CN107935936A - Benzimidazole compound and derivative, Organic Electron Transport Material and its preparation and application - Google Patents

Abstract

The invention belongs to the technical field of organic photoelectric functional molecular materials, and discloses benzimidazole compounds and derivatives, organic electron transport materials and their preparation and application. The organic electron transport material comprises at least one kind of benzimidazole compound derivatives, and the structure of the benzimidazole compound derivatives is formula II or formula III. The method is as follows: (a) under a catalytic system, subjecting a benzimidazole compound to a bis-linked pinacol-based diborane for Suzuki reaction, followed by subsequent treatment to obtain a product containing boric acid ester; (b) in a catalytic system, subjecting The product containing borate is coupled with 3-bromo-1,10-phenanthroline or 2-chloro-4,6-diphenyl-1,3,5-triazine respectively, followed by subsequent treatment to obtain benzene and imidazole compound derivatives. The organic electron transport material of the invention has good thermal stability and film shape stability, which is beneficial to improving the stability of devices; the synthesis method is simple and easy to purify.

Description

Benzimidazole compounds and derivatives, organic electron transport materials and their preparation and application

technical field

The present invention relates to small organic molecule functional materials, especially electron transport materials, in particular to a benzimidazole compound and its derivatives, an organic electron transport material and its preparation method and application. The organic electron transport material includes at least one kind of benzimidazole compound derivatives.

Background technique

Organic light-emitting diodes (OLEDs) have important applications in novel electroluminescent displays and lighting. Among them, the high-performance organic molecular electron transport material is the key functional material of OLED, which assists the injection of electrons from the cathode to the light-emitting layer. Amorphous organic electron transport materials with high thermal stability and thin film morphology stability are crucial for obtaining highly stable organic light-emitting diodes.

The design of electron transport materials requires suitable LUMO (beneficial to electron injection) and HOMO energy levels, high thermal stability and thin film morphology stability, good electron transport properties and film-forming properties. So far, a large number of small organic molecule electron transport materials have been reported, but there are generally challenges in the synthesis and purification of organic small molecule electron transport materials with excellent comprehensive properties.

Contents of the invention

In order to overcome the shortcomings and deficiencies of the prior art, the object of the present invention is to provide a benzimidazole compound and a preparation method thereof. The benzimidazole compound of the present invention is easy to synthesize and purify, and can be used to prepare organic functional molecular materials with both high thermal stability and film shape stability, especially organic electron transport materials.

Another object of the present invention is to provide the above-mentioned benzimidazole compound derivatives and a preparation method thereof. The benzimidazole compound derivatives are also easy to synthesize and purify, and have high thermal stability and film shape stability.

Another object of the present invention is to provide an organic electron transport material. The organic electron transport material contains at least one of the above benzimidazole compound derivatives.

Another object of the present invention is to provide applications of the above-mentioned organic electron transport materials. The organic electron transport material is applied in optoelectronic devices such as organic light emitting diodes.

The object of the present invention is achieved through the following technical solutions:

A kind of benzimidazole compound, its structure is formula I:

Wherein, X=Cl, Br or I.

A benzimidazole compound derivative, the structure of which is formula II or formula III;

An organic electron transport material contains at least one kind of benzimidazole compound derivatives. Further, the organic electron transport material is a benzimidazole compound derivative (recorded as PBI-Na-Phen) whose structural formula is formula II, and a benzimidazole compound derivative whose structural formula is formula III (represented as PBI-Na-Trz ) or a mixture of both.

The preparation method of described benzimidazole compound comprises the following steps:

(1) In an organic solvent, the halogenated naphthoic acid is reacted with thionyl chloride, and subsequent treatment is carried out to obtain the intermediate product halogenated naphthoyl chloride; the halogenated naphthoic acid is 6-bromo-2-naphthoic acid, 6 -Chloro-2-naphthoic acid or 6-iodo-2-naphthoic acid; the halogenated naphthoyl chloride corresponds to 6-bromo-2-naphthoyl chloride, 6-chloro-2-naphthoyl chloride or 6-iodo- 2-naphthoyl chloride; the temperature of reaction described in step (1) is 60～80 ℃, and the reaction times is 14～16 hours; The mol ratio of described halogenated naphthoic acid and sulfur oxychloride is 1:(5～ 6); the organic solvent described in step (1) is chloroform or N,N-dimethylformamide;

