CN110183441B - Preparation method of OLED electron transport material NBphen - Google Patents

Abstract

The invention discloses a preparation method of an OLED electron transport material NBphen. The preparation method comprises the following steps: (1) under the existence of protective gas and a first organic solvent, carrying out contact reaction on 2-bromonaphthalene and metal lithium to obtain a 2-lithium naphthalene organic solution; (2) carrying out contact reaction on a Bphen organic solution and a 2-lithium naphthalene organic solution in the presence of protective gas to obtain a reaction mixture; (3) carrying out hydrolysis reaction on the reaction mixture and water to obtain an oil-water mixture; (4) and extracting an organic phase in an aqueous layer of the oil-water mixture, and then carrying out contact reaction on the organic phase and an oxidant to obtain the NBphen. The method of the invention does not need to be cooled to-78 ℃, the reaction is more convenient and the energy is saved; the reaction has high safety and is convenient for mass preparation.

Description

A kind of preparation method of OLED electron transport material NBphen

technical field

The invention belongs to the technical field of electron transport material synthesis, and more particularly relates to a preparation method of an OLED electron transport material NBphen.

Background technique

In recent years, organic optoelectronic materials represented by organic light-emitting diodes (OLEDs) have shown great commercial application prospects and are widely used in flat panel displays and lighting [J.Smith,E.Bawolek,Y.K. Lee, Electron. Lett., 2015, 51(17), 1312.], has attracted widespread attention from academia and industry. Organic light-emitting materials are an important part of the construction of OLED devices, and the development of new high-efficiency organic light-emitting materials plays a decisive role in improving the performance of OLED devices [Chen Bin, Zhao Zujin, Tang Benzhong. Science Bulletin, 2016, 61(32), 3435 .].

Early OLED devices usually adopt a single-layer structure, and the electron transport, hole transport and light-emitting materials are concentrated in one material, and the brightness is extremely low. In 1987, Deng Qingyun's research group introduced a double-layer device, using Alq ₃ as the electron transport and the light ^- emitting layer, and TPD as the hole transport layer. Appl. Phys. Lett., 1987, 51(12), 913.]. In 1988, Japan proposed a three-layer structure, and the electron transport, luminescence, and hole transport of the device consisted of different materials [C.Adachi, S.Tokito, T.Tsutsui, JpnJ.Appl.Phys., 1988, 27 ( 2), L269.]. Today, with the application of various doping methods and new materials, researchers have been able to develop more diverse device structures, thereby greatly improving the luminescence performance of OLEDs. Electron injection can be performed between metal electrodes and ITO. layer, electron transport layer, organic light-emitting layer, hole transport layer, hole injection layer, etc.

In OLED devices, the mobility of most hole transport materials is 10 ^-3 to 10 ^-4 cm ² /(V·s), while the mobility of electron transport materials is usually 10 ^-4 to 10 ^-6 cm ² / (V·s) [ZQ Zhang, Q. Wang, YFDai, Org. Electron., 2009, 10(3), 491.]. One of the main reasons for the low efficiency and poor stability of the device is the low electron mobility of electron transport materials, poor transport ability, and mismatch with hole materials with strong transport ability. In order to enhance the electron transport ability, build a balance between electrons and holes, and thus improve the performance of OLED devices, it is required to use electron transport materials with higher mobility and more stable performance, and to construct an electron transport layer with a reasonable structure and matching energy levels.

Materials used to make the electron transport layer must have high film-forming stability, thermal stability and electron transport properties. Common electron transport materials include Alq ₃ , Liq, PBD, Bebq, TAZ, Bphen, etc., and their chemical structures are shown in Formula 1 below, respectively. Recent studies have shown that devices using Bphen and other materials doped as electron transport layers have 3.5 times higher brightness and 1.1 to 2.5 times higher current efficiency compared to traditional devices [Yuan Taoli, Wang Xiufeng, Mu Qiang. Optical Journal, 2017, 38(8), 1069.], indicating that Bphen and its derivatives are a class of excellent electron transport materials.

