A nitrogen-containing organic compound and an electroluminescent device thereof

Abstract

The application belongs to the technical field of organic light-emitting materials and semiconductors, and provides a nitrogen-containing organic compound and an electroluminescent device thereof. The structural formula of the nitrogen-containing organic compound is: the electroluminescent device prepared by taking the nitrogen-containing organic compound as an electron transport material effectively reduces a driving voltage, improves light-emitting efficiency and light-emitting brightness, and prolongs a service life.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic light-emitting materials and semiconductor technology, and particularly relates to a nitrogen-containing organic compound and an electroluminescent device thereof. BACKGROUND

[0002] New materials are an important driving force for promoting the innovation of display technology, and have been one of the main tasks of researchers in this field. At present, mature electroluminescent devices mostly use a multi-layer functional layer composite to achieve the function, and the functional layers mainly include a hole injection layer, a hole transport layer, a hole blocking layer, an electron injection layer, an electron transport layer, an electron blocking layer and a light-emitting layer. The main purpose of adding each functional layer is to balance the electrons and holes injected from the cathode and anode, so as to improve the recombination ratio of holes and electrons in the light-emitting layer, improve the exciton utilization rate of the electroluminescent device, and ultimately improve the luminous efficiency and service life of the electroluminescent device.

[0003] However, in the electroluminescent device, the transmission rate of electrons in the carrier is lower than that of holes, and the transmission rate of the two is about one order of magnitude, which makes the number of electrons and holes in the light-emitting layer unbalanced, resulting in reduced luminous efficiency and affecting the performance of the electroluminescent device. And the conventional triarylamine hole transport material is easy to obtain and the material development is extensive, so that the electron transport material is relatively scarce compared with the hole transport material.

[0004] US2016 / 0233434 Al discloses a compound with excellent electron transport capacity and an electroluminescent device comprising the compound, but the driving voltage is high, and the brightness and service life are insufficient.

[0005] Therefore, it is an urgent problem for those skilled in the art to develop a new type of high-efficiency electron transport material. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a nitrogen-containing organic compound and an electroluminescent device thereof, which solve the technical problems of high driving voltage, insufficient brightness and service life of the electroluminescent device caused by the existing electron transport material.

[0007] The present application is realized by the following technical scheme:

[0008] In a first aspect of the present application, a nitrogen-containing organic compound is provided, and the structural formula of the nitrogen-containing organic compound is shown as formula (1):

[0009]

[0010] In the formula: is structure C;

[0011] A is selected from substituted or unsubstituted C6-C10 aryl; 30 ;

[0012] B is a 5-6 membered ketone-containing nitrogen heterocycle; Y1-Y5 are each independently selected from ketone, CR and H, at least one of Y1-Y5 is ketone and at most one is H, when one of Y1-Y5 is H, the remaining four form a 5-membered nitrogen heterocycle with N; R is selected from F, substituted or unsubstituted phenyl, cyano, trifluoromethyl, C1-C6 alkyl, C3-C6 cycloalkyl and substituted or unsubstituted C2-C8 alkenyl; when there are more than two groups of CR in Y1-Y5, the two adjacent R are bonded or not bonded; "— " represents a chemical bond;

[0013] X1-X6 are each independently selected from N and C, and two of X1-X6 are N.

[0014] In the nitrogen-containing organic compound of the present application, two of X1-X6 are N, because if the number of N is too small, the electron transport ability is weak when the nitrogen-containing organic compound is used as an electron transport material, and if the number of N is too large, the nitrogen-containing organic compound is difficult to synthesize, therefore, in the present application, two of X1-X6 are N.

[0015] In the present application, the term "aryl" refers to an all-carbon monocyclic or fused polycyclic (that is, rings that share adjacent pairs of carbon atoms) groups with a conjugated pi electron system.

[0016] In the present application, the substituted or unsubstituted C6-C10 aryl refers to the C6-C10 aryl which can be further substituted by a substituent, or can not be substituted by a substituent; when the C6-C10 aryl is substituted by a substituent, the substituent is phenyl. 30 30 30

[0017] Preferably, in the nitrogen-containing organic compound, A is selected from , , , , and , wherein "— " represents the bonding position of A and C, and "— " represents the bonding position of A and B. Preferably, in the nitrogen-containing organic compound, when R is a substituted phenyl, the substituent is selected from methyl and tert-butyl.

[0018]

[0019] ​​​​​​Preferably, in the nitrogen-containing organic compound, when R is a substituted C2-C8 alkenyl group, the substituent is selected from the group consisting of methyl, t-butyl, F, trifluoromethyl, cyano, and phenyl.

[0020] Preferably, the formula (1) is one of the following formulae (1-1), (1-2), (1-3), and (1-4):

[0021] .

[0022] Preferably, the nitrogen-containing organic compound is selected from one of the following compounds:

[0023] .