(2) In an organic solvent, the o-aminodiphenylamine and the halogenated naphthoyl chloride are reacted in an ice-water bath, and the follow-up treatment obtains an unclosed intermediate product; the mol ratio of the o-aminodiphenylamine and the halogenated naphthoyl chloride is 1 :(1.2～1.3);

The organic solvent described in the step (2) is a mixture of dichloromethane and triethylamine or a mixture of tetrahydrofuran and triethylamine, and in the mixture, dichloromethane: triethylamine or tetrahydrofuran: the volume ratio of triethylamine is 4 :1-6:1, the time of the reaction is 10～12 hours;

(3) Carry out the ring-closing reaction of the unclosed intermediate product in step (2), and follow-up treatment to obtain the ring-closed halogen-containing intermediate product, that is, the benzimidazole compound (2-(6-halogen-2-yl)-1-benzene base-1H-benzimidazole); the ring-closing reaction described in step (3) is carried out in glacial acetic acid, and the condition of described reaction is to react at 90-100 ℃ for 12-16 hours.

The follow-up treatment described in step (1) refers to subjecting the reaction product to distillation under reduced pressure.

The follow-up treatment in step (2) refers to subjecting the reaction product to vacuum distillation, dissolving it with an organic solvent, adding water, extracting, drying the organic layer with a desiccant, filtering, vacuum distillation, recrystallization, and suction filtration. The organic solvent is dichloromethane; the water is distilled water or deionized water; the desiccant is anhydrous magnesium sulfate; the recrystallization refers to recrystallization with ethanol.

The follow-up treatment in step (3) refers to subjecting the reaction product to distillation under reduced pressure, dissolving it with an organic solvent, adding water, extracting, drying the organic layer with a desiccant, filtering, distillation under reduced pressure, and separating by column chromatography. The organic solvent is dichloromethane; the water is distilled water or deionized water; the desiccant is anhydrous magnesium sulfate.

The reactions in steps (2) and (3) are carried out under an inert atmosphere.

The preparation method of described benzimidazole compound derivative, comprises the following steps:

(a) Under the catalytic system, suzuki the benzimidazole compound (2-(6-halogen-2-yl)-1-phenyl-1H-benzimidazole) and double pinacol base diborane Coupling reaction (Suzuki reaction), follow-up treatment, obtains the product containing borate; The condition of reaction described in step (a) is 80～90 ℃ of reaction 3～4h; Described benzimidazole compound (closed halogen-containing The molar ratio of the intermediate product 2-(6-halogen-naphthalene-2-yl)-1-phenyl-1H-benzimidazole) to the double pinacol base diborane is 1: (1.4～1.5); Catalyst system comprises palladium catalyst, and described palladium catalyst is bis(triphenylphosphine) palladium dichloride; The molar ratio of -phenyl-1H-benzimidazole) and palladium catalyst is 1: (0.03～0.04); Described reaction takes organic solvent as reaction medium, and described organic solvent is conventional organic solvent, is preferably tetrahydrofuran; Described The catalytic system also includes a basic compound, which is preferably potassium acetate;

(b) In the catalytic system, the borate-containing product of step (a) is mixed with 3-bromo-1,10-phenanthroline or 2-chloro-4,6-diphenyl-1,3, The 5-triazine is subjected to coupling reaction and subsequent treatment to obtain benzimidazole compound derivatives with two structures respectively.

The mol ratio of the product containing borate described in step (b) to 3-bromo-1,10-phenanthroline or 2-chloro-4,6-diphenyl-1,3,5-triazine is 1: (1～1.2);

The catalytic system described in step (b) comprises catalyst, and described catalyst is palladium catalyst, and described palladium catalyst is palladium acetate and tricyclohexylphosphine (or tetrakis (triphenylphosphine) palladium); Described catalytic system also comprises alkali An alkaline aqueous solution and a phase transfer agent, the alkaline aqueous solution is potassium carbonate solution or sodium carbonate aqueous solution, and the phase transfer agent is ethanol;

The conditions of the coupling reaction in step (b) are 90-100° C. for 10-12 hours, and the reaction uses an organic solvent as the reaction medium, and the organic solvent is preferably toluene.

The follow-up treatment in step (a) refers to distilling the reaction product under reduced pressure, dissolving it with an organic solvent, adding water, extracting, drying the organic layer with a desiccant, filtering, distilling under reduced pressure, and separating by column chromatography. The organic solvent is dichloromethane; the water is distilled water or deionized water; the desiccant is anhydrous magnesium sulfate.