As a derivative of Bphen, NBphen (2,9-bis(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline, 2,9-bis(naphthalen-2-yl)-4 ,7-diphenyl-1,10-phenanthroline) is a new type of electron transport material whose molecular structure is shown in Equation 2 below. NBphen has better thermal stability than Bphen. Its glass transition temperature is 105°C, and Bphen is 63°C; in thermogravimetric analysis, the thermal weight loss of NBphen reaches 0.5% at 370°C, while that of Bphen is 260°C. Relevant studies have confirmed that the n-type electron transport layer formed by NBphen and commonly used doping materials such as Cs-based derivatives can improve the electron transport efficiency and also have the advantages of easy evaporation and so on. It can reach 39820cd·m ^-2 , which is obviously better than the brightness of traditional devices under the same conditions (25000cd·m ^-2 ) [L.-Y.Shen, X.-M.Wu, Y.-L.Hua, Acta Phys. - Chim. Sin., 2012, 28(6), 1497.].

With the advent of the commercialization of OLED materials, the market prospect of NBphen as an electron transport material is very broad, but its preparation method has not been reported in the open literature, and the number of related foreign patents is very small, and the traditional butyl Lithium route, the synthetic method is shown in the following formula 3, the disadvantage of this method is that butyllithium is a dilute solution, which cannot exist stably in the air and is flammable and explosive. The reaction is cumbersome and dangerous, and is only suitable for multiple small preparations in the laboratory.

现有国外专利中NBphen的合成路线

Synthetic route of NBphen in existing foreign patents

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of synthetic method of OLED electron transport material NBphen, in order to overcome the flammable and explosive butyllithium existing in the traditional butyllithium route, the reaction needs to be strictly anaerobic and anhydrous operation so that the reaction needs to be at -78 ℃ The problems of cumbersome and high-risk operations such as performing at low temperature make the preparation method convenient and efficient, which is beneficial to large-scale preparation.

In order to achieve the above purpose, the present invention provides a preparation method of an OLED electron transport material NBphen, the preparation method comprising:

(1) in the presence of protective gas and the first organic solvent, 2-bromonaphthalene and metallic lithium are carried out contact reaction to obtain 2-lithium naphthalene organic solution;

(2) in the presence of protective gas, the Bphen organic solution and the 2-lithium naphthalene organic solution are subjected to a contact reaction to obtain a reaction mixture;

(3) hydrolysis reaction is carried out with described reaction mixture and water, obtain oil-water mixture;

(4) extracting the organic phase in the water layer of the oil-water mixture, and then contacting and reacting the organic phase with an oxidizing agent to obtain the NBphen.

The technical scheme of the present invention has the following beneficial effects:

(1) the method of the present invention uses metal lithium to replace organic lithium reagents such as n-butyl lithium (tert-butyl lithium) to carry out lithiation reaction to 2-bromonaphthalene, and metal lithium can be easily weighed and processed in the air; lithium The lithiation reaction can be carried out at 0 to 50 °C without cooling to -78 °C, which makes the reaction more convenient and saves energy; even if the lithiation reaction solution comes into contact with air, it will not burn like butyllithium, which increases the risk of burning. The safety of the reaction is convenient for large-scale preparation;

(2) The method of the present invention has simple operation and post-processing steps, does not need to be purified by column chromatography, and is suitable for industrial production;

(3) In the prior art, butyllithium is used for the reaction, and the overall yield of NBphen is only 50-70%, while in the method of the present invention, the overall yield of NBphen can reach 89-92%.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Detailed ways

Preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention are described below, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

The invention provides a preparation method of OLED electron transport material NBphen, the preparation method comprises:

(1) in the presence of protective gas and the first organic solvent, 2-bromonaphthalene and metallic lithium are carried out contact reaction to obtain 2-lithium naphthalene organic solution;

(2) in the presence of protective gas, the Bphen organic solution and the 2-lithium naphthalene organic solution are subjected to a contact reaction to obtain a reaction mixture;

(3) hydrolysis reaction is carried out with described reaction mixture and water, obtain oil-water mixture;

(4) extracting the organic phase in the water layer of the oil-water mixture, and then contacting and reacting the organic phase with an oxidizing agent to obtain the NBphen.

