Chiral d-f transition rare earth complex and application thereof as electroluminescent material

Abstract

An electroluminescent material comprising a complex (R / S)-RN8-EuI2 having the structure: a complex EuX2-N4 having the structure: a complex EuX2-cycloN4 having the structure: wherein X is a negative one valence ion such as F, Cl, Br, I, OCN, SCN, CN, CF3SO3, BF4 or PF6, each R is independently selected from H, C1-C 18 alkyl, halogen substituted alkyl, halogen atom, aryl, halogen substituted aryl, alkyl substituted aryl, O, N, S heteroaryl, O, N, S containing ligand alkyl, M is Eu(II), Ce(III), Yb(II), Sm(II) and the like metal ions having d-f transition luminescence, and there is at least one chiral site at the "*".

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electroluminescent materials. Specifically relates to a chiral d-f transition rare earth complex and its application as an electroluminescent material. BACKGROUND

[0002] As a natural phenomenon, polarized light exists widely in nature. Among them, the circularly polarized light manipulation technology has wide application prospects in the fields of 3D display, optical sensing, spin electronic devices, optical communication, information storage, etc.

[0003] At present, the circularly polarized light emitting materials are mostly obtained by the synthesis of chiral raw materials. The intensity of the emitted light is measured by the g factor, the larger the absolute value, the stronger the intensity of the polarized light, and the theoretical limit is 2. By increasing the number of chiral groups, designing the spatial stacking mode, shortening the distance between the chiral groups and the light emitting center, and changing the form of the light emitting material, etc., the g factor of the chiral light emitting material can be improved to a certain extent.

[0004] At present, the commonly used light emitting materials in the research of organic light emitting diodes (OLED) include fluorescent materials, phosphorescent materials, thermally activated delayed fluorescence materials (TADF), rare earth f-f transition light emitting materials, etc. By introducing chirality to the light emitting molecules, circularly polarized light of different intensities can be obtained. The commonly used circularly polarized light OLED (CP-OLED) light emitting materials in the literature can be divided into chiral thermally activated delayed fluorescence (TADF) materials with maximum external quantum efficiency EQE max = 32.6%, corresponding to g = 2.0 × 10 -3 ; g max = 6.0 × 10 -2 , corresponding to external quantum efficiency EQE = 3.5%, chiral conjugated polymers (g max = -0.8, corresponding to EQE not reported), chiral phosphorescent transition metal complexes (EQE max = 23.2%, corresponding to g = -3.0 × 10 -4 ; g max = -0.38, corresponding to EQE not reported), chiral f-f transition light emitting lanthanide (III) rare earth complexes (EQE max = 0.05%, corresponding to g = -0.88; EQE = 5.0 × 10 -3 , corresponding to g max = -1.0). It can be seen that the current CP-OLED light emitting materials generally have the problem of high efficiency and high optical activity. SUMMARY

[0005] Compared with these materials, d-f transition light-emitting materials have the advantages of high exciton utilization, short excited state lifetime, and easy adjustment of luminescence, and are expected to prepare high-efficiency and stable OLEDs. So far, the EQE of d-f transition Eu(II) complex OLEDs can reach 17.7%, and the maximum brightness can reach 25470 cd m max -2 The EQE of Ce(III) complex can reach 20.8%, and the maximum brightness can reach 31160 cd m max -2 .

[0006] The inventors of the present application hope to take advantage of the high efficiency of d-f transition light-emitting materials, and explore the possibility of combining chiral light-emitting materials with d-f transition light-emitting materials, in order to break the difficult problem that chiral light-emitting materials have high efficiency and high g factor. At present, there is no research on d-f transition rare earth complex CP-OLED. With the experience of high g factor chiral light-emitting materials, the inventors selected N8-EuI2 with excellent electroluminescent properties as a template, and introduced as many chiral atoms as possible into the N8 skeleton as close to the luminescent center Eu(II) as possible, in order to obtain high g factor electroluminescent materials on the basis of high efficiency.

[0007] Although the above advantages exist, there is no related report on chiral Eu(II) complex at present, so the structure-activity relationship of the luminescent asymmetry factor is not clear. Therefore, more efforts must be made to rationally design Eu(II) complexes and deeply understand the circularly polarized luminescence mechanism to improve the chiral performance of the materials and corresponding devices. The inventors of the present application believe that the multi-dentate N ligand can effectively synthesize Eu(II) complexes with point chirality, axial chirality and plane chirality while maintaining the high efficiency of Eu(II) complexes. Therefore, in the specific embodiments of the present application, the inventors of the present application selected ligands (R / S)-MeN8 and (R / S)- i -PrN8 to design four Eu(II)-containing azamacrocyclic complexes named (R / S)-MeN8-EuI2 and (R / S)- i -PrN8-EuI2. A series of crystal analysis, spectroscopy, chirality and theoretical research were carried out to reveal the photophysical and circularly polarized luminescence properties of these Eu(II) complexes. Then, due to the high efficiency, high luminescent asymmetry factor and good thermal / air stability of this kind of complexes, they were exemplarily selected as the light-emitting layer materials of CP-OLED. The optimized device has excellent performance, with a maximum EQE of 15.6%, a maximum brightness of 23000 cd·m -2 , and a maximum electroluminescent asymmetry factor of 3.9 × 10 3 ​​CP-OLED devices, which can be used as light emitting materials with the most advanced phosphorescent metal complexes or TADF molecules, show comparable performance.

[0008] Embodiments of the present application provide an electroluminescent material comprising a complex (R / S)-RN8-EuI2, which has the structure shown below:

[0009]

[0010] wherein X is a negative ion such as F, Cl, Br, I, OCN, SCN, CN, CF3SO3, BF4 or PF6, each R is independently selected from H, C1-C 18 halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S heteroaryl, alkyl containing O, N, S coordination site, M is Eu(II), Ce(III), Yb(II), Sm(II) and the like metal ions having d-f transition light emission, and at least one chiral site at “*”; preferably, all “*” are chiral sites;

[0011] Alternatively, the electroluminescent material comprises a complex EuX2-N4, which has the structure shown below:

[0012]

[0013] wherein X is a negative ion such as F, Cl, Br, I, OCN, SCN, CN, CF3SO3, BF4 or PF6, each R is independently selected from H, C1-C 18 halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S heteroaryl, alkyl containing O, N, S coordination site, M is Eu(II), Ce(III), Yb(II), Sm(II) and the like metal ions having d-f transition light emission, and at least one chiral site at “*”; preferably, all “*” are chiral sites;

[0014] Alternatively, the electroluminescent material comprises a complex EuX2-cycloN4, which has the structure shown below:

[0015] wherein X is a negative ion such as F, Cl, Br, I, OCN, SCN, CN, CF3SO3, BF4 or PF6, each R is independently selected from H, C1-C 18Alkyl, halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S heteroaryl, alkyl containing O, N, S coordination sites, M is a metal ion with df transition luminescence such as Eu(II), Ce(III), Yb(II), Sm(II), etc., and there is at least one chiral site at the "*" position; preferably, all "*" positions are chiral sites.