[0024] In a second aspect of the present application, an electroluminescent device is provided, comprising a cathode layer, an anode layer and an organic layer between the cathode layer and the anode layer, the organic layer comprising a hole transport layer (HTL), an emission material layer (EML) and an electron transport layer (ETL), the hole transport layer being between the anode layer and the emission material layer, and the electron transport layer being between the cathode layer and the emission material layer; the material of the electron transport layer comprising a nitrogen-containing organic compound as shown in formula (1).

[0025] Preferably, the electroluminescent device comprises, in order from the anode layer to the cathode layer, a substrate, an anode layer, a hole injection layer (HIL), a hole transport layer, an electron blocking layer (EBL), an emission material layer, a hole blocking layer (HBL), an electron transport layer, an electron injection layer (EIL), a cathode layer and a high-refractive covering protection layer (CPL).

[0026] As the substrate, it is required to have high mechanical strength, excellent thermal stability, excellent waterproofness and excellent transparency; and polyethylene terephthalate (PET) plastic is preferred.

[0027] As the anode layer, in order to enable the hole to be smoothly injected into the organic layer, the anode layer material is preferably a material with a large work function. As specific examples of the anode layer material that can be used in the present application, there are metals such as vanadium, chromium, copper and zinc or their alloys; oxides such as zinc oxide, aluminum oxide and tin dioxide; and conductive polymers such as polypyrrole and polyaniline.

[0028] The materials used in the hole injection layer, the hole transport layer, the electron blocking layer, the emission material layer, the hole blocking layer and the electron injection layer of the present application are selected from corresponding materials with excellent cost performance in the industry, and the compatibility between the layers needs to be determined through a series of tests and screening processes.

[0029] Preferably, the material of the hole injection layer of the present application is MoO3.

[0030] Preferably, the material of the hole transport layer of the present application is selected from one of the following materials:

[0031]

[0032] .

[0033] Preferably, the material of the electron blocking layer of the present application is selected from one of the following materials:

[0034] .

[0035] Preferably, the material of the light emitting layer of the present application comprises a host light emitting material and a guest light emitting material, the host light emitting material comprises a first host light emitting material and a second host light emitting material; wherein the first host light emitting material is selected from and , the second host light emitting material is , the mass ratio of the first host light emitting material and the second host light emitting material is 30:70~60:40, the guest light emitting material used in combination is , the mass fraction of the guest light emitting material in the entire light emitting layer is 0.1%~3.0%.

[0036] Preferably, the material of the hole blocking layer of the present application is selected from one of the following materials:

[0037] .

[0038] Preferably, the material of the electron injection layer of the present application is LiF.

[0039] As the cathode layer, in order to make the electron easily injected to the functional organic layer, the cathode layer material is preferably a material with small work function. As a specific example of the cathode layer material that can be used in the present application, it can be a metal such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin and lead, or an alloy thereof, for example, Mg-Al, Mg-Ag.

[0040] The high refractive index cover layer used in the present application can improve the refractive index of the surface of the cathode layer and improve the light extraction efficiency; the cover layer material is preferably .

[0041] In the third aspect of the present application, a preparation method of the electroluminescent device is provided. After pretreatment and cleaning, the substrate is adhered with an anode layer, and then a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transport layer and an electron injection layer with a set thickness are successively evaporated under low temperature conditions. The cathode layer and the cover protection layer are continuously sputtered under low temperature, and finally the device is packaged by using conventional device packaging means to obtain the electroluminescent device.

[0042] In a fourth aspect, the present application provides a display panel comprising the electroluminescent device as described above.

[0043] Compared with the prior art, the present application has the following advantages:

[0044] The nitrogen-containing organic compound of the present application has the following advantages: 1) Firstly, the electron-withdrawing effect of the ketone group (C=O) in the nitrogen-containing heterocycle B with ketone group can reduce the lowest unoccupied molecular orbital (LUMO) energy level of the molecule, which is beneficial to the energy level matching of the electron transport layer and the light-emitting layer, so as to improve the electron mobility, facilitate the electron transfer from the cathode layer to the light-emitting layer, thereby reducing the driving voltage and improving the light-emitting performance of the electroluminescent device; secondly, the rigid cyclic structure of the nitrogen-containing heterocycle B with ketone group can promote intermolecular π-π stacking to form an ordered electron transport channel and reduce the electron transport resistance; thirdly, the cyclic backbone of the nitrogen-containing heterocycle B with ketone group endows the molecule with higher thermal stability (not easy to thermally decompose) and chemical stability (anti-oxygen and anti-humidity), thereby prolonging the service life of the electroluminescent device. 2) The aryl group A as a bridge linking the nitrogen-containing heterocycle B with ketone group and structure C can not only enhance the π-π stacking of the molecule, but also form an ordered electron transport channel to reduce the electron transport resistance. 3) The nitrogen atom in structure C can form a weak coordination with the cathode layer (such as Ca, Al, etc.) in the electroluminescent device to reduce the electron injection barrier; at the same time, structure C can enhance the rigidity of the molecular backbone, which cooperates with the cyclic backbone of the nitrogen-containing heterocycle B with ketone group to reduce the structural distortion caused by molecular thermal motion and improve the thermal decomposition temperature (Td) of the material, which is suitable for high-temperature evaporation film formation.

