KR20170009185A - Oxadiazole derivatives, preparation method thereof and electron tranport layer having the same - Google Patents

Abstract

The present invention relates to oxadiazole derivatives, a preparation method thereof, and to an electron transfer layer comprising the oxadiazole derivatives. According to the present invention, the oxadiazole derivatives represented by chemical formula 1 has excellent measured values of circulating voltage and circulating current and are stable at a thin film state, thereby being useful as an electron transfer layer of an organic electroluminescent element such as an organic light emitting device (OLED).

Description

TECHNICAL FIELD The present invention relates to an oxadiazole derivative, a method for preparing the same, and an electron transport layer containing the oxadiazole derivative, and a preparation method thereof and an electron transport layer having the same.

The present invention relates to an oxadiazole derivative, a method for producing the same, and an electron transport layer comprising the oxadiazole derivative. The electron transport layer can be applied to an organic electroluminescent device such as an organic light emitting diode (OLED).

Since the organic electroluminescent device is a self-luminescent device, it is brighter than a liquid crystal device and has excellent visibility and clear display, and active research has been conducted. In 1987, C. W.Tang et al. Of Eastman Kodak Company developed a laminated structure device in which various roles are shared among various materials, thereby realizing an organic electroluminescent device using organic materials. They obtained a high luminance of 1000 ㏅ / ㎡ or higher at a voltage of 10 V or less by laminating a phosphor capable of transporting electrons and an organic material capable of transporting holes and injecting both charges into the phosphor layer to emit light.

Many improvements have been made to the practical use of the organic electroluminescent device so far and various roles are further subdivided so that the anode, the hole injecting layer, the hole transporting layer, the light emitting layer, the electron transporting layer, the electron injecting layer, and the cathode are sequentially formed on the substrate High efficiency and durability were achieved by the electroluminescent device.

The light-emitting layer may be produced by doping a fluorescent substance or a phosphorescent light emitting material with a charge-transporting compound generally referred to as a host material. The selection of the organic material in the organic electroluminescent device greatly influences various characteristics such as the efficiency and durability of the device.

In the organic electroluminescent device, the charges injected from both electrodes are recombined in the light emitting layer to emit light. Since the moving speed of the holes is faster than the electron moving speed, the efficiency deterioration due to part of the holes escaping from the light emitting layer It becomes a problem. Therefore, there is a demand for an electron transporting material that allows electrons to move easily.

Tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq), which is a typical light emitting material, is generally used as an electron transporting material, but the electron transfer rate is known to be slow. For this reason, as a material having a high moving speed, 2- (4-biphenylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole (hereinafter abbreviated as PBD) (See Non-Patent Document 1).

However, it was pointed out that the stability in the thin film state was insufficient, such as easy crystallization of PBD, and satisfactory device characteristics were not obtained.

Thus, the present inventors have found that the oxadiazole derivative represented by the formula (1) has excellent cyclic voltammetry and is stable in a thin film state, and is useful as an electron transport layer of an organic electroluminescent device such as an organic light emitting diode And completed the present invention.

Jpn. J. Appl. Phys., 27, L269 (1988)

An object of the present invention is to provide an oxadiazole derivative represented by the formula (1).

Another object of the present invention is to provide a process for preparing the oxadiazole derivative.

Another object of the present invention is to provide an electron transport layer comprising the oxadiazole derivative.

Another object of the present invention is to provide an organic electroluminescent device including the electron transport layer.

In order to achieve the above object,

The present invention provides an oxadiazole derivative represented by the following general formula (1).

[Chemical Formula 1]

In Formula 1,

X is carbon or nitrogen;

L is a single bond, C _1-6 linear or branched alkylene or C _1-6 linear or branched alkylenyl;

R ¹ is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-12 aryl is C _1-6 Linear or branched alkyl, C _1-6 straight or branched alkoxy, or -NO ₂ , wherein said 6-12 atom heteroaryl may be fused with a C _6-10 aryl;

R ² is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said aryl of C _6-12 is C _1-10 Linear or branched alkyl, C _1-6 straight chain or branched alkoxy.

