Chiral electron transport material and its use in electroluminescent devices

Abstract

The application discloses a kind of chiral electronic transmission materials, by introducing natural chiral binaphthol element, through nucleophilic substitution reaction formation oxygen eight-membered ring lock axial chiral configuration, then peripheral modification has good electronic transmission capacity nitrogen heterocyclic aromatic hydrocarbon, realize material simultaneously possess chiral optical / electronic activity and good electronic transmission capacity, and peripheral modification nitrogen heterocyclic aromatic hydrocarbon can further be formed by aggregation state under intermolecular hydrogen bond effect realizes strong intermolecular interaction, further strengthens spin selection effect and electronic transmission capacity.Based on the chiral small molecule electronic transmission material provided in the application can be used in electron transmission layer or electron type host material in light-emitting layer in electroluminescent device, undertake electronic transmission and spin selection function, to realize more simple, more efficient circularly polarized electroluminescent device.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials technology, and in particular to a chiral electron transport material and its application in electroluminescent devices. Background Technology

[0002] Organic light-emitting diodes (OLEDs), also known as organic light-emitting diodes, are devices that convert electrical energy into light energy. These devices utilize organic semiconductors and light-emitting materials, where charge carriers are injected from two electrodes and recombine in the light-emitting layer under an electric field, causing light emission. Compared to traditional liquid crystal displays, OLEDs offer numerous inherent advantages, including ultra-thinness, fast response time, high resolution, low power consumption, vibration resistance, low-temperature resistance, and flexibility.

[0003] Circularly polarized luminescence (CPL) refers to the selective emission of left- or right-polarized light of different intensities by luminescent materials after being excited by light or electricity. Therefore, it has great application prospects in information storage, display, and biotherapy.

[0004] Circularly polarized organic light-emitting diodes (CP-OLEDs) based on CPL have a series of significant advantages over traditional OLEDs and linearly polarized OLEDs, such as providing a wider viewing angle, higher optical efficiency, better color performance, and in particular, significantly improving issues such as screen ambient light reflection.

[0005] In the development of CP-OLEDs, chiral luminescent materials have been extensively studied as the most direct strategy for achieving circularly polarized light output, undergoing continuous iterations from chiral polymers to chiral metal complexes and circularly polarized luminescent (CPL) materials with thermally activated delayed fluorescence properties. Although these materials have limitations in their luminescence asymmetry factor (g... PL Significant progress has been made in both device efficiency and performance, but high g-efficiency has not been achieved at the same time. PL Breakthroughs have yet to be achieved in CPL materials with high efficiency and high device performance.

[0006] Currently, among the high-efficiency CP-OLED devices based on CPL materials reported in the literature, those that meet the maximum external quantum efficiency (η) are... EQE,max In over 25% of the examples, the intrinsic g of the material... PL The value can basically only be maintained at (10) -4 ~10 -3 The fundamental reason for this is that conventional CPL materials are all electrically permissible but magnetically forbidden, leading to g PL The value is hard to exceed 10 -2 At the horizontal level, although rare earth metal elements are introduced, g can be achieved by constructing magnetically permissible ff transition energies. PLThe numerical value is greatly improved (exceeding 0.1), but this will result in a significant reduction in luminous efficiency, a longer excited-state lifetime, and an increase in non-radiative transitions, leading to very low device efficiency that cannot meet the requirements of commercial applications. Summary of the Invention

[0007] The purpose of this invention is to provide a chiral electron transport material in which random charges (holes or electrons with mutually canceling spin directions) can achieve spin polarization of the transported charge through the chiral-induced spin selection effect after passing through the chiral charge transport material. After recombination in the luminescent layer, spin-polarized excitons are formed, and circularly polarized light emission can also be achieved through radiative transition. This enables the material to simultaneously possess chiral activity and good electron transport capability, thereby overcoming the defects existing in the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] This invention provides a chiral electron transport material having the molecular structure shown in Formula I or Formula II:

[0010]

[0011]

[0012] Wherein, groups Ar1 and Ar2 are each independently selected from aromatic substituents, group Ar3 is any one of H, benzene ring, cyclohexane, naphthyl ring, phenanthrene ring, dipyridylethylene, 2-naphthonitrile, o-phenanthroline or 1-indanone; group X is any one of O, S, Se or CR2NR.

[0013] In one alternative embodiment, Ar1 and Ar2 are each independently selected from aromatic rings with good electron transport capabilities, including monocyclic aromatic hydrocarbons or polycyclic aromatic hydrocarbon substituents, wherein the monocyclic aromatic hydrocarbons include any one of pyridinyl, pyrimidinyl, benzonitrile, 3-phenylpyridinyl or pyrazinyl.

[0014] The polycyclic aromatic hydrocarbon substituents include any one of quinolinyl, isoquinolinyl, quinoxalinyl, benzo[b]oxazolyl, benzo[d]thiazolyl, benzo[b]thiopheneyl, benzofuranyl, 1-phenyl-1H-benzimidazolyl, biphenyl, anthraceneyl, o-phenanthrolyl, phenazinyl, or dibenzothiopheneyl.

