Chiral electron transport material and application thereof in electroluminescent device

Abstract

The invention discloses a chiral electron transport material which is prepared by introducing a natural chiral binaphthol element, carrying out nucleophilic substitution reaction to form an oxa eight-membered ring locking axial chiral configuration, and then modifying aza polycyclic aromatic hydrocarbon with good electron transport capacity on the periphery. The material simultaneously has chiral optical / electrical activity and good electron transmission capability, and the peripherally modified aza-polycyclic aromatic hydrocarbon can further form intermolecular hydrogen-bond interaction under an aggregation state to realize strong intermolecular interaction, so that the spin selection effect and the electron transmission capability are further enhanced. The chiral small-molecule electron transport material provided by the invention can be used as an electron type main body material in an electron transport layer or a luminescent layer in an electroluminescent device, and has electron transport and spin selection functions, so that a simpler and more efficient circular polarization electroluminescent device can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic materials, and in particular to a chiral electron transport material and an application thereof in an electroluminescent device. Background Art

[0002] Organic electroluminescent devices, also known as organic light-emitting diodes (OLEDs), refer to organic semiconductors and luminescent materials that, under the drive of an electric field, inject carriers from the two poles and recombine in the luminescent layer to cause luminescence. They are devices based on organic luminescent materials that convert electrical energy into light energy. Compared with traditional liquid crystal display technology, OLEDs have many inherent advantages, such as ultra-lightness, fast response speed, high resolution, low power consumption, anti-vibration, low temperature resistance, and flexibility.

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

[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 especially significantly improving screen ambient light reflection and other issues.

[0005] In the development of CP-OLED, chiral luminescent materials have been widely studied as the most direct strategy to achieve circularly polarized light output, and have undergone continuous iterations from chiral polymers to chiral metal complexes and circularly polarized luminescent (CPL) materials with thermally activated delayed fluorescence properties. PL ) or device efficiency have made great progress, but at the same time can achieve high g PL However, there is still no breakthrough in CPL materials with high value and high device efficiency.

[0006] Currently, among the high-efficiency CP-OLED devices based on CPL materials reported in the literature, the maximum external quantum efficiency (η EQE,max ) exceeds 25% of the sample, the material intrinsic g PL The value can basically only be maintained at (10 -4 ~10 -3 ) level. The fundamental reason is that conventional CPL materials are all allowed to undergo electrical transitions but forbidden to undergo magnetic transitions, which results in g PL The value is unlikely to exceed 10 -2 level, although the introduction of rare earth metal elements can achieve g by constructing ff transitions that allow magnetic transitions PLThe numerical value is greatly improved (can exceed 0.1), but it will also lead to a significant reduction in luminous efficiency, a long excited state lifetime, and an increase in non-radiative transitions, resulting in very low device efficiency and inability to meet commercial applications. Summary of the invention

[0007] The purpose of the present invention is to provide a chiral electron transport material. After the irregular charges (holes or electrons whose spin directions cancel each other out) pass through the chiral charge transport material, the spin polarization of the transported charges can be achieved through the chirality-induced spin selection effect, and then they are recombined through the light-emitting layer to form spin-polarized excitons, and then circularly polarized luminescence can be achieved through radiation transition, so that the material has both chiral activity and good electron transport ability, so as to solve the defects existing in the prior art.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The present invention provides a chiral electron transport material having a molecular structure shown in the following formula I or formula II:

[0010]

[0011]

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

[0013] In an optional embodiment, Ar1 and Ar2 are each independently selected from an aromatic ring having good electron transport ability, including a monocyclic aromatic hydrocarbon or a polycyclic condensed aromatic hydrocarbon substituent, and the monocyclic aromatic hydrocarbon includes any one of a pyridyl group, a pyrimidyl group, a benzonitrile group, a 3-phenylpyridyl group or a pyrazinyl group;

[0014] The polycyclic condensed-ring aromatic hydrocarbon substituents include any one of quinolyl, isoquinolyl, quinoxalinyl, benzo[b]oxazolyl, benzo[d]thiazolyl, benzo[b]thienyl, benzofuranyl, 1-phenyl-1H-benzimidazolyl, biphenyl, anthracenyl, o-phenanthroline, phenazine or dibenzothienyl.