Also, as shown in the following Reaction Scheme 1,

Synthesizing an acylhydrazone compound represented by the formula (4) by reacting a compound represented by the formula (2) and a compound represented by the formula (3) by mechanical pulverization under no solvent conditions (step 1); And

(Step 2) of synthesizing an oxadiazole derivative represented by the formula (1) by an oxidative cyclization reaction by adding an oxidizing agent to the compound represented by the formula (4) obtained in the step 1 under no solvent condition;

Wherein R < 1 > and R < 2 >

[Reaction Scheme 1]

In the above Reaction Scheme 1,

X, L, R < ¹ > and R < ² >

Further, the present invention provides an electron transport layer comprising the oxadiazole derivative represented by the above formula (1).

The present invention also provides an organic electroluminescent device having a laminated structure including a light emitting layer and an electron transporting layer between an anode and a cathode,

Wherein the electron transport layer comprises an oxadiazole derivative represented by the general formula (1).

The oxadiazole derivative represented by the formula (1) according to the present invention has excellent cyclic voltammetry and is stable in a thin film state, and thus can be useful as an electron transport layer of an organic electroluminescent device such as an organic light emitting diode (OLED).

1 is a schematic view showing a general structure of an organic electroluminescent device.
2 is a graph showing UV-vis absorption and fluorescence spectra of the compound of Example 1-4 according to the present invention ((a): Example 1 (b): Example 2 (c): Example 3 , (d): Example 4).
3 is a graph showing UV-vis absorption and fluorescence spectra of the compounds of Examples 5-7 and Comparative Example 1 according to the present invention ((a): Example 5, (b): Example 6, (c) : Example 7, (d): Comparative Example 1).
4 is a graph showing the cyclic voltammetry values of the compound of Example 1-4 according to the present invention ((a): Example 1 (b): Example 2 (c): Example 3 ): Example 4).
5 is a graph showing the cyclic voltammetry values of the compounds of Examples 5-7 and Comparative Example 1 according to the present invention ((a): Example 5, (b): Example 6, (c) 7, (d): Comparative Example 1).

Hereinafter, the present invention will be described in detail.

The present invention provides an oxadiazole derivative represented by the following general formula (1).

In Formula 1,

X is carbon or nitrogen;

L is a single bond, C _1-6 linear or branched alkylene or C _1-6 linear or branched alkylenyl;

R ¹ is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-12 aryl is C _1-6 Linear or branched alkyl, C _1-6 straight or branched alkoxy, or -NO ₂ , wherein said 6-12 atom heteroaryl may be fused with a C _6-10 aryl;

R ² is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said aryl of C _6-12 is C _1-10 Linear or branched alkyl, C _1-6 straight chain or branched alkoxy.

Preferably, X is carbon or nitrogen;

L is a single bond or a C _1-3 straight or branched alkylenyl;

R ¹ is C _6-8 aryl, or 6-8 membered heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-8 aryl is C _1-3 Linear or branched alkoxy of ₁ to 6 carbon atoms, or -NO ₂ , and the 6-12-membered heteroaryl may be fused with a C _6-8 aryl;

R ² is C _6-8 aryl, or 6-8 membered heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-12 aryl is C _1-6 Linear or branched chain alkyl, C < ₁ > ₃ linear or branched alkoxy may be substituted.

Examples of the oxadiazole derivative represented by the above formula (1) include the following compounds, and the chemical structures of these compounds are shown in Table 1 below.

