Linear aza-polycyclic aromatic hydrocarbon compound as well as preparation method and application thereof

Abstract

The invention provides a linear aza-polycyclic aromatic hydrocarbon compound as well as a preparation method and application thereof, and relates to the technical field of organic electroluminescent materials. According to the compound provided by the invention, a plurality of N atoms (greater than or equal to 4) are introduced into proper positions in a linear acene skeleton (the number of condensed rings is greater than or equal to 5), and localized and staggered front line orbit distribution is generated by virtue of electronegativity difference synergistic induction of the C and N atoms, namely HOMO / LUMO orbits are localized and are alternately distributed on a single atom or an isolated double bond; and the transition ratio of the bond formation / anti-bond orbit is effectively inhibited. The number of condensed rings of a linear acene skeleton is limited to be larger than or equal to 5, so that the horizontal orientation rate of molecules is improved, higher optical coupling output of luminescent molecules in a device is promoted, more importantly, bond length averaging is achieved, stretching vibration in the transition process is greatly restrained, and the molecular rigidity is improved; the emission spectrum (FWHM is narrowed to 10-20 nm) is narrowed, and meanwhile, the high fluorescence quantum yield (PLQY can reach 90% or above) is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescent materials, and in particular to a linear nitrogen-polycyclic aromatic hydrocarbon compound, a preparation method and applications thereof. Background Art

[0002] Organic light-emitting diode (OLED) technology, with its advantages such as ultra-thin structure, flexible and bendable properties, and self-luminescence, has become the core solution for the new generation of display industry. The evolution of its luminescent material system has gone through three important stages: 1) The first generation of fluorescent materials can only emit light using singlet excitons, and the internal quantum efficiency has a theoretical limit (≤25%), which seriously restricts the energy efficiency of devices; 2) The second generation of phosphorescent materials, by introducing heavy metal atoms such as iridium and platinum, can capture triplet excitons, achieving a theoretical 100% exciton utilization rate, but faces a high cost bottleneck caused by dependence on precious metal resources. In addition, the emission spectrum color purity of current phosphorescent complexes is generally low, which cannot meet the future demand for ultra-high-definition displays; 3) The third generation of thermally activated delayed fluorescence (TADF) materials, based on the reverse intersystem crossing (RISC) mechanism, realizes full exciton utilization, breaking away from the limitations of precious metals while showing significant cost competitiveness.

[0003] In recent years, the development of multiresonance (MR) materials based on the TADF mechanism has become a key path to achieving high-color-purity luminescence. These materials utilize localized spatial separation of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) within the molecule (i.e., the HOMO is localized to electron-rich nitrogen / oxygen atoms, while the LUMO is concentrated to electron-deficient boron / carbonyl units), resulting in non-bonding / non-bonding transitions. This reduces the proportion of bonding / antibonding transitions caused by frontier orbital delocalization, effectively suppressing high-frequency double bond stretching vibrations during transitions, reducing ground-state-excited state structural relaxation, and significantly reducing the Stokes shift, thereby significantly narrowing the emission spectrum's full-width at half-maximum (FWHM) (25–35 nm). To achieve higher color purity to meet the demands of future ultra-high-definition displays, while constructing higher-order B / N hetero-fused rings based on existing MR technology through rigid skeleton reinforcement or π system expansion strategies can further compress the FWHM to below 15 nm, this leads to two key drawbacks: 1) a dramatic increase in molecular weight (MW > 1000 g mol) and 2) a significant increase in molecular weight (MW > 1000 g mol). -1), which leads to an increase in the sublimation temperature of the material and deterioration in film-forming performance, making it incompatible with the current mainstream vacuum evaporation process; 2) Structural derivatization is limited and the preparation cost is increased. The construction of high-order boron-nitrogen polycyclic aromatic hydrocarbons inevitably requires multi-step electrophilic borylation reactions. On the one hand, the uncertainty of the sites in multi-step borylation leads to low yields, limited structural design, and many by-products that are not conducive to the purification of the final product. On the other hand, the long technical route leads to a sharp increase in preparation costs. In particular, panel companies or display material companies led by Europe, the United States, Japan and South Korea have completed a systematic patent layout in the field of MR material basic structure, forming a technical barrier to the independent development of my country's OLED industry chain. There are fundamental contradictions in the existing improvement plans. The modification strategy of reducing the molecular weight often leads to spectral broadening, sacrificing the color purity advantage, while local structural optimization is difficult to break through the core patent blockade, and the derivatization capability is insufficient.

[0004] Therefore, the development of new MR material structures that have ultra-narrow spectral emission (FWHM < 15 nm), easy vacuum sublimation, simple synthesis, stable chemical properties and completely independent intellectual property rights has become an urgent need to break through the existing process compatibility bottlenecks and patent barriers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is the shortcomings of existing MR molecules in terms of spectrum narrowing. In order to solve the above problem, the present invention proposes the following technical solutions:

[0006] In a first aspect, the present invention provides a linear nitrogen-polycyclic aromatic hydrocarbon compound, which has a linear nitrogen-polycyclic aromatic hydrocarbon skeleton, wherein the linear nitrogen-polycyclic aromatic hydrocarbon skeleton is composed of a nitrogen-containing six-membered heterocyclic ring and a benzene ring fused along the horizontal axis to form a linear nitrogen-benzone structure, and the number of fused rings in the horizontal axis direction is ≥5, and the number of N atoms in the linear nitrogen-benzone structure is ≥4.