[0015] In an optional embodiment, the Ar3 is selected from H, and the molecular structure of the chiral electron transport material is shown in the following formula III:

[0016]

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

[0018]

[0019]

[0020]

[0021]

[0022] The present invention also provides a method for preparing a chiral electron transport material, wherein the preparation method of formula I comprises the following steps:

[0023]

[0024] 3,6-Dibromo-4,5-difluoro-1,2-phenylenediamine reacts with a diketone derivative under acid catalysis to undergo dehydration condensation to generate a quinoxaline derivative intermediate, which is then subjected to nucleophilic substitution with a chiral binaphthol molecule to form an oxygen-containing eight-membered heterocyclic intermediate, which is then subjected to a Suzuki coupling reaction with boronic acid compounds of Ar1 and Ar2 in a stepwise manner under Pd catalyst conditions to obtain the final product of formula I.

[0025] The present invention also provides a method for preparing a chiral electron transport material, wherein the preparation method of formula II comprises the following steps:

[0026]

[0027] The benzodiazole derivative intermediate and the chiral binaphthol derivative are subjected to intramolecular nucleophilic substitution to form an oxygen-containing eight-membered heterocyclic intermediate, which is then reacted with the boronic acid compounds of Ar1 and Ar2 in a stepwise manner under the condition of a Pd catalyst through Suzuki coupling reaction to obtain the final product of formula II.

[0028] The invention also provides the use of the chiral electron transport material in preparing an electroluminescent device.

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

[0030] In an optional embodiment, the functional layer includes an electron transport layer, and the electron transport layer contains 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 to form an oxygen-containing eight-membered ring with a locked axial chiral configuration through a nucleophilic substitution reaction, and then modifies the periphery with an aza-containing condensed aromatic hydrocarbon having good electron transport ability, so that the material simultaneously has circular polarization chiral activity and good electron transport ability, and the aza-containing condensed aromatic hydrocarbon modified on the periphery can further form intermolecular hydrogen bonds in an aggregated state to achieve strong intermolecular interactions, further enhance the spin selection effect and electron transport ability, and achieve high luminescence efficiency.

[0033] (2) The structure of the present invention comprises a chiral binaphthol unit and a monocyclic or polycyclic aromatic hydrocarbon substituent having electron transport properties, and the energy levels and distances between the two parts are matched. The structure of the present invention has circular polarization chirality and good electron transport properties. 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 a suitable molecular weight. It can not only be used in the electron transport layer in CP-OLED, but also can achieve spin selection through functional layers such as chiral receptors used in the light-emitting layer and electron blocking layers. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

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

[0044] Fig.10 LUMO and HOMO orbital distribution diagram of the chiral electron transport material R / S-CPETL-17 prepared in Example 6;

[0045] Fig.11 is the absorption and emission spectrum curve of R / S-CPETL-01 in toluene solution;

[0046] Fig.12 is the absorption and emission spectrum curve of R / S-CPETL-04 in toluene solution;

[0047] Fig.13 is the absorption and emission spectrum curve of R / S-CPETL-16 in toluene solution;

[0048] Fig.14 is the absorption and emission spectrum curve of R / S-CPETL-17 in toluene solution;

[0049] Fig.15 Circularly polarized emission spectra of R / S-CPETL-01, R / S-CPETL-08 and R / S-CPETL-17 in dilute toluene solutions;

[0050] Fig.16 Circularly polarized emission spectra of R / S-CPETL-01, R / S-CPETL-08 and R / S-CPETL-17 in pure film state;

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

[0052] Fig.18 is a graph showing the change in external quantum efficiency of a CP-OLED device prepared based on the materials of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4 as a function of brightness;

[0053] Fig.19It is a brightness-current efficiency / power efficiency curve diagram of the CP-OLED devices prepared based on Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4;

[0054] Fig. 20 The electro-circularly polarized luminescence spectra of the CP-OLED devices prepared based on Comparative Examples 2 and 3;