1) 2-phenyl-5- (quinolin-3-yl) -1,3,4-oxadiazole;

2) ( E ) -2-phenyl-5- (1-phenylprop-1-en-2-yl) -1,3,4-oxadiazole;

3) ( E ) -2- (4-methoxyphenyl) -5- (1-phenylprop-1-en-2-yl) -1,3,4-oxadiazole;

4) ( E ) -2- (2-methoxystyryl) -5- (pyridin-3-yl) -1,3,4-oxadiazole;

5) Synthesis of ( E ) -2- (1-phenylprop-1-en-2-yl) -5- (pyridin-

6) 2- (4-tert-butylphenyl) -5- (2-nitrophenyl) -1,3,4-oxadiazole; And

7) 2- (4-tert-Butylphenyl) -5- (quinolin-2-yl) -1,3,4-oxadiazole.

Example Chemical structural formula Example Chemical structural formula One

5

2

6

3

7

4

-

The oxadiazole derivative represented by the formula (1) according to the present invention has excellent cyclic voltammetry and is stable in a thin film state, and thus can be useful as an electron transport layer of an organic electroluminescent device such as an organic light emitting diode (OLED).

Also, as shown in the following Reaction Scheme 1,

Synthesizing an acylhydrazone compound represented by the formula (4) by reacting a compound represented by the formula (2) and a compound represented by the formula (3) by mechanical pulverization under no solvent conditions (step 1); And

(Step 2) of synthesizing an oxadiazole derivative represented by the formula (1) by an oxidative cyclization reaction by adding an oxidizing agent to the compound represented by the formula (4) obtained in the step 1 under no solvent condition;

Wherein R < 1 > and R < 2 >

[Reaction Scheme 1]

In the above Reaction Scheme 1,

X, L, R < ¹ > and R < ² >

In the preparation method according to the present invention, the step 1 is a step of reacting a compound represented by the general formula (2) and a compound represented by the general formula (3) by a mechanical pulverization method under no solvent, to obtain an acylhydrazone compound represented by the general formula .

The 'no solvent condition' in the above step 1 means that the chemical reaction proceeds in a solventless state using mechanical grinding. This can be an eco-friendly way to reduce the relative E-factor rather than the reaction with organic solvents. (E-factor = total waste (kg) / product (kg)). This can be developed into a sustainable chemical synthesis process.

The synthesis method using the solvent-free condition of the present invention can prevent the production of other by-products by a small amount of water in the solvent, and can prevent the intermediate to be synthesized from returning to the starting material by water.

Specifically, in the present invention, the acylhydrazone compound represented by the formula (4) of the step 1 has an immune form and thus shows poor stability to water. When the solventless reaction is applied, the anhydrous state can be maintained, .

In the step 1, for example, a grinding by a mechanical grinding method includes a ball mill, an attrition mill, and a rod mill. Preferably, in consideration of efficiency and economical efficiency, Can be applied. Water is generated during the reaction of obtaining the acylhydrazone compound represented by the general formula (4) by the solvent-free method. When the reaction using the ball mill is carried out, it evaporates easily in the ball mill and does not greatly affect the reaction.

When the milling time is too long, there is a problem that the synthesized material adheres to the wall of the ball mill cell and is difficult to separate easily from the barrier wall. On the other hand, when the milling time is too short, Min. ≪ / RTI > By grinding, reaction time can be greatly reduced and the product can be obtained without additional work.

The mixing ratio of the compound represented by Formula 2 and the compound represented by Formula 3 is preferably 1: 0.9 to 1.2.

In the production process according to the present invention, in the step 2, an oxidizing agent is added to the compound represented by the general formula (4) obtained in the above step 1 under no solvent, To synthesize a diazole derivative.

In particular, the solventless synthesis method of the present invention is preferably a solventless / single-pot method by performing cyclization by adding an oxidizing agent in-situ to a reaction vessel having an acylhydrazone group represented by the formula (4) . Such a solventless / single-pot synthesis method is suitable for mass production because it shows a high yield even in a large-scale apparatus and does not require any additional process.

In step 2, the oxidant is a hypervalent iodine series, for example, bis (trifluoroacetoxy) iodobenzene (BTI), (bisacetoxy iodo) benzene (DIB) Decoxybenzoic acid (IBX), des-martin periodine (DMP), and preferably BTI.

