EL element, using a polymer or dye capable of forming a thin film in an amorphous state is more preferable than using a fatty acid or the like that forms a crystalline thin film.
It is possible to achieve high operational stability based on uniform film characteristics and excellent light transmission due to the absence of grain boundaries. Also in the electrophotographic organic photoreceptor, a photosensitive layer in which a charge generating agent or a charge transporting agent is uniformly dispersed or dissolved in a polymer in an amorphous state is generally formed.

However, it has been very difficult to form an organic thin film in an amorphous state with low molecular weight organic molecules such as the oxadiazole derivative represented by the general formula [2] described above. That is, in order to make such a low-molecular-weight organic molecule into a thin film in an amorphous state, it is necessary to control the film-forming conditions extremely strictly. Even if an organic thin film in an amorphous state can be formed, the obtained organic thin film is unstable and easily crystallized,
Moreover, since the glass transition temperature is low and the heat resistance is poor,
There is a problem that the deterioration is further accelerated by the heat generated when the element is driven. Therefore, the organic thin film element using the organic thin film of the oxadiazole derivative as described above has insufficient operational stability, life characteristics, etc., and has not yet been put into practical use.

[0006]

As described above, since it is difficult to form a stable organic thin film in an amorphous state with the conventionally known oxadiazole derivative, it is possible to obtain an organic compound having good operation stability and life characteristics. A thin film element could not be realized.

In view of such problems, an object of the present invention is to provide an oxadiazole derivative which can be easily formed into a thin film in an amorphous state and can form an organic thin film which is stable and has excellent heat resistance. I am trying.

[0008]

Means and Actions for Solving the Problems The oxadiazole derivative of the present invention, which has been made to achieve the above object, is a novel oxadiazole derivative represented by the following general formula [1].

[0009]

[Chemical 3] (In the formula, R _{1 to} R ₃ may be the same or different and each represents a hydrogen atom, a halogen atom or a monovalent group.)

That is, the oxadiazole derivative of the present invention is characterized by having a radial molecular skeleton, whereby the cohesive force between molecules is reduced, the crystallinity is lowered, and a stable amorphous state is obtained. Can be held. Further, since it has a larger molecular weight than the conventional oxadiazole derivative represented by the general formula [2], it has a high glass transition temperature in an amorphous state and is more excellent in heat resistance.

In the oxadiazole derivative of the present invention, the monovalent group represented by R _{1 to} R ₃ in the above general formula [1] is an unsubstituted or substituted alkyl group having 1 to 50 carbon atoms,
Examples thereof include unsubstituted or substituted aryl groups having 6 to 50 carbon atoms, unsubstituted or substituted heterocyclic groups, alkoxy groups, carbonyl groups, amino groups, nitro groups, cyano groups, sulfonyl groups, hydroxyl groups and the like. In the present invention, R _{1 to} R ₃ are particularly preferably a substituted phenyl group, and in this case, it is possible to control electronic properties and optical properties by selecting a substituent of the phenyl group. It becomes very easy to design the device. For example, a molecule having a hole-transporting ability can be obtained by selecting an electron-donating group as a substituent, and a molecule having an electron-transporting ability can be obtained by selecting an electron-accepting group as a substituent. Specifically, as such a substituent, an unsubstituted or substituted alkyl group having 1 to 50 carbon atoms,
Examples include unsubstituted or substituted aryl groups having 6 to 50 carbon atoms, unsubstituted or substituted heterocyclic groups, alkoxy groups, carbonyl groups, amino groups, nitro groups, cyano groups, sulfonyl groups, hydroxyl groups, and phenyl groups with halogen atoms. May be substituted.

