An organic electroluminescent material based on pyrazine derivatives, its preparation method and application

Abstract

This invention discloses an organic electroluminescent material based on a pyrazine derivative, its preparation method, and its applications, belonging to the technical field of electroluminescent materials. The preparation method includes the following steps: mixing and reacting a diamine compound and a diketone compound to obtain an intermediate; then mixing the obtained intermediate with diphenylamine for a coupling reaction to obtain the organic electroluminescent material based on the pyrazine derivative. This invention also discloses the electroluminescent material prepared by the above method and its application in electroluminescent devices. This invention combines AIE (Alternating Electroluminescent) properties in a single molecule and possesses acid-induced color-changing properties. Utilizing these acid-induced color-changing properties, it can be applied in the field of fluorescent anti-counterfeiting and has great application potential in displays, lighting technology, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of electroluminescent materials technology, and particularly relates to an organic electroluminescent material based on pyrazine derivatives, its preparation method and application. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are increasingly popular in display and phototherapy lighting applications due to their advantages such as high-quality color, low energy cost, light weight, and flexibility. However, several challenges have arisen before OLEDs can be truly applied to large displays such as televisions, primarily including color purity, stability, and limited external quantum efficiency (EQE) in solid-state applications. Currently, commercially available emitting materials for OLED displays are generally phosphorescent materials, such as iridium and platinum complexes, which can effectively collect singlet (25%) and triplet (75%) excitons, potentially providing close to 100% internal quantum efficiency. However, these phosphorescent materials require the use of expensive rare noble metals, increasing manufacturing costs. Small organic molecule fluorophores based on donor-acceptor (DA) molecular structures are among the candidates for preparing high-efficiency OLEDs due to their simple structure, good reproducibility, easy purification, and balanced charge transport properties.

[0003] The molecular arrangement of fluorescent molecules in the solid state significantly affects their photoluminescence quantum yield (PLQY) and the EQE of devices. Due to the inherent aggregation properties of molecules during thin film fabrication, quenching effects typically occur through aggregation-induced quenching (ACQ). In recent years, there has been increasing interest in emitters with aggregation-induced emission (AIE) properties. These emitters exhibit weak fluorescence in organic solutions but transform into highly efficient strong emitters when fabricating solid thin films. AIE emitters are suitable for device fabrication, and their aggregation-induced quenching (ACQ) performance is superior to that of ordinary emitters, significantly reducing fabrication complexity and thus increasing yield.

[0004] To date, an increasing number of AIE materials exhibiting mechanochromic properties have been developed and applied in various fields, including pressure sensors, information security and storage, optoelectronic devices, and wearable systems. However, current mechanochromic materials with AIE properties still suffer from drawbacks such as complex operation or prolonged conversion time, which hinder their practical application.

[0005] Therefore, how to provide a mechanical color-changing material with AIE properties that is simple to operate and highly efficient is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an organic electroluminescent material based on pyrazine derivatives, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing an organic electroluminescent material based on a pyrazine derivative includes the following steps:

[0009] A diamine compound and a diketone compound are mixed and reacted to obtain an intermediate. The obtained intermediate is then mixed with diphenylamine and coupled to obtain the organic electroluminescent material based on the pyrazine derivative.

[0010] Preferably, the diamine compound and the diketone compound react in an organic solution.

[0011] Preferably, the organic solution includes an ethanol solution and / or an acetic acid solution.

[0012] Preferably, the molar ratio of the diamine compound to the diketone compound is 1:1.

[0013] This invention is carried out through a cyclocondensation reaction to generate a condensation product containing a pyrazine ring under acidic conditions.

[0014] Preferably, the diamine compound is pyridine-3,4-diamine.

[0015] Preferably, the diketone compound is 1,2-bis(4-bromophenyl)ethane-1,2-dione or 3,6-dibromophenanthroline-9,10-dione.

[0016] Beneficial effects: The reaction equation for the preparation of the intermediate is as follows:

[0017]

[0018] Preferably, the mixing reaction is carried out at a temperature of 90°C for 10 hours in an oxygen-free atmosphere.

[0019] Preferably, the molar ratio of the intermediate to diphenylamine is 1:2.3.

[0020] Preferably, the coupling reaction is a Buchwald-Hartwig coupling reaction, the temperature of the coupling reaction is 110°C, the time is 24 hours, and the atmosphere is an oxygen-free atmosphere.