[0016] According to one embodiment of the present invention, for example, the luminescent material comprises (a) (R / S)-MeN8-EuI2, (b) (R / S)- i The structural formulas of the above complexes are as follows: (c) (R / S)-MeN8-Ce(OTf)3, (d) (R / S)-N4Me4-EuI2, (e) (R / S)-N4Me6-EuI2, (f) (R / S)-N4Me2Et4-EuI2, (g) (R / S)-cycloMeN4-EuI2, (h) (R / S)-hexcycloN4-EuI2.

[0017]

[0018]

[0019] Embodiments of the present invention also provide an electroluminescent device, the electroluminescent device comprising a cathode, an anode, and a light-emitting layer located between the cathode and the anode, wherein the light-emitting layer comprises the electroluminescent material as described above.

[0020] According to one embodiment of the present invention, for example, the light-emitting layer is a mixture of a guest material and a host material, wherein the guest material includes electroluminescent materials as described above, and the host material includes m-MTDATA, mCP, mCBP, CzSi, DCPPO, PCzAc, CBP, TCTA, TAPC, DPEPO, mCPCN, BCPO, etc., with a doping concentration of 1wt%-99wt%, preferably 7wt%-10wt%, and most preferably 10wt%, wherein the doping concentration is the percentage of the mass of the guest material to the total mass of the guest material and the host material.

[0021] According to one embodiment of the present invention, for example, the electroluminescent device further includes an electron transport layer located between the cathode and the light-emitting layer, the electron transport layer including TmPyPB, DPEPO, TSPO1, Bphen and / or TPBi.

[0022] According to an embodiment of the present application, for example, the electroluminescent device further comprises a hole transport layer between the anode and the light-emitting layer; preferably, the hole transport layer comprises PCzAc, mCP, m-MTDATA, NPB, PEDOT:PSS, TCTA and / or TAPC.

[0023] According to an embodiment of the present application, for example, the electroluminescent device further comprises an electron transport layer between the cathode and the light-emitting layer and a hole transport layer between the anode and the light-emitting layer.

[0024] Preferably, the hole transport layer comprises TAPC and the electron transport layer comprises Bphen.

[0025] According to an embodiment of the present application, for example, the thickness of the light-emitting layer is 10-40 nm, preferably 15-30 nm, preferably 20-25 nm, most preferably 25 nm.

[0026] According to an embodiment of the present application, for example, the electroluminescent device further comprises a hole blocking layer between the light-emitting layer and the electron transport layer; preferably, the material of the hole blocking layer is TSPOl.

[0027] Preferably, the electroluminescent device further comprises a second hole transport layer between the anode and the hole transport layer; preferably, the material of the second hole transport layer is NPB.

[0028] According to an embodiment of the present application, for example, the structure of the electroluminescent device is: ITO / MoO3(2 nm) / cyclohexylidenebis[N,N'-bis(p-tolyl)aniline] (TAPC, 50 nm) / (R / S)-MeN8-EuI2: 4,4',4"-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA, 10 wt%, 20 nm) / 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene (TmPyPB, 50 nm) / LiF (1 nm) / Al (100 nm). BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the chemical structure of the complex, wherein (a) (R / S)-MeN8-EuI2, (b) (R / S)- i- PrN8-EuI2, (c) (R / S)-MeN8-Ce(OTf)3, (d) (R / S)-N4Me4-EuI2, (e) (R / S)-N4Me6-EuI2, (f) (R / S)-N4Me2Et4-EuI2, (g) (R / S)-MeN4-EuI2, (h) (R / S)-cyclohexN4-EuI2

[0030] Figure 2 is a schematic diagram of the crystal structure of the complex in the embodiments of the present application, wherein (a) (R / S)-MeN8-EuI2, (b) (R / S)- i - PrN8-EuI2, (c) (S)-MeN8-Ce(OTf)3, (d) (R)-N4Me4-EuI2, (e) (S)-N4Me6-EuI2, (f) (S)-N4Me2Et4-EuI2. DETAILED DESCRIPTION

[0031] The chiral d-f transition rare earth complex of the present application and its application as electroluminescent material will be further described below in conjunction with specific examples. It should be understood that the following examples are only illustratively and explain the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above content of the present application is covered in the scope of the present application. The corresponding full name of the compound is as follows:

[0032] m-MTDATA 4,4',4''-tris[phenyl(m-methylphenyl)amino]triphenylamine

[0033] mCP N,N'-dicyclohexyl-3,5-benzene

[0034] mCBP 3,3-di(9H-carbazol-9-yl)biphenyl

[0035] CzSi 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole

[0036] DCPPO Bis(9H-carbazol-9-yl)(phenyl)phosphine oxide

[0037] PCzAc 9,9-dimethyl-10-(9-phenyl-9H-carbazol-3-yl)-9,10-dihydroacridine

[0038] CBP 4,4'-Bis(9-carbazolyl)-1,10-biphenyl

[0039] TCTA Tris(4-(9-carbazolyl)phenyl)amine

[0040] TAPC 4,4'-Cyclohexylbis[N,N-bis(4-methylphenyl)benzenamine]

[0041] DPEPO Bis[2-((oxo)diphenylphosphoranyl)] ether

[0042] mCPCN 9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazole-3-carbonitrile

[0043] BCPO Bis-4-(N-carbazolyl)phenyl)phenylphosphine oxide

[0044] TmPyPB 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene

[0045] Bphen 4,7-diphenyl-1,10-phenanthroline

[0046] TPBi 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene

[0047] TSPO1 Diphenyl[4-(triphenylsilyl)phenyl]phosphine oxide

[0048] NPB N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine

[0049] PEDOT:PSS Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)

[0050] Preparation methods and test methods.

[0051] All chemicals used in the synthesis process were commercially available and used as received unless otherwise stated. 1 H-NMR was measured on a Bruker-400 MHz NMR. Tetramethylsilane (TMS) was used as internal reference for chemical shift correction, where δ TMS Elemental analysis was performed on a VARIO EL analyzer. Eu 2+ All syntheses of complexes were carried out in a glovebox. Solid Eu 2+ All spectroscopic tests of complexes were carried out after paraffin encapsulation between two quartz plates, solutions were tested in N2 atmosphere with a stoppered cuvette. Commercial paraffin was purified by oxidation using KMnO4 and column chromatography to remove the fluorescent whitening agent.

