Bipyridine compound and its preparation method and application

Abstract

The present invention discloses bipyridine compounds and their preparation methods and applications, and belongs to the field of organic light-emitting materials and semiconductor technology. The compound is based on 6,6'-bis (pyrimidine-5-yl)-2,2'-bipyridine as the main skeleton, and different substituents are substituted at the 4-position / 4'-position of pyridine and the 2-position / 2'-position of pyrimidine to adjust its electron distribution, and the central symmetric compound formed can be used as an efficient electron transport material or a guest luminescent material with excellent performance. It is proved by performance test that the 6,6'-bis (pyrimidine-5-yl)-2,2'-bipyridine compounds of the present invention can be applied to electron transport layer as efficient electron transport material, or applied to the light-emitting layer of OLED device as guest luminescent material, can effectively improve the efficiency of electroluminescent device, and extend the service life of electroluminescent device.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic light-emitting materials and semiconductors, and particularly relates to a bipyridine compound and a preparation method and application thereof. Background Art

[0002] As a key driver of innovation in display technology, new materials have always been a major priority for researchers in this field. Currently, mature organic light-emitting diode (OLED) devices are often implemented using a multilayered functional composite approach. These functional layers primarily include hole injection, hole transport, hole blocking, electron injection, electron transport, electron blocking, and the light-emitting layer. The primary purpose of these layers is to balance the holes and electrons injected from the cathode and anode, thereby facilitating their recombination in the light-emitting layer, improving the device's exciton utilization, and ultimately increasing its luminous efficiency and lifetime.

[0003] However, in organic electroluminescent devices, the transport rate of electrons is lower than that of holes, with the difference being approximately one order of magnitude. This leads to an imbalance in the number of electrons and holes in the light-emitting layer, resulting in reduced luminescence efficiency and poor device performance. Furthermore, conventional triarylamine hole-transport materials are readily available and widely developed, making electron-transport materials significantly scarcer than hole-transport materials.

[0004] International patent application publication number WO 2024144192A1 discloses an organic compound and an organic electroluminescent diode using the same. These compounds can be used in the electron transport layer of OLED devices, but they suffer from high driving voltages and low current efficiency. Therefore, developing a light-emitting layer material and electron transport layer material with high luminous efficiency and high electron transport performance, improving the electron transport rate and thereby balancing the injection of positive and negative carriers, thereby improving the device's luminous efficiency and extending its overall device life, is a pressing issue for those skilled in the art. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a bipyridine compound and a preparation method and application thereof, so as to solve the technical problems of low efficiency and short life of existing luminescent materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention discloses a bipyridine compound, the structure of which is shown in Formula 1:

[0008]

[0009] Where:

[0010] R1 and R2 are independently selected from a C1-C6 alkyl group, a vinyl group, a F atom, a cyano group, a D atom, a phenyl group or a pentafluorophenyl group;

[0011] R3 and R4 are independently selected from substituted or unsubstituted C6~C30 aryl, substituted or unsubstituted C2~C10 alkenyl or cycloalkenyl, substituted or unsubstituted C6~C20 heteroaryl;

[0012] R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula.

[0013] The second aspect of the present invention discloses a method for preparing the above-mentioned bipyridine compound, comprising the following steps:

[0014] Step 1, reactant A n Under the action of H2O2 and AcOH, an oxidation reaction occurs to obtain intermediate A n-1 ;

[0015] Among them, A n The structural formula is , R1 and R2 are independently selected from C1-C6 alkyl, vinyl, F atom, cyano, D atom, phenyl or pentafluorophenyl; R3 and R4 are independently selected from substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C2-C10 alkenyl or cycloalkenyl, substituted or unsubstituted C6-C20 heteroaryl; R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula; A n-1 The structural formula is ;

[0016] Step 2, Intermediate A n-1 Using CH2Cl2 as solvent and DMF as catalyst, bromination reaction is carried out under the action of phosphorus oxybromide to generate intermediate A n-2 ;

[0017] Among them, A n-2 The structural formula is ;

[0018] Step 3, Intermediate A n-2 The intermediate A is generated by Miyaura borylation reaction with pinacol diboric acid ester in the presence of a base and a catalyst. n-3 ;

[0019] Among them, A n-3 The structural formula is ;

[0020] Step 4, Intermediate A n-3and reactant B in the presence of a base and a catalyst to undergo a Suzuki reaction to generate a bipyridine compound as shown in general formula 1;

[0021] Among them, the structural formula of reactant B is .

[0022] Preferably, in step 3, the base is KOAc and the catalyst is Pd(dppf)Cl2.

[0023] Preferably, in step 4, the base is K2CO3 and the catalyst is Pd(PPh3)4.

[0024] The third aspect of the present invention discloses an electroluminescent device, which includes a substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode layer. The light-emitting layer contains a host light-emitting material and a guest light-emitting material, and the guest light-emitting material or the electron transport layer material is selected from the above-mentioned bipyridine compound.