In order to synthesize the oxadiazole derivative of the present invention, first, 1,3,5-benzenetricarboxylic acid trichloride and carboxylic acid hydrazide having the atom or group represented by R _{1 to} R ₃ above are prepared. React. After this,
By performing a dehydration reaction of tris (dihydrazide) obtained with phosphorus oxychloride or the like, the above general formula [1]
An oxadiazole derivative represented by is synthesized. In the case of synthesizing an oxadiazole derivative having different R ₁ , R ₂ and R ₃ in the above general formula [1], first, for example, R ₁
Using a large excess of 1,3,5-benzenetricarboxylic acid trichloride with respect to the carboxylic acid hydrazide having the atom or group represented by, only one carboxylic acid group of 1,3,5-benzenetricarboxylic acid trichloride is used. React. Then, similarly, a carboxylic acid hydrazide having an atom or a group represented by R ₂ in the carboxylic acid group of 1,3,5-benzenetricarboxylic acid trichloride and a carboxylic acid hydrazide having an atom or a group represented by R ₃ The oxadiazole derivative as described above can be easily synthesized by sequentially reacting with each other and then performing a dehydration reaction. Further, 1,3,5-benzenetricarboxylic acid trichloride is reacted with two or three kinds of carboxylic acid hydrazides at once, and then dehydration reaction is carried out, followed by separation of a target oxadiazole derivative by chromatography. Good.

The method for forming the organic thin film of the oxadiazole derivative of the present invention includes casting method, vapor deposition method and LB method.
Ordinary film-forming methods such as a method, a water surface spreading method, and an electrolysis method can be adopted. Of these, the vapor deposition method is particularly preferable because it is simple and suitable for forming a laminate of organic thin films. The film thickness of such an organic thin film is set according to the characteristics generally required for an element to be produced, but can be appropriately selected within the range of 100 to 1000 A (angstrom).

Further, when such an organic thin film is formed, a polymer that easily becomes amorphous can be added to the organic thin film for the purpose of stabilizing the amorphous state of the film. However, in this case, in order to fully exhibit the physical properties originally possessed by the oxadiazole derivative of the present invention, the content of the polymer in the organic thin film is preferably 50% by weight or less.

When an organic thin film element is prepared by using the oxadiazole derivative of the present invention, basically, the organic thin film formed by the above film forming method can be used as a single layer, but organic molecules having various functions can be used. By stacking these organic thin films, it is possible to realize an element having a high composite function. The structure and operation principle of the organic thin film element having various functions, which is prepared by using the oxadiazole derivative of the present invention, will be briefly described below. (1) Organic EL element

An organic compound having a two-layer structure of a light emitting layer containing a fluorescent dye and a hole transport layer or an electron transport layer, or a three-layer structure having a light emitting layer between the hole transport layer and the electron transport layer, or a multilayer structure of more layers. It is characterized in that it has a laminated structure of thin films sandwiched by two electrodes, at least one of which is a transparent electrode. In either case, electrons and holes are injected into the light emitting layer, recombine, and emit light. The electron transport layer and the hole transport layer have a function of increasing the injection probability. (2) Organic solar cell element

A two-layer structure of a charge generation layer containing a dye which absorbs visible light to generate electrons and holes and a hole transport layer or an electron transport layer, or a charge generation layer between the hole transport layer and the electron transport layer. It is characterized in that it has a laminated structure of an organic thin film having a three-layer structure or a multi-layer structure having more than two layers, and a structure sandwiched by two electrodes, at least one of which is a transparent electrode. In any case, it has a function of preventing the generated electrons and holes from recombining, efficiently performing charge separation, and increasing photoelectric conversion efficiency. (3) Organic photoconductor for electrophotography

It has a structure of an organic thin film in which two layers of a charge generating layer containing a dye which absorbs visible light to generate electrons and holes and a hole transporting layer or an electron transporting layer are sequentially laminated on a metal. To do.

First, in the case of the hole transport layer, the surface is negatively charged by corona discharge or the like. In the case of the electron transport layer, it is positively charged. After that, when recording light is incident,
Electrons and holes are generated only in the areas exposed to the light. In the hole transport layer, holes are efficiently transported to the film surface to cancel out negative charges. If the toner is pre-charged negatively, the toner adheres only to the portion exposed to the light, and then the toner image can be transferred to the paper. In the electron transport layer, electrons are efficiently transported to the film surface, and the positive charge is canceled. If the toner is positively charged in advance, the toner adheres only to the part exposed to the light, and then the toner image can be transferred onto the paper. (4) Organic rectifying device Hole transport layer (P-type semiconductor) and electron transport layer (N-type semiconductor)
It is characterized in that it has a structure in which the laminated structure of the organic thin film having the two-layer structure is sandwiched by two electrodes.