The follow-up treatment in step (b) refers to adding a water layer to the reaction product, extracting the water layer with an organic solvent, drying the organic layer with a desiccant, filtering, distilling under reduced pressure, and separating by column chromatography. The organic solvent is dichloromethane; the water is distilled water or deionized water; the desiccant is anhydrous magnesium sulfate.

The reactions in steps (a) and (b) are carried out under an inert atmosphere.

The organic small molecule electron transport material is used for preparing organic electroluminescent devices, as the electron transport of organic electroluminescent devices.

Principle of the present invention is as follows:

The naphthyl-substituted electron-deficient benzimidazole structural unit (i.e. benzimidazole compound) of the present invention is coupled with a common electron-deficient unit 1,10-phenanthroline or 1,3,5-triazine to endow the target product ( Derivatives are used as electron transport materials) with excellent electron transport properties; the use of 2,6-position naphthyl as a bridging group enhances the rigidity of the molecule and helps to improve the thermal stability of the material and the shape stability of the film.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The organic small molecule electron transport material (benzimidazole compound derivative) of the present invention adopts 2,6-position naphthyl bridging group, which enhances the rigid structure of the target compound and improves the thermal stability and film morphology of the material Stability, which is conducive to enhancing the long-term stability of organic light-emitting diode devices;

(2) With respect to 3-(4-(1-phenyl-1H-benzimidazol-2-yl)phenyl)-1,10-phenanthroline (PBI-p-Phen), the benzo of the present invention The imidazole compound derivative PBI-Na-Phen has better film stability, although the thermal decomposition temperature and glass transition temperature of the two are similar; specifically, the material PBI-p-Phen, from the molten state, enters the amorphous state after cooling, However, when the temperature was raised to about 180°C, it began to crystallize; and under the same circumstances, the PBI-Na-Phen of the present invention entered an amorphous state from a molten state after cooling, and when the temperature was raised to 300°C, no crystallization was found;

(3) Relative to 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole (Li Chong, A triazine-based derivative compound and its application on OLED, Chinese invention patent application number: 201210311281.3), the glass transition temperature of the benzimidazole compound derivative PBI-Na-Trz of the present invention is 115 ° C, and the crystallization temperature is 183°C, all higher than 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole, indicating PBI -Na-Trz has better film shape stability; at the same time, PBI-Na-Trz has a higher decomposition temperature;

(3) The benzimidazole compound of the present invention and the benzimidazole compound derivative used as an organic small molecule electron transport material are simple to synthesize and easy to purify, which is beneficial to meet the actual application requirements of OLED devices.

Description of drawings

Fig. 1a is the H NMR spectrum of 2-(6-bromonaphthalene-2-yl)-1-phenyl-1H-benzimidazole (i.e. benzimidazole compound) of Example 1;

Fig. 1 b is the proton nuclear magnetic resonance spectrum figure of the small organic molecule electron transport material PBI-Na-Phen of embodiment 2;

Fig. 2 a is the thermogravity curve of the small organic molecule electron transport material PBI-Na-Phen of embodiment 2;

Fig. 2b is the differential scanning calorimetry curve of the organic small molecule electron transport material PBI-Na-Phen of embodiment 2;

Fig. 3 is the ultraviolet-visible absorption and phosphorescence emission spectrum of the organic small molecule electron transport material PBI-Na-Phen of embodiment 2;

Fig. 4 is the proton nuclear magnetic resonance spectrum figure of the small organic molecule electron transport material PBI-Na-Trz of embodiment 3;

Fig. 5 a is the thermal weight loss curve of the small organic molecule electron transport material PBI-Na-Trz of embodiment 3;

Fig. 5 b is the differential scanning calorimetry curve of the organic small molecule electron transport material PBI-Na-Trz of embodiment 3;

Fig. 6 is the ultraviolet-visible absorption and phosphorescence emission spectrum of the organic small molecule electron transport material PBI-Na-Trz of embodiment 3;

Figures 7a and 7b are respectively the existing material 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole The thermogravimetric curve (Figure 7a) and differential scanning calorimetry curve (Figure 7b) of the.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto.