[0055] Fig.21 The electro-circularly polarized luminescence spectra of CP-OLED devices prepared based on R / S-CPETL-01 and R / S-CPETL-17;

[0056] Fig. 22 It is a schematic structural diagram of a CP-OLED device provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the present application, the following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application from the perspectives of material synthesis, basic photophysical properties, and application in CP-OLED. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work 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) comprises the following steps:

[0060]

[0061] 3,6-dibromo-4,5-difluorobenzene-1,2-diamine (20mmol) was placed in a 150mL two-necked flask. After pumping through the flask three times, 15mL of glyoxal and 80mL of glacial acetic acid were respectively injected with a syringe under nitrogen protection. The flask was heated to 100°C for 48h. After cooling, the reaction mixture was poured into a 500mL separatory funnel and extracted with a mixed solvent of dichloromethane / water. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / ethyl acetate 4:1) to obtain a brown-yellow solid, namely intermediate 1, with a yield of 67%. HRMS (ESI) theoretical calculation was 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), cesium carbonate (15 mmol) were placed in a 150 mL two-necked flask, evacuated three times, and then injected with 80 mL of ultra-dry N,N-dimethylformamide by syringe under argon protection, heated to 120°C for overnight reaction, and after cooling, the reaction mixture was poured into a 500 mL separatory funnel, extracted with a mixed solvent of dichloromethane / water, and the organic phases were combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / ethyl acetate 4:1) to obtain a brown-yellow solid, namely intermediate R / S-2, with a yield of 78%, and HRMS (ESI) theoretical calculation C 28 H 13 Br4N2O2, [M+H] + 729.0395, measured value 729.0392.

[0063] The intermediate R / S-2 (5mmol), 4-pyridine boronic acid (5mmol), tetrakis(triphenylphosphine)palladium (0.5mmol), potassium carbonate (25mmol) were placed in a 150mL two-necked flask, and after pumping three times, 60mL of a deoxygenated toluene and ethanol water mixture (Tol:EtoH:H2O=30:7:7) was injected with a syringe under argon protection, and the mixture was heated to 90°C for overnight reaction. After cooling, the reaction mixture was poured into a 500mL separatory funnel, extracted with a dichloromethane / water mixed solvent, and the organic phases were combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a light yellow solid, that is, a chiral electron transport material, code-named R / S-CPETL-01, with a yield of 42%, and HRMS (ESI) theoretical calculation C 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 the chiral electron transport material (R / S-CPETL-04) comprises the following steps:

[0069]

[0070] The reaction process for preparing intermediate 1 and intermediate R / S-2 is the same as the steps described in Example 1, and will not be repeated here. Intermediate R / S-2 (5mmol), 7-isoquinolineboronic acid (10mmol), tetrakis(triphenylphosphine)palladium (0.6mmol), and potassium carbonate (25mmol) are placed in a 150mL two-necked flask. After pumping three times, 80mL of a deoxygenated toluene and ethanol water mixture (Tol:EtoH:H2O=20:5:5) is injected with a syringe under argon protection. The temperature is raised to 90°C and reacted overnight. After cooling, the reaction mixture is poured into a 500mL separatory funnel and extracted with a dichloromethane / water mixed solvent. The organic phases are combined and the organic solvent is removed by reduced pressure distillation to obtain a crude product. The crude product is separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a light yellow solid, i.e., a chiral electron transport material, code-named R / S-CPETL-04, with a yield of 39%. HRMS (ESI) theoretical calculation C 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) comprises the following steps:

[0075]

[0076] The reaction process for preparing intermediate 1 and intermediate R / S-2 is the same as the steps described in Example 1, and will not be repeated here. Intermediate R / S-2 (5mmol), phenylboronic acid (10mmol), tetrakis(triphenylphosphine)palladium (0.5mmol), and potassium carbonate (25mmol) are placed in a 150mL two-necked flask. After pumping three times, 60mL of a deoxygenated toluene and ethanol water mixture (Tol:EtoH:H2O=20:5:5) is injected with a syringe under argon protection, and the temperature is raised to 95°C for overnight reaction. After cooling, the reaction mixture is poured into a 500mL separatory funnel, extracted with a dichloromethane / water mixed solvent, and the organic phases are combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product is separated and purified by silica gel column chromatography (eluent, petroleum ether / ethyl acetate 4:1) to obtain a light yellow solid, i.e., a chiral electron transport material, code-named R / S-CPETL-08, with a yield of 46%, and HRMS (ESI) theoretical calculation C 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 the chiral electron transport material (R / S-CPETL-10) comprises the following steps:

[0081]

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

[0083] The intermediate R / S-3 (10mmol), 4-pyridine boronic acid (15mmol), ferrocene palladium dichloride (1mmol), and cuprous chloride (20mmol) were placed in a 150mL two-necked flask. After pumping through it three times, 80mL of ultra-dry N,N-dimethylformamide was injected with a syringe under argon protection. The temperature was raised to 120°C and reacted for 48 hours. After cooling, the reaction mixture was poured into a 500mL separatory funnel and extracted with a mixed solvent of dichloromethane / water. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a light yellow solid, that is, a chiral electron transport material, code-named R / S-CPETL-10, with a yield of 38%. HRMS (ESI) theoretical calculation C 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 the chiral electron transport material (R / S-CPETL-16) comprises the following steps:

[0087]

[0088] The reaction process for preparing the intermediate R / S-3 is the same as that in Example 4, and will not be described again here. The intermediate R / S-3 (10mmol), pyrimidine-5-boric acid (15mmol), ferrocene palladium dichloride (1mmol), and cuprous chloride (20mmol) are placed in a 150mL two-necked flask, and after pumping three times, 80mL of ultra-dry N,N-dimethylformamide is injected with a syringe under argon protection, and the temperature is raised to 120°C for reaction for 48h. After cooling, the reaction mixture is poured into a 500mL separatory funnel, extracted with a mixed solvent of dichloromethane / water, and the organic phases are combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product is separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a yellow solid, that is, a chiral electron transport material, code-named R / S-CPETL-16, with a yield of 43%, and HRMS (ESI) theoretical calculation C 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) comprises the following steps:

[0092]

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

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

[0095] The intermediate R / S-4 (10mmol), pyrimidine-5-boric acid (15mmol), ferrocene palladium dichloride (2mmol), and cuprous chloride (25mmol) were placed in a 150mL two-necked flask. After pumping through three times, 80mL of ultra-dry N,N-dimethylformamide was injected with a syringe under argon protection. The temperature was raised to 120°C and reacted for 48 hours. After cooling, the reaction mixture was poured into a 500mL separatory funnel and extracted with a mixed solvent of dichloromethane / water. The organic phases were combined and the organic solvent was removed by vacuum distillation to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a light yellow solid, that is, a chiral electron transport material, code-named R / S-CPETL-17, with a yield of 42%. HRMS (ESI) theoretical calculation C 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 the chiral electron transport material (R / S-CPETL-31) comprises the following steps:

[0099]

[0100] Take 3,6-dibromo-4,5-difluorobenzene-1,2-diamine (20mmol) and 1,2-naphthoquinone (20mmol) in a 150mL two-necked flask, pump it through three times, and then inject 80mL of glacial acetic acid with a syringe under nitrogen protection. Heat to 100℃ and react for 48h. After cooling, pour the reaction mixture into a 500mL separatory funnel, extract with a dichloromethane / water mixed solvent, combine the organic phases, and distill them under reduced pressure to remove the organic solvent to obtain a crude product. The crude product is separated and purified by silica gel column chromatography (eluent, petroleum ether / ethyl acetate 4:1) to obtain a brown-yellow solid, namely intermediate 5, with a yield of 62%. 1 HRMS (ESI) Theoretical Calculation C 16 H7Br2F2N2, [M+H] + 425.0503, the measured value is 425.0507.