According to the present invention, preferably, the Bphen organic solution is a Bphen organic solution after degassing.

According to the present invention, preferably, in step (1), the first organic solvent is at least one of ether, tetrahydrofuran, benzene, toluene, dichloromethane, chloroform, DMF and carbon tetrachloride; the first organic solvent is The organic solvent is a dry first organic solvent;

The 2-bromonaphthalene is added dropwise to the reaction vessel in the form of an organic solution of 2-bromonaphthalene formed by 2-bromonaphthalene and the first organic solvent; wherein, in the organic solution of the 2-bromonaphthalene, 2-bromonaphthalene is The mass ratio of naphthalene to the first organic solvent is 1:3-10;

The reaction temperature of the contact reaction is 25-45° C., and the reaction time is 1-8 h.

According to the present invention, preferably, in the organic solution of 2-bromonaphthalene, the mass ratio of 2-bromonaphthalene to the first organic solvent is 1:4-5.

In the present invention, in step (1), the reactant metal lithium is added in excess, and after the reaction is completed, the excess metal lithium is removed by filtration.

According to the present invention, preferably, in step (2), the solvent used in the Bphen organic solution is at least one of ether, tetrahydrofuran, benzene, toluene, dichloromethane, chloroform, DMF and carbon tetrachloride, and the The solvent is a dry solvent, and the mass ratio of Bphen to the solvent is 1:3-6;

The molar ratio of Bphen to 2-lithium naphthalene is 1:2-5, preferably 1:2.5;

The contact reaction is to first react at 0° C. for 1-8 hours, and then raise the temperature to 40-60° C. to continue the reaction for 8-12 hours.

According to the present invention, preferably, the mass ratio of the Bphen to the solvent is 1:8-10.

According to the present invention, preferably, in step (3), the reaction mixture is cooled to 0° C., and then subjected to a hydrolysis reaction with water.

In the present invention, in step (3), water is preferably deionized water, and water is added in excess.

According to the present invention, preferably, in step (4), the oxidant is at least one of manganese dioxide, SeO ₂ , dichlorodicyanoquinone (DDQ) and potassium permanganate; preferably manganese dioxide;

The extraction is performed with dichloromethane;

The reaction temperature of the contact reaction is 20-50° C., and the reaction time is 6-12 h.

In the present invention, in step (4), the extraction is preferably performed multiple times; the oxidant is added in excess; the reaction progress degree of the contact reaction in step (4) is preferably monitored by TLC.

According to the present invention, preferably, the protective gas is nitrogen.

In the present invention, after the reaction is completed, the solid matter is removed by filtration, the filtrate is concentrated and the resulting pale yellow solid is collected by filtration, washed with cold ethanol, dried and recrystallized in ethanol to obtain the target product.

In the present invention, each raw material used for preparing NBphen can be obtained commercially.

In the preparation method of NBphen of the present invention, theoretically, every 1g of metal lithium sheet is used, which can replace 70ml 2mol/l butyllithium solution, or 90ml 1.6mol/l butyllithium solution, under laboratory conditions, no need The special reaction vessel can conveniently operate the reaction of 5-10g metal lithium scale, and each time 30-60g of NBphen product is obtained, which not only reduces the cost of raw materials, but also facilitates pilot scale-up. If the reactor is used for operation, the preparation scale can be increased to the kilogram level by simply scaling up.

The present invention is further illustrated below by embodiment:

The synthetic routes for the reactions of the following examples are shown in formula I.