[0007] It should be noted that the number of fused rings in the transverse direction ≥ 5 can ensure better horizontal orientation and conjugated extension of the molecule, and the number of N atoms in the linear azaacene structure ≥ 4 helps to achieve localized dislocation distribution of the frontier orbitals to narrow the emission spectrum of the molecule.

[0008] Furthermore, the linear nitrogen-polycyclic aromatic hydrocarbon compound has a molecular structure represented by the following general formula (I):

[0009] General formula (Ⅰ);

[0010] In Formula I, R1, R2, and R3 are independently selected from substituents that can simultaneously improve solubility and inhibit intermolecular stacking; n is 0 or 1; W, X, Y, and Z are independently selected from C or N, and A1-A4 are independently a benzene ring structure, a pyrazine ring structure, or are absent.

[0011] A further technical solution is that the substituent capable of simultaneously improving solubility and inhibiting intermolecular stacking is selected from at least one of the following substituents:

[0012]

[0013] Understandably, substituents such as isopropyl, tert-butyl, adamantyl, tert-butylphenyl, and tetramethylcyclohexyl have good solubility and greater steric hindrance, which can improve solubility and inhibit intermolecular stacking.

[0014] A further technical solution is that when n is 0, A2 is a pyrazine ring structure, and A1, A3, and A4 are independently a benzene ring structure, a pyrazine ring structure, or do not exist.

[0015] A further technical solution is that the compound is any one of the following structural formulas:

[0016]

[0017]

[0018]

[0019]

[0020]

[0021] In the second aspect, the present invention provides a method for preparing a linear nitrogen-polycyclic aromatic hydrocarbon compound. The process route for synthesizing a linear nitrogen-polycyclic aromatic hydrocarbon compound is shown in Figure 14 The specific steps include:

[0022] The halogenated hydrocarbons were reacted with nitrophenylboronic acid naphthalene ester derivatives through palladium-catalyzed Suzuki coupling reaction and nitro reduction-oxidation ring closure to generate ortho-indole and carbazole intermediates.

[0023] reacting the ortho-indolecarbazole intermediate with an aromatic halide to obtain a final product of formula (I);

[0024] Among them, the ortho-indolecarbazole intermediate has a structure shown in general formula (II),

[0025] General formula (II);

[0026] In the general formula (II), R1, R2, and R3 are independently selected from substituents that can simultaneously improve solubility and inhibit intermolecular stacking, W is independently selected from C or N, and A1 and A2 are independently a benzene ring structure, a pyrazine ring structure, or are absent;

[0027] Aromatic halides have the structure shown in the general formula (III):

[0028] General formula (III);

[0029] In the general formula (III), X, Y, and Z are independently selected from C or N, A3 and A4 are independently a benzene ring structure, a pyrazine ring structure, or are absent, and L1 and L2 are independently selected from the halogen elements F, Cl, Br, or I.

[0030] Furthermore, the reaction of the ortho-indolecarbazole intermediate with an aromatic halide to obtain the final product of the general formula (I) specifically includes: reacting the ortho-indolecarbazole intermediate with an aromatic halide (fluorinated or chlorinated) under strong alkaline conditions through a multi-stage nucleophilic substitution reaction to obtain the final product of the general formula (I), or reacting the ortho-indolecarbazole intermediate with an aromatic halide (brominated or iodinated) through a palladium-catalyzed CN coupling reaction to obtain the final product of the general formula (I).

[0031] A further technical solution is that the palladium catalyst includes at least one of tetrakis(triphenylphosphine)palladium, bis(triphenylphosphine)palladium chloride, palladium acetate, palladium chloride, bis(dibenzylideneacetone)palladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, bis(acetonitrile)dichloropalladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-trichloromethane complex, and tris(dibenzylideneacetone)palladium.

[0032] In a third aspect, the present invention further provides the use of a linear nitrogen-polycyclic aromatic hydrocarbon compound as described in the first aspect, or a linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method described in the second aspect, in the preparation of organic electroluminescent devices and color conversion materials.

[0033] In a fourth aspect, the present invention provides an organic light-emitting layer film, which includes a linear nitrogen-polycyclic aromatic hydrocarbon compound described in the first aspect, or a linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method described in the second aspect.

[0034] In a fifth aspect, the present invention provides an organic electroluminescent device, wherein at least one organic functional layer in the structure of the organic electroluminescent device uses a linear nitrogen-polycyclic aromatic hydrocarbon compound described in the first aspect, or a linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method described in the second aspect, and is preferably used as the light-emitting layer in the organic electroluminescent device.

[0035] Compared with the prior art, the present invention can achieve the following technical effects:

[0036] The present invention provides a linear nitrogen-polycyclic aromatic hydrocarbon compound. The compound is prepared by introducing multiple N atoms (≥4) at appropriate positions in a linear paraben skeleton (number of condensed rings ≥5), and utilizing the electronegativity difference between C and N atoms to synergistically induce a localized and staggered distribution of frontier orbitals, i.e., the HOMO / LUMO orbitals are localized and alternately distributed on a single atom or isolated double bond, effectively suppressing the proportion of bonding / antibonding orbital transitions. By limiting the number of condensed rings in the linear paraben skeleton to ≥5, it is not only beneficial to improve the horizontal orientation rate of the molecule and promote the luminescent molecule to achieve higher light coupling output in the device, but more importantly, it is beneficial to achieve bond length averaging, greatly suppressing stretching vibrations during the transition process, improving molecular rigidity, and achieving a high fluorescence quantum yield (PLQY of more than 90%) while narrowing the emission spectrum (FWHM narrowed to 10-20 nm).