[0021] Preferably, the intermediate and diphenylamine undergo a coupling reaction in toluene solution in the presence of a catalyst;

[0022] The catalysts include Pd2(dpa)3, Cs2CO3 and (t-Bu)3P.HBF4.

[0023] Beneficial effects: The reaction mechanism of the above coupling reaction is as follows:

[0024] (1) Oxidative addition: First, the active zero-valent palladium species [Pd] is generated through activation. 0 It undergoes oxidative addition with the CX bond (where X is a halogen) to form a divalent palladium complex.

[0025] (2) Amine affinity addition: Next, the amine undergoes ligand exchange with the divalent palladium complex to form an intermediate.

[0026] (3) Deprotonation: The intermediate is deprotonated by a strong base to generate another intermediate.

[0027] (4) Reduction and elimination: Finally, the intermediate undergoes reduction and elimination to generate the target compound, namely the N-arylated product of the amine, while the zero-valent palladium is recycled and enters the next catalytic cycle.

[0028] The reaction equations for the above reactions are as follows:

[0029]

[0030]

[0031] Organic electroluminescent materials based on pyrazine derivatives were prepared using the methods described above.

[0032] Preferably, the structural formula of the electroluminescent material is:

[0033] , .

[0034] Beneficial Effects: In the organic fluorescent molecules t-BuDPAiPP and t-BuDPAPQ designed in this invention, a donor-acceptor-donor structure (DAD) is formed by linking pyrazine derivatives (iPP and PQ) with t-BuDPA. The iPP and PQ motifs have good electron-withdrawing capabilities, which may help to obtain a smaller singlet-triplet bandgap (ΔEST) and promote system-to-system anti-crossover (RISC). Nitrogen atoms can promote spin-orbit coupling (SOC), thereby further enhancing the RISC process. In addition, PQ has both rigidity and planarity, which can promote favorable π-electron flow and high PLQY. Diphenylamine can promote the AIE effect through spatial conformational distortion. The electroluminescent materials provided by this invention are prepared by solution processing, and used as luminescent materials (guest materials) to dope with host materials to prepare luminescent layers. They can be applied to single-emitting-layer organic small molecule electroluminescent devices and have good conversion efficiency.

[0035] The above-mentioned application of pyrazine derivative-based organic electroluminescent materials in the field of fluorescent anti-counterfeiting.

[0036] The above-mentioned application of pyrazine derivative-based organic electroluminescent materials in electroluminescent devices.

[0037] An electroluminescent device includes a light-emitting layer comprising the aforementioned organic electroluminescent material.

[0038] Preferably, the electroluminescent material has a mass fraction of 3-15% in the light-emitting layer of the electroluminescent device.

[0039] More preferably, the light-emitting layer is prepared by mixing an electroluminescent material with a host material.

[0040] More preferably, the main material is PhCzBCz.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] The organic electroluminescent material based on pyrazine derivatives provided by this invention possesses aggregation-induced emission (AIE) and acid-induced color change properties. Its structure is a DAD-type molecule, where the confined rotation of the acceptor around the donor contributes to the AIE effect and increases the band gap energy by increasing the transition energy between the ground and excited states. The electroluminescent material provided by this invention not only exhibits excellent AIE properties but also acid-induced color change. Furthermore, this invention combines AIE properties with acid-induced color change performance in a single molecule, which can be applied to fluorescent anti-counterfeiting fields and has great application potential in displays and lighting technologies. In addition, the organic electroluminescent devices prepared using the organic small-molecule electroluminescent material of this invention exhibit good performance. Specifically, organic light-emitting devices (OLEDs) prepared using t-BuDPAiPP and t-BuDPAPQ achieved maximum EQEs of 1.5% and 0.77%, respectively, with emission peaks at 546 and 595 nm. The organic small-molecule electroluminescent material of this invention has significant application value in the development of multifunctional orange electroluminescent materials. Finally, the preparation method of the present invention is simple and the reaction conditions are mild, which is conducive to its widespread production and application. Attached Figure Description

[0043] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0044] Figure 1 The UV-Vis absorption spectra of the products from Examples 1-2 in different solutions are shown.

[0045] Wherein, (a) is Example 1, and (b) is Example 2;

[0046] Figure 2 The fluorescence emission spectra of the products from Examples 1-2 in different solutions are shown.