[0045] The electroluminescent device of the present application uses the nitrogen-containing organic compound as an efficient electron transport material for the electron transport layer, which effectively reduces the driving voltage, improves the light-emitting efficiency and luminance, and prolongs the service life. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0047] Figure 1 is a cross-sectional view of the electroluminescent device of the present application;

[0048] Figure 2 is the nuclear magnetic resonance spectrum of compound 1 of the present application;

[0049] Figure 3NMR spectrum of compound 50 of the present application;

[0050] Figure 4 NMR spectrum of compound 75 of the present application;

[0051] Figure 5 NMR spectrum of compound 81 of the present application;

[0052] Figure 6 NMR spectrum of compound 88 of the present application;

[0053] Figure 7 NMR spectrum of compound 89 of the present application.

[0054] BRIEF DESCRIPTION OF DRAWINGS

[0055] 1 - substrate, 2 - anode layer, 3 - hole injection layer, 4 - hole transport layer, 5 - electron blocking layer, 6 - light emitting layer, 7 - hole blocking layer, 8 - electron transport layer, 9 - electron injection layer, 10 - cathode layer, 11 - cover layer. DETAILED DESCRIPTION

[0056] Other advantages and benefits of the present application will become apparent to those skilled in the art, upon consideration of the following detailed description of embodiments of the application. The present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0057] The following examples were prepared using conventional equipment in the art. Unless otherwise indicated, the experimental procedures in the following examples were performed according to conventional procedures, or according to the procedures recommended by the manufacturer. Unless otherwise indicated, the process equipment or apparatus in the following examples were conventional equipment or apparatus in the art. The following examples were prepared using various starting materials, all of which were conventional commercially available products, unless otherwise indicated, and were of conventional specifications in the art.

[0058] In addition, the following specific examples can be used by those skilled in the art to prepare compounds 1-87.

[0059] Important reactants involved in the present application:

[0060] .

[0061] wherein, the above reactants, compounds C1, C2, C3, C4 are obtained by chemical synthesis, and the others are commercially available.

[0062] Preparation Example 1 (synthesis of compound 1)

[0063] (1) Synthesis of compound C1:

[0064]

[0065] Step one:

[0066] Procedure: under nitrogen protection, 4-bromo-2-chloropyridine (96 g, 0.5 mol), 2-formylphenylboronic acid (75 g, 0.5 mol), 800 mL of tetrahydrofuran (THF), 200 mL of H2O, K2CO3 (138 g, 1.0 mol) were sequentially added into a 500 mL three-necked flask, stirred and heated to 40°C, the solution was clear, then Pd(PPh3)4 (11.6 g, 10 mmol) was added, then heated to 70°C and continuously reacted for 12 h until the reaction was completed; the reaction solution was cooled to room temperature, extracted with dichloromethane, the organic phases were combined, dried with anhydrous magnesium sulfate, filtered, concentrated, and the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:20) to obtain compound C1-1, 80.5 g, yield 74%, HPLC content 98.8%.

[0067] Step two:

[0068] Operation process: under nitrogen protection, in a 2.5L three-necked flask, compound C1-1 (65g, 0.3mol), benzoic acid amine (123g, 0.9mol), 1000mL of N,N-dimethylformamide (DMF), 4-chlorobenzenesulfonic acid (CBSA) (5.8g, 0.03mol) were added in turn, a white LED light was turned on for irradiation, stirring was started until the solution was clear, a catalyst fac-Ir(ppy)3 (3.9g, 6mmol) was added, the system was heated to 80℃, the LED light was irradiated at this temperature for 12h until the reaction was completed. After the reaction was completed, the DMF was removed by low-temperature and reduced-pressure concentration, 1L of water was added, and the pH value was adjusted to 6-8 with an appropriate amount of saturated sodium bicarbonate, the aqueous phase was extracted with dichloromethane for several times, the organic phases were combined, dried with anhydrous magnesium sulfate, filtered, concentrated, and the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:18) to obtain compound C1-2, 40.6g in weight, the yield was 63%, and the HPLC content was 98%.