[0015] In one alternative embodiment, the Ar3 is selected from H, and the molecular structure of the chiral electron transport material is shown in Formula III below:

[0016]

[0017] In one alternative embodiment, the chiral electron transport material is any one of the following structural formulas:

[0018]

[0019]

[0020]

[0021]

[0022] This invention also provides a method for preparing a chiral electron transport material, wherein the preparation method of Formula I includes the following steps:

[0023]

[0024] 3,6-Dibromo-4,5-difluoro-1,2-phenylenediamine and a diketone derivative undergo dehydration condensation under acid catalysis to generate a quinoxaline derivative intermediate, which then undergoes intramolecular nucleophilic substitution with a chiral binaphthol to form an oxa-eight-membered heterocyclic intermediate. Finally, the intermediate undergoes stepwise reaction with boric acid compounds of Ar1 and Ar2 under Pd catalyst conditions via Suzuki coupling to obtain the final product of formula I.

[0025] This invention also provides a method for preparing a chiral electron transport material, wherein the preparation method of Formula II includes the following steps:

[0026]

[0027] The benzodiazole derivative intermediate undergoes intramolecular nucleophilic substitution with a chiral binaphthol derivative to form an oxa-eight-membered heterocyclic intermediate, which is then reacted stepwise with boric acid compounds of Ar1 and Ar2 under Pd catalyst conditions via Suzuki coupling reaction to yield the final product of formula II.

[0028] This invention also provides the application of chiral electron transport materials in the fabrication of electroluminescent devices.

[0029] In one alternative embodiment, at least one functional layer of the electroluminescent device comprises the chiral electron transport material.

[0030] In one alternative embodiment, the functional layer includes an electron transport layer containing the chiral electron transport material.

[0031] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0032] (1) The chiral electron transport material provided by the present invention introduces a natural chiral binaphthol moiety, which forms an oxa-eight-membered ring-locked chiral configuration through a nucleophilic substitution reaction. Then, it is modified with a nitrogen-containing fused-ring aromatic hydrocarbon with good electron transport capability on the periphery. This enables the material to have both circular polarization chiral activity and good electron transport capability. Furthermore, the nitrogen-containing fused-ring aromatic hydrocarbon modified on the periphery can further enhance the spin selection effect and electron transport capability by forming intermolecular hydrogen bonds in the aggregated state, thereby achieving a strong intermolecular interaction and a high efficiency of luminescence.

[0033] (2) The structure of the present invention comprises a binatol chiral unit and a monocyclic or polycyclic aromatic hydrocarbon substituent with electron transport characteristics. The energy levels and distances between the two parts are matched, and it has circular polarization chirality and good electron transport characteristics. When applied to electroluminescent devices, it can achieve strong stability, high transmission efficiency and low cost.

[0034] (3) The chiral electron transport material provided by the present invention has a suitable LUMO energy level, strong chiral activity and suitable molecular weight. It can be used not only as an electron transport layer in CP-OLED, but also as a spin selector through functional layers such as chiral acceptors and electron blocking layers used in the light-emitting layer. Attached Figure Description

[0035] Figure 1 The ground-state optimized configuration diagram of the chiral electron transport material R / S-CPETL-01 prepared in Example 1 is shown.

[0036] Figure 2 The diagram shows the LUMO and HOMO orbital distributions of the chiral electron transport material R / S-CPETL-01 prepared in Example 1.

[0037] Figure 3 The ground-state optimized configuration diagram of the chiral electron transport material R / S-CPETL-04 prepared in Example 2 is shown.

[0038] Figure 4 The diagram shows the LUMO and HOMO orbital distributions of the chiral electron transport material R / S-CPETL-04 prepared in Example 2.

[0039] Figure 5 The ground-state optimized configuration diagram of the chiral electron transport material R / S-CPETL-08 prepared in Example 3 is shown.

[0040] Figure 6 The diagram shows the LUMO and HOMO orbital distributions of the chiral electron transport material R / S-CPETL-08 prepared in Example 3.

[0041] Figure 7The ground-state optimized configuration diagram of the chiral electron transport material R / S-CPETL-16 prepared in Example 5 is shown.

[0042] Figure 8 The diagram shows the LUMO and HOMO orbital distributions of the chiral electron transport material R / S-CPETL-16 prepared in Example 5.

[0043] Figure 9 The ground-state optimized configuration diagram of the chiral electron transport material R / S-CPETL-17 prepared in Example 6 is shown.

[0044] Figure 10 The diagram shows the LUMO and HOMO orbital distributions of the chiral electron transport material R / S-CPETL-17 prepared in Example 6.

[0045] Figure 11 The absorption and emission spectrum of R / S-CPETL-01 in toluene solution is shown.

[0046] Figure 12 The absorption and emission spectrum of R / S-CPETL-04 in toluene solution is shown.

[0047] Figure 13 The absorption and emission spectrum of R / S-CPETL-16 in toluene solution is shown.

[0048] Figure 14 The absorption and emission spectrum of R / S-CPETL-17 in toluene solution is shown.

[0049] Figure 15 The circularly polarized emission spectra of R / S-CPETL-01, R / S-CPETL-08, and R / S-CPETL-17 in dilute toluene solution are shown.

[0050] Figure 16 The circularly polarized emission spectra of R / S-CPETL-01, R / S-CPETL-08, and R / S-CPETL-17 in their pure film state are shown.

[0051] Figure 17 The current density-voltage-brightness curves of CP-OLED devices prepared based on the materials of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4 are shown.

[0052] Figure 18 The graph shows the external quantum efficiency of CP-OLED devices prepared based on the materials of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4 as a function of brightness.

[0053] Figure 19The graph shows the brightness-current efficiency / power efficiency curves of the CP-OLED devices prepared based on Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4.