[0037] Furthermore, the linear nitrogen-polycyclic aromatic hydrocarbon compounds of the present invention introduce large steric groups (such as adamantyl, tetramethylcyclohexyl, etc.) on the periphery of the condensed ring skeleton plane that can improve molecular solubility and inhibit intermolecular stacking, thereby weakening the aggregation fluorescence quenching effect of the large planar luminescent skeleton and improving the luminescence efficiency of the luminescent molecules in thin films or devices.

[0038] Furthermore, the compounds of the present invention have a linear nitrogen-polycyclic aromatic hydrocarbon skeleton, which can not only construct different linear nitrogen-benzo fused rings by changing the number and position of N atoms and the number of horizontally parallel fused rings, but also introduce different substituent groups at multiple modification sites in both the horizontal and vertical dimensions to derive at least 70 structures, which have better derivatization properties than the conventional C / N multiple resonance skeletons reported in existing literature.

[0039] The present invention provides a method for preparing linear nitrogen-polycyclic aromatic hydrocarbon compounds, which adopts the simple and mature Suzuki coupling and CN coupling. Compared with the B / N system, it has a wide source of raw materials and a short technical route, produces fewer by-products, has high reaction site selectivity, and greatly reduces production and separation and purification costs.

[0040] This invention provides a linear nitrogen-polycyclic aromatic hydrocarbon compound containing only three elements, C, H, and N, prior to the second period. It exhibits high interatomic bond energy and excellent stability. When used in electroluminescent devices, it can achieve strong stability, an extremely narrow full width at half maximum (FWHM), and high device efficiency. This invention provides an independent material solution for high-resolution OLED display and lighting applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 The optimized ground state configuration diagram, HOMO orbital distribution diagram and LUMO orbital distribution diagram of the compound LNF-1 provided in the embodiment of the present invention.

[0043] Figure 2 The optimized ground state configuration diagram, HOMO orbital distribution diagram, and LUMO orbital distribution diagram of the compound LNF-12 provided in an embodiment of the present invention.

[0044] Figure 3 The optimized ground state configuration diagram, HOMO orbital distribution diagram, and LUMO orbital distribution diagram of the compound LNF-25 provided in the examples of the present invention.

[0045] Figure 4 The optimized ground state configuration diagram, HOMO orbital distribution diagram and LUMO orbital distribution diagram of the compound LNF-29 provided in the examples of the present invention.

[0046] Figure 5 The optimized ground state configuration diagram, HOMO orbital distribution diagram, and LUMO orbital distribution diagram of the compound LNF-37 provided in the examples of the present invention.

[0047] Figure 6 The optimized ground state configuration diagram, HOMO orbital distribution diagram and LUMO orbital distribution diagram of the compound LNF-49 provided in the examples of the present invention.

[0048] Figure 7 This is an emission spectrum diagram of different compounds provided in the embodiments of the present invention in toluene solution.

[0049] Figure 8 Molecular structures of the materials HATCN, TAPC, TCTA, BO5TCz, mCBP, ANT-BIZ, DBFPO involved in the preparation of organic electroluminescent devices, as well as the comparative luminescent materials Contr-1 and Contr-2.

[0050] Figure 9 The current-voltage-brightness curves of the light-emitting devices prepared using the light-emitting materials of Examples 1-2 and Comparative Examples 1-2 of the present invention are shown.

[0051] Figure 10The power efficiency-brightness and current efficiency-brightness curves of the light-emitting devices made using the light-emitting materials of Examples 3-6 of the present invention are shown.

[0052] Figure 11 The external quantum efficiency-brightness curves of the light-emitting devices prepared using the light-emitting materials of Examples 1-2 and Comparative Examples 1-2 of the present invention are shown.

[0053] Figure 12 The external quantum efficiency-brightness curves of the light-emitting devices made using the light-emitting materials of Examples 3-6 of the present invention are shown.

[0054] Figure 13 This is a schematic structural diagram of an OLED device provided by an embodiment of the present invention.

[0055] Figure 14 The synthetic route of the linear nitrogen-polycyclic aromatic hydrocarbon compound provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0056] To better demonstrate the superiority of the linear nitrogen-polycyclic aromatic hydrocarbon compound provided by the present invention in the application of electroluminescent devices, the synthesis, photophysical studies and applications of representative example molecules of different derivative types in devices are provided below.

[0057] Representative Example Molecular Synthesis Technology Route

[0058] Synthesis of LNF-1:

[0059]

[0060] (1) To a clean two-necked flask, add 5,8-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)quinoxaline (382.1 mg, 1.0 mmol), 6-bromo-1,1,4,4-tetramethyl-7-nitro-1,2,3,4-tetrahydronaphthalene (624.4 mg, 2.0 mmol), Pd(PPh3)4 (23.1 mg, 0.02 mmol), and potassium carbonate (552.8 mg, 4.0 mmol). Continuously introduce argon, add 1,4-dioxane / water (20 mL / 20 mL), and reflux at 110°C for 12 h. After cooling to room temperature, extract with dichloromethane, and concentrate the combined organic phases under reduced pressure. The crude solid product was purified by column chromatography using dichloromethane / petroleum ether as eluent to obtain a black solid intermediate 1 (yield 83%), which was used directly in the next reaction.