[0047] Wherein, (a) is Example 1, and (b) is Example 2;

[0048] Figure 3 The fluorescence emission spectra of the products from Examples 1-2 in methanol / water mixtures with different water volume fractions are shown below.

[0049] Wherein, (a) is Example 1, and (b) is Example 2;

[0050] Figure 4 This is a simulation diagram of the effect of the products of Examples 1-2 in the field of fluorescent anti-counterfeiting;

[0051] Wherein, (a) is Example 1, and (b) is Example 2;

[0052] Figure 5 The current density-voltage-brightness graphs are for the PhCzBCz doped electroluminescent devices produced in Examples 1-2.

[0053] Wherein, (a) is Example 1, and (b) is Example 2;

[0054] Figure 6 The current efficiency-luminance diagrams are shown for the PhCzBCz electroluminescent devices doped with the products of Examples 1-2.

[0055] Wherein, (a) is Example 1, and (b) is Example 2;

[0056] Figure 7 The electroluminescence spectra of the PhCzBCz-doped electroluminescent devices from Examples 1-2 are shown below.

[0057] Wherein, (a) is Example 1, and (b) is Example 2;

[0058] Figure 8 The graph shows the external quantum efficiency of the PhCzBCz electroluminescent devices doped with the products of Examples 1-2.

[0059] Among them, (a) is Example 1 and (b) is Example 2. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0062] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0063] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0064] In the embodiments of the present invention 1 H NMR, 13 The C NMR spectra were determined using a Bruker-400 NMR instrument.

[0065] Example 1

[0066] A method for preparing an organic electroluminescent material (t-BuDPAiPP) based on a pyrazine derivative includes the following steps:

[0067] (1) Preparation of intermediate 1: In a 100 ml double-necked flask, pyridine-3,4-diamine (0.445 g, 4.08 mmol), 1,2-bis(4-bromophenyl)ethane-1,2-dione (1.500 g, 4.08 mmol) and 50 ml of 95% ethanol solution were added sequentially. The mixture was stirred at 90 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature and the ethanol in the system was removed. The mixture was then extracted three times (3 × 30 mL) with water and dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate for 6 h. The mixture was filtered to obtain the crude product. The crude product was separated by silica gel column chromatography using petroleum ether and ethyl acetate in a 4:1 (V / V) ratio to obtain 1.1854 g of white solid intermediate 1 (2,3-bis(4-bromophenyl)pyrido[3,4-b]pyrazine), with a yield of 66.19%.

[0068] 1 H NMR (400 MHz, CDCl3) δ 9.58 (s, 1 H), 8.84 (d, J = 5.8 Hz, 1 H), 7.97(d, J = 5.8 Hz, 1 H), 7.53 (d, J = 8.5 Hz, 4H), 7.42 (dd, J = 8.6, 3.0 Hz, 4H). HRMS calce for C 19 H 11 Br2N3 [M] + 438.9320 found 438.8912.

[0069] (2) Preparation of t-BuDPAiPP: In a 100 ml double-necked flask, 2,3-bis(4-bromophenyl)pyrido[3,4-b]pyrazine (0.339 g, 0.773 mmol), bis(4-(tert-butyl)phenyl)amine (0.500 g, 1.78 mmol), Pd2(dpa)3 (0.0425 g, 0.046 mmol), Cs2CO3 (1.001 g, 3.09 mmol), (t-Bu)3P.HBF4 (0.014 g, 0.046 mmol) and 50 ml of 99.8% toluene solution were added sequentially. The reaction was stirred at 110 ℃ under an anaerobic atmosphere for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and the toluene in the system was removed. The mixture was extracted three times (3 × 30 mL) with water and dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate for 6 h, and then filtered. The crude product was then separated by silica gel column chromatography using petroleum ether and ethyl acetate in a 9:1 (V / V) ratio as eluents to obtain 0.383 g of an orange solid, 4,4'-(pyrido[3,4-b]pyrazine-2,3-diyl)bis(N,N-bis(4-(tert-butyl)phenyl)aniline), with a yield of 58.89%, denoted as t-BuDPAiPP.