[0025] Preferably, the host luminescent material is composed of a first host luminescent material and a second host luminescent material in a mass ratio of (30-60):(70-40).

[0026] Preferably, the mass fraction of the guest luminescent material in the entire luminescent layer is 0.1% to 3.0%.

[0027] A fourth aspect of the present invention discloses a display panel, which includes the above-mentioned electroluminescent device.

[0028] A fifth aspect of the present invention discloses an electronic device comprising the above-mentioned electroluminescent device.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The bipyridine compound provided by the present invention has 1) 6,6'-bis(pyrimidin-5-yl)-2,2'-bipyridine as the main skeleton. Both the pyrimidine and bipyridine structures have strong electron-accepting capabilities. This structural combination gives the compound good electron transport performance, enabling rapid and efficient electron transport, improving electron mobility, and contributing to improved device luminescence efficiency and response speed. At the same time, the rigid bipyridine and pyrimidine structures give the compound high thermal and chemical stability, enabling it to maintain structural integrity and performance stability during the preparation and use of electroluminescent devices, thereby helping to extend the service life of the devices. 2) Using 6,6'-bis(pyrimidin-5-yl)-2,2'-bipyridine as the main skeleton, different substituents are substituted at the 4 / 4' position of pyridine and the 2 / 2' position of pyrimidine to adjust its electron distribution, forming an axisymmetric or centrosymmetric compound; for axisymmetric or centrosymmetric compounds, the molecular spatial arrangement will be more regular, the intermolecular forces will be balanced, and a more orderly stacking pattern can be formed, reducing scattering and trapping during electron transport, allowing electrons to migrate more efficiently in the material, thereby reducing the device's driving voltage and improving the device's luminous efficiency; at the same time, the symmetrical structure has higher molecular stability and is not easily degraded due to structural distortion or breakage during long-term power-on luminescence, which helps to extend the service life of OLED devices. Therefore, the bipyridine compound of the present invention can be used as a high-efficiency electron transport material in the electron transport layer, and can also be used as an excellent guest luminescent material in the light-emitting layer. Performance tests have shown that the 6,6'-bis(pyrimidin-5-yl)-2,2'-bipyridine compound of the present invention can be used as a high-efficiency electron transport material in the electron transport layer or as a guest luminescent material in the light-emitting layer of an OLED device, which can effectively improve the efficiency of the electroluminescent device and extend the service life of the electroluminescent device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a cross-sectional view of the organic electroluminescent device of the present invention;

[0032] Figure 2 is the nuclear magnetic spectrum of compound 1 of the present invention;

[0033] Figure 3 is the NMR spectrum of compound 19 of the present invention;

[0034] Figure 4 is the NMR spectrum of compound 70 of the present invention. DETAILED DESCRIPTION

[0035] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0036] Herein, "room temperature" refers to a temperature of about 20°C to 35°C, or about 23°C to 28°C, or about 25°C. It can be 20°C, 25°C, 30°C or 33°C.

[0037] The present invention provides a bipyridine compound, the structure of which is shown in Formula 1:

[0038]

[0039] Where:

[0040] R1 and R2 are independently selected from a C1-C6 alkyl group, a vinyl group, a F atom, a cyano group, a D atom, a phenyl group or a pentafluorophenyl group;

[0041] R3 and R4 are independently selected from substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C2-C10 alkenyl or cycloalkenyl, or substituted or unsubstituted C6-C20 heteroaryl; when the C6-C30 aryl is substituted, the substituent is selected from F, cyano, trifluoromethyl, methyl, tert-butyl, or phenyl; when the C6-C20 heteroaryl is substituted, the substituent is selected from F, cyclopropyl, phenyl, or carbonyl;

[0042] R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula.

[0043] The present invention also provides a method for preparing the above-mentioned bipyridine compound, comprising the following steps:

[0044]

[0045] Step 1: Reactant A n Under the action of H2O2 and AcOH, an oxidation reaction occurs to obtain intermediate A n-1 ;

[0046] Step 2: Intermediate A n-1 Using CH2Cl2 as solvent and DMF as catalyst, bromination reaction is carried out under the action of phosphorus oxybromide to generate intermediate A n-2 ;

[0047] Step 3: Intermediate A n-2 The intermediate A is generated by Miyaura borylation reaction with pinacol diboric acid ester in the presence of a base and a catalyst.n-3 ;

[0048] Wherein, the base is preferably KOAc, and the catalyst is preferably Pd(dppf)Cl2;

[0049] Step 4: Intermediate A n-3 and reactant B in the presence of a base and a catalyst to undergo a Suzuki reaction to generate a bipyridine compound as shown in general formula 1;

[0050] Among them, the base is preferably K2CO3, and the catalyst is preferably Pd(PPh3)4.