In any case, as in the case of the PN junction of the inorganic semiconductor, only the electrons and holes are transported, so that the rectifying action occurs. Like the inorganic semiconductor, the hole transport layer may be doped with an acceptor and the electron transport layer may be doped with a small amount of donor to increase the current density.

[0021]

EXAMPLES As examples of the present invention, Examples 1 to 5 are examples of synthesis and film formation of the oxadiazole derivative of the present invention, and Examples 6 to 13 are various organic compounds using these oxadiazole derivatives. The example which produced the thin film element is shown. Example 1 (synthesis, film formation example)

First, 2 g of 1,3,5-benzenetricarboxylic acid trichloride and 8 g of p-t-butylbenzoic acid hydrazide were reacted in anhydrous pyridine. The reaction mixture was poured into water and the precipitate was filtered. The precipitate was washed with hydrochloric acid and water, and then recrystallized with a mixed solvent of methanol / ethanol to obtain tris (dihydrazide) as needle crystals.

Next, 1 g of this tris (dihydrazide) was refluxed in 30 ml of phosphorus oxychloride. After the phosphorus oxychloride was distilled off, the reaction product was washed well with water and methanol. Then, this was recrystallized with a mixed solvent of ethanol / toluene to obtain 0.7 g of an oxadiazole derivative represented by the following structural formula [3]. The infrared absorption spectrum of the obtained oxadiazole derivative is shown in FIG. 1, and the proton NMR spectrum is shown in FIG. From the differential scanning calorimetric analysis, it was found that the glass transition temperature of this oxadiazole derivative in the amorphous state was 139 ° C.

[0024]

[Chemical 4]

This oxadiazole derivative was resistance-heated under a vacuum of 10 ⁻⁶ Torr to give a thickness of 300 A on quartz glass.
It was vapor-deposited. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. This film was left under a nitrogen stream at room temperature for 3 months, and then observed under a microscope and scattered light was measured.
As a result, it was confirmed that no non-uniform structure was observed and a uniform amorphous state was maintained.

Further, a solution in which this oxadiazole derivative was dissolved in chloroform and a solution in which it was dissolved by heating were prepared, and each of these solutions was spin-coated on quartz glass to obtain a thin film having a thickness of 1000A. Further, this oxadiazole derivative and polymethylmethacrylate having a molecular weight of 200,000 were dissolved in equal weight chloroform and spin-coated on a quartz coat to obtain a thin film having a thickness of 2000A. When the obtained organic thin film was similarly left under a nitrogen stream at room temperature for 3 months, it was observed under a microscope and scattered light was observed, and no heterogeneous structure was observed at all, and a uniform amorphous state was maintained. Was confirmed. Example 2 (synthesis, film formation example)

An oxadiazole derivative represented by the following structural formula [4] was synthesized by the same synthetic method as in Example 1.
The infrared absorption spectrum of the oxadiazole derivative obtained is shown in FIG. 3, and the proton NMR spectrum is shown in FIG. From the differential scanning calorimetric analysis, it was found that the glass transition temperature of this oxadiazole derivative in the amorphous state was 169 ° C.

[0028]

[Chemical 5]

This oxadiazole derivative was resistance-heated under a vacuum of 10 ^-6 torr to a thickness of 300 A on quartz glass.
It was vapor-deposited. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. This film was left under a nitrogen stream at room temperature for 3 months, and then observed under a microscope and scattered light was measured.
As a result, it was confirmed that no non-uniform structure was observed and a uniform amorphous state was maintained. Example 3 (synthesis, film formation example)

An oxadiazole derivative represented by the following structural formula [5] was synthesized by the same synthetic method as in Example 1.
The infrared absorption spectrum of the oxadiazole derivative obtained is shown in FIG. 5, and the proton NMR spectrum is shown in FIG. From the differential scanning calorimetric analysis, it was found that the glass transition temperature of this oxadiazole derivative in the amorphous state was 147 ° C.