[0101] Intermediate 5 (10 mmol), (R / S)-6,6'-dibromo-1,1'-bi-2-naphthol (10 mmol), cesium carbonate (15 mmol) were placed in a 150 mL two-necked flask, evacuated three times, and then injected with 80 mL of ultra-dry N,N-dimethylformamide by syringe under argon protection, heated to 120°C for overnight reaction, and after cooling, the reaction mixture was poured into a 500 mL separatory funnel, extracted with a mixed solvent of dichloromethane / water, and the organic phases were combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / ethyl acetate 4:1) to obtain a brown-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] The intermediate R / S-6 (5mmol), 4-pyridine boronic acid (5mmol), tetrakis(triphenylphosphine)palladium (0.5mmol), potassium carbonate (25mmol) were placed in a 150mL two-necked flask, evacuated three times, and then 60mL of a deoxygenated toluene and ethanol water mixture (Tol:EtoH:H2O=30:7:7) was injected with a syringe under argon protection, and the mixture was heated to 90°C for overnight reaction. After cooling, the reaction mixture was poured into a 500mL separatory funnel, extracted with a dichloromethane / water mixed solvent, and the organic phases were combined and distilled under reduced pressure to remove the organic solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography (eluent, petroleum ether / methanol 15:1) to obtain a white solid, that is, a chiral electron transport material, code-named 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] 1. Theoretical simulation

[0106] In order to illustrate the superiority of a chiral electron transport material provided by the present invention, the following provides theoretical simulation data of the key parameters of some of the molecules in the above embodiments based on Gaussian 16 software, and the results are shown in Table 1 below. The optimization of all ground state configurations is based on the B3LYP / def2-svp level, the gaseous single molecule state is defaulted, and the results obtained under dispersion correction are considered. The excited state energy level and configuration optimization are based on the optimized ground state configuration obtained by TD-DFT calculation. The basis set and functional selected for calculation are consistent with the ground state, and the visualization of all orbits is based on Gaussview 6.0 software.

[0107] Table 1 Calculation results of frontier orbital energy levels

[0108]

[0109] According to the results in Table 1 above, all the results are consistent with expectations, that is, the LUMO energy levels calculated for the selected representative embodiment molecules are all between -3..31 and -2.20 eV, which is consistent with the matching requirements of the electron transport layer or the electron-type host energy level of the current conventional electroluminescent device. In addition, the changes in the peripheral substituents and the central fused heterocyclic ring can accurately and effectively adjust the LUMO energy level, electrochemical band gap and other parameters to meet the specific device requirements. For example, compared with 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] In order to further demonstrate the effects of changes in substituents and central electron transport building blocks on their electrochemical and chiral activities, the advantageous configurations and frontier orbital distributions of representative molecules in the embodiments are selected and listed here. Representative structural molecules R / S-CPETL-01, R / S-CPETL-04 and R / S-CPETL-08 are selected for the general structural formula I of the present invention, and representative structural molecules R / S-CPETL-16 and R / S-CPETL-17 are selected for the general structural formula II.

[0111] like Figure 1-10 As shown, Figure 1-10 In the figure, A is the front view (left side), and B is the side view (right side). (a) is the HOMO (left side) and (b) is the LUMO (right side). Figure 1-10 It can be seen that no matter whether it is the representative molecule of general formula I or general formula II, or the change of peripheral substituents, the basic framework of the molecule is basically consistent. First, the eight-membered ring formed by nucleophilic substitution of chiral binaphthol can well lock its chiral configuration, and lock it with a suitable axial chiral dihedral angle (~45°), which is conducive to the construction of a stable and efficient chiral center. The change of peripheral substituents maintains almost the same configuration at the single molecule level, but the introduction of peripheral nitrogen-containing electron-deficient heterocyclic rings can regulate intermolecular interactions by forming intermolecular hydrogen bonds under aggregated conditions, providing a powerful means of regulation for the amplification of its chiral signal. Secondly, 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 central core fragments of quinoxaline derivatives or diazole derivatives parallel to the chiral axis. The change of peripheral substitution can slightly adjust the LUMO orbital distribution. Through a comprehensive multi-channel strategy, under the premise of ensuring good electron transmission ability, the aggregation behavior is optimized by fine-tuning the substituents to achieve the amplification of chiral activity.