[0069] Step three:

[0070] Operation process: under nitrogen protection, in a 2.5L three-necked flask, compound C1-2 (107g, 0.5mol), pinacol diboronic acid (127g, 0.5mol), potassium acetate (KOAc) (98g, 1.0mol), 1,4-dioxane 1000mL were added in turn, stirring was started, the system was heated to 60℃, then Pd(dppf)Cl2 (7.3g, 0.01mol) was added, then the temperature was continuously increased to 100℃, and the reaction was continuously carried out for 8h until compound C1-2 was completely reacted. After the reaction was completed, the reaction liquid was directly filtered, the filtrate was collected, the filtrate was concentrated under reduced pressure and dry, then 1000mL of toluene was added to dissolve it, and then it was washed with water, the organic phase was dried and concentrated, the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 15:1), the column eluate was concentrated under reduced pressure until solid precipitated, then the temperature was decreased to 15℃ for crystallization, the filter was stopped, and the compound C1 was obtained by drying, 122g in weight, the yield was 80%, the HPLC content was 99%, and the LC-MS (Liquid Chromatograph-Mass Spectrometer) showed that the molecular weight was 307.2.

[0071] (2) Synthesis of compound 1:

[0072]

[0073] Step one:

[0074] Operation process: under nitrogen protection, compound C1 (31 g, 0.1 mol), compound A1 (29 g, 0.1 mol), 200 mL of THF, 40 mL of H2O, K2CO3 (28 g, 0.2 mol) were sequentially added into a 1.0 L three-necked flask, and stirred and heated to 40°C. After the solution was clear, 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 h. The reaction solution was cooled to room temperature, extracted with ethyl acetate, and the organic phases were combined, dried over anhydrous magnesium sulfate, filtered, concentrated, and the residue was purified by silica gel column chromatography (dichloromethane / petroleum ether = 1:12) to obtain compound 1-1, 30.1 g, yield 78%, HPLC content 98%, LC-MS showed the molecular weight was 385.0.

[0075] Step two:

[0076] Operation process: under nitrogen protection, compound 1-1 (3.9 g, 0.01 mol), compound B4 (2.2 g, 0.01 mol) and 50 mL of toluene were added into a 100 mL three-necked flask, stirred until the solution was clear, Pd2(dba)3 (0.18 g, 0.2 mmol), Am-phos [(4-(N,N-dimethylamino)phenyl] di-tert-butyl phosphine (0.08 g, 0.3 mmol), sodium tert-butoxide (1.9 g, 0.02 mol) were added, the reaction solution was heated to 110°C, and the reaction was continued for 10 h. After the reaction was completed, the hot solution was filtered with diatomite, the filtrate was cooled to room temperature, purified water was added for washing, and the organic phase was retained after separation. The aqueous phase was extracted with ethyl acetate, and the organic phases were combined, dried over anhydrous magnesium sulfate, concentrated, and columned (dichloromethane / petroleum ether = 1:10) to obtain compound 1, 3.8 g, yield 73%, HPLC content 99%, LC-MS showed the molecular weight was 526.2. The nuclear magnetic resonance spectrum of compound 1 is shown in Figure 2

[0077] NMR data of compound 1: 1 H NMR (500 MHz, CDOD3) δ 9.30 (s, 1H), 9.12 (s,1H), 8.97 (s, 1H), 8.36 (s, 1H), 8.20 (d, J = 25.0 Hz, 2H), 7.99 (d, J ​= 10.0 Hz, 3H), 7.88 (s, 1H), 7.80 - 7.70 (m, 5H), 7.65 (s, 1H), 7.57 (s, 2H), 7.50 (s, 1H), 7.44 (s, 1H), 7.37 (s, 1H), 7.14 (s, 1H), 5.59 (s, 1H).

[0078] Compound Preparation Example 2 (synthesis of compound 50)

[0079] (1) Synthesis of compound C2:

[0080]

[0081] Procedure: the synthesis process of compound C2 was similar to the synthesis process of compound C1-2 to compound C1 in compound preparation example 1, using 2-bromo-1,10-phenanthroline (130, 0.5 mol) instead of compound C1-2 (107 g, 0.5 mol), to obtain compound C2, 124 g in weight, yield 81%, HPLC content 99%, LC-MS showed that the molecular weight was 307.2.

[0082] (2) Synthesis of compound 50:

[0083]

[0084] Step one:

[0085] Procedure: the synthesis process of compound 50-1 was similar to the synthesis process of compound C1 to compound 1-1 in compound preparation example 1, using compound C2 (31 g, 0.1 mol) instead of compound C1 (31 g, 0.1 mol), and using compound A3 (34 g, 0.1 mol) instead of compound A1 (29 g, 0.1 mol), to obtain compound 50-1, 34.4 g in weight, yield 79%, HPLC content 98%, LC-MS showed that the molecular weight was 435.1.