If the amount of the oxidizing agent is excessively increased, peroxidation may occur. If the amount of the oxidizing agent is too small, the reaction yield may be lowered due to the unreacted starting material. Therefore, the amount of the acyl hydrazone compound represented by Chemical Formula 4 may be 1.1-1.3 equivalents.

The mechanism when BTI is used as an oxidizing agent for promoting the oxidative cyclization reaction is that the BTI is coordinated to the nitrogen (N) of the acylhydrazone compound represented by Chemical Formula 4 , The CF ₃ COO ^- off BTI drops the proton in N, and when the carbonyl oxygen attacks the carbon cation, the cyclization reaction occurs and further the hydrogen cations fall off, resulting in 1,3,4-oxadiazole It is made.

[Reaction Scheme 2]

The oxidative cyclization is carried out by mechanical pulverization for 1-120 minutes, preferably 5-20 minutes, and then at 50-150 ° C, preferably 70-100 ° C for 10-120 minutes, preferably 50-100 ° C Min for a few minutes. First, mechanical pulverization can be carried out using a mortar bowl. When the reaction is carried out using an oxidizing agent such as BTI, trifluoroacetic acid and iodobenzene are formed as byproducts, Fluoroacetic acid can be removed.

In one preferred example, the oxadiazole derivative represented by the formula (1) obtained in the above step 2 may be further subjected to vacuum drying by chromatography or recrystallization to separate the oxadiazole derivative. This is because a simple column or recrystallization can easily remove the byproduct, iodobenzene. Through this purification process, a pure oxadiazole derivative can be obtained.

Further, the present invention provides an electron transport layer comprising the oxadiazole derivative represented by the above formula (1).

The electron transport layer according to the present invention can be applied to all electronic devices that require it for the purpose of facilitating electron transportation and is particularly preferable as any one of the constituent layers included in the organic electroluminescent device, 1 is shown in Fig.

The present invention also provides an organic electroluminescent device having a laminated structure including a light emitting layer and an electron transporting layer between an anode and a cathode, wherein the electron transporting layer comprises an oxadiazole derivative represented by the above formula (1) An electroluminescent device is provided.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

< Example  1> 2-phenyl-5- (quinolin-3-yl) -1,3,4- Oxadiazole  Produce

Benzoyl hydrazine (10 mmol) and 3-quinolinecarboxaldehyde (10 mmol) were placed in a dry ball mill (Mixer Mill MM400, Retsch) and replaced without solvent for 1 hour. And reacted for 1 hour to obtain the corresponding N-acylhydrazone derivative in a quantitative yield. The N-acylhydrazone derivative (10 mmol) and [bis (trifluoroacetoxy) iodo] benzene (10.1 mmol), which had not been subjected to further purification, were replaced with a mortar. After changing at room temperature, the mixture was put into a vial and heated in an oven at 80 ° C. for about 1 hour until the reaction was completed without closing the lid. Usually, the reaction time is within one hour. After completion of the reaction, the reaction mixture is separated by column chromatography (ethyl acetate: hexane) or recrystallization, and then dried under reduced pressure to obtain the desired compound (yield 97%).

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 9.63 (d, 1H, J = 2.1 Hz), 8.89 (d, 1H, J = 2.0 Hz), 8.23-8.19 (m, 3H), 7.98 (d, 1H, J = 8.0 Hz), 7.84 (dt, 1H, J = 1.4 Hz, J = 7.6 Hz), 7.67 (dt, 1H, J = 1.4 Hz, J = 7.6 Hz), 7.61-7.53 (m, 3H);

¹³ C NMR (75 MHz, CDCl ₃ )? 165.0, 162.8, 149.0, 147.5, 134.6, 132.0, 131.6, 129.6, 129.1, 128.6, 127.9, 127.1, 127.0, 123.5, 117.3.