[0051] In the above reaction formula, R1 and R2 are independently selected from C1~C6 alkyl, vinyl, F atom, cyano, D atom, phenyl or pentafluorophenyl; R3 and R4 are independently selected from substituted or unsubstituted C6~C30 aryl, substituted or unsubstituted C2~C10 alkenyl or cycloalkenyl, substituted or unsubstituted C6~C20 heteroaryl; R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula.

[0052] The present invention also provides an electroluminescent device, such as Figure 1 As shown, from the anode to the cathode, the structure includes, in order: substrate 1, anode layer 2, hole injection layer (HIL) 3, hole transport layer (HTL) 4, electron blocking layer (EBL) 5, emission layer (EML) 6, hole blocking layer (HBL) 7, electron transport layer (ETL) 8, electron injection layer (EIL) 9, cathode layer 10, and high refractive index capping layer 11. The hole injection layer 3, hole transport layer 4, electron blocking layer 5, emission layer 6, hole blocking layer 7, electron transport layer 8, and electron injection layer 9 together constitute a functional organic layer.

[0053] The substrate 1 needs to have high mechanical strength, excellent thermal stability, excellent water resistance, and excellent transparency; polyethylene terephthalate (PET) plastic is preferred.

[0054] In order to facilitate hole injection into the organic layer, the anode material used in the anode layer 2 is preferably a material with a large work function. Specific examples of anode materials that can be used in the present invention include metals such as vanadium, chromium, copper, zinc, and gold, or alloys thereof; oxides such as zinc oxide, aluminum oxide, and tin dioxide; and conductive polymers such as polypyrrole and polyaniline.

[0055] Functional organic layers can be formed on electrodes through various methods such as vacuum thermal evaporation, spin coating, and printing. Compounds used for the functional organic layers other than the light-emitting layer 6 can include small organic molecules, large organic molecules, polymers, and combinations thereof. Materials used for the hole injection layer 3, hole transport layer 4, electron blocking layer 5, hole blocking layer 7, electron transport layer 8, and electron injection layer 9 are selected from the corresponding functional layer materials with excellent cost-effectiveness in the industry. The compatibility of the various functional layers is determined through a series of tests and screening processes.

[0056] As the material of the hole injection layer 3, MoO3 is preferable.

[0057] The hole transport layer 4 may be made of one of the following materials:

[0058]

[0059] .

[0060] The material of the electron blocking layer 5 may be selected from one of the following materials:

[0061] .

[0062] The light-emitting layer 6 is formed by composite co-evaporation of a host light-emitting material and a guest light-emitting material, wherein the host light-emitting material is composed of a first host light-emitting material and a second host light-emitting material; wherein the first host light-emitting material is selected from or , the second host luminescent material is selected from The mass ratio of the first host luminescent material to the second host luminescent material is (30-60):(70-40). The guest luminescent material used in combination is selected from one of the compounds represented by Formula 1. In the compound of Formula 1 used as the guest luminescent material, R3 and R4 contain strong luminescent groups, including but not limited to naphthalene, anthracene, phenanthrene, pyrene, perylene, or carbazole. Compounds of Formula 1 containing strong luminescent groups have a high fluorescence quantum yield and can efficiently absorb energy and release it as light, reducing energy loss in non-radiative ways such as heat, thereby significantly improving the overall luminescence intensity of the material. The mass fraction of the guest luminescent material in the total mass of the luminescent layer 6 is 0.1% to 3.0%.

[0063] The material of the hole blocking layer 7 can be selected from One of them.

[0064] The material of the electron transport layer 8 can be selected from any one of the compounds shown in general formula 1 of the present invention; the compound of general formula 1 used as the material of the electron transport layer 8 contains a strong electron-withdrawing group, and the strong electron-withdrawing group includes but is not limited to pyrimidine, pyridine, cyano, trifluoromethyl or pentafluorophenyl. The strong electron-withdrawing group can stabilize the negative charge and promote the injection and transport of electrons.

[0065] As the material of the electron injection layer 9 , LiF is preferable.

[0066] In order to facilitate electron injection into the functional organic layer, the cathode material of the cathode layer 10 is preferably a material with a low work function. Specific examples of cathode materials that can be used in the present invention include metals such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and lead, or alloys thereof; multilayer structures such as LiF-Al, LiO2-Al, Mg-Al, and Mg-Ag.

[0067] As a high refractive index cover layer 11, it can improve the refractive index of the surface of the cathode layer 10 and increase the light extraction rate; preferably .

[0068] The present invention also provides a method for preparing the above-mentioned organic electroluminescent device, comprising adhering an anode layer 2 to a substrate 1 after pretreatment and cleaning, and then sequentially vapor-depositing a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting layer 6, a hole blocking layer 7, an electron transport layer 8 and an electron injection layer 9 of set thicknesses under low temperature conditions, and continuing to sputter-deposit a cathode layer 10 and a high-refractive-index covering layer 11 under low temperature conditions, and finally packaging the test device using conventional device testing and packaging methods to obtain an organic electroluminescent device.