[0086] Step two:

[0087] Procedure: the synthesis process of compound 50 was similar to the synthesis process of compound 1-1 to compound 1 in compound preparation example 1, using compound 50-1 (4.4 g, 0.01 mol) instead of compound 1-1 (3.9 g, 0.01 mol), and using compound B10 (1.6 g, 0.01 mol) instead of compound B4 (2.2 g, 0.01 mol), to obtain compound 50, 3.8 g in weight, yield 73%, HPLC content 99%. The nuclear magnetic resonance spectrum of compound 50 is shown in Figure 3 .

[0088] LC-MS shows the nuclear magnetic hydrogen spectrum data of compound 50: 1 H NMR (500 MHz, CDOD3) δ 8.80 (s,1H), 8.42 (d, J = 30.0 Hz, 2H), 8.23 (d, J = 10.0 Hz, 4H), 7.88 (s, 1H), 7.65 (s,1H), 7.62 – 7.51 (m, 7H), 7.43 (s, 1H), 7.34 (s, 1H), 7.13 (s, 1H), 1.32 (s,2H), 1.05 (s, 2H).

[0089] Compound preparation example 3 (synthesis of compound 75)

[0090] (1) Synthesis of C3:

[0091]

[0092] Step one:

[0093] Operation process: take 2.0L three-necked flask, add 4,7-phenanthroline (54g, 0.3mol), 65% fuming sulfuric acid 600mL, bromine (72g, 0.45mol) in turn, start stirring, heat the reaction system to 150℃, react for 36h, monitor the complete reaction of raw materials by thin layer chromatography (TLC), and then reduce to room temperature, slowly pour the reaction system into a large amount of ice water under stirring condition, adjust the pH to 6.8 with 20wt% sodium hydroxide solution, extract with dichloromethane, dry the organic phase with anhydrous sodium sulfate, concentrate the obtained crude product, purify by column chromatography, and recrystallize the concentrated liquid with toluene to obtain compound C3-1, with a yield of 83%, HPLC content of 97%, and GC-MS shows that the molecular weight is 259.0.

[0094] Step two:

[0095] Operation process: the synthesis process of compound C3 is referred to the synthesis process of compound C1-2 to compound C1 in compound preparation example 1, and compound C3-1 (89, 0.3mol) is used to replace compound C1-2 (107g, 0.5mol) to obtain compound C3, with a weight of 75g, a yield of 82%, an HPLC content of 99%, and LC-MS shows that the molecular weight is 307.2.

[0096] (2) Synthesis of compound 75:

[0097]

[0098] Step one: The synthesis process of compound 75-1 was carried out according to the synthesis process of compound C1 to compound 1-1 in the compound preparation example 1, compound C3 (31 g, 0.1 mol) was used to replace compound C1 (31 g, 0.1 mol), compound A4 (34 g, 0.1 mol) was used to replace compound A1 (29 g, 0.1 mol), and compound 75-1 was obtained, weighing 34.4 g, with a yield of 79%, HPLC content of 98%, and LC-MS showing a molecular weight of 435.1.

[0099] Step two:

[0100] Operation process: The synthesis process of compound 75 was carried out according to the synthesis process of compound 1-1 to compound 1 in the compound preparation example 1, compound 75-1 (4.4 g, 0.01 mol) was used to replace compound 1-1 (3.9 g, 0.01 mol), and compound B14 (2.2 g, 0.01 mol) was used to replace compound B4 (2.2 g, 0.01 mol), and compound 75 was obtained, weighing 3.9 g, with a yield of 74%, HPLC content of 99%, and LC-MS showing a molecular weight of 526.2. The nuclear magnetic spectrum of compound 75 is shown in Figure 4

[0101] NMR data of compound 75: 1 H NMR (500 MHz, CDOD3) δ 9.18 (s, 1H), 8.94 –8.79 (m, 3H), 8.42 – 8.31 (m, 3H), 8.25 – 8.09 (m, 3H), 7.97 (s, 1H), 7.75(s, 2H), 7.42 (d, J = 30.0 Hz, 2H), 7.23 (d, J = 25.0 Hz, 3H), 1.35 (s, 9H), 0.96(s, 2H), 0.75 (s, 2H).

[0102] Compound preparation example 4 (synthesis of compound 81)

[0103] (1) Synthesis of compound C4:

[0104]

[0105] Step one:

[0106] ​Operation process: under nitrogen protection, 4-bromo-1-naphthylamine (111 g, 0.5 mol), 1.0 L of THF, ethyl chloroformate (ClCO2Et) (65 g, 0.6 mol), triethylamine (TEA) (61 g, 0.6 mol) were sequentially added into a 2.5 L three-necked flask, and stirring was started. The system was heated to 80℃ for 6 h until the reaction was completed. The reaction solution was concentrated, and the residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:20) to obtain compound C4-1, 107.4 g in yield, 73% in HPLC content, and 294.0 in LC-MS molecular weight.