[0054] Figure 20 The electro-circularly polarized emission spectra of the CP-OLED devices prepared based on Comparative Example 2 and Comparative Example 3 are shown.

[0055] Figure 21 The electro-circularly polarized emission spectra of CP-OLED devices fabricated based on R / S-CPETL-01 and R / S-CPETL-17 are shown.

[0056] Figure 22 This is a schematic diagram of the structure of a CP-OLED device according to an embodiment of the present invention. Detailed Implementation

[0057] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings, focusing on material synthesis, basic photophysical properties, and application in CP-OLED. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0058] Example 1

[0059] The preparation method of the chiral electron transport material (R / S-CPETL-01) includes the following steps:

[0060]

[0061] 20 mmol of 3,6-dibromo-4,5-difluorobenzene-1,2-diamine was placed in a 150 mL two-necked flask. After three purging cycles, 15 mL of glyoxal and 80 mL of glacial acetic acid were injected separately using a syringe under nitrogen protection. The mixture was heated to 100 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate 4:1) to obtain a brownish-yellow solid, i.e., intermediate 1, with a yield of 67%. HRMS (ESI) theoretical calculations showed that C8H3Br2F2N2, [M+H] + 324.9303, the measured value is 324.9309.

[0062] Intermediate 1 (10 mmol), (R / S)-6,6'-dibromo-1,1'-bi-2-naphthol (10 mmol), and cesium carbonate (15 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultradry N,N-dimethylformamide was injected using a syringe under argon protection. The mixture was heated to 120 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate 4:1) to obtain a brownish-yellow solid, namely intermediate R / S-2, with a yield of 78%. HRMS (ESI) theoretical calculation C 28 H 13 Br4N2O2, [M+H] + 729.0395, measured value 729.0392.

[0063] Intermediate R / S-2 (5 mmol), 4-pyridineboronic acid (5 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol), and potassium carbonate (25 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 60 mL of a deoxygenated toluene-ethanol-water mixture (Tol:EtoH:H2O = 30:7:7) was injected under argon protection using a syringe. The mixture was heated to 90 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / methanol 15:1) to obtain a pale yellow solid, which is the chiral electron transport material, designated R / S-CPETL-01, with a yield of 42%. HRMS (ESI) theoretical calculations showed C0. 48 H 29 N6O2,

[0064] [M+H] + 721.7995, measured value 721.7990.

[0065] 1 H NMR(500MHz,Chloroform-d)δ8.99(s,1H),8.68(dd,J=9.9,5.0Hz,4H),8.31(t,J=1.4Hz,1H),8.12–8.02(m,2H),7.83–7.76(m,3H),7.65–

[0066] 7.59 (m, 3H).

[0067] Example 2

[0068] The preparation method of chiral electron transport material (R / S-CPETL-04) includes the following steps:

[0069]

[0070] The reaction process for preparing intermediate 1 and intermediate R / S-2 is the same as that described in Example 1, and will not be repeated here. Intermediate R / S-2 (5 mmol), 7-isoquinoline boric acid (10 mmol), tetrakis(triphenylphosphine)palladium (0.6 mmol), and potassium carbonate (25 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of a deoxygenated toluene-ethanol-water mixture (Tol:EtoH:H2O = 20:5:5) was injected under argon protection using a syringe. The mixture was heated to 90 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixed solvent. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / methanol 15:1) to obtain a pale yellow solid, which is the chiral electron transport material, designated R / S-CPETL-04, with a yield of 39%. HRMS (ESI) theoretical calculations showed C0. 64 H 37 N6O2,

[0071] [M+H] + 922.0395, measured value 922.0397.

[0072] 1 H NMR(500MHz,Chloroform-d)δ9.31(d,J=1.5Hz,3H),8.95–8.84(m,3H),8.75(dd,J=7.5,1.5Hz, 1H),8.65(d,J=1.4Hz,1H),8.62–8.52(m,5H),8.55–8.46(m,2H),8.47–8.38(m,3H),8.28(s,1H ),7.95–7.87(m,2H),7.90–7.81(m,2H),7.78–7.66(m,4H),7.59(d,J=7.5Hz,1H),7.31(d,J=7. 5Hz,1H),7.23(dd,J=7.5,1.4Hz,1H),7.05–6.98(m,2H),7.00–6.92(m,2H),6.73–6.66(m,2H).

[0073] Example 3

[0074] The preparation method of the chiral electron transport material (R / S-CPETL-08) includes the following steps:

[0075]

[0076] The reaction process for preparing intermediate 1 and intermediate R / S-2 is the same as that described in Example 1, and will not be repeated here. Intermediate R / S-2 (5 mmol), phenylboronic acid (10 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol), and potassium carbonate (25 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 60 mL of a deoxygenated toluene-ethanol-water mixture (Tol:EtoH:H2O = 20:5:5) was injected under argon protection using a syringe. The mixture was heated to 95 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixed solvent. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate 4:1) to obtain a pale yellow solid, which is the chiral electron transport material, designated R / S-CPETL-08, with a yield of 46%. HRMS (ESI) theoretical calculations showed C0. 52 H 33 N2O2,

[0077] [M+H] + 717.8475, measured value 717.8480.

[0078] 1 H NMR(500MHz,Chloroform-d)δ8.97(s,1H),8.22(d,J=1.5Hz,1H),8.12–8.04(m,2H),7.67–7.56(m,6H),7.48–7.37(m,4H),7.40–7.29(m,2H).