[0069] The present invention further provides a display panel, wherein the display panel comprises the electroluminescent device of the present invention.

[0070] The present invention also provides an electronic device comprising the electroluminescent device of the present invention.

[0071] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the contents described herein, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims appended hereto. In addition, those skilled in the art may refer to the preparation method of the compound of formula 1 above and the following specific examples to prepare compounds 1 to 83.

[0072] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The process equipment or devices not specifically specified in the following examples are all conventional equipment or devices in the art. 11 、B1~B 38 The synthesis can be carried out according to the chemical method given in the examples, reactants A1~A 10 The other raw materials used, unless otherwise specified, are conventional commercial products, and their specifications are conventional in the art.

[0073] The structural formula of a representative compound of the bipyridine compound provided by the present invention is as follows:

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] .

[0091] The important reactant A involved in the present inventionn The structural formula is as follows:

[0092] .

[0093] The structural formula of the important reactant B involved in the present invention is as follows:

[0094]

[0095]

[0096]

[0097] .

[0098] 1. Preparation of Bipyridine Compounds

[0099] Example 1 Synthesis of Compound 1

[0100] 1. Synthesis of intermediate B1:

[0101]

[0102] Step 1:

[0103] Operation process: Under nitrogen protection, 2-bromobiphenyl (117 g, 0.5 mol) and 800 mL of anhydrous THF were added to a 2000 mL three-necked flask in sequence, stirred, and the system was cooled to At 78 °C, butyl lithium (240 mL, 0.6 mol, 2.5 mol / L) was added dropwise. The reaction was stirred at 78°C for 30 min, the reaction system was slowly raised to room temperature, and the reaction was carried out at room temperature for 1 h. The temperature of the reaction system was then lowered to -78°C again, and hexafluoroacetone gas (5 mol) was introduced into the reaction system at -78°C. The reaction system was then maintained at -78°C for 30 min, slowly raised to room temperature, and continued to react at room temperature for 1 h. After the reaction was completed, a small amount of ice water was added to quench the reaction, the solvent was removed, and the intermediate B was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:15) to obtain intermediate B. 1-1 , weighing 105 g, with a yield of 65.3% and a molecular weight of 320.1 according to GC-MS.

[0104] Step 2:

[0105] Operation process: Under nitrogen protection, add intermediate B in a 1000 mL three-necked flask in sequence 1-1(96 g, 0.3 mol), thionyl chloride 500 mL and pyridine (47 g, 0.6 mol) were stirred and reacted at 78 ° C for 2 h. After the reaction was completed, the excess thionyl chloride in the reaction solution was removed by vacuum distillation, and the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:15) to obtain intermediate B 1-2 , weighing 86 g, with a yield of 94.9% and a molecular weight of 302.1 according to GC-MS.

[0106] Step 3:

[0107] Operation process: Under nitrogen protection, add intermediate B in a 2000 mL three-necked flask in sequence 1-2 (76 g, 0.25 mol), DMF 800 mL and NBS (49 g, 0.275 mol) were stirred and reacted at 60 ° C for 3 h. After the reaction was completed, the solvent in the reaction solution was distilled off under reduced pressure, and the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:18) to obtain intermediate B 1-3 , weighing 87 g, with a yield of 91.3% and a molecular weight of 380.0 according to GC-MS.

[0108] Step 4:

[0109] Operation process: Under nitrogen protection, add intermediate B in a 2000 mL three-necked flask in sequence 1-3 (76 g, 0.2 mol), bipyralidone (56 g, 0.22 mol), potassium acetate (39 g, 0.4 mol) and 1,4-dioxane 700 mL were stirred and heated to 60 ° C. Pd (dppf) Cl2 (2.9 g, 4 mmol) was added and then the temperature was continued to rise to 100 ° C. The reaction was continued for 8 h until the intermediate B was obtained. 1-3 After the reaction is complete, the reaction solution is directly filtered and the filtrate is collected. The filtrate is concentrated under reduced pressure to dryness, dissolved in 500 mL of toluene, and then washed with water. The organic phase is dried and concentrated. The residue is purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 15:1). The column liquid is concentrated under reduced pressure until solid precipitates and then stopped. The temperature is lowered to 10°C. After crystallization is complete, it is filtered and dried to obtain intermediate B. 1-4 , weighing 68 g, yield 79.8%, HPLC content 99%, LC-MS showed a molecular weight of 429.2.

[0110] Step 5:

[0111] Operation process: Under nitrogen protection, add B 1-4(47.9 g, 0.1 mol), 2-bromo-5-chloropyrimidine (19.3 g, 0.1 mol), 400 mL of THF, 100 mL of H2O and K2CO3 (27.6 g, 0.2 mol) were stirred and heated to 40°C. After the solution clarified, Pd(PPh3)4 (2.3 g, 2 mmol) was added, and then the temperature was raised to 70°C and the reaction was continued for 12 hours until the reaction was complete. The reaction solution was cooled to room temperature and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, filtered, and concentrated. The residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:10) to obtain B1, weighing 31.9 g, with a yield of 77%, an HPLC content of 99%, and a molecular weight of 414.1 according to GC-MS.