Embodiment 1 benzimidazole compound

A benzimidazole compound (2-(6-bromonaphthalene-2-yl)-1-phenyl-1H-benzimidazole), its structure is as follows:

The preparation method of described benzimidazole compound comprises the following steps:

S1: Preparation of 6-bromo-2-naphthoyl chloride (1), the reaction equation is as follows:

Under ice bath conditions, 6-bromo-2-naphthoic acid (5.0g, 19.91mmol) and thionyl chloride (14.2g, 119.48mmol) were added to a certain amount of chloroform (30ml), and the reaction was stirred at 60°C for 14 After ~16 hours, after the reaction was completed, chloroform was distilled off under reduced pressure to obtain 6-bromo-2-naphthoyl chloride (compound 1) as a white solid.

S2: Preparation of 6-bromo-N-(2-(phenylamino)phenyl)-2-naphthylcarboxamide (2), the reaction equation is as follows:

6-Bromo-2-naphthoyl chloride (compound 1) (5.36g, 19.91mmol) and o-aminodiphenylamine (3.0g, 16.59mmol) were dissolved in a mixed solvent of dichloromethane and triethylamine (50ml, 4: 1v/v), under _N2 atmosphere, the reaction was stirred in an ice bath for 10-12 hours. After the reaction was completed, dichloromethane and triethylamine were distilled off under reduced pressure, dissolved in dichloromethane, distilled water was added and extracted with dichloromethane. The obtained organic layer was dried with anhydrous magnesium sulfate and filtered, dichloromethane was distilled off under reduced pressure, the obtained crude product was recrystallized from ethanol, and filtered by suction to obtain a white solid 6-bromo-N-(2-(phenylamino)benzene base)-2-naphthylcarboxamide (compound 2), yield 54.5% (3.7g);

S3: Preparation of 2-(6-bromonaphthalene-2-yl)-1-phenyl-1H-benzimidazole (3), the reaction equation is as follows:

Compound 2 (3.7g, 8.86mmol) was dissolved in glacial acetic acid (50ml), stirred and reacted at 100°C for 12-16 hours under _N2 atmosphere. Distilled water was added and extracted with dichloromethane, the organic layer was dried with anhydrous magnesium sulfate and filtered, dichloromethane was distilled off under reduced pressure, and the obtained crude product was separated by column chromatography to obtain a white solid 2-(6-bromonaphthalene- 2-yl)-1-phenyl-1H-benzimidazole (compound 3), yield 84.7% (3.0 g).

The H NMR spectrum of 2-(6-bromonaphthalene-2-yl)-1-phenyl-1H-benzimidazole (i.e. benzimidazole compound) of the present embodiment (Example 1) is shown in Figure 1a .

Example 2: Organic Electron Transport Materials

An organic small molecule electron transport material (PBI-Na-Phen) with high thermal stability and thin film morphology stability is a benzimidazole compound derivative with the following structure:

The preparation method of described organic small molecule electron transport material (PBI-Na-Phen), comprises the following steps:

T1: 1-phenyl-2-(6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)naphthalen-2-yl)- The preparation of 1H-benzimidazole (4), reaction equation is as follows:

2-(6-bromonaphthalene-2-yl)-1-phenyl-1H-benzimidazole (compound 3) (3.0g, 7.51mmol) and biborpinacol ester (2.86g, 11.27mmol) and potassium acetate (2.21g, 22.53mmol) were added to a certain amount of tetrahydrofuran (60ml), and under _N2 atmosphere, bistriphenylphosphine palladium dichloride (158mg, 0.225mmol) was added, and at 80°C Stir the reaction for 3 to 4 hours. After the reaction is over, distill off the tetrahydrofuran under reduced pressure, dissolve it with dichloromethane, add distilled water and extract it with dichloromethane. The obtained organic layer is dried with anhydrous magnesium sulfate and filtered, distilled off under reduced pressure Chloromethane, the obtained crude product was separated by column chromatography to obtain 1-phenyl-2-(6-(4,4,5,5-tetramethyl-1,3,2-dioxaborin as a white solid Cyclopentan-2-yl)naphthalen-2-yl)-1H-benzimidazole (compound 4), yield 86.56% (2.9g);

T2: Preparation of 3-(6-(1-phenyl-1H-benzimidazol-2-yl)naphthalene-2-yl)-1,10-phenanthroline (PBI-Na-Phen), the reaction equation is as follows :

Compound 4 (1.5g, 3.36mmol) and 3-bromo-1,10-phenanthroline (0.95g, 3.67mmol) were dissolved in toluene (50ml), and an appropriate amount of ethanol (6ml) and potassium carbonate aqueous solution (2M, 4ml, 8mmol), under N Atmosphere, add palladium acetate (15mg, _0.067mmol ) and tricyclohexyl phosphorus (75mg, 0.13mmol), stir and react at 90 ℃ for 10～12 hours; Distilled water was added to the mixture to separate the toluene layer, the aqueous layer was extracted with dichloromethane, the extracted organic layer was dried over anhydrous magnesium sulfate and filtered, the dichloromethane was distilled off under reduced pressure, and the obtained crude product was separated by column chromatography to obtain White solid organic molecular electron transport material (PBI-Na-Phen), yield 83.58% (1.4g).