[0052] Synthesis of N-p-toluenesulfonyl-2-methylazacyclopropane (Me-Azi): 700 mL of dichloromethane (DCM) was added to a 1 L three-necked flask, followed by the sequential addition of 2-aminopropanol (0.133 mol, 10.00 g), p-toluenesulfonyl chloride (TsCl) (0.277 mol, 52.80 g), and the catalyst 4-dimethylaminopyridine (DMAP) (0.013 mol, 1.58 g) and stirring. Triethylamine (TEA) (0.40 mol, 40.49 g) was slowly added dropwise to the reaction mixture under a nitrogen atmosphere and at 0 °C, completing the addition in approximately 1 h. After the addition was complete, the mixture was allowed to return to room temperature naturally, and the reaction proceeded overnight. The next day, the reaction mixture was washed with 260 mL of saturated NH4Cl solution, and the organic phase was separated. The aqueous phase was then washed three times with 100 mL of DCM. The organic phases were combined, dried over anhydrous Na2SO4, and the solvent was evaporated to obtain an orange-yellow oily crude product. After separation by column chromatography (eluent: a 1:8 mixture of ethyl acetate and petroleum ether), colorless needle-like crystals that are easily supercooled were obtained, with a yield of 56.9%. 1 H NMR (400 MHz, CDCl3): δ 1.15 (d, 3H, J =5.6 Hz); 1.93 (d, 1H, J =4.6 Hz); 2.34 (s, 3H); 2.50 (d, 1H, J =7.0 Hz); 2.72 (m,1H); 7.24 (d, 2H, J =8.0 Hz); 7.73 (d, 2H, J =8.0 Hz).

[0053] N-p-Toluenesulfonyl-2-isopropylazacyclopropane ( i Synthesis of 2-aminopropanol (-Pr-Azi): 13.72 g valine (0.133 mol) was used instead of 2-aminopropanol as the amino alcohol raw material. The reaction conditions and post-treatment were the same as those for Me-Azi. The yellow viscous solid obtained by rotary evaporation was recrystallized from petroleum ether (PE). The supernatant was separated by decantation, and upon cooling, fluffy colorless needle-like crystals precipitated. The yield was 50.3%. 1H NMR (400 MHz, CDCl3): δ 0.80 (d, J = 6.8 Hz, 3H), 0.90 (d, J =6.8 Hz, 3H), 1.41 (m, 1H), 2.10 (d, J = 4.4Hz, 1H), 2.45 (s, 3H), 2.51 (m,1H), 2.62 (d, J = 6.8 Hz, 1H), 7.33 (d, J = 8.0 Hz, 2H), 7.83 (d, J = 8.0 Hz,2H).

[0054] Synthesis of tris(N-p-toluenesulfonyl-2-aminopropyl)amine (Me-Ts-NTEA): Me-Azi (33.51 mmol, 7.094 g) was added to a 100 mL pressure-resistant reaction flask at room temperature, followed by the sequential addition of 1.55 mL of 7 M ammonia-methanol solution and 3.87 mL of ultra-dry methanol. The flask was sealed and heated to 45 °C in an oil bath for 4 days. After the reaction was completed, 40 mL of methanol (MeOH) was added and refluxed for 2 h. The solvent was evaporated to dryness, and the mixture was separated by column chromatography (eluent: a 1:4 mixture of ethyl acetate, petroleum ether, and anhydrous methanol) to obtain a white solid in 64.3% yield. 1 H NMR (400 MHz, CDCl3): δ 0.96 (d, J=6.4 Hz, 9H), 2.13 (dd, J=13.0 and 3.8 Hz, 3H), 2.38 (s, 9H), 2.51 (dd, J=12.9 and 11.1 Hz, 3H), 3.64-3.67 (m, 3H), 5.74 (br d, J=5.6 Hz, 3H), 7.23 (d, J=7.9 Hz, 6H), 7.83 (d, J=8.2 Hz, 6H).

[0055] Tris(N-p-toluenesulfonyl-2-amino-3-methylbutyl)amine i Synthesis of -Pr-Ts-NTEA: The synthesis method is similar to that of Me-Ts-NTEA. After reacting in an oil bath at 50°C for 4 days, the white powdery solid precipitated by cooling was filtered, and the reactants were washed away with methanol to obtain the product, with a yield of 69.5%. 1 H NMR (400 MHz, CDCl3): δ 0.78 (d, J = 6.9 Hz, 9H), 0.80(d, J = 6.9 Hz, 10H),. 1.70 (pd, J= 6.9, 4.2 Hz, 3H), 2.13 (td, J = 12.0, 11.3,4.6 Hz, 3H), 2.38 (s, 9H), 2.96 (t, J = 12.1 Hz, 3H), 3.82 (ddt, J = 11.5, 8.6,4.5 Hz, 3H), 6.20 (d, J = 7.0 Hz, 3H), 7.23 (d, J = 8.1 Hz, 6H), 7.80 – 7.87 (m,7H).

[0056] Synthesis of tris(2-aminopropyl)amine (Me-NTEA): Me-Ts-NTEA (7.682 mmol, 5.018 g) and phenol (74.13 mmol, 6.976 g) were added to a 250 mL single-necked flask, followed by the addition of 100 mL of 48% hydrobromic acid. The mixture was refluxed under a nitrogen atmosphere for 2 days, during which the solution changed from colorless to orange-red and then to dark red. After the reaction was complete, the reaction solution was allowed to cool naturally to room temperature, where the system was observed to separate into a black oil phase and a dark orange-red aqueous phase. The aqueous phase was separated, and the pH was adjusted to approximately 1 with 4 M sodium hydroxide (NaOH) solution, followed by washing with ethyl acetate (EA) until pale yellow to colorless. Then, NaOH solution was added again to adjust the pH of the aqueous phase to greater than 13, and the product was extracted with DCM. The organic phase was dried with anhydrous Na2SO4 and filtered. The filtrate was evaporated to dryness to obtain a light yellow oily liquid. The fraction distilled under reduced pressure at 104-107℃ was collected to obtain a colorless and transparent oily liquid. When left to stand, it solidified to form transparent feather-like crystals, with a yield of 50.5%. 1 H NMR (400 MHz, CDCl3): δ 0.95 –1.05 (m, 3H), 1.71 (s, 6H), 2.13 – 2.29 (m, 6H), 3.10 (dqd, J = 9.7, 6.3, 3.3Hz, 3H).