< Example  2> ( E ) -2-phenyl-5- (1- Phenylprop En-2-yl) -1,3,4- Oxadiazole  Produce

Pure target compound (yield: 94%) was obtained in the same manner as in Example 1 except that alpha-methyl-trans-cinnamaldehyde was used instead of 3-quinolinecarboxaldehyde in the starting material of Example 1.

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 8.14-8.11 (m, 2H), 7.62 (d, 1H, J = 1.3 Hz), 7.56-7.35 (m, 8H), 2.47 (d, 3H, J = 1.5 Hz );

¹³ C NMR (75 MHz, CDCl ₃ )? 166.6, 164.2, 135.4, 134.2, 131.6, 129.5, 128.9, 128.4, 126.8, 123.8, 121.3, 14.5.

< Example  3> ( E ) -2- (4- Methoxyphenyl ) -5- (1- Phenylprop En-2-yl) -1,3,4- Oxadiazole  Produce

The procedure of Example 1 was repeated, except that 4-methoxybenzohydrazide was used instead of benzoyl hydrazine in the starting material of Example 1 to obtain the desired compound (yield: 94%).

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 8.06-8.03 (m, 2H), 7.57 (s, 1H), 7.48-7.40 (m, 4H), 7.36-7.33 (m, 1H), 7.02-7.00 (m, 2H), 3.87 (s, 3H), 2.44 (d, 3H, J = 1.3 Hz);

¹³ C NMR (75 MHz, CDCl ₃ )? 166.1, 164.1, 162.2, 135.6, 133.7, 129.5, 128.6, 128.4, 128.1, 121.5, 116.4, 114.4, 55.3, 14.5.

< Example  4> E ) -2- (2- Methoxystyryl ) -5- (pyridin-3-yl) -1,3,4- Oxadiazole  Produce

Except that nicotonic hydrazide was used instead of benzoyl hydrazine in the starting material of Example 1 and 2-methoxy cinnamaldehyde was used in place of 3-quinolinecarboxaldehyde in the other starting materials of Example 1 The procedure of Example 1 was repeated to obtain pure target compound (yield: 82%).

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 9.36 (d, 1H, J = 1.7 Hz), 8.79 (dd, 1H, J = 4.8 Hz, J = 1.5 Hz), 8.44 (dt, 1H, J = 8.0 Hz, J = 1.9 Hz), 7.94 (d, 1H, J = 16.7 Hz), 7.58 (dd, 1H, J = 7.7 Hz, J = 1.5 Hz), 7.49 1H), 7.39 (td, 1H, J = 8.4 Hz, J = 1.6 Hz), 7.27 (d, 1H, J = 16.5 Hz), 7.03 = 8.3 Hz), 3.96 (s, 3H);

_{^{13 C NMR (75MHz, CDCl 3}} ) δ 165.3, 161.7, 158.0, 152.1, 147.8, 135.3, 144.1, 131.3, 128.6, 123.7, 123.4, 120.8, 120.5, 111.1, 110.1, 55.5.

< Example  5> E ) -2- (1- Phenylprop En-2-yl) -5- (pyridin-3-yl) -1,3,4- Oxadi Manufacture of Azol

Except that nicotonic hydrazide was used instead of benzoyl hydrazine in the starting material of Example 1 and alpha-methyl-trans-cinnamaldehyde was used in place of 3-quinolinecarboxaldehyde in the other starting materials of Example 1 The procedure of Example 1 was repeated to give pure target compound (yield: 91%).

^{1 H NMR (300MHz, DMSO)} δ 9.40 (s, 1H), 8.86 (d, 1H, J = 4.0 Hz), 8.79 (d, 1H, J = 8.2 Hz), 7.83 (td, 1H, J = 8.6 Hz , J = 1.8 Hz), 7.76 (s, 1H), 7.51-7.36 (m, 5H), 2.48 (s, 3H);

¹³ C NMR (75 MHz, CDCl ₃ ) 隆 167.7, 160.4, 147.7, 143.5, 138.1, 136.1, 134.9, 129.6, 128.7, 128.5, 125.8, 122.4, 120.4, 14.5.