[0112] 2. Synthesis of compound 1:

[0113]

[0114] Step 1:

[0115] Operation process: A1 (54 g, 0.2 mol), 400 mL of acetic acid and 35% hydrogen peroxide (97 g, 1.0 mol) were added to a 1000 mL three-necked flask in sequence, stirred, reacted at 80°C for 11 h, and then concentrated under reduced pressure to remove the solvent. 1 L of pure water was added to dilute the residue. A large amount of precipitate was generated at the same time. After filtering, it was rinsed with a large amount of water and dried in vacuum at 40°C to obtain intermediate A. 1-1 , weighing 39 g, with a yield of 92% and a purity of 97%.

[0116] Step 2:

[0117] Operation process: Under nitrogen protection, add intermediate A in a 1.0 L three-necked flask in sequence 1-1 (42 g, 0.2 mol), 0.5 L dichloromethane and DMF (7.3 g, 0.1 mol), stirred, slowly added tribromide oxyphosphorus (69 g, 0.24 mol) at 0 ° C. After the addition was complete, the temperature was raised to room temperature and the reaction was continued for 10 h until the reaction was complete. Then, saturated sodium carbonate solution was slowly added, and the pH value of the solution was adjusted to 7.5. The liquid was separated, and the organic phase was retained. The aqueous phase was extracted with 1.5 L dichloromethane 3 times, 0.5 L each time. The organic phases were combined and post-treated to obtain intermediate A. 1-2 , weight 55 g, yield 64%, purity 98%.

[0118] Step 3:

[0119] Operation process: Under nitrogen protection, add intermediate A in a 1.0 L three-necked flask in sequence 1-2(43 g, 0.1 mol), pinacol diboronate (51 g, 0.2 mol), potassium acetate (19.6 g, 0.2 mol) and 400 mL 1,4-dioxane were stirred, the system was heated to 60 ° C and Pd (dppf) Cl2 (1.5 g, 2 mmol) was added, and then the temperature was continued to rise to 100 ° C. The reaction was continued for 8 h until intermediate A was obtained. 1-2 After the reaction is complete, the reaction solution is directly filtered and the filtrate is collected. The filtrate is concentrated to dryness under reduced pressure, dissolved in 500 mL of toluene and then washed with water. The organic phase is dried and concentrated. The residue is purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 15:1). The column liquid is concentrated under reduced pressure until solid precipitates and then stopped. The temperature is lowered to 10°C. After crystallization is complete, it is filtered and dried to obtain intermediate A. 1-3 , weighing 42 g, yield 80%, HPLC content 99%, LC-MS showed a molecular weight of 521.4.

[0120] Step 4:

[0121] Operation process: Under nitrogen protection, add A 1-3 (5.2 g, 0.01 mol), B1 (8.3 g, 0.02 mol), 40 mL THF, 10 mL H2O and K2CO3 (5.5 g, 0.2 mol) were stirred and heated to 40°C. After the solution was clarified, Pd(PPh3)4 (0.46 g, 0.4 mmol) was added, and then the temperature was raised to 70°C and the reaction was continued for 12 h until the reaction was completed. The reaction solution was cooled to room temperature and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, filtered and concentrated. The residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:10) to obtain compound 1, weighing 7.9 g, with a yield of 77%, an HPLC content of 99%, and a molecular weight of 1025.3 according to LC-MS.

[0122] The H NMR spectrum of compound 1 is as follows Figure 2 Shown: 1H NMR (500 MHz, CD3OD ) δ 9.65 (s, 4H), 8.90 (s, 2H), 8.02 (d, J = 21.5 Hz, 4H), 7.90 (s, 2H), 7.76 (s, 2H), 7.68 (s,2H), 7.53 (s, 2H), 7.34 (s, 2H), 7.24 (s, 2H), 1.32 (s, 18H).

[0123] Example 2 Synthesis of Compound 19

[0124] 1. Synthesis of intermediate B4:

[0125]

[0126] Operation process: The synthesis process of intermediate B4 refers to intermediate B 1-4 The synthesis process of B1 was carried out by replacing intermediate B with compound (4,4-difluorocyclohex-1-en-1-yl)boronic acid (16.2 g, 0.1 mol). 1-4 (47.9 g, 0.1 mol) to give intermediate B4, weighing 20.3 g, with a yield of 74% and an HPLC content of 98%.

[0127] 2. Synthesis of compound 19:

[0128]

[0129] Step 1:

[0130] Operation process: A 11 The synthesis process of reference B 1-4 To the synthesis process of B1, replace 2-bromo-5-chloropyrimidine (19.3 g, 0.1 mol) with compound 4,4'-dibromo-2,2'-bipyridine (31.4 g, 0.1 mol) and replace intermediate B with pentafluorophenylboronic acid (44.5 g, 0.21 mol) 1-4 (47.9 g, 0.1 mol), to give A 11 , weighing 35.6 g, yield 73%, HPLC content 97%, LC-MS showed a molecular weight of 489.1.