[0057] Tris(2-amino-3-methylbutyl)amine i Synthesis of -Pr-NTEA: Add to a 250 mL single-necked flask iPr-Ts-NTEA (6.167 mmol, 4.533 g) with phenol (59.51 mmol, 5.601 g), then 100 mL 40% hydrobromic acid, reflux under nitrogen atmosphere for 2 days. The post-treatment after the reaction is finished is similar to Me-NTEA, but the light yellow oily liquid obtained by DCM phase rotary evaporation is pure product without distillation, yield 87.6%. 1 H NMR (400 MHz, CDCl3): δ 0.90 (d, J = 6.7 Hz, 9 H), 0.91 (d, J = 6.7 Hz, 9 H), 1.50 (octet, J = 6.6 Hz, 3 H), 1.89 (br.s, 6 H), 2.26–2.29 (m, 6 H), 2.67–2.72 (m, 3 H).

[0058] Synthesis of 3,8,12,17,20,25-hexamethyl-1,4,7,10,13,16,21,24- octaazabicyclo[8.8.8]hexacosane (MeN8): 1 g Me-NTEA (5.310 mmol), 38 mL isopropanol and 1.52 mL TEA were added into a 100 mL three-necked flask under -78 ℃ dry ice-acetone bath, mechanical stirring was started to mix them well. 1.14 g 40% glyoxal aqueous solution diluted with 7.6 mL isopropanol was added into a dropping funnel, then the glyoxal solution was added into the flask slowly under nitrogen atmosphere, the dropping rate was controlled at 2 s / drop. After the dropping was finished, the reaction system was gradually returned to room temperature, transferred into a 250 mL flask, 1.52 g sodium borohydride (40.10 mmol, excess) was added in batches, then 20 mL methanol was added, stirred overnight under nitrogen atmosphere. After overnight, the solvent of the reaction system was rotary evaporated, the obtained solid was soaked with DCM for 20 min under nitrogen atmosphere, then filtered, the filtrate was rotary evaporated to get light yellow solid. The crude product was dried in a vacuum drying oven at 100 ℃ overnight, then put into a sublimation apparatus, sublimed at 185 ℃, 0.1 Pa for 24 h, colorless flaky transparent crystal was obtained, yield 18.3%. 1 H NMR (400 MHz,CDCl3): δ 1.02 (q, J = 3.9, 3.5 Hz, 18H), 1.21 (d, J = 6.1 Hz, 6H), 1.84 (d, J=12.8 Hz, 6H), 2.37– 2.71 (m, 6H), 2.69 – 3.05 (m, 12H).

[0059] 3,8,12,17,20,25-Hexaisopropyl-1,4,7,10,13,16,21,24-Octazabicyclo[8.8.8]hexacosane ( i Synthesis of -PrN8): The synthesis method is similar to that of N8Me6, for 1 g i -Pr-NTEA (3.670 mmol) was transferred to a single-necked flask, and 2 g of sodium borohydride (52.76 mmol) was added in batches, followed by 13 mL of methanol and stirring for 2 days. The post-treatment was the same as for N8Me6; the crude product, after vacuum drying, was placed in a sublimation apparatus and sublimated at 160 °C and 0.1 Pa for 24 h to obtain colorless granular transparent crystals, with a yield of 8.7%. 1 H NMR (400 MHz, CDCl3): δ 0.86 (d, J = 6.8 Hz, 18H), 0.91 (d, J = 6.9Hz, 18H), 1.71 (pd, J = 7.0, 4.4 Hz, 6H), 2.18 (dd, J = 13.1, 10.1 Hz, 6H), 2.26(dd, J = 13.0, 7.3 Hz, 12H), 2.52 – 2.69 (m, 6H), 2.92 (q, J = 8.5, 6.4 Hz, 6H).

[0060] Synthesis of (R / S)-MeN8-EuI2: At room temperature, under a nitrogen atmosphere, a tetrahydrofuran solution containing 59 mg (R / S)-MeN8 (0.128 mmol) was added dropwise to a tetrahydrofuran solution containing 52 mg EuI2 (0.128 mmol). The solution changed from nearly colorless to yellow, and an orange-red powder precipitated. The product was obtained by filtration and drying. Elemental analysis calculated C. 24 H 54 EuI2N8(860.52): C, 33.50; H, 6.33; N, 13.02; Elemental analysis results: C, 33.55; H, 6.39; N, 12.77.

[0061] (R / S)- iSynthesis of -PrN8-EuI2: At room temperature, under a nitrogen atmosphere, 80 mg (R / S) of -PrN8-EuI2 was added dropwise to a solution containing 52 mg EuI2 (0.128 mmol) tetrahydrofuran. i A solution of -PrN8 (0.128 mmol) in tetrahydrofuran initially changed from nearly colorless to pale green, exhibiting a bright green glow under UV excitation. With stirring, the solution deepened in color, and a pale green powder precipitated. The product was obtained by filtration and drying. The complex can be purified by vacuum sublimation at 280 °C. Elemental analysis calculated C... 36 H 78 EuI2N8(1028.85): C, 42.03; H, 7.64; N, 10.89; Elemental analysis results: C, 41.57; H, 7.41; N, 10.63.

[0062] Synthesis of (S)-MeN8-Ce(OTf)3: At room temperature, under a nitrogen atmosphere, 45 mg (R / S)-Ce(OTf)3 was added dropwise to a methanol solution containing 59 mg Ce(OTf)3 (0.1 mmol). i A 0.1 mmol PrN8 methanol solution remained colorless until it emitted a bright blue light upon UV excitation. With stirring, the solution turned slightly brown. After drying, recrystallization from DCM / n-hexane yielded the pure product. Elemental analysis calculated C. 27 H 54 CeF9N8O9S3: C, 31.12; H, 5.22; N, 10.75; Elemental analysis results: C, 31.48; H, 5.67; N, 10.43.

[0063] ( R / S )-N,N'-1,2-cyclohexanebis(2-chloroacetamide) (( R / S Synthesis of ()-N2O2Cl2): ( R / S Cyclohexanediamine (3.42 g, 30.0 mmol) and potassium carbonate (10.3 g, 75.0 mmol) were added to a solvent consisting of 23 mL of dichloromethane (DCM) and 18 mL of water. Chloroacetyl chloride (6.72 g, 60.0 mmol) was slowly added dropwise under an ice-water bath. After the addition was complete, the mixture was allowed to return to room temperature and stirred for 12 h, at which point a white solid precipitated. The DCM was removed by rotary evaporation, and the mixture was filtered. The resulting white solid was then dried under vacuum at 60 °C for 12 h to obtain the product. The yield was 9.42 g, with a yield of 93%. 1 H NMR (CDCl3): δ1.36 (m, 4H, -NH-(CH-CH2-(C H 2)2-CH2-CH)-NH-), 1.82–2.10 (m, 4H, -NH-(CH-C H 2-(CH2)2-C H 2-CH)-NH-),3.77 (m, 2H, -NH-(C H -CH2-(CH2)2-CH2-C H )-NH-), 4.01 (br s, 4H, -C H 2-Cl), 6.82(br s, 2H, N H -CO).