[0061] (2) Intermediate 1 (592.7 mg, 1.0 mmol) and triphenylphosphine (786.9 mg, 3.0 mmol) were dissolved in 30 mL of o-dichlorobenzene and stirred at reflux for 12 h. After the reaction was completed, the organic layer was extracted with ethyl acetate, and after vacuum distillation, the residual water was removed with magnesium sulfate. The crude product was dried and separated by column chromatography (eluent: dichloromethane / petroleum ether) to obtain brown intermediate 2 (yield 95%), which was used directly in the next reaction.

[0062] (3) Intermediate 2 (528.7 mg, 1.0 mmol), 6,7-difluoroquinoxaline (166.1 mg, 1.0 mmol) and cesium carbonate (1.6 g, 5.0 mmol) were dissolved in 40 mL of N-methylpyrrolidone and stirred at 180°C for 6 h. After cooling to room temperature, water and methanol were added to form a precipitate, which was filtered and washed with methanol several times to obtain a light brown solid LNF-1 (yield 85%). HRMS (ESI, m / z): caclcd for C 44 H 42 N6, 654.3471[M]+, found 654.3474. 1 HNMR(500 MHz,Chloroform-d)δ9.34(s,2H),8.91(s,2H),8.78(s,2H),8.31(s,2H),8.18(s,2H),1.94–1.89(m,8H),1.33(s,24H).

[0063] Synthesis of LNF-12:

[0064]

[0065] (1) To a clean two-necked flask, 1,4-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenazine (432.1 mg, 1.0 mmol), 2-nitro-5-adamantylbromobenzene (1.4 g, 2.0 mmol), Pd(PPh3)4 (23.1 mg, 0.02 mmol), and potassium carbonate (552.8 mg, 4.0 mmol) were added. Argon was continuously introduced, and toluene / ethanol / water (40 mL / 10 mL / 10 mL) was added. The mixture was refluxed for 12 h. After the reaction was completed, the organic layer was extracted with ethyl acetate, and the residual water was removed with magnesium sulfate. The crude product was dried and separated by column chromatography (eluent: dichloromethane / petroleum ether) to obtain yellow solid intermediate 3 (yield 94%), which was directly used in the next reaction.

[0066] (2) Intermediate 3 (690.8 mg, 1.0 mmol) and triphenylphosphine (786.9 mg, 3.0 mmol) were dissolved in 30 mL of o-dichlorobenzene and stirred at reflux for 12 h. After the reaction was completed, the organic layer was extracted with ethyl acetate, distilled under reduced pressure, and dried over magnesium sulfate. The crude product was dried and separated by column chromatography (eluent: dichloromethane / petroleum ether) to obtain orange intermediate 4 (yield 91%), which was used directly in the next reaction.

[0067] (3) Intermediate 4 (626.8 mg, 1.0 mmol), 6,7-difluoroquinoxaline (166.1 mg, 1.0 mmol) and cesium carbonate (1.6 g, 5.0 mmol) were dissolved in 50 mL of N-methylpyrrolidone and stirred at 180°C for 6 h. After cooling to room temperature, water and methanol were added to form a precipitate, which was filtered and washed with methanol several times to obtain an orange solid LNF-12 (yield 82%). HRMS (ESI, m / z): caclcd for C 52 H 44 N6, 752.3627[M]+, found 752.3642. 1 HNMR(500 MHz,Chloroform-d)δ8.54(d,J=2.1 Hz,2H),7.92(d,J=7.7 Hz,2H),7.88–7.85(m,2H),7.84(dd,J=8.3,1.2 Hz,2H),7.61(dd,J=7.7,2.2 Hz,2H),7.60–7.58(m,2H),7.58–7.56(m,2H),2.17–2.11(m,6H),1.94(d,J=4.8 Hz,12H),1.70(d,J=11.1 Hz,12H).

[0068] Synthesis of LNF-25:

[0069]

[0070] To a clean two-necked flask, 3,8-di-tert-butyl-11,12-dihydroindole[2,3-A]carbazole (810.7 mg, 2.2 mmol), 1,2,4,5-tetrafluorobenzene (150.1 mg, 1.0 mmol), and cesium carbonate (1.6 g, 5.0 mmol) were added. After dehydration and deoxygenation, 25 mL of DMSO was added and the mixture was refluxed at 160°C under an argon atmosphere for 24 h. After completion of the reaction, 300 mL of water was added and the crude product was filtered to obtain a light brown color. After elution with ethanol, ethyl acetate, and acetone, a light yellow powder, LNF-25, was obtained (yield 87%). HRMS (ESI, m / z): caclcd for C58 H 54 N4, 806.4348[M]+, found 806.4351. 1 HNMR(500MHz,Chloroform-d)δ8.60(s,2H),8.29–8.26(m,4H),8.21(s,4H),7.92(d,J=7.7 Hz,4H),7.41(dd,J=7.7,2.1 Hz,4H),1.36(s,36H).