[0079] Example 4

[0080] The preparation method of chiral electron transport material (R / S-CPETL-10) includes the following steps:

[0081]

[0082] 20 mmol of 4,7-dibromo-5,6-difluoro-benzo[c][1,2,5]oxadiazole, 25 mmol of (R / S)-6,6'-dibromo-1,1'-bi-2-naphthol, and 40 mmol of cesium carbonate were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultra-dry N,N-dimethylformyl was injected under nitrogen protection using a syringe. The mixture was heated to 120 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 3:1) to obtain a pale yellow solid, namely intermediate R / S-3, with a yield of 60%. HRMS (ESI) theoretical calculation C 26 H 11 Br4N2O3, [M+H] + 719.0005, the actual measured value is 719.0002.

[0083] Intermediate R / S-3 (10 mmol), 4-pyridineboronic acid (15 mmol), ferrocene palladium dichloride (1 mmol), and cuprous chloride (20 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultradry N,N-dimethylformamide was injected using a syringe under argon protection. The mixture was heated to 120 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / methanol 15:1) to obtain a pale yellow solid, which was the chiral electron transport material, designated R / S-CPETL-10, with a yield of 38%. HRMS (ESI) theoretical calculations showed C0. 46 H 27 N6O3, [M+H] + 711.7605, measured value 711.7608.

[0084] 1 H NMR(500MHz,Chloroform-d)δ8.68(dd,J=9.9,5.1Hz,4H),8.30(d,J=1.4Hz,1H),8.11–8.03(m,2H),7.83–7.76(m,3H),7.58(dt,J=5.1,2.8Hz,3H).

[0085] Example 5

[0086] The preparation method of chiral electron transport material (R / S-CPETL-16) includes the following steps:

[0087]

[0088] The reaction process for preparing intermediate R / S-3 was the same as in Example 4 and will not be described again here. Intermediate R / S-3 (10 mmol), pyrimidine-5-boronic acid (15 mmol), ferrocene palladium dichloride (1 mmol), and cuprous chloride (20 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultradry N,N-dimethylformamide was injected using a syringe under argon protection. The mixture was heated to 120 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixed solvent. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluting agent: petroleum ether / methanol 15:1) to obtain a yellow solid, which is the chiral electron transport material, designated R / S-CPETL-16, with a yield of 43%. HRMS (ESI) theoretical calculations showed C1... 42 H 23 N 10 O3, [M+H] + 715.7125, measured value 715.7129.

[0089] 1 H NMR(500MHz,Chloroform-d)δ9.19–9.09(m,4H),9.10–9.01(m,2H),8.30(t,J=1.5Hz, 1H),8.11–8.02(m,2H),7.81(ddd,J=7.5,3.1,1.5Hz,1H),7.57(dd,J=7.4,3.9Hz,1H).

[0090] Example 6

[0091] The preparation method of the chiral electron transport material (R / S-CPETL-17) includes the following steps:

[0092]

[0093] 20 mmol of 4,7-dibromo-5,6-difluorobenzo[c][1,2,5]selenodiazole, 25 mmol of (R / S)-6,6'-dibromo-1,1'-bi-2-naphthol, and 35 mmol of cesium carbonate were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultra-dry N,N-dimethylformyl was injected under nitrogen protection using a syringe. The mixture was heated to 120 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 3:1) to obtain a pale yellow solid, namely intermediate R / S-4, with a yield of 76%. HRMS (ESI) theoretical calculation C 26 H 11 Br4N2O2Se,

[0094] [M+H] + 781.9725, the actual measured value is 781.9724.

[0095] Intermediate R / S-4 (10 mmol), pyrimidine-5-boronic acid (15 mmol), ferrocene palladium dichloride (2 mmol), and cuprous chloride (25 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultradry N,N-dimethylformamide was injected using a syringe under argon protection. The mixture was heated to 120 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / methanol 15:1) to obtain a pale yellow solid, which was the chiral electron transport material, designated R / S-CPETL-17, with a yield of 42%. HRMS (ESI) theoretical calculations showed C1... 42 H 23 N 10 O2Se, [M+H] + 778.6845, measured value 778.6847.

[0096] 1 H NMR(500MHz,Chloroform-d)δ9.17(s,1H),9.04(s,1H),8.90(s,2H),8.82(s,2H),8.13 (d,J=1.5Hz,1H),7.98(d,J=7.5Hz,1H),7.84(dd,J=7.6,1.5Hz,1H),7.67–7.59(m,2H).

[0097] Example 7

[0098] The preparation method of chiral electron transport material (R / S-CPETL-31) includes the following steps:

[0099]

[0100] 20 mmol of 3,6-dibromo-4,5-difluorobenzene-1,2-diamine and 20 mmol of 1,2-naphthoquinone were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of glacial acetic acid was injected using a syringe under nitrogen protection. The mixture was heated to 100 °C and reacted for 48 h. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate 4:1) to obtain a brownish-yellow solid, intermediate 5, with a yield of 62%. 1 HRMS (ESI) theoretical calculation C 16 H7Br2F2N2, [M+H] + 425.0503, the actual measured value is 425.0507.