[0064] ( R / S )-N,N'-1,2-cyclohexanebis(2-(dimethylamino)acetamide) (( R / S Synthesis of ()-N4O2Me4): ( R / S 4.33 g (16.5 mmol) of N₂O₂Cl₂ was added to an ethanolic solution of dimethylamine (33 wt%, 160 mL, 0.860 mol), and the mixture was stirred at room temperature for 2 days. After the reaction was complete, the solvent was removed under vacuum, the solid was dissolved in 100 mL of DCM, washed three times with water (3 × 100 mL), dried with potassium carbonate, filtered, and the solvent was removed under vacuum to obtain the product. Yield: 1.50 g, yield: 32%. 1 H NMR (CDCl3): δ 1.22-1.38 (m, 4H, -NH-(CH-CH2-(C H 2)2-CH2-CH)-NH-), 1.72–2.05 (m, 4H, NH-(CH-C H 2-(CH2)2-C H 2-CH)-NH-), 2.24 (s, 12H, -N-(C H 3)2), 2.84-2.94 (m, 4H, NH-CO-C H 2-), 3.75 (m, 2H, NH-(C H -CH2-(CH2)2-CH2-C H )-NH-).

[0065] ( R / S )-N 1 N 1Dimethyl-1,2-cyclohexanebis(N 2 Dimethyl-1,2-cyclohexanebis(N 2 Dimethyl-1,2-cyclohexanebis(N R / S Dimethyl-1,2-cyclohexanebis(N R / S Dimethyl-1,2-cyclohexanebis(N 1 H NMR (400 MHz, CDCl3): δ 1.03 (m, 2H, NH-(CH-C H 2-(CH2)2-CH2-CH)-NH-), 1.23(m, 2H, -NH-(CH-CH2-(C H 2)2-CH2-CH)-NH-), 1.73 (m, 2H, -NH-(CH-CH2-(C H 2)2-CH2-CH)-NH-), 2.05 (m, 2H, NH-(CH-C H 2-(CH2)2-CH2-CH)-NH-), 2.16 (m, 2H, -NH-(C H -CH2-(CH2)2-CH2-C H )-NH-), 2.23 (s, 12H, -N-(C H 3)2), 2.25 (br s, 2H, -N H ), 2.40(m, 4H, -C H 2-N-(CH3)2), 2.53 (dt, -C H 2-CH2-N-(CH3)2), 2.82 (dt, C H 2-CH2-N-(CH3)2)。

[0066] Dimethyl-1,2-cyclohexanebis(N R / S Dimethyl-1,2-cyclohexanebis(N R / SN₄Me₄ (66.0 mg, 0.250 mmol) and EuI₂ (101 mg, 0.250 mmol) were each dissolved in 20 mL of THF. The EuI₂ THF solution was then slowly added dropwise to the N₄Me₄ THF solution, yielding a clear green solution that emitted blue-green light upon excitation at 365 nm. The mixture was stirred at room temperature for 24 h. After the reaction was complete, 20 mL of n-hexane was added to the solution, precipitating a green solid. The product was obtained by filtration. The yield was 90 mg, with a yield of 54%. Elemental analysis calculated C₂. 14 H 32 EuI₂N₄·0.5THF: C, 27.54; H, 5.13; N, 8.03; Elemental analysis results: C, 27.69; H, 5.51; N, 7.84.

[0067] ( R / S )-N,N'-dimethyl-1,2-cyclohexanebis(2-chloro-N-methylacetamide) (( R / S Synthesis of ()-N2O2Me2Cl2): ( R / S 8.52 g (60.0 mmol) of 1,2-dimethyl-1,2-cyclohexanediamine and 20.7 g (150 mmol) of potassium carbonate were added to a solvent consisting of 46 mL of DCM and 36 mL of water. Chloroacetyl chloride (13.4 g, 120 mmol) was slowly added dropwise under an ice-water bath. After the addition was complete, the mixture was allowed to return to room temperature and stirred for 12 h, at which point a white solid precipitated. The DCM was removed by rotary evaporation, and the mixture was filtered. The resulting white solid was then dried under vacuum at 60 °C for 12 h to obtain the product, with a yield of 14.5 g and a yield of 91%. 1 HNMR (400 MHz, CDCl3): δ 1.35 (m, 4H, -N-(CH-CH2-(C H 2)2-CH2-CH)-N-), 1.72–1.87 (m,4H, N-(CH-C H 2-(CH2)2-C H 2-CH)-N-), 2.90 (s, 6H, CO-NC H 3), 4.00-4.08 (m, 4H, -N-CO-C H 2-), 4.56-4.64 (m, 2H, -N-(C H -CH2-(CH2)2-CH2-C H )-N-).

[0068] R S )-N,N'-dimethyl-1,2-cyclohexanebis(2-(dimethylamino)-N- methylacetamide) ( R S )-N4Me6O2) synthesis: ( R S )-N2O2Me2Cl2(2.56 g, 8.72 mmol) was added to a solution of dimethylamine in ethanol (33 wt%, 86 mL, 0.460 mol) and stirred at room temperature for 2 days. After completion of the reaction, the solvent was evaporated and the solid was dissolved in 100 mL DCM, washed with water 3 times (3 x 100 mL), dried over potassium carbonate, filtered and the solvent evaporated to give the product. Yield: 1.40 g, 51%. 1 H NMR (400 MHz, CDCl3): δ 1.35 (m, 4H, -N-(CH-CH2-(C H 2)2-CH2-CH)-N-), 1.48-1.80 (m, 4H, N-(CH-C H 2-(CH2)2-C H 2-CH)-N-), 2.28 (s, 12H, -N-(C H 3)2), 2.85 (s,6H, CO-N-C H 3), 2.96-3.12 (m, 4H, -N-CO-C H 2-), 4.62 (m, 2H, -N-(C H -CH2-(CH2)2-CH2-C H )-N-)..