[0112] 2. Basic Photophysical and Electrochemical Properties

[0113] In order to further illustrate the potential application value of the electron transport material provided by the present invention in CP-OLED, the basic photophysical properties 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 examples of the present invention were characterized in detail. The UV-visible absorption spectra, photoluminescence and circular polarization spectra were obtained in the corresponding toluene dilute solutions (1*10 -5 M), in addition, in order to explore the difference in chiral activity between the aggregated state and the single molecule state of these chiral molecules, the circularly polarized luminescence spectrum in the pure film state was also measured and attached to the solution condition. The results are shown in Table 2 below.

[0114] Table 2 Basic photophysical and electrochemical properties

[0115]

[0116]

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

[0118] As shown in Table 2, the material molecules of all examples show a high luminescence asymmetry factor (g PL ~10 -3 ) show that these materials have good spin selectivity differences for photoexcitation, especially the introduction of heavy atom Se (R / S-CPETL-17) can significantly promote spin-orbit coupling, which is beneficial to g PL Accordingly, the luminescence asymmetry factor (g PL ) have achieved a significant amplification (~10 -2 The results show that the introduction of nitrogen-containing heterocycles in the periphery is effective in enhancing the interaction between molecules and improving the spin selectivity of materials.

[0119] In order to demonstrate the detailed differences and variation patterns in absorption and emission of the material molecules prepared by the present invention, the present 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 core).

[0120] The results are as follows Figures 11 to 14 As shown. Figures 11 to 14 It can be seen that the change of peripheral substituents and the introduction of heavy atoms have a certain influence on the absorption and emission of molecules. Substituents with larger condensed rings and heavy atoms will cause the absorption and emission peaks to red-shift as a whole. The optical / electrochemical band gap of the molecule can be properly adjusted to match different devices. The absorption cutoff of all compounds falls before the visible light, which effectively avoids the self-absorption of the electron layer on the device's luminescence.

[0121] Fig.15 and 16 The circularly polarized emission spectra of the representative molecules of general formula I, R / S-CPETL-01 and R / S-CPETL-08, and the representative molecule of general formula II, R / S-CPETL-17, in dilute toluene solution and in pure film state are shown respectively. Fig.15 and 16 It can be seen that the circularly polarized emission spectra of the enantiomers of the representative molecules in the embodiment in toluene solution all show a typical mirror symmetry relationship, and the peak of the circularly polarized spectrum is basically consistent with the steady-state luminescence spectrum, which determines the reliability of the circularly polarized spectrum. The molecules covered by the present invention all show obvious chiral optical activity, and the introduction of atoms in the single-molecule state can significantly promote the enhancement of the circularly polarized luminescence signal. In addition, in the aggregated state, the enhancement of intermolecular interactions can achieve a great enhancement of the chiral signal, which fully illustrates the effectiveness of the molecular design concept of the present invention and its feasibility of achieving efficient spin selection in electroluminescent devices.

[0122] 3. Device Application

[0123] (I) Implementation and application examples

[0124] The following application examples illustrate the effect of using the chiral electron transport material prepared by the present invention as an electron transport layer in a CP-OLED device.

[0125] The following combination Fig. 22The device structure of the present invention is described in detail through the 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 obtained in 7 embodiments. The CP-OLED devices prepared by using the chiral electron transport materials of these 7 embodiments as electron transport layer materials are named as implementation device 1 / 11 (R-CPETL01 / S-CPETL01), implementation device 2 / 21 (R-CPETL04 / S-CPETL04), implementation device 3 / 31 (R-CPETL08 / S-CPETL08), implementation device 4 / 41 (R-CPETL10 / S-CPETL10), implementation device 5 / 51

[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 the present invention refers to Fig. 22 The device 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-hexaazatriphenylene, 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-di(9H-carbazole-9-yl)benzene, mCP) arranged in sequence. , a light-emitting layer 105 (BN-22% doped with 5-(4,6-diphenyl-1,3,5-triazine-2-yl)-7,7-dimethyl-5,7-dihydroindeno[2,1-b]carbazole, DMIC-TRZ), a hole blocking layer 106 (2,4,6-tris[3-(diphenylphosphino)phenyl]-1,3,5-triazine, PO-T2T), an electron transport layer 107 (chiral electron transport materials with different codes obtained in different embodiments of the present invention, ETL), a cathode interface layer 108 (8-hydroxyquinoline lithium, Liq), and a cathode 109 (Al).