[0071] Synthesis of LNF-29:

[0072]

[0073] To a clean two-necked flask, 3,8-di-tert-butyl-11,12-dihydroindoline[2,3-A]carbazole (810.7 mg, 2.2 mmol), tetrachloropyrazine (217.9 mg, 1.0 mmol), and cesium carbonate (1.6 g, 5.0 mmol) were added. After dehydration and deoxygenation, 25 mL of DMSO was added and the mixture was refluxed at 160°C under an argon atmosphere for 24 h. After completion of the reaction, 300 mL of water was added and the crude yellow product was filtered. After elution with ethanol, ethyl acetate, and acetone, a white powder, LNF-29, was obtained (yield 91%). HRMS (ESI, m / z): caclcd for C 56 H 52 N6, 808.4253[M]+, found 808.4258. 1 H NMR (500 MHz, Chloroform-d) δ 8.34–8.33 (m, 4H), 8.32 (s, 4H), 8.14 (d, J = 7.7 Hz, 4H), 7.58 (dd, J = 7.7, 2.2 Hz, 4H), 1.36 (s, 36H).

[0074] Synthesis of LNF-37:

[0075]

[0076]

[0077] (1) To a clean two-necked flask, add 4,4-di-tert-butylbenzil (322.4 mg, 1.0 mmol) and 3,6-dibromo-1,2-phenylenediamine (319.1 g, 1.2 mmol). Continuously purge with argon, add 1-butanol (50 mL), and stir under reflux for 12 h. After the reaction, filter the precipitate and wash with methanol to obtain a yellow solid intermediate 5 (yield: 96%), which is used directly in the next reaction.

[0078] (2) Intermediate 5 (552.4 g, 1.0 mmol), 2-nitrobenzeneboronic acid (333.9 g, 2.0 mmol), Pd(PPh3)4 (57.8 mg, 0.05 mmol) and potassium carbonate (552.8 mg, 4.0 mmol) were added to a reaction flask. 30 mL of ultra-dry tetrahydrofuran was added to dissolve the mixture under anhydrous and oxygen-free conditions. Nitrogen was continuously introduced and refluxed for 12 h. The organic phases were extracted with ethyl acetate, combined, washed with saturated brine, dried over anhydrous sodium sulfate, and evaporated under reduced pressure. The crude product was purified by column chromatography (eluent: petroleum ether / ethyl acetate) to obtain brown solid intermediate 6 (yield: 91%), which was used directly in the next reaction.

[0079] (3) Intermediate 6 (636.8 mg, 1.0 mmol) and triphenylphosphine (786.9 mg, 3.0 mmol) were dissolved in 30 mL of o-dichlorobenzene and stirred at reflux for 12 h. After the reaction was complete, the organic layer was extracted with ethyl acetate, distilled under reduced pressure, and dried over magnesium sulfate. The crude product was dried and separated by column chromatography (eluent: dichloromethane / petroleum ether) to obtain brown intermediate 7 (yield 92%), which was used directly in the next reaction.

[0080] (4) Intermediate 7 (1.3 g, 2.2 mmol), 1,2,4,5-tetrafluorobenzene (150.1 mg, 1.0 mmol) and cesium carbonate (1.6 g, 5.0 mmol) were dehydrated and deoxygenated, and 50 mL of DMSO was added. The mixture was refluxed at 160°C for 24 h. After the reaction was completed, 400 mL of water was added and the crude product was filtered to obtain a light brown product. The product was washed with ethanol, ethyl acetate and acetone in sequence to obtain a white powder LNF-37 (yield 86%). HRMS (ESI, m / z): caclcd for C 86 H 70 N8, 1214.5723[M]+, found1214.5727. 1 H NMR (500 MHz, Chloroform-d) δ8.80 (s, 2H), 8.53 (dd, J=7.3, 1.4 Hz, 4H), 7.95 (dd, J=6.3, 1.7 Hz, 4H), 7.85–7.82 (m, 8H), 7.46 (ddd, J=7.3, 6.4, 1.3 Hz,4H),7.38–7.35(m,8H),7.32(td,J=7.2,1.4 Hz,4H),1.34(s,36H).

[0081] Synthesis of LNF-49:

[0082]

[0083] (1) 5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-amine (406.6 mg, 2.0 mmol), 1,4-dibromo-2,3-difluorobenzene (271.9 g, 1.0 mmol) and potassium tert-butoxide (673.3 mg, 6.0 mmol) were added to a clean two-necked flask. Argon was continuously introduced and 30 mL of DMSO was added. The mixture was stirred and refluxed for 12 h. 200 mL of water was added, and the organic layers were combined, washed with water, and dried over anhydrous sodium sulfate. The solid after vacuum distillation was purified by column chromatography (eluent: ethyl acetate / petroleum ether) to obtain a white solid intermediate 8 (yield: 85%), which was used directly in the next reaction.

[0084] (2) Intermediate 8 (476.7 g, 1.0 mmol), 6,7-dibromo-2,3-dichloroquinoxaline (356.8 g, 1.0 mmol) and potassium carbonate (552.8 mg, 4.0 mmol) were added to a reaction flask. After dehydration and deoxygenation, ultra-dry DMF was injected and the mixture was refluxed at 90°C for 24 h. After the reaction, 200 mL of water was added and the mixture was extracted with ethyl acetate. The organic phases were combined, washed with saturated NaCl solution, dried over anhydrous sodium sulfate, and distilled under reduced pressure. The solid was purified by column chromatography (eluent: ethyl acetate / petroleum ether) to obtain yellow solid intermediate 9 (yield: 92%), which was directly used in the next reaction.