[0031]

[Chemical 6]

This oxadiazole derivative was resistance-heated under a vacuum of 10 ^-6 torr to a thickness of 300 A on quartz glass.
It was vapor-deposited. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. This film was left under a nitrogen stream at room temperature for 3 months, and then observed under a microscope and scattered light was measured.
As a result, it was confirmed that no non-uniform structure was observed and a uniform amorphous state was maintained. Example 4 (synthesis, film formation example)

An oxadiazole derivative represented by the following structural formula [6] was synthesized by the same synthetic method as in Example 1.
FIG. 7 shows the infrared absorption spectrum of the oxadiazole derivative obtained. From the differential scanning calorimetry, the glass transition temperature of this oxadiazole derivative in the amorphous state is
It was found to be 140 ° C.

[0034]

[Chemical 7]

This oxadiazole derivative was resistance-heated under a vacuum of 10 ⁻⁶ Torr to a thickness of 300 A on quartz glass.
It was vapor-deposited. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. This film was left under a nitrogen stream at room temperature for 3 months, and then observed under a microscope and scattered light was measured.
As a result, it was confirmed that no non-uniform structure was observed and a uniform amorphous state was maintained. Example 5 (synthesis, film formation example)

An oxadiazole derivative represented by the following structural formula [7] was synthesized by the same synthetic method as in Example 1.
The infrared absorption spectrum of the obtained oxadiazole derivative is shown in FIG. 8, and the proton NMR spectrum is shown in FIG. From the differential scanning calorimetric analysis, it was found that the glass transition temperature of this oxadiazole derivative in the amorphous state was 108 ° C.

[0037]

[Chemical 8]

This oxadiazole derivative was resistance-heated under a vacuum of 10 ⁻⁶ Torr to give a thickness of 300 A on quartz glass.
It was vapor-deposited. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. This film was left under a nitrogen stream at room temperature for 3 months, and then observed under a microscope and scattered light was measured.
As a result, it was confirmed that no non-uniform structure was observed and a uniform amorphous state was maintained. Comparative Example 1

A linear oxadiazole derivative represented by the following structural formula [8] was vapor-deposited on quartz glass at a thickness of 300 A by resistance heating under a vacuum of 10 ^-6 torr. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. After leaving this film for 1 month at room temperature under a nitrogen stream, it was observed under a microscope and scattered light was measured. As a result, it was confirmed that the scattered light increased and a structure like a crystal grain was observed even under a microscope, and the film was non-uniform.

[0040]

[Chemical 9] Comparative example 2

A linear oxadiazole derivative represented by the following structural formula [9] was vapor-deposited on quartz glass at a thickness of 300 A by resistance heating under a vacuum of 10 ⁻⁶ Torr. The film thickness was controlled using a crystal oscillator. The film was uniform and transparent. After leaving this film for 1 month at room temperature under a nitrogen stream, it was observed under a microscope and scattered light was measured. As a result, it was confirmed that the scattered light increased and a structure like a crystal grain was observed even under a microscope, and the film was non-uniform. Also, differential scanning calorimetry analysis revealed that the glass transition temperature of the oxadiazole derivative in the amorphous state was as low as 77 ° C.

[0042]

[Chemical 10] Example 6 (organic EL device)

On the ITO glass, a triphenylamine derivative represented by the following structural formula [10] as a hole transport layer, pentaphenylcyclobutadiene as a light emitting layer, and an oxadiene represented by the structural formula [3] as an electron transport layer. An azole derivative was vapor-deposited at 500 A, 300 A, and 500 A, respectively, to form an organic thin film having a three-layer structure. After this, an area of 0.2 cm ² composed of an alloy of magnesium and silver (atomic ratio 10: 1) was formed on the organic thin film. 6 electrodes are formed to form the organic E of the present embodiment.
An L element was created.