[0107] Step two:

[0108] Operation process: under nitrogen protection, compound C4-1 (59 g, 0.2 mol), hexamethylenetetramine (urotropine, (CH2)6N4) (42 g, 0.3 mol), 500 mL of trifluoroacetic acid (TFA) were sequentially added into a 2.0 L three-necked flask, and stirring was started. The reaction was carried out at room temperature for 4 h until the reaction was completed. The reaction solution was concentrated, and then 600 mL of ethanol (EtOH) and KOH (34 g, 0.6 mol) were added into the three-necked flask. Stirring was started, and potassium ferricyanide (K3Fe(CN)6) (99 g, 0.3 mol) was added. The reaction system was heated to 80℃, and the reaction was continuously carried out for 8 h. After the reaction was completed, the system was cooled to room temperature, and 15% dilute hydrochloric acid was added to the system until the pH value was neutral. Ethyl acetate was added for extraction for several times, and the organic phase was combined, dried, and concentrated to obtain a residue. The residue was purified and separated by silica gel column chromatography (dichloromethane / petroleum ether = 1:15) to obtain compound C4-2, 30.7 g in yield, 52% in HPLC content, and 259.0 in LC-MS molecular weight.

[0109] Step three:

[0110] Operation process: the synthesis process of compound C4 was the same as that of compound C1-2 to compound C1 in compound preparation example 1. Compound C4-2 (52 g, 0.2 mol) was used to replace compound C1-2 (107 g, 0.5 mol) to obtain compound C4, 50 g in yield, 81% in HPLC content, and 307.2 in LC-MS molecular weight.

[0111] (2) Synthesis of compound 81:

[0112]

[0113] Step one:

[0114] Procedure: The synthesis of compound 81-1 was performed following the procedure of compound preparation example 1, compound C1 to compound 1-1, using compound C4 (31 g, 0.1 mol) instead of compound C1 (31 g, 0.1 mol), and compound A2 (27 g, 0.1 mol) instead of compound A1 (29 g, 0.1 mol) to give compound 81-1, 29.3 g, 80% yield, 98% HPLC purity, LC-MS showed the molecular weight of 367.1.

[0115] Step two:

[0116] Procedure: The synthesis of compound 81 was performed following the procedure of compound preparation example 1, compound 1-1 to compound 1, using compound 81-1 (3.7 g, 0.01 mol) instead of compound 1-1 (3.9 g, 0.01 mol), and compound B12 (2.0 g, 0.01 mol) instead of compound B4 (2.2 g, 0.01 mol) to give compound 81, 3.8 g, 72% yield, 99% HPLC purity, LC-MS showed the molecular weight of 532.2. The NMR spectra of compound 81 are shown in Figure 5

[0117] NMR data of compound 81: 1 H NMR (500 MHz, CDOD3) δ 9.74 (s, 1H), 9.36(s, 1H), 8.97 (s, 1H), 8.06 (s, 1H), 8.01 (s, 1H), 7.93 (d, J = 5.0 Hz, 2H),7.84 (s, 1H), 7.79 (s, 2H), 7.65 (s, 1H), 7.60 (s, 1H), 7.49 – 7.37 (m, 6H),7.13 (s, 1H), 2.45 (s, 2H), 2.20 (s, 2H), 1.47 (dd, J = 30.0, 20.0 Hz, 6H).

[0118] Compound preparation example 5 (synthesis of compound 88)

[0119]

[0120] Step one:

[0121] ​Procedure: The procedure for the synthesis of compound 88-1 was carried out according to the procedure for the synthesis of compound C1 to compound 1-1 in the compound preparation example 1, using compound C4 (31 g, 0.1 mol) instead of compound C1 (31 g, 0.1 mol), and using compound A5 (36 g, 0.1 mol) instead of compound A1 (29 g, 0.1 mol) to give compound 88-1, 37.2 g in yield, 81%, HPLC content 98%, LC-MS showed the molecular weight 459.1.

[0122] Step two:

[0123] Procedure: The procedure for the synthesis of compound 88 was carried out according to the procedure for the synthesis of compound 1-1 to compound 1 in the compound preparation example 1, using compound 88-1 (4.6 g, 0.01 mol) instead of compound 1-1 (3.9 g, 0.01 mol), and using compound B16 (2.2 g, 0.01 mol) instead of compound B4 (2.2 g, 0.01 mol) to give compound 88, 4.3 g in yield, 73%, HPLC content 99%, LC-MS showed the molecular weight 594.3. The NMR spectra of compound 88 are shown in Figure 6

[0124] The NMR data of compound 88:1H NMR (500 MHz, CDOD3) δ 9.74 (s, 1H), 9.36 (s, 1H), 8.97 (s, 1H), 8.52 (s, 1H), 8.19 (d, J = 37.5 Hz, 2H), 8.01 – 7.79 (m, 5H), 7.70 (s, 2H), 7.57 (s, 1H), 7.47 (s, 2H), 7.35 (s, 1H), 7.24 (s, 1H), 1.27 (d, J = 6.6 Hz, 11H), 1.01 (s, 2H). J J The NMR data of compound 88:1H NMR (500 MHz, CDOD3) δ 9.74 (s, 1H), 9.36 (s, 1H), 8.97 (s, 1H), 8.52 (s, 1H), 8.19 (d, J = 37.5 Hz, 2H), 8.01 – 7.79 (m, 5H), 7.70 (s, 2H), 7.57 (s, 1H), 7.47 (s, 2H), 7.35 (s, 1H), 7.24 (s, 1H), 1.27 (d, J = 6.6 Hz, 11H), 1.01 (s, 2H).