[0131] Step 2:

[0132] Operation process: Intermediate A 11-1 The synthetic process refers to intermediate A1 to intermediate A 1-1 The synthesis process uses intermediate A 11 (48.8 g, 0.1 mol) replaced intermediate A1 (54 g, 0.2 mol) to obtain intermediate A 11-1 , weighing 47 g, with a yield of 91%.

[0133] Step 3:

[0134] Operation process: Intermediate A 11-2 The synthetic process refers to intermediate A 1-1 To intermediate A 1-2 The synthesis process uses intermediate A 11-1 (52 g, 0.1 mol) replaced intermediate A 1-1 (42 g, 0.2 mol), to obtain compound intermediate A11-2 , weighing 40.7 g, yield 63%, HPLC content 98%, LC-MS showed a molecular weight of 646.9.

[0135] Step 4:

[0136] Operation process: Intermediate A 11-3 The synthetic process refers to intermediate A 1-2 To intermediate A 1-3 The synthesis process uses intermediate A 11-2 (32 g, 0.05 mol) to replace intermediate A 1-2 (43 g, 0.1 mol), to obtain compound intermediate A 11-3 , weighing 29 g, yield 79%, HPLC content 98%, LC-MS showed a molecular weight of 741.2.

[0137] Step 5:

[0138] Operation process: Intermediate A 11-3 The synthetic process refers to intermediate A 1-3 The synthesis process of compound 1 was to replace B1 (8.3 g, 0.02 mol) with intermediate B4 (5.8 g, 0.02 mol) and use A 11-3 (7.4 g, 0.01 mol), replacing A 1-3 (5.2 g, 0.01 mol) to obtain intermediate A 11-3 , weighing 29 g, yield 79%, HPLC content 99%, LC-MS showed a molecular weight of 741.2.

[0139] The H NMR spectrum of compound 19 is as follows Figure 3 Shown: 1H NMR (500 MHz, Chloroform )δ 9.76 (s,4H), 9.50 (s, 2H), 8.52 (s, 2H), 6.22 (s, 2H), 2.75 (d, J = 12.5 Hz, 1H), 2.65(d, J = 22.1 Hz, 7H), 2.10 (s, 4H).

[0140] Example 3 Synthesis of Compound 70

[0141]

[0142] Step 1:

[0143] Operation process: Under nitrogen protection, carbazole (16.7 g, 0.1 mol), 2-bromo-5-chloropyrimidine (20.3 g, 0.105 mol) and 200 mL of toluene were added to a 500 mL three-necked flask and stirred until the solution was clear. Pd2(dba)3 (1.83 g, 2 mmol), Am-phos (0.80 g, 3 mmol) and sodium tert-butoxide (19 g, 0.2 mol) were added. The reaction solution was heated to 120°C and the reaction was continued for 10 h. After the reaction was completed, it was filtered while hot using diatomaceous earth. The filtrate was cooled to room temperature and washed with purified water. After separation, the organic phase was retained and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous magnesium sulfate, concentrated, and passed through a column (dichloromethane / petroleum ether = 15:1) to obtain B. 18 , weighing 21.8 g, with a yield of 77%.

[0144] Step 2:

[0145] Operation process: The synthesis process of compound 70 refers to intermediate A 1-3 To the synthesis process of compound 1, use B 18 (5.6 g, 0.02 mol) to replace B1 (8.3 g, 0.02 mol), and A 11-3 (7.4 g, 0.01 mol) replaced A 1-3 (5.2 g, 0.01 mol) to give compound 70, weighing 7.2 g, with a yield of 74%, an HPLC content of 99%, and a molecular weight of 975.3 according to LC-MS.

[0146] The H NMR spectrum of compound 70 is as follows Figure 4 As shown: 1 H NMR (500 MHz, CD3OD )δ 9.95 (s, 4H), 9.50 (s, 2H), 8.54 (d, J = 15.0 Hz, 4H), 8.19 (s, 2H), 7.52 (s, 2H), 7.40 (s,2H), 7.16 (dd, J = 27.5, 17.5 Hz, 8H).

[0147] Other intermediates B The synthetic process of the intermediates B4 and B 18 The synthesis process of compounds 2 to 18, compounds 20 to 69, and compounds 71 ​​to 83 were all carried out with reference to the synthesis methods of compounds 1, 19, and 70, except that the corresponding A (A1 to A 11 )、B(B1~B 38) to replace it.

[0148] The composition structures of some compounds of the present invention are shown in Table 1.

[0149] Table 1 Composition and structure of some compounds

[0150]

[0151] 2. Preparation of electroluminescent devices containing bipyridine compounds

[0152] According to the structural information of the light-emitting layer 6 of the electroluminescent device given in Table 2, the electroluminescent devices of Examples 1 to 39 and Comparative Examples 1 to 3 were prepared.