Immediately after the production of this organic EL device, the initial luminance was measured under a vacuum at a direct current voltage of 10 V, and 1000 cd / m ² was measured for all three electrodes. The brightness of Further, after the organic EL device was left under a nitrogen stream at room temperature for 1 month, the initial luminance of the remaining 3 electrodes was measured in the same manner.
Both are 1000 cd / m ² Brightness was obtained, and deterioration of device characteristics due to storage was not observed.

[0045]

[Chemical 11] Example 7 (organic EL device)

Oxadiazole represented by the structural formula [3]
Oxazide represented by the above structural formula [5] instead of the derivative
Same as Example 6 except that the azole derivative is used.
An organic EL device was prepared by the same method. This organic EL element
Immediately after creation, the child is initially set to a DC voltage of 10 V under vacuum.
When the brightness was measured, the measured three electrodes were 1000 cd / m
² The brightness of Furthermore, this organic EL element is
After leaving at room temperature for 1 month, the initial brightness of the remaining 3 electrodes
When measured in the same manner, both are 1000 cd / m² The brightness of
Obtained, no deterioration in device characteristics due to storage
It was Example 8 (organic EL device)

An organic EL device was prepared in the same manner as in Example 6 except that the oxadiazole derivative represented by the above structural formula [4] was used in place of pentaphenylcyclobutadiene. Immediately after the production, the initial luminance of this organic EL device was similarly measured at a direct current voltage of 10 V, and 1000 cd / m ² was measured for all three electrodes. The brightness of Furthermore, after leaving this organic EL device under a nitrogen stream at room temperature for one month, the initial luminance of the remaining three electrodes was measured and found to be 1000 cd / m ^2. Brightness was obtained, and deterioration of device characteristics due to storage was not observed. Example 9 (organic EL device)

An organic EL device was prepared in the same manner as in Example 6 except that the oxadiazole derivative represented by the above structural formula [7] was used in place of pentaphenylcyclobutadiene. Immediately after the production, the initial luminance of this organic EL device was similarly measured at a direct current voltage of 10 V, and 1000 cd / m ² was measured for all three electrodes. The brightness of Furthermore, after leaving this element for 1 month at room temperature under a nitrogen stream, the initial luminance of the remaining 3 electrodes was measured in the same manner, and all were 1000 cd / m ^2. Brightness was obtained, and deterioration of device characteristics due to storage was not observed. Example 10 (organic solar cell element)

On the ITO glass, a triphenylamine derivative represented by the above structural formula [10] as a hole transport layer, copper phthalocyanine as a charge generation layer, and an oxadiazole represented by the above structural formula [6] as an electron transport layer. Each of the derivatives was vapor-deposited at 500 A to form an organic thin film having a three-layer structure. After this, the area on the organic thin film 0.2 cm ² Six aluminum electrodes of No. 3 were formed to prepare an organic solar cell element of this example.

Immediately after production of this organic solar cell element, a tungsten lamp light, which was cut off ultraviolet light having a wavelength of 400 nm or less, was irradiated from the ITO glass side, and the initial photoelectric conversion efficiency was measured. 1.5
%Met. Furthermore, after leaving this organic solar cell element under nitrogen flow at room temperature for 3 months, the initial photoelectric conversion efficiency of the remaining 3 electrodes was measured in the same manner, and it was found that the deterioration of element characteristics due to storage was 1.3 to 1.5%. There wasn't. Example 11 (organic solar cell element)

An organic solar cell was prepared in the same manner as in Example 10, except that the oxadiazole derivative represented by the structural formula [3] was used in place of the oxadiazole derivative represented by the structural formula [6]. A battery element was created. Immediately after the production of this organic solar cell element, a tungsten lamp light that cut off ultraviolet light having a wavelength of 400 nm or less was irradiated from the ITO glass side to measure the initial photoelectric conversion efficiency.
The measured three electrodes were 1.0 to 1.2%. Furthermore, when this organic solar cell element was left under a nitrogen stream at room temperature for 3 months and the initial photoelectric conversion efficiency of the remaining 3 electrodes was measured in the same manner, deterioration of the element characteristics due to storage was confirmed to be 1.0 to 1.1%. There wasn't. Example 12 (organic photoconductor for electrophotography)