Example 1

The present embodiment provides a method for preparing an OLED electron transport material NBphen, which specifically includes the following steps:

(1) Under nitrogen protection, a dry ether solution (30 ml) of 2-bromonaphthalene (8.28 g, 40 mmol) was added to a dropping funnel containing 1.3 g of chopped metal lithium chips and 20 ml of dry ether at 25° C. within 2 h. In a 100ml round-bottomed flask of diethyl ether, continue stirring at 25°C for 2h after dropping, and filter to remove the remaining solid materials such as metal lithium flakes to obtain 2-lithium naphthalene organic solution;

(2) Dissolve Bphen (3.32 g, 10 mmol) in 20 ml of dry ether, cool down to 0° C. with an ice-water bath after three cycles of degassing, and add the above 2- Lithium naphthalene organic solution, continue to react for 1h after dripping, the reaction is heated to 40°C for 30min and kept for 8h to obtain a reaction mixture;

(3) after the above-mentioned reaction mixture is cooled to room temperature, it is further cooled to 0° C. with an ice-water bath, then 20ml of deionized water is added in three times in 20min, and stirred for 30min to obtain an oil-water mixture;

(4) After separating the above oil-water mixture, the aqueous layer was extracted with dichloromethane (25ml x 3), the organic phases were combined, 50g of active manganese dioxide was added, and the mixture was stirred at 25°C for 10h. After the reaction, the black solid was removed by filtration, the filtrate was concentrated and the resulting pale yellow solid was collected by filtration, washed with cold ethanol, dried and recrystallized in ethanol to obtain the target product NBphen 5.39g with a yield of 92.1%. ¹ H NMR (600 MHz, CDCl ₃ ) δ 9.03 (s, 2H), 8.79-8.81 (dd, 2H), 8.31 (s, 2H), 8.11-8.13 (dd, 2H), 8.08-8.10 (m, 2H ), 7.95-7.96(m, 2H), 7.88(s, 2H), 7.67(d, 2H), 7.65-7.66(m, 2H), 7.54-7.62(m, 10H).

Example 2

(1) Under nitrogen protection, a dry ether solution (100 ml) of 2-bromonaphthalene (20.70 g, 100 mmol) was added dropwise to a solution containing 3.3 g of chopped lithium metal pieces and a dropping funnel at 25° C. within 4 h. 60ml of dry ether in a 500ml round-bottomed flask, reflux at 40°C for 2h after dripping, and filter to remove the remaining solid materials such as metal lithium flakes to obtain 2-lithium naphthalene organic solution;

(2) Dissolve Bphen (13.28 g, 40 mmol) in 60 ml of dry toluene, cool down to 0° C. with an ice-water bath after three cycles of degassing, and add the above-mentioned 2-lithium through a dropping funnel within 2 h under nitrogen protection The organic solution of naphthalene, after the dripping is completed, the reaction is continued for 2 hours, and the reaction is heated to 45 ° C for 30 minutes and maintained for 12 hours to obtain a reaction mixture;

(3) After cooling the above reaction mixture to room temperature, it was further cooled to 0°C with an ice-water bath, then 50ml of deionized water was added in three times in 45min, and stirred for 1h to obtain an oil-water mixture;

(4) After separating the above oil-water mixture, the aqueous layer was extracted with dichloromethane (50ml x 3), the organic phases were combined, 200g of active manganese dioxide was added, and the mixture was stirred at 40°C for 8h. After the reaction, the black solid was removed by filtration, the filtrate was concentrated and the resulting pale yellow solid was collected by filtration, washed with cold ethanol, dried and recrystallized in ethanol to obtain the target product NBphen 20.95g with a yield of 89.5%. ¹ H NMR (600 MHz, CDCl ₃ ) δ 9.03 (s, 2H), 8.79-8.81 (dd, 2H), 8.31 (s, 2H), 8.11-8.13 (dd, 2H), 8.08-8.10 (m, 2H ), 7.95-7.96(m, 2H), 7.88(s, 2H), 7.67(d, 2H), 7.65-7.66(m, 2H), 7.54-7.62(m, 10H).