[0153] Table 2 Light-emitting layer structure of electroluminescent devices

[0154]

[0155] Note: "Compound ratio" refers to the vapor deposition mass ratio of the first host luminescent material, the second host luminescent material, and the guest luminescent material.

[0156] Example 1 Electroluminescent device containing compound 3

[0157] An electroluminescent device containing compound 3, which comprises, from anode to cathode, PET plastic, indium tin oxide (ITO), MoO3, HT-1, EB-1, a light-emitting layer 6, HB-1, an electron transport layer 8 (compound 3), LiF, Al-Mg (Al:Mg=9:1), and CPL;

[0158] In the light-emitting layer 6 , CBP and BCP are used as host light-emitting materials, and BD-1 is used as a guest light-emitting material, and the mass ratio of the three is 49:49:2.

[0159] The method for preparing the electroluminescent device containing compound 3 comprises the following steps:

[0160] 1. Use 1.5 mm PET plastic as substrate 1 and 0.15 mm ITO material as anode layer 2. Use alkaline washing, pure water washing, drying, and then ultraviolet-ozone washing to remove organic residues on the surface of PET plastic and ITO material.

[0161] 2. A layer of ITO material was adhered to PET plastic. Using a vacuum evaporation device, a 20 nm thick MoO3 film was deposited as a hole injection layer 3. Then, a 45 nm thick HT-1 was evaporated as a hole transport layer 4. Subsequently, a 30 nm thick EB-1 was evaporated as an electron blocking layer 5. A 60 nm thick light-emitting layer 6 consisting of CBP, BCP, and BD-1 in a mass ratio of 49:49:2 was further evaporated on EB-1. Then, a 10 nm thick HB-1 was evaporated on the light-emitting layer 6 as a hole blocking layer 7. Then, a 30 nm thick compound 3 was evaporated as an electron transport layer 8. Finally, a 16 nm thick LiF was evaporated on the electron transport layer 8 as an electron injection layer 9. After the electron injection layer 9 was evaporated, a 10 nm thick Al-Mg (Al:Mg=9:1) alloy was sputtered as a cathode layer 10 by low-temperature sputtering. Finally, a 40 nm thick CPL was evaporated on the cathode layer 10 as a high refractive index cover layer 11.

[0162] 3. MoO3, HT-1, EB-1, light-emitting layer 6, HB-1, electron transport layer 8 (compound 3) and LiF layer are vacuum-encapsulated to produce an organic electroluminescent device.

[0163] Example 2 to Example 32

[0164] The difference from Example 1 is that in the electron transport layer 8, compounds 6, 7, 9, 12, 13, 14, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 34, 35, 45, 46, 47, 54, 55, 56, 57, 58, 62, 64 and 65 are selected as electron transport layer materials, respectively.

[0165] Example 33 to Example 39

[0166] The difference from Example 1 is that in the light-emitting layer 6, compounds 20, 68, 75, 76, 79, 80 and 83 are respectively selected to replace the guest light-emitting layer material BD-1, and the rest remain unchanged.

[0167] Comparative Example 1

[0168] The difference from Example 1 is that in the electron transport layer 8, the organic compound and organic electroluminescent diode using same as in the international patent application with publication number WO 2024144192A1 is used. As electron transport materials.

[0169] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(45 nm) / EB-1(30 nm) / CBP: BCP:BD-1=49:49:2 (60 nm) / HB-1(10 nm) / Inv10(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0170] Comparative Example 2

[0171] The difference from Example 1 is that the electron transport layer 8 uses the organic compound and organic electroluminescent diode using same as in the international patent application with publication number WO 2024144192A1. As electron transport materials.

[0172] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(45 nm) / EB-1(30 nm) / CBP: BCP: BD-1=49:49:2 (60 nm) / HB-1(10 nm) / Inv14(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0173] Comparative Example 3

[0174] The difference from Example 1 is that in the light-emitting layer 6, the organic compound and organic electroluminescent diode using same as in the international patent application with publication number WO 2024144192A1 is used. As a guest luminescent material, the first host luminescent material , the second host luminescent material The evaporation mass ratio of the three materials is 49:49:2. ET-1 is used as the electron transport layer material.

[0175] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(45 nm) / EB-1(30 nm) / CBP: BCP:Inv173=49:49:2(60 nm) / HB-1(10 nm) / ET-1(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0176] The electroluminescent devices from the above examples and comparative examples were fabricated into 30 mm x 30 mm samples. Under the same device fabrication conditions, the anode and cathode were connected using a known driving circuit in the industry to characterize the OLEDs. The driving voltage and luminous efficiency of the organic light-emitting devices were measured at a current density of 10 mA / cm2, and the time required for the luminance to reach 95% of its initial luminance (LT) was measured at a current density of 15 mA / cm2. 95 , i.e. lifespan). The test results are shown in Table 3.