[0069] R S )-N 1 ,N 1 '-dimethyl-1,2-cyclohexanebis(N 1 ,N 2 ,N 2 -trimethylethane-1,2-diamine ( R S )-N4Me6) synthesis: In a glove box, LiAlH4(855 mg, 22.5 mmol) was slowly dispersed in 20 mL tetrahydrofuran (THF) and then slowly added dropwise to a solution of ( R S ​​​​​​​​The mixture was placed in a 100 mL round-bottom flask containing 20 mL of THF solution of 1.40 g (4.50 mmol) of N₄Me₆O₂. After sealing, the flask was refluxed under N₂ protection for 24 h. After the reaction was complete, excess LiAlH₄ was quenched with 2 mL of water, filtered, and the filtrate was evaporated to dryness to obtain a yellow, oily crude product. Sublimation at 90 °C yielded a colorless, oily product. Yield: 630 mg, 55%. 1 H NMR (400 MHz, CDCl3): δ 1.06-1.26 (m, 4H, -N-(CH-CH2-(C H 2)2-CH2-CH)-N-),1.65–1.86 (m, 4H, N-(CH-C H 2-(CH2)2-C H 2-CH)-N-), 2.24 (s, 12H, -N-(C H 3)2), 2.25(s, 6H, CH2-NC H 3), 2.32-2.45 (m, 8H, -NC H 2-C H 2-N-), 2.61-2.65 (m, 2H, -N-(C H -CH2-(CH2)2-CH2-C H )-N-).

[0070] ( R / S Synthesis of )-N4Me6-EuI2: In a glove box, ( R / S )-N4Me6 (71.0 mg, 0.250 mmol) and EuI2 (101 mg, 0.250 mmol) were each dissolved in 20 mL of THF, and then the EuI2 THF solution was slowly added dropwise to ( R / S A pale green, clear solution was obtained by stirring in a THF solution of 1-N4Me6. Upon further stirring, a pale green solid precipitated, emitting blue light upon excitation at 365 nm. The mixture was stirred at room temperature for 24 h. After the reaction was complete, the product was obtained by filtration. The yield was 120 mg, with a yield of 70%. Elemental analysis calculated C... 16 H 36 EuI2N4: C, 27.84; H, 5.26; N, 8.12; Elemental analysis results: C, 27.97; H, 5.30; N, 8.10.

[0071] ( R / S)-N,N'-dimethyl-1,2-cyclohexanebis(2-(diethylamino)-N-methylacetamide) (( R / S Synthesis of ()-N4Me2Et4O2): ( R / S 2.56 g (8.72 mmol) of N₂O₂Me₂Cl₂ was added to an ethanolic solution of diethylamine (33 wt%, 86 mL, 0.460 mol), and the mixture was stirred at room temperature for 2 days. After the reaction was complete, the solvent was removed under vacuum, the solid was dissolved in 100 mL of DCM, washed three times with water (3 × 100 mL), dried with potassium carbonate, filtered, and the solvent was removed under vacuum to obtain the product. Yield: 1.88 g, yield: 59%. 1 H NMR (400 MHz, DMSO): δ 1.08 (t, 12H, -N-(CH2-C H 3)2), 1.10-1.21 (m, 4H,-N-(CH-CH2-(C H 2)2-CH2-CH)-N-), 1.48–1.80 (m, 4H, N-(CH-C H 2-(CH2)2-C H 2-CH)-N-),2.65 (m, 8H, -N-(C H 2-CH3)2), 3.25 (s, 4H, -N-CO-C H 2-), 3.27 (s, 6H, CO-NC H 3), 4.16 (m, 2H, -N-(C H -CH2-(CH2)2-CH2-C H )-N-).

[0072] ( R / S )-N 1 N 1 '-Dimethyl-1,2-cyclohexanebis(N 2 N 2 -dimethyl-N 1 1,2-methylpropane-1,2-diamine) (( R / S Synthesis of )-N4Me2Et4: In a glove box, LiAlH4 (855 mg, 22.5 mmol) was slowly dispersed in 20 mL of tetrahydrofuran (THF), and then slowly added dropwise to a solution containing ( R / SThe mixture was placed in a 100 mL round-bottom flask containing 20 mL of THF solution of 1.66 g (4.50 mmol) of N₄Me₂Et₄O₂. After sealing, the flask was refluxed under N₂ protection for 24 h. After the reaction was complete, excess LiAlH₄ was quenched with 2 mL of water, filtered, and the filtrate was evaporated to dryness to obtain a pale yellow oily crude product. Sublimation at 90 °C yielded a colorless oily product. Yield: 756 mg, 49%. 1 H NMR (400 MHz, DMSO): δ 0.95 (t, 12H, -N-(CH2-C H 3)2), 1.10-1.26 (m, 4H, -N-(CH-CH2-(C H 2)2-CH2-CH)-N-), 1.33-1.60 (m, 4H, N-(CH-C H 2-(CH2)2-C H 2-CH)-N-), 2.24 (s, 6H, -NC H 3), 2.41-2.55 (m, 18H, -N-(C H 2-CH3)2, -NC H 2-C H 2-N-, -N-(C H -CH2-(CH2)2-CH2-C H )-N-).

[0073] ( R / S Synthesis of )-N4Me2Et4-EuI2: In a glove box, take ( R / S )-N4Me2Et4 (85.0 mg, 0.250 mmol) and EuI2 (101 mg, 0.250 mmol) were each dissolved in 20 mL of THF, and then the EuI2 THF solution was slowly added dropwise to ( R / S In a THF solution of N₄Me₂Et₄, a pale green clear solution was obtained. Upon continued stirring, a pale green solid precipitated, emitting blue light upon excitation at 365 nm. The mixture was stirred at room temperature for 24 h. After the reaction was complete, the product was obtained by filtration. The yield was 115 mg, with a yield of 62%. Elemental analysis calculated C... 16 H 36 EuI2N4: C, 32.18; H, 5.94; N, 7.51; Elemental analysis results: C, 32.00; H, 5.77; N, 7.26.

[0074] Photophysical measurements: UV-Visible absorption spectra were obtained using a Shimadzu UV-3100 spectrometer. Steady-state / transient PL spectra were recorded on an Edinburgh Instruments FLS980 spectrophotometer (Edinburgh Instruments Ltd.) equipped with a pulsed laser. Photoluminescence quantum yields (PLQY) of crystalline powders were measured by an absolute PLQY measurement system on a Hamamatsu C9920-02.

[0075] Thermal stability analysis: Thermogravimetric analysis was recorded using a Q600 SDT instrument at a fixed N2 flow rate, with a heating rate of 15 ° / min from room temperature to 700 °C.

[0076] Preparation and testing of OLEDs: Indium tin oxide (ITO) anodes were obtained commercially with a sheet resistance of 14 Ω / square -1 and a thickness of 80 nm. Prior to preparation, the ITO substrates were cleaned with deionized water, acetone, and ethanol. Organic and metal layers were deposited in different vacuum chambers with a pressure lower than 1 x 10 -4 Pa. A quartz crystal monitor was used to monitor the thickness of each layer and the evaporation rate of all materials. For organic materials, the deposition rate was kept at 0.5-1 Å s -1 , and for cathodes, at 2-3 Å s -1 . The active area of each device was 4 mm 2 . All electrical tests and optical measurements were performed in atmospheric conditions, and the devices were encapsulated in a glovebox. EL spectra, current density-voltage-brightness (J-V-L), and EQE data were measured by a computer-controlled Keithley 2400 source meter, an absolute EQE measurement system (C9920-12), and a photon multichannel analyzer (PMA-12, Hamamatsu Photonics).