[0070] 1 H NMR (400 MHz, CDCl3) δ 9.56 (m, 1H), 8.76 (dd, J = 20.5, 5.7 Hz,1H), 7.92 (d, J = 15.0 Hz, 1H), 7.53 (q, J = 8.8 Hz, 2H), 7.45 (d, J = 1.8Hz, 2H), 7.39 (m, 1H), 7.31 (dd, J = 8.6, 1.7 Hz, 7H), 7.07 (d, J = 8.7 Hz,8H), 7.03 (m, 4H), 1.33 (s, 36H). 13C NMR (101 MHz, CDCl3) δ 149.74, 149.40,147.14, 146.85, 146.24, 144.37, 143.86, 143.64, 131.70, 131.27, 130.87,130.54, 130.23, 126.33, 126.24, 125.12, 125.01, 120.49, 120.18, 34.42,31.46. HRMS calce for C 59 H 63 N5 [M + H] +841.5083 found 842.5136.

[0071] Example 2

[0072] A method for preparing an organic electroluminescent material (t-BuDPAPQ) based on a pyrazine derivative, comprising the following steps:

[0073] (1) Preparation of intermediate 2: In a 100 ml double-necked flask, pyridine-3,4-diamine (0.300 g, 2.75 mmol), 3,6-dibromophenanthrene-9,10-dione (1.001 g, 2.75 mmol), 10 ml of 95% ethanol solution, and 50 ml of 95% acetic acid solution were added sequentially. The mixture was stirred at 90 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, the ethanol in the system was removed, and the mixture was extracted three times (3 × 30 mL) with water and dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate for 6 h, and then filtered. The crude product was separated by silica gel column chromatography using a 7:1 (V / V) ratio of petroleum ether and ethyl acetate as eluents to obtain 0.9870 g of white solid intermediate 2 (3,6-dibromodibenzo[f,h]pyrido[3,4-b]quinoxaline), with a yield of 82.14%.

[0074] 1 H NMR (400 MHz, CDCl3) δ 9.78 (s, 1H), 9.25 (d, J = 8.6 Hz, 2H), 8.90 (d, J = 3.4 Hz, 1H), 8.61 (d, J = 5.2 Hz, 2H), 8.14 (d, J = 6.2 Hz, 1H), 7.90(d, J = 8.6 Hz, 2H). HRMS calce for C 19 H9Br2N3 [M] + 436.9163 found 437.1928.

[0075] (2) Preparation of t-BuDPAPQ: In a 100 ml double-necked flask, 3,6-dibromodibenzo[f,h]pyrido[3,4-b]quinoxaline (0.500 g, 1.14 mmol), bis(4-(tert-butyl)phenyl)amine (0.739 g, 2.63 mmol), Pd2(dpa)3 (0.0629 g, 0.068 mmol), Cs2CO3 (1.492 g, 4.58 mmol), (t-Bu)3P.HBF4 (0.020 g, 0.069 mmol) and 50 ml of 99.8% toluene solution were added sequentially. The reaction was stirred at 110 ℃ under an anaerobic atmosphere for 24 h. The reaction was stopped, cooled to room temperature, and toluene was removed from the system. The system was extracted three times (3 × 30 mL) with water and dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate for 6 h, and then filtered. The crude product was separated by silica gel column chromatography using petroleum ether and ethyl acetate in a ratio of 8:1 (v / v) as eluents to obtain an orange-red solid N. 3 N 3 N 6 N 6 0.532 g of tetrakis(4-(tert-butyl)phenyl)dibenzo[f,h]pyrido[3,4-b]quinoxaline-3,6-diamine was obtained with a yield of 55.59%, and was designated as t-BuDPAPQ.

[0076] 1 H NMR (400 MHz, CDCl3) δ 9.61 (s, 1H), 9.09 (dd, J = 8.9, 3.5 Hz, 2H), 8.74 (d, J = 5.8 Hz, 1H), 7.99 (d, J = 5.8 Hz, 1H), 7.63 (d, J = 2.1 Hz,2H), 7.37 (ddd, J = 13.8, 8.9, 2.1 Hz, 2H), 7.28 (dd, J = 8.8, 2.5 Hz, 8H), 7.07 (dd, J = 8.6, 3.8 Hz, 8H), 1.34 (s, 36H). 13 C NMR (101 MHz, CDCl3) δ151.48, 150.96, 147.15, 146.86, 144.06, 134.26, 133.43, 128.26, 127.64, 126.32, 124.89, 124.65, 123.38, 122.83, 122.49, 121.87, 121.35, 114.76,114.18, 34.44, 31.47. HRMS calce for C59 H 61 N5 [M + H] + 839.4927 found 840.4980.