[0101] Intermediate 5 (10 mmol), (R / S)-6,6'-dibromo-1,1'-bi-2-naphthol (10 mmol), and cesium carbonate (15 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultradry N,N-dimethylformamide was injected using a syringe under argon protection. The mixture was heated to 120 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixture. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate 4:1) to obtain a brownish-yellow solid, namely intermediate R / S-6, with a yield of 73%. HRMS (ESI) theoretical calculation C 36 H 17 Br4N2O2, [M+H] + 829.1595, measured value 829.1594.

[0102] Intermediate R / S-6 (5 mmol), 4-pyridineboronic acid (5 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol), and potassium carbonate (25 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 60 mL of a deoxygenated toluene-ethanol-water mixture (Tol:EtoH:H2O = 30:7:7) was injected under argon protection using a syringe. The mixture was heated to 90 °C and reacted overnight. After cooling, the reaction mixture was poured into a 500 mL separatory funnel and extracted with a dichloromethane / water mixed solvent. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / methanol 15:1) to obtain a white solid, which is the chiral electron transport material, designated R / S-CPETL-31, with a yield of 41%. 1 HRMS (ESI) theoretical calculation C 56 H 33 N6O2,

[0103] [M+H] + 821.9195, measured value 821.9197.

[0104] 1 H NMR(500MHz,Chloroform-d)δ9.75(dd,J=7.1,1.8Hz,1H),9.45(d,J=7.5Hz,1H),8.68(dd,J=9.9,5.1Hz,7H),8.43(dd,J=7.4,1.4Hz,1H),8 .31(d,J=1.5Hz,1H),8.14–8.04(m,3H),7.85–7.59(m,12H),7.56(dd,J=6.3,3.4Hz,3H),7.11(d,J=7.5Hz,1H),6.88(dd,J=7.5,1.5Hz,1H).

[0105] I. Theoretical Simulation

[0106] To illustrate the superiority of the chiral electron transport material provided by this invention, theoretical simulation data of key molecular parameters for some of the above embodiments based on Gaussian 16 software are provided below, as shown in Table 1. Optimization of all ground-state configurations is based on the B3LYP / def2-svp level, assuming a gaseous single-molecule state, and considering results obtained under dispersion correction. Optimization of excited-state energy levels and configurations is based on this optimized ground-state configuration obtained using TD-DFT calculations. The basis sets and functionals used in the calculations are consistent with those of the ground state. Visualization of all orbitals is achieved using Gaussview 6.0 software.

[0107] Table 1 Calculation results of the frontline orbital energy level

[0108]

[0109] As shown in Table 1 above, all results are in line with expectations. Specifically, the calculated LUMO energy levels of the selected representative examples are all between -3.31 and -2.20 eV, consistent with the matching requirements of current conventional electroluminescent devices for the electron transport layer or the host electron mode energy level. Furthermore, changes in peripheral substituents and the central fused heterocycle can precisely and effectively adjust parameters such as the LUMO energy level and electrochemical band gap to meet specific device requirements. For example, compared to R / S-CPETL-01 with quinoxaline as the central core, the introduction of benzoxadiazole (R / S-CPETL-10) can effectively reduce the LUMO to -3.18 eV.

[0110] To further demonstrate the impact of changes in substituents and central electron transport building blocks on its electrochemical and chiral activities, the preferred configurations and frontier orbital distributions of representative molecules from the examples are selected and listed here. For structural formula I of this invention, representative structural molecules R / S-CPETL-01, R / S-CPETL-04, and R / S-CPETL-08 were selected; for structural formula II, representative structural molecules R / S-CPETL-16 and R / S-CPETL-17 were selected.

[0111] like Figure 1-10 As shown, Figure 1-10 In the image, A is a frontal view (left side), and B is a side view (right side). (a) is a HOMO (left side) image, and (b) is a LUMO (right side) image. From Figure 1-10 As can be seen, regardless of whether it is the representative molecule of general formula I or general formula II, or the change of the peripheral substituents, the basic molecular framework is basically consistent. First, the eight-membered ring formed by nucleophilic substitution in chiral binaphthol can effectively lock its chiral configuration, and lock it with a suitable axial chiral dihedral angle (~45°), which is conducive to constructing a stable and efficient chiral center. Changes in the peripheral substituents maintain an almost consistent configuration at the single-molecule level. However, the introduction of the peripheral nitrogen-containing electron-deficient heterocycle can, under the conditions of aggregation, regulate intermolecular interactions by forming intermolecular hydrogen bonds, providing a powerful means of amplifying its chiral signal. Second, the HOMO orbitals of all molecules are basically concentrated on the electron-rich chiral binaphthol moiety, and the LUMO orbitals are basically concentrated on the electron-deficient core fragment of the quinoxaline derivative or diazole derivative parallel to the chiral axis. Changes in peripheral substitution can slightly adjust the distribution of LUMO orbitals. By comprehensively using a multi-channel strategy, while ensuring good electron transport capabilities, the aggregation behavior can be optimized by fine-tuning the substituents to achieve the amplification of chiral activity.

[0112] II. Basic Photophysical and Electrochemical Properties

[0113] To further elucidate the potential application value of the electron transport materials provided by this invention in CP-OLEDs, the basic photophysical and electrochemical properties of the materials (R / S-CPETL-01, R / S-CPETL-04, R / S-CPETL-08, R / S-CPETL-10, R / S-CPETL-16, R / S-CPETL-17, R / S-CPETL-31) obtained in the embodiments of this invention were characterized in detail. Ultraviolet-Vis absorption spectra, photoluminescence, and circular polarization spectral data were obtained from the corresponding dilute toluene solutions (1*10⁻⁶). -5 In addition, to investigate the difference in chiral activity between the aggregated and monomolecular states of these chiral molecules, their circularly polarized emission spectra in the pure film state were also measured and appended after the solution conditions. The results are shown in Table 2 below.