[0085] (3) Intermediate 9 (760.6 mg, 1.0 mmol), intermediate 8 (476.7 mg, 1.0 mmol), Pd2(dba)3 (45.79 mg, 0.05 mmol), TTBP (6.07 mg, 0.03 mmol) and t-BuONa (288.30 mg, 3.0 mmol) were placed in a reaction flask, dehydrated and deoxygenated, and then 50 mL of redistilled toluene was added. The mixture was refluxed at 130°C for 24 h. After cooling, the solvent was evaporated to dryness, dissolved in ethyl acetate, extracted with deionized water (100 mL) and stirred. Hexane was added to the ethyl acetate solution to precipitate the product, stirred for 1 h, filtered, and the remaining solid was washed with deionized water (50 mL). After vacuum drying, a white solid LNF-49 (yield 91%) was obtained. HRMS (ESI, m / z): caclcd for C 76 H 78 N6, 1074.6288[M]+, found 1074.6291. 1H NMR(500 MHz,Chloroform-d)δ8.68(s,2H),8.37(s,2H),8.25(s,2H),8.20(s,2H),8.14(s,2H),8.11(s,2H),8.00(s,2H),1.95–1.88(m,16H),1.33(s,48H).

[0086] Theoretical simulation and electrochemical and photophysical characterization

[0087] To illustrate the superiority of the linear nitrogen-polycyclic aromatic hydrocarbon compounds provided by the present invention for electroluminescent device applications, we provide theoretical simulation results for key parameters of the six examples described above, using Gaussian 16 software. Details are summarized in Table 1. In the actual calculations, considering that the primary functions of all peripheral substituents (tert-butyl, adamantyl, tetramethylcyclohexyl, and tert-butylphenyl) are to improve solubility and provide steric hindrance to inhibit intermolecular aggregation, with minimal impact on the optoelectronic properties of the single-molecule conjugated backbone, these peripheral substituents were rationally simplified to H to simplify the computational effort while maintaining experimental accuracy. All ground-state configurations were optimized at the B3LYP / 6-311G** level, assuming the gaseous single-molecule state and taking dispersion correction into account. Excited-state energy levels and configurations were optimized based on this optimized ground-state configuration using TD-DFT calculations. The basis set and functionals used in the calculations were consistent with those for the ground state. All orbitals were visualized using Gaussview 6.0 software.

[0088] Table 1. Calculated results of frontier orbital energy levels and electrochemically measured energy levels

[0089]

[0090] Among them, a) is the data obtained by theoretical simulation calculation, and b) is the HOMO estimated by the oxidation curve of cyclic voltammetry. LUMO = HOMO + Eg, Eg is the optical band gap, obtained from the long-wavelength edge of the absorption spectrum.

[0091] From the theoretical calculation results in Table 1, it can be seen that the HOMO energy levels of all the molecules in the embodiments are between -5.71 and -4.84 eV, and the LUMO energy levels are between -1.57 and -2.66 eV, which can match the energy levels of conventional p-type (such as mCBP, TCTA) or n-type host materials (DBFPO), which is conducive to the fine optimization of the device structure. A lateral comparison found that the skeleton changes of linear nitrogen-polycyclic aromatic hydrocarbons have a greater impact on the HOMO / LUMO energy levels. As the number of lateral condensed rings increases, the band gap narrows. The sp3 hybridization of N atoms is conducive to improving the HOMO, while the sp2 hybridization of N atoms (i.e., the introduction of C=N double bonds) will reduce the corresponding LUMO, thereby achieving the regulation of the emission spectrum light color. In order to verify the reliability of the theoretical calculation, the present invention adopts cyclic voltammetry to measure the HOMO energy levels of the molecules in the above embodiments in dichloromethane solution. The test results are basically consistent with the theoretical calculation trend. According to LUMO=HOMO+E g We estimated the LUMO energy levels of these molecules, and the measured estimated LUMO energy levels are between -2.02 and -3.20, which can match conventional electron transport materials such as ANT-BIZ.

[0092] To further demonstrate the effects of the linear nitrogen-polycyclic aromatic hydrocarbon skeleton provided by the present invention on the suppression of stretching vibration and the narrowing of emission spectra, we used GaussView 6.0 software to visualize the HOMO and LUMO orbitals of the molecules in the above examples. The visualized molecular ground state dominant configuration diagram and orbital distribution diagram are shown in the attached figure. Figures 1 to 6 . Since the nitrogen-polycyclic aromatic hydrocarbon molecules designed by the present invention all adopt linear conjugated extension, all molecules show a good planar rigid configuration, and the linear conjugated derivatization is conducive to achieving the average bond length of alternating single and double bonds, thereby effectively suppressing the stretching vibration during the molecular transition process. Due to the difference in electronegativity between C and N atoms, the electrons in the CN covalent bond are more distributed on the N atom side, and multiple CN covalent bonds are connected together to form a multi-resonance frontier orbital distribution. In addition, in the present invention, the N atom doping sites are specially limited, that is, the number of C atoms between any two N atoms along the horizontal axis must be an odd number (1 or 3), thereby ensuring the consistency of the resonance form, which is conducive to the formation of localized and alternatingly distributed frontier orbitals. As shown in the attached Figures 1 to 6As shown, the LUMO orbitals of all molecules basically show the characteristics of localized and staggered distribution along the horizontal axis, but the HOMO distribution between different molecules shows certain differences. The introduction of the C=N double bond reduces the electron cloud density of the entire linear aza-acene skeleton, so the HOMO begins to gradually distribute in the vertical axis direction (indole-carbazole skeleton), prompting the molecule to present a more uniform frontier orbital distribution on the entire two-dimensional conjugated skeleton. In summary, the design strategy of the aza-linear acene molecule provided by the present invention can achieve the localized staggered alternating distribution of the frontier orbital, greatly suppress the molecular excited state vibration relaxation, and can simultaneously achieve high luminous efficiency and extremely narrow emission spectrum.