[0077] Technical effect

[0078] Performance characterization and fabrication of single-emitting-layer polymer electroluminescent devices and testing of their luminescent performance:

[0079] 1. Testing Method

[0080] The UV-Vis absorption spectra of the products in Examples 1-2 were measured using a U-3900 UV-Vis spectrometer, and the fluorescence emission spectra were measured using a Hitachi F-700 fluorescence spectrometer.

[0081] The single-emitting-layer polymer electroluminescent device based on organic small molecule compound materials consists of the following components: an indium tin oxide (ITO) conductive glass substrate, PhCzBCz and TmPyPB as the host material and electron transport layer, respectively, and organic small molecules doped into PPF hosts with different doping concentrations as the emitting layer (EML). The substrate, host material, electron transport layer, and emitting layer are stacked sequentially. The products of Examples 1-2 account for 3-15 wt.% of the emitting layer in the electroluminescent device.

[0082] The polymer electroluminescent device is prepared by sequentially stacking ITO / PEDOT:PSS, (30 nm) / emitting layer, (x wt%, 30 nm) / TmPyPB, and (40 nm) / Liq (1 nm) / Al. The fabrication method includes the following steps:

[0083] In 3×10 -6 OLEDs were fabricated on an ITO glass substrate (110 nm, 15 Ω / m²) under substrate pressure. The effective area of ​​each device was 0.09 cm². 2 The deposition rate and thickness of all materials were monitored using an oscillating quartz crystal. The doped layer was deposited by utilizing two different sensors to monitor the deposition rates of the host material and the dopant material (electroluminescent material). The deposition rate of the host material was controlled at 0.2 nm·s. -1 The deposition rate of the doped material is adjusted according to the volume ratio of the dopant in the host material. The electroluminescence (EL) and current density-voltage (JV) characteristics of the device are measured using a constant current source (Keithley 2400 SourceMeter) combined with a photometer (Photo Research SpectraScan PR655).

[0084] 2. Effect Characterization

[0085] Figure 1 The images show the UV-Vis absorption spectra of Examples 1-2 in different solutions. (a) represents Example 1, and (b) represents Example 2.

[0086] like Figure 1 As shown, the two molecules exhibit similar absorption in different solvents, indicating that their ground-state electronic structure is independent of solvent polarity. In solution, their UV-Vis absorption spectra show two prominent bands: broad absorption peaks near 435 and 480 nm are mainly due to intramolecular charge transfer (ICT) between the diphenylamine donor and the pyrazine acceptor; strong absorption peaks at 335 nm and 299 nm are formed due to π-π* transitions. Since both molecules retain the same donor group, the position of the ICT absorption band is related to the intensity of the acceptor unit.

[0087] Figure 2 The images show the fluorescence emission spectra of Examples 1-2 in different solutions. Among them, (a) is Example 1 and (b) is Example 2.

[0088] like Figure 2 As shown, the emission spectrum exhibits a color shift from the low-polarity solvent to toluene to the high-polarity solvent dichloromethane, confirming the ICT transition in the emitter. This is due to the difference in dipole moments between the excited and ground states. t-BuDPAiPP and t-BuDPAPQ show the shortest emission wavelengths in toluene solution (535 nm and 570 nm, respectively) and the longest emission wavelengths in dichloromethane solution (606 nm and 647 nm, respectively).

[0089] Figure 3 The images show the fluorescence emission spectra of methanol / water mixtures with different water volume fractions in Examples 1-2. (a) represents Example 1, and (b) represents Example 2.

[0090] like Figure 3 As shown, when the water volume fraction (f) w As the fluorescence intensity of t-BuDPAiPP increased from 0 to 30%, the fluorescence intensity of both t-BuDPAiPP and t-BuDPAPQ remained almost unchanged. When the fluorescence intensity of t-BuDPAiPP increased from 0 to 30%, the fluorescence intensity of t-BuDPAiPP decreased significantly. w When the concentration increased from 40% to 80%, the fluorescence intensity significantly increased, reaching 80% f w It reaches its peak at t-BuDPAPQ f, approximately 9.8 times higher than 0%. w When the fluorescence intensity increased from 40% to 70%, it significantly increased at 70% fluorescence intensity. wThe fluorescence intensity reached its peak at a water volume fraction of approximately 10.7 times that at 0%. This indicates that at higher water volume fractions, these molecules begin to aggregate, and this aggregation leads to enhanced fluorescence. This demonstrates that t-BuDPAiPP and t-BuDPAPQ possess AIE properties.