[0125] Compound preparation example 6 (synthesis of compound 89)

[0126]

[0127] Step one:

[0128] ​​The operation process of synthesizing compound 89-1 is as follows: the synthesis process of compound 89-1 is referred to the synthesis process of compound C1 to compound 1-1 in compound preparation example 1, compound C4 (31 g, 0.1 mol) is used to replace compound C1 (31 g, 0.1 mol), and compound A6 (39 g, 0.1 mol) is used to replace compound A1 (29 g, 0.1 mol), to obtain compound 89-1, 38.8 g in weight, the yield is 80%, the HPLC content is 98%, and the LC-MS shows that the molecular weight is 487.1.

[0129] Step two:

[0130] The operation process of synthesizing compound 89 is as follows: the synthesis process of compound 89 is referred to the synthesis process of compound 1-1 to compound 1 in compound preparation example 1, compound 89-1 (4.9 g, 0.01 mol) is used to replace compound 1-1 (3.9 g, 0.01 mol), and compound B17 (2.4 g, 0.01 mol) is used to replace compound B4 (2.2 g, 0.01 mol), to obtain compound 89, 4.8 g in weight, the yield is 74%, the HPLC content is 99%, and the LC-MS shows that the molecular weight is 648.3. The nuclear magnetic spectrum of compound 89 is shown in Figure 7

[0131] The nuclear magnetic hydrogen spectrum data of compound 89 is as follows: 1H NMR (500 MHz, CDOD3) δ 9.74 (s, 1H), 9.60 (s, 1H), 9.36 (s, 1H), 9.28 (s, 1H), 9.07 – 8.92 (m, 3H), 8.37 (s, 1H), 8.29 (d, J = 15.0 Hz, 2H), 8.15 (s, 1H), 7.96 (s, 1H), 7.84 (s, 1H), 7.67 (d, J = 30.0Hz, 2H), 7.57 (s, 1H), 7.47 (s, 2H), 7.35 (s, 1H), 7.24 (s, 1H), 2.08 (d, J =29.3 Hz, 4H), 1.71 (d, J = 50.0 Hz, 4H), 1.28 (s, 9H).

[0132] The synthesis of other compounds is carried out by referring to the synthesis method of compound 1, 50, 75, 81, 88 and 89, and selecting corresponding compound A (A1-A6), compound B (B1-B24) and compound C (C1-C4).

[0133] The structure schematic diagram of the electroluminescent device in each embodiment and the comparative example of the present application is as follows:​Figure 1 As shown, 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, a cathode layer 10 and a cover layer 11.

[0134] The electroluminescent devices of Examples 2-26 and Comparative Examples 1-4 were prepared according to the electroluminescent device preparation method of Example 1.

[0135] Example 1: Electroluminescent device containing compound 1

[0136] From the anode layer to the cathode layer, the device comprises a PET substrate, indium tin oxide (ITO), MoO3, HT-1, EB-1, the light emitting layer 6, HB-1, the electron transport layer 8, LiF, Al-Mg and CPL; the material used for the CPL is ;

[0137] In the light emitting layer 6, CBP and BCP are used as the host light emitting material, and BD-1 is used as the guest light emitting material, and the mass ratio of the three is 49:49:2.

[0138] The preparation method of the above electroluminescent device containing compound 1 comprises the following steps:

[0139] 1. A 1.5 mm PET substrate was used as the substrate 1, and a 0.15 mm ITO material was used as the anode layer 2. The PET substrate and ITO material were washed by alkali washing, pure water washing, drying, and then ultraviolet-ozone washing to remove organic residues on the surface of the PET substrate and ITO material.