[0114] Table 2. Basic photophysical and electrochemical properties

[0115]

[0116]

[0117] As shown in Table 2, the absorption and emission peaks shift with the changes in the peripheral substituents and the central core. However, the absorption peaks and absorption cutoffs in the long wavelength direction of all compounds fall in the ultraviolet region. The absorption of conventional visible light luminescent materials is negligible, indicating that these materials can meet the most basic requirements for the fabrication of full-spectrum devices in the visible light region.

[0118] As shown in Table 2, the material molecules in all embodiments exhibit a high luminescence asymmetry factor (g). PL ~10 -3 This indicates that these materials exhibit good spin selectivity differences for photoexcitation, especially the introduction of the heavy atom Se (R / S-CPETL-17), which significantly promotes spin-orbit coupling and greatly benefits g. PL The improvement is reflected in the luminescence asymmetry factor (g) of the material molecules prepared in this invention. PL Significant amplification (~10) was achieved in the pure film state. -2 (On a scale of magnitude), especially molecules with a large number of nitrogen-containing heterocycles on the periphery, such as R / S-CPETL-01 and R / S-CPETL-17, fully demonstrate the effectiveness of introducing nitrogen-containing heterocycles on the periphery in enhancing intermolecular interactions and improving the spin selectivity of materials.

[0119] To demonstrate the subtle differences and variation patterns in absorption and emission of the material molecules prepared by this invention, this invention provides the absorption and emission spectra of two representative molecules of general formula I, R / S-CPETL-01 and R / S-CPETL-04 (with different peripheral substituents), and two representative molecules of general formula II, R / S-CPETL-16 and R / S-CPETL-17 (with different heteroatoms in the central nucleus).

[0120] The results are as follows: Figures 11 to 14 As shown. By Figures 11 to 14 It is known that changes in peripheral substituents and the introduction of heavy atoms have a certain impact on molecular absorption and emission. Substituents with larger fused rings and heavy atoms will cause the overall absorption and emission peaks to redshift. Appropriately adjustable optical / electrochemical band gaps of molecules can be used to match different devices. The absorption cutoff of all compounds falls before visible light, effectively avoiding the self-absorption of light emission by the electronic layer.

[0121] Figure 15 and 16 The circularly polarized emission spectra of representative molecules of general formula I, R / S-CPETL-01 and R / S-CPETL-08, and representative molecule of general formula II, R / S-CPETL-17, are presented in dilute toluene solution and in the pure film state. Figure 15 and 16 It is evident that the enantiomers of the representative molecules in the examples exhibit typical mirror symmetry in their circularly polarized emission spectra in toluene solution, and the peak values ​​of the circularly polarized spectra are in good agreement with the steady-state emission spectra, confirming the reliability of the circularly polarized spectra. The molecules covered by this invention all demonstrate significant chiral optical activity, and the introduction of atoms in the unimolecular state significantly enhances the circularly polarized emission signal. Furthermore, in the aggregated state, the enhanced intermolecular interactions result in a substantial enhancement of the chiral signal, fully demonstrating the effectiveness of the molecular design concept of this invention and its feasibility in achieving efficient spin selection in electroluminescent devices.

[0122] III. Device Applications

[0123] (I) Implementation and Application Examples

[0124] The following application examples illustrate the effect of the chiral electron transport material prepared in this invention as an electron transport layer in CP-OLED devices.

[0125] The following combination Figure 22The device structure is illustrated through seven embodiments using the corresponding molecular materials R / S-CPETL-01, R / S-CPETL-04, R / S-CPETL-08, R / S-CPETL-10, R / S-CPETL-16, R / S-CPETL-17, and R / S-CPETL-31. These embodiments demonstrate the application effect of the chiral electron transport material of the present invention as an electron transport layer material in CP-OLED devices. The CP-OLED devices fabricated using the chiral electron transport materials of these seven embodiments as electron transport layer materials are named Embodiment 1 / 11 (R-CPETL01 / S-CPETL01), Embodiment 2 / 21 (R-CPETL04 / S-CPETL04), Embodiment 3 / 31 (R-CPETL08 / S-CPETL08), Embodiment 4 / 41 (R-CPETL10 / S-CPETL10), Embodiment 5 / 51, and Embodiment 6, respectively.

[0126] (R-CPETL16 / S-CPETL16), implementation device 6 / 61 (R-CPETL17 / S-CPETL17) and implementation device 7 / 71 (R-CPETL31 / S-CPETL31).

[0127] The organic electroluminescent device provided by this invention refers to... Figure 22 The structure shown comprises, from bottom to top, an anode layer 100 (ITO), a hole injection layer 101 (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene, HAT-CN), a hole transport layer 102 (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], TAPC), a hole transport layer 103 (tris(4-(9H-carbazole-9-yl)phenyl)amine, TCTA), and a hole blocking layer 104 (1,3-bis(9H-carbazole-9-yl)phenyl, mCP). The light-emitting layer 105 (BN-22% doped with 5-(4,6-diphenyl-1,3,5-triazine-2-yl)-7,7-dimethyl-5,7-dihydroindo[2,1-b]carbazole, DMIC-TRZ), the hole-blocking layer 106 (2,4,6-tris[3-(diphenylphosphine)phenyl]-1,3,5-triazine, PO-T2T), the electron transport layer 107 (chiral electron transport materials with different codes obtained in different embodiments of the present invention, ETL), the cathode interface layer 108 (lithium 8-hydroxyquinoline, Liq), and the cathode 109 (Al).