Example 3

(1) Under nitrogen protection, a dry THF solution (250 ml) of 2-bromonaphthalene (62.20 g, 300 mmol) was added dropwise to a solution containing 10 g of chopped metal lithium pieces and 100 ml of lithium through a dropping funnel at 25°C within 4 h. In a 500ml round-bottomed flask of dry THF, after dripping, continue stirring at 25°C for 1h, heat to 45°C and continue stirring for 3h, filter to remove the remaining solid materials such as metal lithium flakes, and obtain 2-lithium naphthalene organic solution;

(2) Dissolve Bphen (39.85g, 120mmol) in 200ml of dry THF, cool down to 0°C with an ice-water bath after three cycles of degassing, and add the above-mentioned 2-lithium through a dropping funnel within 3h under nitrogen protection The organic solution of naphthalene, after the dripping is completed, the reaction is continued for 4 hours, and the reaction is heated to 60 °C for 30 minutes and maintained for 12 hours to obtain a reaction mixture;

(3) After cooling the above reaction mixture to room temperature, it was further cooled to 0°C with an ice-water bath, then 120ml of deionized water was added in three times in 45min, and stirred for 3h to obtain an oil-water mixture;

(4) After separating the above oil-water mixture, the aqueous layer was extracted with dichloromethane (150ml x 3), the organic phases were combined, 600g of active manganese dioxide was added, and the mixture was stirred at 45°C for 12h. After the reaction, the black solid was removed by filtration, the filtrate was concentrated and the resulting pale yellow solid was collected by filtration, washed with cold ethanol, dried and recrystallized twice in ethanol to obtain the target product NBphen 62.55g with a yield of 89.1%. ¹ H NMR (600 MHz, CDCl ₃ ) δ 9.03 (s, 2H), 8.79-8.81 (dd, 2H), 8.31 (s, 2H), 8.11-8.13 (dd, 2H), 8.08-8.10 (m, 2H ), 7.95-7.96(m, 2H), 7.88(s, 2H), 7.67(d, 2H), 7.65-7.66(m, 2H), 7.54-7.62(m, 10H).

Example 4

(1) Under nitrogen protection, a dry carbon tetrachloride solution (50 ml) of 2-bromonaphthalene (10.35 g, 50 mmol) was added dropwise to a solution containing 1.7 g of sheared metal through a dropping funnel at 25° C. within 2 h. Lithium flakes and 10ml dry carbon tetrachloride were placed in a 250ml round-bottomed flask, and after dripping was completed, stirring was continued at 35°C for 2 hours, and the remaining solid materials such as metal lithium flakes were removed by filtration to obtain 2-lithium naphthalene organic solution;

(2) Dissolve Bphen (4.32 g, 13 mmol) in 30 ml of dry toluene, cool down to 0°C with an ice-water bath after three cycles of degassing, and add the above-mentioned 2-lithium through a dropping funnel within 1 h under nitrogen protection The organic solution of naphthalene, after the dripping is completed, the reaction is continued for 2 hours, and the reaction is heated to 45 ° C for 30 minutes and maintained for 9 hours to obtain a reaction mixture;

(3) After cooling the above reaction mixture to room temperature, it was further cooled to 0°C with an ice-water bath, then 30 ml of deionized water was added in three times in 30 min, and stirred for 1 h to obtain an oil-water mixture;