[0077] Example 1 Structure of the complexes

[0078] Four complexes (R / S)-MeN8-EuI2and (R / S)-i-PrN8-EuI2were synthesized in a glovebox by mixing EuI2and the corresponding ligand in methanol or tetrahydrofuran, and the products were confirmed by elemental analysis. The coordination geometry was investigated by single-crystal X-ray diffraction (SCXRD) (see attached figures in the description). Compared to (R / S)-MeN8-EuI2, the introduction of isopropyl groups in (R / S)-i-PrN8-EuI2increased the steric hindrance, resulting in an increase in the average Eu-N bond length (2.712 Å for (R / S)-MeN8-EuI2vs. 2.737 Å for (R / S)-i-PrN8-EuI2). i Figure 2 (R / S)-i-PrN8-EuI2. R i (R / S)-i-PrN8-EuI2. R (R / S)-i-PrN8-EuI2.​​R )- i The average bond length of -PrN8-EuI2 is 2.771 Å. The increased bond length reduces the interaction force between the ligand and the central metal, i.e., weakens the ligand field. This results in smaller splitting of the 5d orbital in Eu(II), while the 4f orbital, located in the inner shell, is unaffected by the external ligand field. The energy difference required for electrons to transition from the lowest energy level (LUMO) of the 5d orbital back to the 4f orbital (HOMO) increases, leading to a blue shift in the emission spectrum.

[0079] Example 2: Photophysical properties of the coordination compound

[0080] In order to systematically study chiral Eu 2+ The inventors determined the steady-state, transient, and circularly polarized emission spectra of the complex. A methanol solution of (R / S)-MeN8-EuI2 showed orange-yellow emission at a maximum wavelength of (…). λ max The wavelength is 587 nm. The change from methyl to isopropyl increases the Eu-N bond length due to the steric hindrance of the isopropyl group, resulting in (R / S)- i -PrN8-EuI2 λ max The excitation lifetime of these complexes is 560 nm. The excited-state lifetimes of these complexes are over 1000 nanoseconds (Table 1). Compared to luminescent materials characterized by charge transfer (CT) mechanisms, the full width at half maximum (FWHM) of these complexes in solid powders is relatively narrow (the narrowest being only 51 nm). The excitation bandwidth of these complexes is wide and uncharacteristic, ranging between 230 nm–500 nm (EuX2-N8 and EuX2-N8M6) and 230 nm–600 nm (EuX2-N4). Based on the above photophysical studies, and considering that the ligands in the complex system are saturated organic compounds with extremely high energy levels, the possibility of ligand-metal charge transfer (LMCT) is ruled out. Therefore, the excitation and emission processes can be viewed as Eu... 2+ Electron transitions in ions, where the ground state is 4f 7 [ 8 S 7 / 2 The excited state is 4f. 6 [ 7 F0]5s 1 .

[0081] UV-Vis spectroscopy indicates that (R / S)-MeN8-EuI2 and (R / S)- i -PrN8-EuI2 exhibits high energy absorption at 250 nm (ε>1000 L·mol⁻¹). -1 ·cm -1 It exhibits low energy absorption peaks at 413 and 404 nm (ε = 747 L mol). 1 cm 1 , (R / S-MeN8-EuI2) and ε = 771 L mol 1 cm 1 , (R / S)- i -PrN8-EuI2), in agreement with their excited states. Since the f-d transition is Laporte and spin allowed, the molar absorption is large.

[0082] Table 1. Summary of the photophysical properties of the four europium subcomplexes 1

[0083]

[0084] 1 R / S are two chiral different materials, their luminescence properties are identical except for the chiral direction.

[0085] The inventors have tested the luminescence properties of the four complex doped films using circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy. The four complexes were all doped in m-MTDATA (doping concentration 10 wt%). Their CD spectra show clear mirror symmetry. This strong Cotton effect, which can be attributed to the d-f transition, indicates that the chiral groups introduced successfully introduced chirality into the Eu(II) center. Almost symmetrical emission spectra were also observed from the CPL spectra. The luminescence dissymmetry factors of the four complexes are: -3 ((R)-MeN8-EuI2), -5.7 × 10 -3 ((S)-MeN8-EuI2), 6.4 × 10 -3 ((R)- i -PrN8-EuI2) and -5.6 × 10 -3 ((S)- i -PrN8-EuI2), further confirming the chiral nature of the excited states.

[0086] (R / S)-N4Me4-EuI2crystalline powder emits bright sky blue light under 365 nm UV excitation with a maximum emission wavelength at 488 nm; in contrast, (R / S)-N4Me6-EuI2crystalline powder shows a blue-shifted emission spectrum under UV excitation with a maximum emission wavelength at 481 nm; (R / S)-N4Me2Et4-EuI2shows a further blue-shifted emission spectrum with a maximum peak at 465 nm, presenting a deep blue light emission with CIE of (0.13, 0.08). The excited state lifetimes of (R / S)-N4Me4-EuI2, (R / S)-N4Me6-EuI2, (R / S)-N4Me2Et4-EuI2corresponding to the three complex powders are 584 ns, 665 ns, 724 ns, respectively, which are consistent with the excited state lifetimes of Eu(II) complexes reported in the literature for the 5 d-f transition. The PLQYs are 46%, 93%, 97%, respectively. The experimentally measured emission peak width (32 ~ 35 nm) and the excited state lifetime as short as several hundred nanoseconds indicate that the emission process is likely to be a Laporte-allowed 5 f 6 5 d 1 transition between the excited state (4 f 7 ) and the ground state (4 d -4 f ) of the central Eu(II).

[0087] The emission spectrum of the complex is blue-shifted from (R / S)-N4Me4-EuI2, (R / S)-N4Me6-EuI2to (R / S)-N4Me2Et4-EuI2. This is related to the fact that the 5 d orbital of Eu(II) complex is susceptible to the ligand field. Referring to the crystal structure, from N4Me4-EuI2to N4Me6-EuI2, the introduction of methyl group increases the steric hindrance, making the space around Eu(II) smaller, which can no longer accommodate a molecule of THF coordination, so that the coordination number is reduced from 7 to 6, finally making the ligand field weaken, the 5 d orbital splitting becomes smaller, and thus the 5 d orbital lowest unoccupied molecular orbital (LUMO) of the complex is raised, and finally the energy gap (E g ) of the transition of the electron from the 5 d orbital lowest unoccupied molecular orbital to the ground state (HOMO) is larger, so the light emission is blue-shifted. From N4Me6-EuI2to N4Me2Et4-EuI2, the increase of the alkyl chain makes the Eu-N bond and Eu-I bond length increase, and the force of the ligand on the 5 d orbital decreases, which also makes the ligand field weaken, and similarly makes the 5 dThe track fission becomes small, and the light emission is blue shifted.