[0093] To further illustrate the advantages of the molecular design of the present invention, the present invention calculated the photophysical data of the above-mentioned molecules based on Franck-condon analysis and MOMAP vibration analysis (Appendix Table 2). The calculation results show that all molecules exhibit large radiative transition oscillator strength (f) and small reorganization energy (λ reorg ), especially with the effective expansion of the linear skeleton and the introduction of C=N double bonds, such as LNF-37 and LNF-49, the reorganization energy dropped significantly to ∼550 cm -1 Correspondingly, the present invention also provides the emission spectra and fluorescence quantum yield (PLQY) of the above-mentioned example molecules in toluene solution. The key values ​​are presented in Table 2 and the emission spectra are presented in the attached Figure 7 LNF-37 and LNF-49, which have the lowest reorganization energy, exhibited a PLQY of nearly 100%. Figure 7 As shown, all molecules exhibited narrow emission full-width at half-maximum (FWHM), with LNF-29, LNF-37, and LNF-49 in particular achieving FWHMs less than 15 nm, surpassing the commonly reported B / N-doped multi-resonance molecules. Furthermore, the molecules provided by this invention significantly reduce synthesis difficulty and molecular structural complexity, utilize readily available raw materials, and are independent of the introduction of B atoms. Their chemical stability is also enhanced, making them more suitable for commercial applications.

[0094] Table 2. Summary of vibrational analysis and photophysical characterization data.

[0095]

[0096] In Table 2, a) is the excitation energy obtained based on the optimized first excited singlet state (S1) structure, b) is the oscillator strength from S1 to S0, c) is the reorganization energy during the transition from the ground state (S0) to S1, d) is the reorganization energy during the transition from S1 to S0, e) is the emission peak in toluene solution, f) is the full width at half maximum of the emission spectrum in toluene solution, and g) is the fluorescence quantum yield in toluene solution.

[0097] OLED device application examples

[0098] In order to evaluate the electroluminescent properties of the linear nitrogen-polycyclic aromatic hydrocarbon structure luminescent molecules provided by the present invention, they are now applied to electroluminescent devices. In addition, to demonstrate the superiority of the molecular design of the present invention, similar nitrogen-fused ring structures Contr-1 and Contr-2 have been reported in the literature as comparative examples to prepare OLED devices with the same structure.

[0099] The schematic diagram of the OLED device structure prepared by the present invention is shown in the attached Figure 13 , which comprises 100 anode layers,

[0100] 101 hole injection layer, 102 first hole transport layer, 103 second hole transport layer, 104 exciton blocking layer / electron blocking layer, 105 light emitting layer, 106 exciton blocking layer / hole blocking layer, 107 electron transport layer, 108 electron injection layer, 109 cathode Al.

[0101] Wherein, the anode layer 100 is made of indium tin oxide (ITO) material;

[0102] The hole injection layer 101 has a thickness of 10 nm and is made of HATCN;

[0103] The first hole transport layer 102 has a thickness of 30 nm and is made of TAPC;

[0104] The second hole transport layer 103 has a thickness of 30 nm and is made of TCTA;

[0105] The electron blocking layer 104 has a thickness of 20 nm and is made of mCBP;

[0106] The luminescent layer 105 has a thickness of 40 nm and uses DBFPO as the host material, BO5TCz as the sensitizer, and the guest material as the molecule of the embodiment or comparative example provided by the present invention. The host material and the sensitizer form a mixed host with a doping ratio of 7:3 (by weight). The doping ratio of the guest material in the luminescent layer is 5 wt%.

[0107] The hole blocking layer 106 has a thickness of 20 nm and is made of DBFPO;

[0108] The electron transport layer 107 has a thickness of 40 nm and is made of ANT-BIZ;

[0109] The electron injection layer 108 has a thickness of 1 nm and is made of lithium fluoride (Liq);

[0110] The cathode layer 109 has a thickness of 20 nm and is made of metal Al.

[0111] The structural formulas of the above materials HATCN, TAPC, TCTA, BO5TCz, mCBP, ANT-BIZ, DBFPO, Contr-1 and Contr-2 are shown in Figure 8 .

[0112] The structures, materials and components of all devices are the same, only the luminescent guest materials are different, see Appendix 3 for details. The key performance data of all devices are summarized in Appendix 3, and the current-voltage and power efficiency / current efficiency-luminance curves of Examples 1-6 and Comparative Examples 1-2 are respectively shown in Appendix 3. Figure 9-12 .