(4) After the above-mentioned oil-water mixture was separated, the aqueous layer was extracted with dichloromethane (40ml x 3), the organic phases were combined, added to 50g potassium permanganate and dissolved in 400ml acetone/water (3:1, v :v) In the mixed solution formed, stir at 25°C for 8h. After the reaction, the black solid was removed by filtration, the filtrate was concentrated and redissolved in 100 ml of dichloromethane, washed 3 times with saturated sodium thiosulfate solution, concentrated to 20 ml on a rotary evaporator, and placed in a low-speed centrifuge (4000 r/min). ) for 4 min, the pale yellow solid at the bottom of the centrifuge tube was collected, washed with cold ethanol, dried and recrystallized in ethanol to obtain the target product NBphen 6.89g, with a yield of 90.5%. ¹ H NMR (600 MHz, CDCl ₃ ) δ 9.03 (s, 2H), 8.79-8.81 (dd, 2H), 8.31 (s, 2H), 8.11-8.13 (dd, 2H), 8.08-8.10 (m, 2H ), 7.95-7.96(m, 2H), 7.88(s, 2H), 7.67(d, 2H), 7.65-7.66(m, 2H), 7.54-7.62(m, 10H).

Various embodiments of the present invention have been described above, and the foregoing descriptions are exemplary, not exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (10)

1. A preparation method of an OLED electron transport material NBphen is characterized by comprising the following steps:

(1) under the existence of protective gas and a first organic solvent, carrying out contact reaction on 2-bromonaphthalene and metal lithium to obtain a 2-lithium naphthalene organic solution; the first organic solvent is at least one of diethyl ether, tetrahydrofuran, benzene, toluene, dichloromethane, chloroform, DMF and carbon tetrachloride;

(2) carrying out contact reaction on a Bphen organic solution and the 2-lithium naphthalene organic solution in the presence of protective gas to obtain a reaction mixture; the solvent used by the Bphen organic solution is at least one of diethyl ether, tetrahydrofuran, benzene, toluene, dichloromethane, chloroform, DMF and carbon tetrachloride;

(3) carrying out hydrolysis reaction on the reaction mixture and water to obtain an oil-water mixture;

(4) extracting an organic phase in a water layer of the oil-water mixture, and then carrying out contact reaction on the organic phase and an oxidant to obtain the NBphen; the oxidant is manganese dioxide and SeO₂At least one of dichlorodicyanobenzoquinone and potassium permanganate.

2. The production method according to claim 1, wherein the Bphen organic solution is a degassed Bphen organic solution.

3. The production method according to claim 1, wherein, in the step (1), the first organic solvent is a dried first organic solvent;

the 2-bromonaphthalene is dropwise added into a reaction container in the form of an organic solution of the 2-bromonaphthalene formed by the 2-bromonaphthalene and a first organic solvent; in the organic solution of the 2-bromonaphthalene, the mass ratio of the 2-bromonaphthalene to the first organic solvent is 1: 3-10;

the reaction temperature of the contact reaction is 25-45 ℃, and the reaction time is 1-8 h.

4. The preparation method according to claim 3, wherein in the organic solution of 2-bromonaphthalene, the mass ratio of 2-bromonaphthalene to the first organic solvent is 1: 4-5.

5. The production method according to claim 1, wherein in the step (2), the solvent is a dried solvent, and the mass ratio of Bphen to the solvent is 1: 3-6;

the molar ratio of the Bphen to the 2-lithium naphthalene is 1: 2-5;

the contact reaction is carried out for 1-8h at 0 ℃, and then the temperature is raised to 40-60 ℃ for continuous reaction for 8-12 h.

6. The preparation method according to claim 5, wherein the mass ratio of the Bphen to the solvent is 1: 8-10.

7. The production method according to claim 1, wherein, in the step (3), the reaction mixture is cooled to 0 ℃ and then subjected to hydrolysis reaction with water.

8. The production method according to claim 1, wherein, in the step (4), the extraction is performed with dichloromethane;

the reaction temperature of the contact reaction is 20-50 ℃, and the reaction time is 6-12 h.

9. The production method according to claim 8, wherein the oxidizing agent is manganese dioxide.

10. The production method according to claim 1, wherein the protective gas is nitrogen.