Structural characterization and performance testing of the small organic molecule electron transport material PBI-Na-Phen prepared in Example 2 below:

(1) Proton NMR spectrum

¹ H NMR (500MHz, DMSO) δ9.58 (d, J = 2.3Hz, 1H), 9.14 (dd, J = 4.3, 1.7Hz, 1H), 8.93 (d, J = 2.3Hz, 1H), 8.56 ( s,1H),8.52(dd,J=8.1,1.7Hz,1H),8.19(s,1H),8.15(dd,J=8.5,1.8Hz,1H),8.10(d,J=8.9Hz,1H ),8.07–8.00(m,3H),7.87(d,J＝7.5Hz,1H),7.79(dd,J＝8.0,4.3Hz,1H),7.69(dd,J＝8.5,1.7Hz,1H) ,7.64–7.56(m,3H),7.54–7.50(m,2H),7.35(dtd,J=15.0,7.1,1.2Hz,2H),7.28(d,J=7.6Hz,1H).

FIG. 1 b is the H NMR spectrum of the small organic molecule electron transport material PBI-Na-Phen of Example 2.

(2) Thermodynamic properties

Thermogravimetric analysis (TGA) was measured on a TGA2050 (TA instruments) thermogravimetric analyzer with nitrogen protection at a heating rate of 20°C/min; differential scanning calorimetry (DSC) used a NETZSCH DSC204F1 thermal analyzer, under nitrogen In the atmosphere, start from -30°C with a heating rate of 10°C/min to 320°C, then cool down at 20°C/min to -30°C, keep the temperature for 5 minutes, and test again at a heating rate of 10°C/min to 320°C. The test results are shown in Figure 2. Figure 2a is the thermogravimetric curve of the small organic molecule electron transport material PBI-Na-Phen prepared in Example 2, and Figure 2b is the organic small molecule electron transport material PBI-Na-Phen prepared in Example 2. Differential scanning calorimetry curve of Phen.

The thermal weight loss curve in Figure 2a shows that the temperature at which PBI-Na-Phen loses 5% of its weight is 399°C, and it has high thermal stability.

The differential scanning calorimetry curve in Figure 2b shows that in the first round of heating, the high temperature resistant functional material PBI-Na-Phen has an obvious melting peak, while in the first round of cooling and the second round of heating, PBI-Na- Phen does not appear crystallization peak and melting peak, and shows obvious glass transition, the corresponding glass transition temperature is 127 ℃. Compared to the crystalline material PBI-p-Phen (3-(4-(1-phenyl-1H-benzimidazol-2-yl)phenyl)-1,10-phenanthroline), PBI-Na-Phen It can form a stable amorphous form and has good film shape stability.

(3) Photophysical properties

3 is the ultraviolet-visible absorption and phosphorescence emission spectra of the small organic molecule electron transport material PBI-Na-Phen prepared in Example 2. From the absorption spectrum in Figure 3, the optical bandgap can be determined to be 3.1eV according to the absorption edge; the singlet energy level E _s =2.80eV can be calculated from the emission spectrum.

Embodiment 3 organic electron transport material

An organic small molecule electron transport material (PBI-Na-Trz) with high thermal stability and thin film morphology stability is a benzimidazole compound derivative with the following structure:

The preparation method of described organic small molecule electron transport material (PBI-Na-Trz), comprises the following steps:

(1) 1-phenyl-2-(6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)naphthalene-2-yl) -1H-benzimidazole (compound 4): this step is the same as in Example 2;

(2) 2-(6-(4,6-diphenyl-1,3,5-triazin-2-yl)naphthalene-2-yl)-1-phenyl-1H-benzimidazole (PBI- Na-Trz) preparation, reaction equation is as follows:

Compound 4 (1.4g, 3.15mmol) and 2-chloro-4,6-diphenyl-1,3,5-triazine (0.90g, 3.36mmol) were dissolved in toluene (50ml), and an appropriate amount of ethanol ( 6ml) and potassium carbonate aqueous solution (2M, 4ml, 8mmol), under N ₂ atmosphere, add tetrakis (triphenylphosphine) palladium, stir and react at 90°C for 10-12 hours; after the reaction is completed, add Distilled water to separate the toluene layer, extracted the water layer with dichloromethane, dried the extracted organic layer with anhydrous magnesium sulfate, filtered, distilled off the dichloromethane under reduced pressure, and separated the obtained crude product by column chromatography. A mixed solvent of dichloromethane and ethyl ether (2:1 v/v) was used to obtain a white solid organic small molecule electron transport material (PBI-Na-Trz), with a yield of 86.48% (1.6g).

Structural characterization and performance testing of the small organic molecule electron transport material PBI-Na-Trz prepared in Example 3 with high thermal stability and film shape stability:

(1) Proton NMR spectrum

¹ H NMR (500MHz, DMSO) δ9.37 (d, J = 0.6Hz, 1H), 8.79 (ddd, J = 7.6, 4.3, 1.4Hz, 5H), 8.30–8.18 (m, 2H), 8.04 (d ,J＝8.8Hz,1H),7.91–7.83(m,1H),7.78–7.72(m,3H),7.71–7.67(m,4H),7.65–7.57(m,3H),7.56–7.49(m ,2H),7.36(dtd,J=14.9,7.1,1.2Hz,2H),7.28(dd,J=7.3,0.9Hz,1H).

FIG. 4 is the hydrogen nuclear magnetic resonance spectrum of the small organic molecule electron transport material PBI-Na-Trz of Example 3.

(2) Thermodynamic properties

Thermogravimetric analysis (TGA) was measured on a TGA2050 (TA instruments) thermogravimetric analyzer with nitrogen protection at a heating rate of 20°C/min; differential scanning calorimetry (DSC) used a NETZSCH DSC204F1 thermal analyzer, under nitrogen In the atmosphere, start from -30°C with a heating rate of 10°C/min to 300°C, then cool down at 20°C/min to -30°C, keep the temperature for 5 minutes, and test again at a heating rate of 10°C/min to 300°C. The test results are shown in Figure 5. Figure 5a is the thermogravimetric curve of the small organic molecule electron transport material PBI-Na-Trz of Example 3; Figure 5b is the differential scanning calorimetry curve of the organic small molecule electron transport material PBI-Na-Trz of Example 3.

It can be seen from the thermogravimetric curve in Figure 5a that the temperature of PBI-Na-Trz at 5% weight loss is 402°C, compared to the material 2-(4-(4,6-diphenyl-1,3,5-triazine- 2-yl)phenyl)-1-phenyl-1H-benzimidazole, whose decomposition temperature is 373°C (Figure 7a), and PBI-Na-Trz has high thermal stability.

The differential scanning calorimetry curve in Figure 5b shows that the organic small molecule electron transport material PBI-Na-Trz melts after the first round of heating, and then enters the glass state after cooling, and the corresponding glass transition temperature is 115 °C; During the round heating, a crystallization peak appeared, and the crystallization temperature was 183°C. And under the same situation, 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole, the crystallization temperature is 174°C, the glass transition temperature is 104°C. Therefore, PBI-Na-Trz has better film morphology stability.

Figures 7a and 7b are respectively the existing material 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole The thermogravimetric curve (Figure 7a) and differential scanning calorimetry curve (Figure 7b) of the.

The structure of the existing material 2-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzimidazole material is:

(3) Photophysical properties

FIG. 6 is the ultraviolet-visible absorption and phosphorescence emission spectra of the small organic molecule electron transport material PBI-Na-Trz of Example 3. FIG. From the absorption spectrum in Figure 6, the optical bandgap can be determined to be 3.02eV according to the absorption edge; the singlet energy level E _s =2.70eV can be calculated from the emission spectrum.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (10)