[0128] The device details are as follows: ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / BN-2:DMIC-TRZ (2wt.%, 45nm) / PO-T2T (10nm) / ETL (40nm) / Liq (2nm) / Al (100nm)

[0129] (II) Comparative Application Examples

[0130] To demonstrate the advantages of the chiral electron transport material provided by this invention in terms of both electron transport efficiency and spin selectivity, corresponding comparative application examples are provided below;

[0131] Comparative Example 1: The device structure is the same as the implementation example, but the electron transport layer is replaced with the classic achiral Tm3PyPB to compare the difference in electron transport efficiency between the electron transport material provided by the present invention and the classic electron transport material. The resulting device is named Comparative Device 1.

[0132] The specific structure is ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / BN-2:DMIC-TRZ (2wt.%, 45nm) / PO-T2T (10nm) / Tm3PyPB (40nm) / Liq (2nm) / Al (100nm);

[0133] Comparative Example 2: The device structure is the same as the application example, but the electron transport layer is replaced with the classic Tm3PyPB and the emissive layer is replaced with the chiral emissive material R-BA34CzBN. This device structure is the current conventional CP-OLED construction method. By comparison, the difference in spin selection of the emissive layer or electron transport layer can be demonstrated. The resulting device is named Comparative Device 2.

[0134] The specific device structure is ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / R-BA34CzBN:DMIC-TRZ (2wt.%, 45nm) / PO-T2T (10nm) / Tm3PyPB (40nm) / Liq (2nm) / Al (100nm);

[0135] Comparative Example 3: The device structure is the same as the application example, but the electron transport layer uses an R / S-CPETL-01 racemic variant and the light-emitting layer is replaced with a chiral light-emitting material R-BA34CzBN. Excluding spin-selection interference, the electron transport efficiency of the electron transport material provided by this invention can be compared laterally with that of the classical Tm3PyPB, and the resulting device is named Comparative Device 3.

[0136] The specific device structure is ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / R-BA34CzBN:DMIC-TRZ (2wt.%, 45nm) / PO-T2T (10nm) / R / S-CPETL-01 (40nm) / Liq (2nm) / Al (100nm);

[0137] Comparative Example 4: The device structure is the same as the application example, but the electron transport layer uses an R / S-CPETL-01 exoracemate to eliminate spin interference. The difference in electron transport efficiency is compared horizontally with Comparative Example 1. The resulting device is named Comparative Device 4.

[0138] The specific device structure is ITO / HAT-CN (5nm) / TAPC (30nm) / TCTA (15nm) / mCBP (10nm) / BN-2:DMIC-TRZ (2wt.%, 45nm) / PO-T2T (10nm) / R / S-CPETL-01 (40nm) / Liq (2nm) / Al (100nm).

[0139] The structural formulas of HAT-CN, TAPC, TCTA, DMIC-TRZ, mCBP, PO-T2T, BN-2, and R-BA34CzBN are as follows:

[0140]

[0141] (III) Comparison between the device in the example and the device in the comparative example

[0142] The general fabrication process for both the implementation and comparison devices is as follows: First, an indium tin oxide (ITO) coated glass substrate with a surface resistivity of 15 ohms per square meter is subjected to continuous ultrasonic treatment with acetone / isopropanol, followed by nitrogen drying. Then, the substrate is treated with ultraviolet ozone (UVO) for 20 minutes in a UV ozone surface treatment machine (Sen Lights Corporation PL16 series). Next, the treated ITO substrate is fed into the deposition system. At 5 × 10⁻⁶... -5 Under a vacuum of Pa, the product is obtained by thermal evaporation at a rate of 0.2 to Pa. The deposition rate is such that the above organic layers are deposited sequentially, and the deposition rate of the cathode aluminum (Al) layer is... The light-emitting area of ​​this device is 0.09 cm². 2The current density-voltage-luminance (JVL) characteristics, external quantum efficiency curves, and electroluminescence spectra of the devices were measured using a Keithley 2400 source meter and an absolute quantum efficiency measurement system (Hamamatsu Photonics, Japan, model C9920-12). (This invention only measures a portion of the devices.) The results are as follows: Figure 17-21 And as shown in Table 3 below.

[0143] Table 3 Comparison of Core Device Indicators

[0144]

[0145] As shown in Table 3 above, by comparing all implemented devices with Comparison Device 1, it can be seen that the external quantum efficiency (η) of all implemented devices is... EQE ), power efficiency (η) p ), current efficiency (η) c The chiral electron transport material provided by this invention is significantly superior to the comparative device 1 in all three core indicators, which fully demonstrates that the chiral electron transport material is significantly superior to the classical electron transport material Tm3PyPB in terms of electron transport efficiency.