[0128] 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] In order to demonstrate the advantages of the chiral electron transport material provided by the present invention in terms of electron transport efficiency and spin selection, the following provides corresponding comparative application examples;

[0131] Comparative Example 1: The device structure is the same as that of 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 that of the embodiment, but the electron transport layer is replaced with the classic Tm3PyPB and the light-emitting layer is replaced with the chiral light-emitting material R-BA34CzBN. This device structure is the current conventional CP-OLED construction method. The difference in spin selection of the light-emitting layer or the electron transport layer can be reflected by comparison. 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 that of the embodiment, but the electron transport layer uses the R / S-CPETL-01 racemate and the light-emitting layer is replaced by the chiral light-emitting material R-BA34CzBN. Excluding the spin selection interference, the electron transport efficiency of the electron transport material provided by the present invention can be compared with the classic Tm3PyPB in a horizontal manner with Comparative Example 2, 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 that of the implementation example, but the electron transport layer uses the R / S-CPETL-01 racemate to eliminate spin interference. The difference in electron transport efficiency is compared horizontally with that of Comparative Example 1, and 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] Among them, 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 of the device of the embodiment and the device of the comparative example

[0142] The general process for the preparation of the implemented and comparative devices is as follows: First, an indium tin oxide (ITO) coated glass substrate with a surface resistance of 15 ohms per square was subjected to continuous ultrasonic treatment with acetone / isopropanol, followed by nitrogen drying. Afterwards, the substrate was subjected to ultraviolet ozone (UVO) treatment for 20 minutes in a UV ozone surface treatment machine (PL16 series from Sen Lights Corporation). Next, the treated ITO substrate was sent to the deposition system. At 5×10 -5 Pa vacuum, by thermal evaporation with a temperature of 0.2 to The deposition rate of the above organic layers is sequentially deposited, and the deposition rate of the cathode aluminum (Al) layer is The device has a light-emitting area of ​​0.09 cm 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). The results are shown in Table 1. Figure 17-21 And as shown in Table 3 below.

[0143] Table 3 Comparison of core indicators of devices

[0144]

[0145] As shown in Table 3, by comparing all the implemented devices with the comparative device 1, the external quantum efficiency (η EQE ), power efficiency (η p ), current efficiency (η c ) are significantly better than the comparison device 1 in the three core indicators, which fully demonstrates that the chiral electron transport material provided by the present invention is significantly better than 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 the CP-OLEDs constructed using conventional chiral luminescent materials generally have poor spin selectivity, and the asymmetry factor (g EL ) is often very low, at 10 -4 ~10 -3 The CP-OLED constructed by the present invention using a chiral electron transport layer to form a spin-polarized current can significantly improve the g EL Compared with the comparison device 2 and the comparison device 3, the implementation device can generally reach 10 -2 level.

[0147] Comparing the comparative device 2 and the comparative device 3, the difference between the two is that the electron transport layer is different, but the external quantum efficiency (η EQE ), power efficiency (η p ), current efficiency (η c ) are significantly better than comparison device 2 and comparison device 3 in the three core indicators, which once again confirms that the electron transport material provided by the present invention can provide higher device efficiency under the same conditions.

[0148] By comparing implementation device 1, implementation device 11 or implementation device 2, implementation device 21 with comparison device 4, it can be seen that the device efficiencies of using a single chiral electron transport material and a racemic form are almost the same, indicating that spin selection has little effect on device efficiency, but there is a big difference in the output light. Only a single chiral electron transport layer can achieve spin selection and circularly polarized luminescence, which fully confirms the existence and effectiveness of spin selection.