[0177] Table 3 Electroluminescent device performance test results

[0178]

[0179] The test data in Table 3 demonstrate that: 1) Compared to the test devices prepared with the electron transport materials Inv10 and Inv14 in the comparative examples (Comparative Examples 1 and 2), the test devices prepared using the bipyridine structure compound of the present invention as the electron transport layer material exhibit significant advantages in overall luminous efficacy, with a significantly lower driving voltage, a more than threefold increase in current efficiency, and an approximately threefold increase in service life. 2) Compared to the test device prepared with the guest luminescent material Inv173 in the comparative example (Comparative Example 3), the test devices prepared using the bipyridine structure compound of the present invention as the guest luminescent material exhibit significant improvements in overall luminous efficacy, with a nearly fourfold increase in current efficiency and a nearly threefold increase in service life. 3) The current efficiency of the devices in Examples 34-39 was significantly improved compared to Example 33, likely because reactant B in compounds 68, 75, 76, 79, 80, and 83 in Examples 34-39 all contain groups with strong π-π conjugation, while the groups in reactant B in Example 33 are weakly conjugated.

[0180] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A bipyridine compound, characterized in that The structure of the bipyridine compound is shown in Formula 1: Where: R1 and R2 are independently selected from a C1-C6 alkyl group, a vinyl group, a F atom, a cyano group, a D atom, a phenyl group or a pentafluorophenyl group; R3 and R4 are independently selected from substituted or unsubstituted C6-C30 aryl, unsubstituted C2-C10 cycloalkenyl, or substituted or unsubstituted C6-C20 heteroaryl; when the C6-C30 aryl is substituted, the substituent is selected from F, cyano, trifluoromethyl, methyl, tert-butyl, or phenyl; when the C6-C20 heteroaryl is substituted, the substituent is selected from F, cyclopropyl, or phenyl; R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula.

2. A bipyridine compound, characterized in that The bipyridine compound is selected from the following compounds: 。 3. The method for preparing the bipyridine compound according to claim 1, wherein The following steps are involved: Step 1, reactant A n Under the action of H2O2 and AcOH, an oxidation reaction occurs to obtain intermediate A n-1 ; Among them, A n The structural formula is , R1 and R2 are independently selected from C1-C6 alkyl, vinyl, F atom, cyano, D atom, phenyl or pentafluorophenyl; R3 and R4 are independently selected from substituted or unsubstituted C6-C30 aryl, unsubstituted C2-C10 cycloalkenyl, substituted or unsubstituted C6-C20 heteroaryl; when the C6-C30 aryl is substituted, the substituent is selected from F, cyano, trifluoromethyl, methyl, tert-butyl or phenyl; when the C6-C20 heteroaryl is substituted, the substituent is selected from F, cyclopropyl or phenyl; R1 and R2 have the same structural formula, and R3 and R4 have the same structural formula; A n-1 The structural formula is ; Step 2, Intermediate A n-1 Using CH2Cl2 as solvent and DMF as catalyst, bromination reaction is carried out under the action of phosphorus oxybromide to generate intermediate A n-2 ; Among them, A n-2 The structural formula is ; Step 3, Intermediate A n-2 The intermediate A is generated by Miyaura borylation reaction with pinacol diboric acid ester in the presence of a base and a catalyst. n-3 ; Among them, A n-3 The structural formula is ; Step 4, Intermediate A n-3 and reactant B in the presence of a base and a catalyst to undergo a Suzuki reaction to generate a bipyridine compound as shown in general formula 1; Among them, the structural formula of reactant B is .

4. The method for preparing a bipyridine compound according to claim 3, wherein In step 3, the base is KOAc and the catalyst is Pd(dppf)Cl2.

5. The method for preparing a bipyridine compound according to claim 3, wherein In step 4, the base is K2CO3 and the catalyst is Pd(PPh3)4.

6. An electroluminescent device, characterized in that The electroluminescent device comprises a substrate (1), an anode layer (2), a hole injection layer (3), a hole transport layer (4), an electron blocking layer (5), a light-emitting layer (6), a hole blocking layer (7), an electron transport layer (8), an electron injection layer (9) and a cathode layer (10), wherein the light-emitting layer comprises a host light-emitting material and a guest light-emitting material, and the guest light-emitting material or the electron transport layer (8) material is selected from the bipyridine compound according to claim 1 or 2.

7. An electroluminescent device according to claim 6, characterized in that: The host luminescent material is composed of a first host luminescent material and a second host luminescent material in a mass ratio of (30-60): (70-40).

8. An electroluminescent device according to claim 6 or 7, characterized in that: The mass fraction of the guest luminescent material in the entire luminescent layer (6) is 0.1% to 3.0%.

9. A display panel, characterized in that: The display panel comprises the electroluminescent device according to any one of claims 6 to 8.

10. An electronic device, characterized in that: The electronic device comprises the electroluminescent device according to any one of claims 6 to 8.

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