< Example  6 > 2- (4- Rat - Butylphenyl ) -5- (2- Nitrophenyl ) -1,3,4- Oxadiazole  Produce

4-tert-butylbenzohydrazide was used instead of benzoyl hydrazine in the starting material of Example 1 and 2-nitrobenzaldehyde was used in place of 3-quinolinecarboxaldehyde in the other starting materials of Example 1 (Yield: 37%). &Lt; tb &gt; &lt; TABLE &gt;

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 8.10 (dd, 1H, J = 7.3 Hz, J = 1.7 Hz), 8.04 (dd, 1H, J = 7.5 Hz, J = 1.7 Hz), 7.99 (d, 2H, J = 8.6 Hz), 7.83-7.72 (m, 2H), 7.54 (d, 1H, J = 8.4 Hz), 1.36 (s, 9H);

¹³ C NMR (75 MHz, CDCl ₃ ) 隆 165.8, 160.9, 155.8, 148.2, 133.0, 132.9, 132.3, 126.9, 126.1, 124.6, 120.5, 118.6, 35.1, 31.1.

< Example  7 > 2- (4- Rat - Butylphenyl ) -5- (quinolin-2-yl) -1,3,4- Oxadiazole  Produce

4-tert-butylbenzohydrazide was used instead of benzoyl hydrazine in the starting material of Example 1 and 2-nitrobenzaldehyde was used in place of 3-quinolinecarboxaldehyde in the other starting materials of Example 1 (Yield: 37%). &Lt; tb &gt; &lt; TABLE &gt;

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 8.10 (dd, 1H, J = 7.3 Hz, J = 1.7 Hz), 8.04 (dd, 1H, J = 7.5 Hz, J = 1.7 Hz), 7.99 (d, 2H, J = 8.6 Hz), 7.83-7.72 (m, 2H), 7.54 (d, 1H, J = 8.4 Hz), 1.36 (s, 9H);

¹³ C NMR (75 MHz, CDCl ₃ ) 隆 165.8, 160.9, 155.8, 148.2, 133.0, 132.9, 132.3, 126.9, 126.1, 124.6, 120.5, 118.6, 35.1, 31.1.

< Comparative Example  1 > 4,4 ' - ( 1E, 1'E ) -2,2'- (1,3,4-oxadiazole-2,5-diyl) bis ( 2-yl) bis (2-methoxyphenol)

(1.2 mmol) of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide and 1.2 mmol of trans-pelubic acid (1 mmol) were added to acetonitrile ) And the mixture was stirred for 30 minutes. Acetonitrile in which hydrazine monohydrate (0.5 mmol) was dissolved was further added thereto, followed by stirring at room temperature for one day. Water was added to terminate the reaction, organic material was extracted with ethyl acetate, and water remaining in the organic layer was removed with MgSO ₄ . And recrystallized to obtain (E) -3- (4-hydroxy-3-methoxyphenyl) -N '- Hydrazide was obtained.

(E) -3- (4-hydroxy-3-methoxyphenyl) acryloyl) acrylate synthesized in the above Lohydrazide was placed in dichloromethane and phosphorus oxychloride (40 mmol) was added and refluxed for one day. Water was added to terminate the reaction, the reaction was neutralized with 1 N sodium hydroxide and the reaction was extracted with dichloromethane. The remaining water was removed with MgSO ₄ . And recrystallized to obtain pure target compound.

_{^{1 H NMR (300MHz, CDCl 3}} ) δ 9.58 (s, 2H), 7.54 (d, 2H, J = 16.3 Hz), 7.40 (d, 2H, J = 1.5 Hz), 7.17 (d, 2H, J = 16.3 (D, 2H, J = 8.0 Hz, J = 1.7 Hz), 6.81 (d, 2H, J = 8.1 Hz), 3.84 (s, 6H);

¹³ C NMR (75 MHz, CDCl ₃ )? 163.5, 148.9, 148.1, 139.1, 126.4, 122.5, 115.6, 110.7, 106.7, 55.8.