[0091] t-BuDPAiPP and t-BuDPAPQ were dissolved in DCM. Cotton swabs were then used to soak the t-BuDPAiPP and t-BuDPAPQ solutions, respectively, and "B, C" patterns were drawn on filter paper. Their performance in the field of fluorescent anti-counterfeiting was tested, and the results are as follows: Figure 4 As shown.

[0092] Figure 4 The images show simulations of the effects of Examples 1-2 in the field of fluorescent anti-counterfeiting, where (a) represents Example 1 and (b) represents Example 2. It can be seen that the drawn pattern diminishes after being exposed to sunlight and fumes from hydrochloric acid vapor. After being fumes from ammonia vapor, the fluorescence of both t-BuDPAiPP and t-BuDPAPQ returns to its initial state. This effect provides a basis for designing fluorescent anti-counterfeiting technologies with different performance characteristics.

[0093] Figure 5 The current density-voltage-brightness diagrams are for the PhCzBCz doped electroluminescent devices in Examples 1-2. Among them, (a) is Example 1 and (b) is Example 2.

[0094] like Figure 5 As shown, the turn-on voltage (Von) of both t-BuDPAiPP and t-BuDPAPQ is 7.4V. The higher turn-on voltage may be due to an imbalance in the mobility of the charging carrier in these devices.

[0095] Figure 6 The current efficiency-luminance diagrams for the PhCzBCz doped electroluminescent devices in Examples 1-2 are shown.

[0096] like Figure 6 As shown, devices based on t-BuDPAiPP and t-BuDPAPQ exhibit 484.6 and 542.6 cd mw, respectively. 2 Maximum brightness and 4.9 and 1.7 cd A -1 Current efficiency (CE).

[0097] Figure 7 The images show the electroluminescence spectra of the PhCzBCz doped electroluminescent devices in Examples 1-2. (a) represents Example 1, and (b) represents Example 2.

[0098] like Figure 7 As shown, the two devices exhibit the same EL spectrum and emit strongly in the orange region, with maximum emission wavelengths of 546 and 594 nm.

[0099] Figure 8 The graphs show the external quantum efficiency of the PhCzBCz doped electroluminescent devices in Examples 1-2. (a) represents Example 1, and (b) represents Example 2.

[0100] like Figure 8 As shown, when the doping concentration of the electroluminescent material is 9%, the EQE of the t-BuDPAiPP organic light-emitting device and the t-BuDPAPQ organic light-emitting device are... max They were 1.5% and 0.77% respectively.

[0101] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an organic electroluminescent material based on a pyrazine derivative, characterized in that, Includes the following steps: A diamine compound and a diketone compound are mixed and reacted to obtain an intermediate. The obtained intermediate is then mixed with diphenylamine and coupled to obtain the organic electroluminescent material based on the pyrazine derivative. The molar ratio of the diamine compound to the diketone compound is 1:1; The diamine compound is pyridine-3,4-diamine; The diketone compound is 1,2-bis(4-bromophenyl)ethane-1,2-dione or 3,6-dibromophenanthrene-9,10-dione; The diphenylamine is ; The pyrazine derivative is iPP. or PQ ; The pyrazine derivative-based organic electroluminescent material is selected from the following structures: 、 。 2. The preparation method according to claim 1, characterized in that, The mixing reaction was carried out at a temperature of 90°C for 10 hours in an oxygen-free atmosphere.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the intermediate to diphenylamine is 1:2.

3.

4. The preparation method according to claim 1, characterized in that, The coupling reaction was a Buchwald-Hartwig coupling reaction, and the temperature of the coupling reaction was 110°C, the time was 24 hours, and the atmosphere was an oxygen-free atmosphere.

5. Organic electroluminescent materials based on pyrazine derivatives prepared by the preparation method according to any one of claims 1-4.

6. The application of the pyrazine derivative-based organic electroluminescent material as described in claim 5 in the field of fluorescent anti-counterfeiting.

7. The application of the pyrazine derivative-based organic electroluminescent material as described in claim 5 in electroluminescent devices.

8. An electroluminescent device, comprising a light-emitting layer, characterized in that, The light-emitting layer comprises the organic electroluminescent material as described in claim 5.

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