[0146] By comparing all the implemented devices with comparative devices 2 and 3, it can be seen that CP-OLEDs constructed using conventional chiral light-emitting materials generally exhibit poor spin selectivity, resulting in a lower asymmetry factor (g) in the harvested electro-circularly polarized spectrum. EL ) is often very low, around 10 -4 ~10 -3 The magnitude of the CP-OLED constructed using a chiral electron transport layer to form a spin polarization current is significantly improved compared to the present invention, which can significantly enhance the device's g-order performance. EL Compared to comparative devices 2 and 3, the implemented devices generally achieve a value of 10. -2 level.

[0147] Comparing Comparison Device 2 and Comparison Device 3, the difference lies in the electron transport layer, but the external quantum efficiency (η) remains the same. EQE ), power efficiency (η) p ), current efficiency (η) c The three core indicators are significantly better than those of comparative device 2 and comparative device 3, which further confirms that the electron transport material provided by the present invention can provide higher device efficiency under the same conditions.

[0148] By comparing implementation devices 1, 11, 2, 21 with comparison device 4, it can be seen that the device efficiency is almost identical when using a single chiral electron transport material and a racemic body, indicating that spin selection has little effect on device efficiency. However, the output light is very different. Only a single chiral electron transport layer can achieve spin selection and circularly polarized light emission, which fully confirms the existence and effectiveness of spin selection.

[0149] Furthermore, there are differences in device efficiency and g between different implementation devices. EL There are also significant differences in this aspect. For example, R / S-CPETL-01 and R / S-CPETL-04, which are modified with more nitrogen-containing heterocycles on the periphery, can form intermolecular hydrogen bonds in the aggregated state, enhance intermolecular interactions, and achieve g EL The amplification of the molecular structure makes it significantly superior to R / S-CPETL-08, which is only modified with a benzene ring on the periphery. However, at the molecular level, the introduction of the heavy atom Se can significantly promote intramolecular spin-orbit coupling and facilitate further modulation of magnetic / electric transitions, thereby achieving g... EL The amplification is therefore implemented using device 6 / 61 (R / S-CPETL-17) g. EL The values ​​are significantly higher than those of embodiments 4 / 41 and 5 / 51 (R / S-CPETL-10 and R / S-CPETL-16). In summary, the CP-OLED constructed using the selected embodiment molecules as the electron transport layer significantly improves both device efficiency and chiral activity compared to the comparative devices, fully demonstrating the superiority of the present invention.

[0150] It should be noted that, given the advantages of the chiral electron transport material of the present invention in the electron transport layer of CP-OLED, its application can be extrapolated to electronic host or other electroluminescent devices, such as the electron transport layer of quantum dot LEDs and perovskite LEDs, which can also generate spin selection effect to achieve circularly polarized light emission. Although no specific embodiment is given here, based on common sense and the rules provided by the present invention, such extrapolation applications also fall within the protection scope of the present invention.

[0151] Although the present invention has been described using the above preferred embodiments, it is not intended to limit the scope of protection of the present invention. Any changes and modifications made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. A chiral electron transport material, characterized in that, It has the molecular structure shown in Formula I or Formula II: Formula I, Formula II, Wherein, groups Ar1 and Ar2 are each independently selected from any one of pyridinyl, pyrimidinyl, formonitrilephenyl, 3-phenylpyridinyl, pyrazinyl, quinolinyl, isoquinolinyl, quinoxalinyl, benzo[b]oxazolyl, benzo[d]thiazolyl, benzo[b]thiopheneyl, benzofuranyl, 1-phenyl-1H-benzimidazolyl, biphenyl, anthraceneyl, o-phenanthrolinel, phenolazinyl, and dibenzothiopheneyl; group Ar3 is any one of H, benzene ring, cyclohexane, naphthyl ring, phenanthrene ring, o-phenanthroline, or 1-indanone; and group X is any one of O, S, and Se.

2. The chiral electron transport material according to claim 1, characterized in that, The Ar3 is selected from H, and the molecular structure of the chiral electron transport material is shown in Formula III below: Formula III.

3. A chiral electron transport material, characterized in that, The chiral electron transport material is any one of the following structural formulas: ， ， ， ， ， ， ， ， ， ， ， ， ， ， ， ， ， ， ， 。 4. The method for preparing the chiral electron transport material according to claim 1, characterized in that, The preparation method of Formula I includes the following steps: ； 3,6-Dibromo-4,5-difluoro-1,2-phenylenediamine and a diketone derivative undergo dehydration condensation under acid catalysis to generate a quinoxaline derivative intermediate, which then undergoes intramolecular nucleophilic substitution with a chiral binaphthol derivative to form an oxa-eight-membered heterocyclic intermediate. Finally, the intermediate undergoes stepwise reaction with boric acid compounds of Ar1 and Ar2 under Pd catalyst conditions via Suzuki coupling to obtain the final product of formula I.

5. The method for preparing the chiral electron transport material according to claim 1, characterized in that, The preparation method of Formula II includes the following steps: ； The benzodiazole derivative intermediate undergoes intramolecular nucleophilic substitution with a chiral binaphthol derivative to form an oxa-eight-membered heterocyclic intermediate, which is then reacted stepwise with boric acid compounds of Ar1 and Ar2 under Pd catalyst conditions via Suzuki coupling reaction to yield the final product of formula II.

6. The application of the chiral electron transport material according to any one of claims 1-2 in the fabrication of electroluminescent devices.

7. The application according to claim 6, characterized in that, At least one functional layer of the electroluminescent device contains the chiral electron transport material.

8. The application according to claim 7, characterized in that, The functional layer includes an electron transport layer, which contains the chiral electron transport material.

Images