< Experimental Example  1> Band gap  Evaluating energy and cyclic voltage and current values

The band gap energy and the cyclic voltammetry value were evaluated in order to determine whether the compound according to the present invention is suitable as an electron transport layer material of an OLED.

(One) Band gap  Energy evaluation

In order to examine the band gap energy, UV-vis absorption and fluorescence spectra of 10 mu M of each of the compounds prepared in Example 1-7 and Comparative Example 1 were measured in an acetonitrile solvent, and the results are shown in Fig. 2-3. In addition, the measured values of FIGS. 2-3 and the band gap energy calculated therefrom are shown in Table 2 below.

2 is a graph showing UV-vis absorption and fluorescence spectra of the compound of Example 1-4 according to the present invention ((a): Example 1 (b): Example 2 (c): Example 3 , (d): Example 4).

3 is a graph showing UV-vis absorption and fluorescence spectra of the compounds of Examples 5-7 and Comparative Example 1 according to the present invention ((a): Example 5, (b): Example 6, (c) : Example 7, (d): Comparative Example 1).

(2) Evaluation of cyclic voltage and current value

The cyclic voltammogram was measured in an acetonitrile solvent containing 0.1 M tetrabutylammonium hexafluorophosphate (Bu ₄ NPF ₆ ). Platinum disk and platinum wire were used as working electrode and counter electrode, respectively. The reference electrode was a silver / nitrated silver (Ag / AgNO ₃ ) electrode. The voltage change rate was 0.1 V / s. The reversible oxidation / reduction reaction took the middle value of each peak voltage, and the irreversible oxidation or reduction reaction took the start voltage of the peak. 4-5 shows a graph of the measured cyclic voltammetry value, and the oxidation potential and the reduction potential are shown in Table 2 below.

4 is a graph showing the cyclic voltammetry values of the compound of Example 1-4 according to the present invention ((a): Example 1 (b): Example 2 (c): Example 3 ): Example 4).

5 is a graph showing the cyclic voltammetry values of the compounds of Examples 5-7 and Comparative Example 1 according to the present invention ((a): Example 5, (b): Example 6, (c) 7, (d): Comparative Example 1).

λ _abs (nm) ? _ems (nm) ? E _g (eV) E _ox (V vs SCE) E _red (V vs SCE) Example 1 336 361 3.70 2.15 -1.55 Example 2 301 366 3.82 1.85 -1.97 Example 3 309 392 3.58 1.69 -1.68 Example 4 334 415 3.37 1.63 -1.74 Example 5 302 391 3.62 1.97 -1.65 Example 6 261 346 4.01 3.06 -0.95 Example 7 341 366 3.62 2.20 -1.63 Comparative Example 1 359 449 3.08 1.26 -1.82

λ _abs : absorption spectrum

λ _ems : fluorescence spectrum

ΔE _g : band gap energy

E _ox : oxidation potential

E _red : reduction potential

As a result, it can be seen that the larger the reduction potential (E _red ) value (i.e., closer to "+"), the easier the electron injection is, and the electron transport layer can be used.

As shown in Table 2, the compounds prepared in Examples 1-7 according to the present invention exhibited similar or better reduction potentials (E _red ) values as compared with the compounds of Comparative Example 1, and thus the organic light emitting diodes It can be seen that the compound can be useful as an electron transport layer of the same organic electroluminescent device.