1. A benzimidazole compound, characterized in that: its structure is formula I: Wherein, X=Cl, Br or I. 2. according to the preparation method of the described benzimidazole compound of claim 1, it is characterized in that: comprise the following steps: (1) In an organic solvent, the halogenated naphthoic acid is reacted with thionyl chloride, and subsequent treatment is carried out to obtain the intermediate product halogenated naphthoyl chloride; the halogenated naphthoic acid is 6-bromo-2-naphthoic acid, 6 -Chloro-2-naphthoic acid or 6-iodo-2-naphthoic acid; the halogenated naphthoyl chloride corresponds to 6-bromo-2-naphthoyl chloride, 6-chloro-2-naphthoyl chloride or 6-iodo- 2-naphthoyl chloride; the molar ratio of said halogenated naphthoic acid to thionyl chloride is 1: (5～6); (2) In an organic solvent, the o-aminodiphenylamine and the halogenated naphthoyl chloride are reacted in an ice-water bath, and the follow-up treatment obtains an unclosed intermediate product; the mol ratio of the o-aminodiphenylamine and the halogenated naphthoyl chloride is 1 :(1.2～1.3); (3) Carrying out a ring-closing reaction on the unclosed intermediate product in step (2), followed by subsequent treatment to obtain a ring-closed halogen-containing intermediate product, namely a benzimidazole compound. 3. according to the preparation method of the described benzimidazole compound of claim 2, it is characterized in that: the temperature of reaction described in step (1) is 60～80 ℃, and the reaction times is 14～16 hours; The organic solvent is chloroform or N,N-dimethylformamide; The organic solvent described in the step (2) is a mixture of dichloromethane and triethylamine or a mixture of tetrahydrofuran and triethylamine, and in the mixture, dichloromethane: triethylamine or tetrahydrofuran: the volume ratio of triethylamine is 4 :1～6:1, the time of described reaction is 10～12 hours; The ring-closing reaction in step (3) is carried out in glacial acetic acid, and the condition of the reaction is to react at 90-100° C. for 12-16 hours. 4. A benzimidazole compound derivative, characterized in that: its structure is formula II or formula III; 5. according to the preparation method of the described benzimidazole compound derivative of claim 4, it is characterized in that: comprise the following steps: (a) Under the catalytic system, the benzimidazole compound and the double-linked pinacol-based diborane are subjected to Suzuki reaction, followed by subsequent treatment to obtain a product containing borate; the benzimidazole compound is as defined in claim 1 ; (b) In the catalytic system, the borate-containing product of step (a) is mixed with 3-bromo-1,10-phenanthroline or 2-chloro-4,6-diphenyl-1,3, The 5-triazine is subjected to coupling reaction and subsequent treatment to obtain benzimidazole compound derivatives with two structures respectively. 6. according to the preparation method of the described benzimidazole compound derivative of claim 5, it is characterized in that: the condition of reaction described in step (a) is 80～90 ℃ of reaction 3～4h; Described benzimidazole compound and bis The mol ratio of joint pinacol base diborane is 1:(1.4～1.5); The catalytic system described in step (a) comprises palladium catalyst; The mol ratio of described benzimidazole compound and palladium catalyst is 1:(0.03 ～0.04); The reaction takes an organic solvent as the reaction medium; The catalytic system also includes a basic compound; The mol ratio of the product containing borate described in step (b) to 3-bromo-1,10-phenanthroline or 2-chloro-4,6-diphenyl-1,3,5-triazine is 1: (1～1.2); The catalytic system described in the step (b) includes a catalyst, the catalyst is a palladium catalyst, and the catalytic system described in the step (b) also includes an alkaline aqueous solution and a phase transfer agent; The condition of the coupling reaction in the step (b) is 90-100° C. for 10-12 hours, and the reaction uses an organic solvent as a reaction medium. 7. according to the preparation method of the described benzimidazole compound derivative of claim 6, it is characterized in that: the palladium catalyst described in step (a) is two (triphenylphosphine) palladium dichloride; The basic compound is potassium acetate; The palladium catalyst described in the step (b) is a mixture of palladium acetate and tricyclohexylphosphine or tetrakis (triphenylphosphine) palladium); the alkaline aqueous solution described in the step (b) is potassium carbonate solution or sodium carbonate aqueous solution, so The phase transfer agent is ethanol. 8. An organic electron transport material comprising at least one of the benzimidazole compound derivatives described in claim 4. 9. according to the described organic electron transport material of claim 8, it is characterized in that: it is the benzimidazole compound derivative of formula II, the benzimidazole compound derivative of formula III or the mixture of both; The benzimidazole compound derivative of formula II Compound derivatives and benzimidazole compound derivatives of formula III are as defined in claim 4. 10. The application of the organic electron transport material according to claim 8 or 9, characterized in that: the organic electron transport material is used for preparing an organic electroluminescent device.