[0149] In addition, the device efficiency and g EL There are also obvious differences in the aspects of g. 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 the intermolecular interaction, and achieve g EL Therefore, it is significantly better than R / S-CPETL-08, which only modifies the benzene ring. However, at the molecular level, the introduction of heavy atom Se can significantly promote spin-orbit coupling within the molecule, which is conducive to further regulating magnetic transition / electric transition, thereby achieving g EL Therefore, the g of device 6 / 61 (R / S-CPETL-17) is implemented EL The value is significantly higher than that of the implementation device 4 / 41 and the implementation device 5 / 51 (R / S-CPETL-10 and R / S-CPETL-16). In general, the CP-OLED constructed by using the selected embodiment molecules as the electron transport layer can be significantly improved in both device efficiency and chiral activity compared with the comparative device, which fully demonstrates the superiority of the present invention.

[0150] It should be noted that, in view of 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 the electron-type host or other electroluminescent devices, such as quantum dot LEDs and perovskite LEDs. The electron transport layer can also produce a spin-selective effect to achieve circularly polarized luminescence. Although no specific embodiments are given here, according to common sense and the rules provided by the present invention, this extrapolated application also falls 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 person skilled in the art who makes various changes and modifications to the above embodiments without departing from the spirit and scope of the present invention still fall within the scope of protection of the present invention.

Claims

1. A chiral electron transport material, characterized in that: It has a molecular structure shown in the following formula I or II: Wherein, the groups Ar1 and Ar2 are each independently selected from aromatic substituents, the group Ar3 is any one of H, benzene ring, cyclohexane, naphthalene ring, phenanthrene ring, dipyridineethylene, 2-naphthonitrile, o-phenanthroline or 1-indanone; the group X is any one of O, S, Se or CR2NR.

2. The chiral electron transport material according to claim 1, characterized in that: Ar1 and Ar2 are each independently selected from an aromatic ring having good electron transport capability, including a monocyclic aromatic hydrocarbon or a polycyclic condensed aromatic hydrocarbon substituent, wherein the monocyclic aromatic hydrocarbon includes any one of pyridyl, pyrimidyl, benzonitrile, 3-phenylpyridyl or pyrazinyl; The polycyclic condensed-ring aromatic hydrocarbon substituents include any one of quinolyl, isoquinolyl, quinoxalinyl, benzo[b]oxazolyl, benzo[d]thiazolyl, benzo[b]thienyl, benzofuranyl, 1-phenyl-1H-benzimidazolyl, biphenyl, anthracenyl, o-phenanthroline, phenazine or dibenzothienyl.

3. 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 the following formula III:

4. The chiral electron transport material according to claim 1, characterized in that: The chiral electron transport material is any one of the following structural formulas:

5. The method for preparing a chiral electron transport material according to claim 1, characterized in that: The preparation method of formula I comprises the following steps: 3,6-Dibromo-4,5-difluoro-1,2-phenylenediamine reacts with a diketone derivative under acid catalysis to undergo dehydration condensation to generate a quinoxaline derivative intermediate, which is then subjected to nucleophilic substitution with a chiral binaphthol molecule to form an oxygen-containing eight-membered heterocyclic intermediate, which is then subjected to a Suzuki coupling reaction with boronic acid compounds of Ar1 and Ar2 in a stepwise manner under Pd catalyst conditions to obtain the final product of formula I.

6. The method for preparing a chiral electron transport material according to claim 1, characterized in that: The preparation method of formula II comprises the following steps: The benzodiazole derivative intermediate and the chiral binaphthol derivative are subjected to intramolecular nucleophilic substitution to form an oxygen-containing eight-membered heterocyclic intermediate, which is then reacted with the boronic acid compounds of Ar1 and Ar2 in a stepwise manner under the condition of a Pd catalyst through Suzuki coupling reaction to obtain the final product of formula II.

7. Use of the chiral electron transport material according to any one of claims 1 to 4 in the preparation of an electroluminescent device.

8. The use according to claim 7, characterized in that: At least one functional layer of the electroluminescent device comprises the chiral electron transport material.

9. The use according to claim 8, characterized in that: The functional layer includes an electron transport layer, and the electron transport layer contains the chiral electron transport material.

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