Claims (11)

An oxadiazole derivative represented by the following Formula 1:
[Chemical Formula 1]

(In the formula 1,
X is carbon or nitrogen;
L is a single bond, C _1-6 linear or branched alkylene or C _1-6 linear or branched alkylenyl;
R ¹ is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-12 aryl is C _1-6 Linear or branched alkyl, C _1-6 straight or branched alkoxy, or -NO ₂ , wherein said 6-12 atom heteroaryl may be fused with a C _6-10 aryl;
R ² is C _6-12 aryl, or 6-12 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said aryl of C _6-12 is C _1-10 Linear or branched alkyl, C _1-6 linear or branched alkoxy, may be substituted.
The method according to claim 1,
X is carbon or nitrogen;
L is a single bond or a C _1-3 straight or branched alkylenyl;
R ¹ is C _6-8 aryl, or 6-8 membered heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-8 aryl is C _1-3 Linear or branched alkoxy of ₁ to 6 carbon atoms, or -NO ₂ , and the 6-12-membered heteroaryl may be fused with a C _6-8 aryl;
R ² is C _6-8 aryl, or 6-8 membered heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, wherein said C _6-12 aryl is C _1-6 Straight-chain or branched-chain alkyl of C _1-3 , straight-chain or branched alkoxy of C _1-3 may be substituted.
The method according to claim 1,
The oxadiazole derivative represented by the above formula (1) is selected from the following group of compounds: oxadiazole derivative:
2-phenyl-5- (quinolin-3-yl) -1,3,4-oxadiazole;
2- (4-tert-butylphenyl) -5- (2-nitrophenyl) -1,3,4-oxadiazole; And
2- (4-tert-butylphenyl) -5- (quinolin-2-yl) -1,3,4-oxadiazole.
The method according to claim 1,
The oxadiazole derivative represented by the above formula (1) is selected from the following group of compounds: oxadiazole derivative:
( E ) -2-phenyl-5- (1-phenylprop-1-en-2-yl) -1,3,4-oxadiazole;
( E ) -2- (4-methoxyphenyl) -5- (1-phenylprop-1-en-2-yl) -1,3,4-oxadiazole;
( E ) -2- (2-methoxystyryl) -5- (pyridin-3-yl) -1,3,4-oxadiazole; And
( E ) -2- (1-phenylprop-1-en-2-yl) -5- (pyridin-3-yl) -1,3,4-oxadiazole.
As shown in Scheme 1 below,
Synthesizing an acylhydrazone compound represented by the formula (4) by reacting a compound represented by the formula (2) and a compound represented by the formula (3) by mechanical pulverization under no solvent conditions (step 1); And
(Step 2) of synthesizing an oxadiazole derivative represented by the formula (1) by an oxidative cyclization reaction by adding an oxidizing agent to the compound represented by the formula (4) obtained in the step 1 under no solvent condition;
(1) &lt; / RTI &gt; wherein &lt; RTI ID = 0.0 &gt;
[Reaction Scheme 1]

(In the above Reaction Scheme 1,
X, L, R ¹ and R ² are the same as defined in the general formula (1).
6. The method of claim 5,
Wherein the mechanical pulverization method of step 1 is a ball mill, attrition mill or rod mill method, and is performed for 1-120 minutes.
6. The method of claim 5,
The iodine-based oxidizing agent is selected from the group consisting of bis (trifluoroacetoxy) iodobenzene (BTI), diacetoxy iodobenzene (DIB), 2-iodoxybenzoic acid (IBX) and des- ). &Lt; / RTI &gt;
6. The method of claim 5,
Wherein the oxidative cyclization reaction of step 2 is carried out by mechanical pulverization for 1-120 minutes and then for 10-120 minutes in an oven at 50-150 ° C.
An electron transport layer comprising an oxadiazole derivative represented by the general formula (1) of claim 1.
10. The method of claim 9,
Wherein the electron transporting layer is one of constituent layers included in the organic electroluminescent device.
An organic electroluminescent device having a laminated structure including a light emitting layer and an electron transporting layer between an anode and a cathode,
Wherein the electron transporting layer comprises an oxadiazole derivative represented by the general formula (1).

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