[0113] First, among the devices prepared based on the present invention, the device results of Comparative Examples 1 and 2 are basically consistent with the corresponding literature reports, with corresponding FWHMs of 49 and 52 nm, respectively. Compared with the comparative examples, the FWHM of the devices prepared based on the materials of the embodiments of the present invention is significantly narrowed. Except for device Example 1, the FWHM of the remaining device examples is less than 20 nm. The FWHM of the narrowest device Examples 3 and 5 is as low as 12-13 nm, reaching the optimal value of narrow-band OLED performance reported in the current literature.

[0114] Secondly, in terms of evaluating the photoelectric conversion efficiency of the core of the device, namely the external quantum efficiency (EQE), power efficiency (PE) and current efficiency (CE). The device embodiments provided by the present invention are significantly better than the comparative examples. For example, the external quantum efficiency of Examples 4 and 5 (~30%) is almost twice that of Comparative Example 1 (15.6%) or Comparative Example 2 (16.2%), which fully demonstrates the superiority of the light-emitting device constructed with the linear nitrogen-containing condensed ring light-emitting material provided by the present invention. In summary, the light-emitting material constructed based on the linear nitrogen-containing polycyclic aromatic hydrocarbon strategy of the present invention not only has an ultra-narrow emission spectrum half-width and high PLQY, but also has significant advantages in corresponding OLED performance.

[0115] Table 3. Summary of key performance data of OLED devices.

[0116]

[0117] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0118] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A linear nitrogen-polycyclic aromatic hydrocarbon compound, characterized in that The compound has a linear nitrogen-polycyclic aromatic hydrocarbon skeleton, wherein the linear nitrogen-polycyclic aromatic hydrocarbon skeleton is formed by condensing a nitrogen-containing six-membered heterocyclic ring and a benzene ring along the horizontal axis to form a linear nitrogen-acene structure, and the number of condensed rings in the horizontal axis direction is ≥5, and the number of N atoms in the linear nitrogen-acene structure is ≥4.

2. The linear nitrogen-polycyclic aromatic hydrocarbon compound according to claim 1, wherein The compound has a molecular structure shown in the following general formula (I): In Formula I, R1, R2, and R3 are independently selected from substituents that can simultaneously improve solubility and inhibit intermolecular stacking; n is 0 or 1; W, X, Y, and Z are independently selected from C or N, and A1-A4 are independently a benzene ring structure, a pyrazine ring structure, or are absent.

3. The linear nitrogen-polycyclic aromatic hydrocarbon compound according to claim 2, wherein The substituent having the ability to improve solubility and inhibit intermolecular stacking is selected from at least one of the following substituents:

4. The linear nitrogen-polycyclic aromatic hydrocarbon compound according to claim 2, characterized in that When n is 0, A2 is a pyrazine ring structure, and A1, A3, and A4 are independently a benzene ring structure, a pyrazine ring structure, or do not exist.

5. The linear nitrogen-polycyclic aromatic hydrocarbon compound according to any one of claims 1 to 4, characterized in that The compound is any one of the following structural formulas:

6. A method for preparing the linear nitrogen-polycyclic aromatic hydrocarbon compound according to any one of claims 1 to 5, characterized in that: The following steps are involved: The halogenated hydrocarbons were reacted with nitrophenylboronic acid naphthalene ester derivatives through palladium-catalyzed Suzuki coupling reaction and nitro reduction-oxidation ring closure to generate ortho-indole and carbazole intermediates. reacting the ortho-indolecarbazole intermediate with an aromatic halide to obtain a final product of formula (I); Among them, the ortho-indolecarbazole intermediate has a structure shown in general formula (II): In the general formula (II), R1, R2, and R3 are independently selected from substituents that can simultaneously improve solubility and inhibit intermolecular stacking, W is independently selected from C or N, and A1 and A2 are independently a benzene ring structure, a pyrazine ring structure, or are absent; The aromatic halogenated compound has a structure shown in the general formula (III): In the general formula (III), X, Y, and Z are independently selected from C or N, A3 and A4 are independently a benzene ring structure, a pyrazine ring structure, or are absent, and L1 and L2 are independently selected from the halogen elements F, Cl, Br, or I.

7. The method for preparing a linear nitrogen-polycyclic aromatic hydrocarbon compound according to claim 6, wherein: The palladium catalyst includes at least one of tetrakis(triphenylphosphine)palladium, bis(triphenylphosphine)palladium chloride, palladium acetate, palladium chloride, bis(dibenzylideneacetone)palladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium, bis(acetonitrile)dichloropalladium, 1,1'-bis[(diphenylphosphino)ferrocene]dichloropalladium-trichloromethane complex, and tris(dibenzylideneacetone)palladium.

8. Use of the linear nitrogen-polycyclic aromatic hydrocarbon compound according to any one of claims 1 to 5, or the linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method according to any one of claims 6 to 7, in the preparation of organic electroluminescent devices and color conversion materials.

9. An organic light-emitting layer thin film, characterized in that: The organic light-emitting layer thin film comprises a linear nitrogen-polycyclic aromatic hydrocarbon compound according to any one of claims 1 to 5, or comprises a linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method according to any one of claims 6 to 7.

10. An organic electroluminescent device, characterized in that: At least one organic functional layer in the structure of the organic electroluminescent device uses a linear nitrogen-polycyclic aromatic hydrocarbon compound according to any one of claims 1 to 5, or a linear nitrogen-polycyclic aromatic hydrocarbon compound prepared by the preparation method according to any one of claims 6 to 7, and is preferably used in the light-emitting layer of the organic electroluminescent device.

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