[0088] Example 3 Thermal and air stability of the complexes

[0089] The thermal stability of the four complexes was investigated by thermogravimetric analysis (TGA). (R / S)-MeN8-EuI2and (R / S)- i -PrN8-EuI2(T d The residual weight percentages of these complexes at 550 °C were constant, theoretically should be the mass percentage of metal halide with respect to the total mass, because the decomposition process is temporarily attributed to the breaking of coordination bonds and the volatilization of organic ligands.

[0090] Then the sublimation properties of these complexes were tested at 10 -5 Pa high vacuum and gradient heating. It was found that (R / S)-MeN8-EuI2and (R / S)- i -PrN8-EuI2could be completely sublimed in a small range of 50 mg around 300 °C and 320 °C (test tube temperature, different from sample temperature). It is worth noting that there was obvious decomposition in a large amount of sublimation, which might be due to the uneven heating in the sublimation boat.

[0091] Example 4 Electroluminescent device

[0092] According to the photophysical properties of Example 2 and the stability study of Example 3, the EuX2-N8 complexes are good candidate light-emitting materials for OLEDs. Since there is a lack of experience of Eu(II) complex devices for OLEDs, it is necessary to work on optimizing the device structure. First, (R / S)-MeN8-EuI2was chosen for device optimization, and subsequent examples included screening of host materials, finding the best combination of hole transport layer (HTL) and electron transport layer (ETL), adjusting the emission layer thickness, and then further following the optimization conditions, adjusting the doping concentration and the thickness of the emission layer of (R / S)-MeN8-EuI2device, the materials used.

[0093] The final optimized OLED structure is ITO / MoO3(2 nm) / 4,4'-cyclohexylidene[N,N-bis(4- methylphenyl)aniline] (TAPC, 50 nm) / (R / S)-MeN8-EuI2or (R / S)- i- PrN8-EuI2: 4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA) (10 wt%, 20 nm) / 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene (TmPyPB, 50 nm) / LiF (1 nm) / Al (100 nm). The best (R / S)-MeN8-EuI2 device has a turn-on voltage (V on ) of 4.7 V, a maximum luminance (L -2 ) of 23000 cd·m max , a maximum current efficiency (CE -1 ) of 56.9 cd·A max , and an excellent performance with the highest EQE of 15.6%. i - PrN8-EuI2 as the light-emitting material shows a V on , L max , CE max , and EQE of 4.5 V, 19000 cd·m -2 , 41.0 cd·A -1 , and 10.0%, respectively. The device results of the embodiments of the present application can be comparable to most mainstream OLEDs (phosphorescent metal complexes or TADF molecules as the light-emitting material).

[0094] By testing the circularly polarized electroluminescence spectra of the four complex devices, the electroluminescence asymmetry factors are: 3.9 × 10 -3 ((R)-MeN8-EuI2), -3.7 × 10 -3 ((S)-MeN8-EuI2), 3.1 × 10 -3 ((R)- i - PrN8-EuI2) and -2.6 × 10 -3 ((S)- i - PrN8-EuI2). Due to the higher asymmetry factor, the device is expected to replace the traditional physical filter method in the field of 3D display light sources, and at the same time, to achieve the purpose of simplifying the device structure and increasing the device brightness.

[0095] The above has described the embodiments of the present application in detail. However, the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An electroluminescent material, characterized in that, The luminescent material is selected from (a) (R / S)-MeN8-EuI2 or (b) (R / S)- i -PrN8-EuI2, the structural formula of the above complex is shown below: ； * has at least one chiral site.

2. An electroluminescent device, characterized by The electroluminescent device comprises a cathode, an anode, and a light-emitting layer between the cathode and the anode, wherein the light-emitting layer comprises the electroluminescent material according to claim 1.

3. The electroluminescent device according to claim 2, wherein The light-emitting layer is a mixture of a guest material and a host material, wherein the guest material comprises the electroluminescent material according to claim 1, and the host material comprises m-MTDATA, mCP, mCBP, CzSi, DCPPO, PCzAc, CBP, TCTA, TAPC, DPEPO, mCPCN, BCPO, and a doping concentration of 1wt%-99wt%, wherein the doping concentration is a percentage of the mass of the guest material in the total mass of the guest material and the host material.

4. The electroluminescent device according to claim 3, characterized in that The electroluminescent device further comprises an electron transport layer between the cathode and the light-emitting layer, wherein the electron transport layer comprises TmPyPB, DPEPO, TSPO1, Bphen and / or TPBi.

5. The electroluminescent device according to claim 3, wherein The electroluminescent device further comprises a hole transport layer between the anode and the light-emitting layer, wherein the hole transport layer comprises PCzAc, mCP, m-MTDATA, NPB, PEDOT:PSS, TCTA and / or TAPC.

6. The electroluminescent device according to claim 5, characterized in that The electroluminescent device further comprises an electron transport layer between the cathode and the light-emitting layer and a hole transport layer between the anode and the light-emitting layer. The hole transport layer comprises TAPC, and the electron transport layer comprises Bphen.

7. The electroluminescent device according to claim 6, characterized in that The thickness of the light-emitting layer is 10-40nm.

8. The electroluminescent device of claim 4, wherein, The electroluminescent device further comprises a hole blocking layer between the light-emitting layer and the electron transport layer, wherein the material of the hole blocking layer is TSPO1.

9. The electroluminescent device according to claim 2, characterized in that The structure of the electroluminescent device is: ITO / MoO3, 2 nm / 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)aniline], 50 nm / (R / S)-MeN8-EuI2or (R / S)- i -PrN8-EuI2: 4,4',4''-tris[phenyl(m-methylphenyl)amino]triphenylamine (m-MTDATA), 10 wt%, 20 nm / 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene, 50 nm / LiF, 1 nm / Al, 100 nm.

10. The electroluminescent device of claim 3, wherein, The doping concentration is 7wt%-10wt%.

11. The electroluminescent device of claim 7, wherein, The thickness of the light-emitting layer is 15-30nm.

12. The electroluminescent device of claim 7, wherein, The thickness of the light-emitting layer is 20-25nm.

13. The electroluminescent device of claim 7, wherein, The thickness of the light-emitting layer is 25nm.

14. The electroluminescent device of claim 8, wherein, The electroluminescent device further comprises a second hole transport layer between the anode and the hole transport layer, wherein the material of the second hole transport layer is NPB.

Images