[0140] 2. A layer of ITO material was adhered to the PET substrate. A vacuum evaporation device was used to evaporate MoO3 with a film thickness of 20 nm as the hole injection layer 3, then evaporate HT-1 with a thickness of 80 nm as the hole transport layer 4, then evaporate EB-1 with a thickness of 30 nm as the electron blocking layer 5, then continue to evaporate the light emitting layer 6 formed by CBP, BCP and BD-1 with a mass ratio of 49:49:2 with a thickness of 60 nm on EB-1, then continue to evaporate HB-1 with a thickness of 10 nm as the hole blocking layer 7 on the light emitting layer 6, then continue to evaporate compound 1 with a thickness of 30 nm as the electron transport layer 8, then continue to evaporate LiF with a thickness of 16 nm as the electron injection layer 9 on the electron transport layer 8, then sputter Al-Mg (Al:Mg=9:1) alloy with a thickness of 10 nm as the cathode layer 10 by low-temperature sputtering after the electron injection layer 9 is evaporated, and finally continue to evaporate CPL with a thickness of 40 nm as the high refractive cover layer 11 on the cathode layer 10.

[0141] 3. Vacuum encapsulation was performed on MoO3, HT-1, EB-1, the light-emitting layer 6, HB-1, the electron transport layer 8 and LiF to obtain the electroluminescent device.

[0142] Examples 2 to 26

[0143] The difference from Example 1 is that Examples 2 to 26 respectively select compounds 2, 3, 4, 5, 9, 11, 50, 59, 60, 61, 62, 63, 64, 70, 71, 72, 75, 81, 83, 84, 85, 86, 87, 88 and 89 as the electron transport material to prepare the electron transport layer 8.

[0144] Comparative Example 1

[0145] The difference from Example 1 is that the electron transport layer 8 is prepared by using the electron transport material in the US patent application with publication number US2016 / 0233434 Al.

[0146] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(80 nm) / EB-1(30 nm) / CBP:BCP:BD-1=49:49:2(60 nm) / HB-1(10 nm) / DCD-1(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0147] Comparative Example 2

[0148] The difference from Example 1 is that the electron transport layer 8 is prepared by using the electron transport material in the US patent application with publication number US2016 / 0233434 Al.

[0149] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(80 nm) / EB-1(30 nm) / CBP:BCP:BD-1=49:49:2(60 nm) / HB-1(10 nm) / DCD-23(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0150] Comparative Example 3

[0151] The difference from Example 1 is that the electron transport layer 8 is prepared by using the electron transport material in the US patent application with publication number US2016 / 0233434 Al.

[0152] ​​​The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(80 nm) / EB-1(30 nm) / CBP:BCP:BD-1=49:49:2(60 nm) / HB-1(10 nm) / DCD-48(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0153] Comparative Example 4

[0154] The difference from Example 1 is that the material in US Patent Application Publication No. US2016 / 0233434A1 is used The electron transport layer 8 is prepared as an electron transport material.

[0155] The structure of the electroluminescent device is: PET substrate / ITO / MoO3(20 nm) / HT-1(80 nm) / EB-1(30 nm) / CBP:BCP:BD-1=49:49:2(60 nm) / HB-1(10 nm) / DCD-61(30 nm) / LiF(16 nm) / Al:Mg=9:1(10 nm) / CPL(40 nm).

[0156] The electroluminescent devices in the above examples and comparative examples are prepared into 30 mm x 30 mm samples, and then the anode layer and the cathode layer are connected by using an industry- known driving circuit to characterize the luminescent performance indicators of the electroluminescent devices. Specifically, the driving voltage and the luminous efficiency of the electroluminescent device are measured at a current density of 10 mA / cm, and the time (LT 50 , i.e. the service life) required for the brightness of the electroluminescent device to become 50% of the initial brightness is measured at a current density of 50 mA / cm. The test results are shown in Table 1.

[0157] Table 1: Performance test results of electroluminescent devices

[0158]

[0159] As can be seen from the test data in Table 1, compared with the electroluminescent devices prepared by using the materials DCD-1, DCD-23, DCD-48 and DCD-61 in Comparative Examples 1-4, the electroluminescent device prepared by using the nitrogen-containing organic compound of the present application as an electron transport material has obvious advantages in comprehensive luminescent performance, wherein the driving voltage is significantly reduced, the current efficiency is increased by more than 2 times, the brightness is increased by about 65%, and the service life is prolonged by about 30%.

[0160] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A nitrogen-containing organic compound, characterized by, The nitrogen-containing organic compound is selected from one of the following compounds: 。 2. An electroluminescent device, characterized by The organic layer comprises a hole transport layer, a light emitting layer and an electron transport layer, the hole transport layer is located between the anode layer and the light emitting layer, and the electron transport layer is located between the cathode layer and the light emitting layer; the material of the electron transport layer comprises the nitrogen-containing organic compound of claim 1.

3. The electroluminescent device according to claim 2, characterized in that The material of the light-emitting layer comprises a host light-emitting material and a guest light-emitting material; the host light-emitting material comprises a first host light-emitting material and a second host light-emitting material, the first host light-emitting material is selected from and , and the second host light-emitting material is .

4. The electroluminescent device according to claim 3, characterized in that The guest light emitting material is .

5. The electroluminescent device of claim 2, wherein, The material of the hole transport layer is selected from one of the following materials: 。

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