First, a polycarbonate film having a thickness of 2 μm in which copper naphthalocyanine was dispersed was formed as a charge generation layer on the aluminum electrode deposited on the glass surface by a casting method. Then, on this, as a carrier transport layer, a triphenylamine derivative represented by the above structural formula [10] and an oxadiazole derivative represented by the above structural formula [6] were dissolved in 20 wt% and 30 wt% respectively of a polycarbonate having a thickness of 2 μm. To form an electrophotographic organic photoconductor of this example. In this carrier transport layer, the triphenylamine derivative has a hole transport ability and the oxadiazole derivative has an electron transport ability.

This organic photoconductor for electrophotography was immediately irradiated with monochromatic light of 630 nm (0.4 μW / cm ^2). )
When the decay of the surface charge potential was measured, it was about 2 cm ² for both positive and negative charges. The sensitivity was / μJ. Further, after the organic photoreceptor for electrophotography was left under a nitrogen stream at room temperature for 3 months, the sensitivity was measured in the same manner. As a result, deterioration of element characteristics due to storage was not observed. Example 13 (organic rectifier)

On the aluminum electrode deposited on the glass surface, the triphenylamine derivative represented by the above structural formula [10] as a hole transport layer and the oxadiazole derivative represented by the above structural formula [6] as a charge transport layer. 2 each
An organic thin film having a two-layer structure was formed by vapor deposition of 00A each. After this, the area on the organic thin film 0.2 cm ² Six aluminum upper electrodes of No. 3 were formed to prepare an organic rectifying device of this example.

Immediately after the organic rectifying device was manufactured, the current-voltage characteristics were measured by cutting off the light under vacuum. As a result, when the aluminum upper electrode was used as a negative electrode, it had a rectifying characteristic in which a current flowed, and the measured six electrodes showed almost the same current-voltage characteristic. Further, the organic rectifier was left for 3 months at room temperature under a nitrogen stream, and then the current-voltage characteristics of 6 electrodes were measured. No change was observed in any of them, and deterioration of the element characteristics due to storage was not observed.

[0056]

As described in detail above, according to the oxadiazole derivative of the present invention, it is possible to easily form a thin film in an amorphous state and form an organic thin film which is stable and has excellent heat resistance. Therefore, by using the oxadiazole derivative of the present invention, it is possible to realize an organic thin film element having excellent operational stability and life characteristics, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a diagram showing an infrared absorption spectrum of an oxadiazole derivative represented by a structural formula [3] synthesized in Example 1.

FIG. 2 is a diagram showing a proton NMR spectrum of an oxadiazole derivative represented by the structural formula [3] synthesized in Example 1.

FIG. 3 shows an infrared absorption spectrum of an oxadiazole derivative represented by Structural Formula [4], which was synthesized in Example 2.

FIG. 4 is a diagram showing a proton NMR spectrum of an oxadiazole derivative represented by the structural formula [4] synthesized in Example 2.

5 is a diagram showing an infrared absorption spectrum of an oxadiazole derivative represented by Structural Formula [5], which was synthesized in Example 3. FIG.

FIG. 6 is a diagram showing a proton NMR spectrum of an oxadiazole derivative represented by the structural formula [5], which was synthesized in Example 3.

7 is a diagram showing an infrared absorption spectrum of an oxadiazole derivative represented by Structural Formula [6], which was synthesized in Example 4. FIG.

FIG. 8 shows an infrared absorption spectrum of an oxadiazole derivative represented by Structural Formula [7], which was synthesized in Example 5.

9 is a diagram showing a proton NMR spectrum of the oxadiazole derivative represented by the structural formula [7] synthesized in Example 5. FIG.

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Claims (1)

[Claims] 1. An oxadiazole derivative represented by the following general formula [1]: [Chemical 1] (In the formula, R _{1 to} R ₃ may be the same or different and each represents a hydrogen atom, a halogen atom or a monovalent group.)