CN115677736A - Chiral d-f transition rare earth complex and application thereof as electroluminescent material - Google Patents
Chiral d-f transition rare earth complex and application thereof as electroluminescent material Download PDFInfo
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Abstract
An electroluminescent material comprises a complex (R/S) -RN 8 ‑EuI 2 It has the following structure:
complex EuX 2 ‑N 4 Having a structure as shown below：
Complex EuX 2 ‑cycloN 4 It has the following structure:
wherein X is a monovalent anion, such as F, cl, br, I, OCN, SCN, CN, CF 3 SO 3 、BF 4 Or PF 6 Each R is independently selected from H and C 1 ‑C 18 The metal ion has d-f transition luminescence, such as Eu (II), ce (III), yb (II), sm (II) and the like, and the 'x' position has at least one chiral site.
Description
Technical Field
The invention belongs to the field of electroluminescent materials. In particular to a chiral d-f transition rare earth complex and application thereof as an electroluminescent material.
Background
As a natural phenomenon, polarized light widely exists in nature. The circular polarization state manipulation technology of light has wide application prospects in the fields of 3D display, optical sensing, spintronic devices, optical communication, information storage and the like.
Currently, circular polarization luminescent materials are mostly obtained by synthesis of chiral raw materials. The luminous polarization intensity is measured by a g factor, the larger the absolute value is, the larger the polarization intensity is, and the theoretical upper limit is 2. The g factor of the chiral luminescent material can be improved to a certain extent by increasing the number of chiral groups, designing a spatial stacking mode, shortening the distance between the chiral groups and a luminescent center, changing the form of the luminescent material and the like.
The luminescent materials commonly used in the research of Organic Light Emitting Diodes (OLED) at present comprise fluorescent materials, phosphorescent materials, thermal activation delayed fluorescent materials (TADF), rare earth f-f transition luminescent materials and the like. By introducing chirality to the luminescent molecules, circularly polarized luminescence of different intensities can be obtained. The circularly polarized light OLED (CP-OLED) luminescent material common in the literature can be divided into chiral Thermally Activated Delayed Fluorescence (TADF) material and eEQE with maximum external quantum efficiency max =32.6%, for g =2.0 × 10 -3 ；g max ＝6.0×10 -2 Corresponding to external quantum efficiency EQE = 3.5%), chiral conjugated polymer (g) max = 0.8, corresponding EQE not reported), chiral phosphorescent transition metal complexes (EQE) max 23.2%, corresponding g = -3.0 × 10 -4 ；g max = -0.38 corresponding EQE not reported), lanthanide (III) rare earth complex emitting chiral f-f transition (EQE) max =0.05%, corresponding to g = -0.88; EQE =5.0 × 10 -3 Corresponds to g max = 1.0), and the like. It can be seen that the existing CP-OLED light-emitting materials generally have the problem that high efficiency and high optical rotation are difficult to achieve.
Disclosure of Invention
Compared with the materials, the d-f transition luminescent material has the comprehensive advantages of high exciton utilization rate, short excited state service life, easy regulation of luminescence and the like, and is expected to prepare the efficient and stable OLED. Up to now, EQE of d-f transition luminescence Eu (II) complex OLEDs max Can reach 17.7%, maximum brightness can reach 25470cd m -2 (ii) a Ce (III) Complex EQE max Can reach 20.8%, and maximum brightness can reach 31160cd m -2 。
The inventor of the present invention hopes to explore the possibility of combining chiral luminescence with a d-f transition luminescent material by utilizing the advantage of high efficiency of the d-f transition luminescent material, so as to overcome the difficulty that the chiral luminescent material has high efficiency and high g factor and is difficult to obtain. At present, the research on the d-f transition rare earth complex CP-OLED is blank. The inventor selects N with excellent electroluminescent property by the experience of the existing high-g factor chiral luminescent material 8 -EuI 2 As a template, by applying a force to N 8 Chiral atoms which are as much as possible and are as close to a luminescence center Eu (II) as possible are introduced into the framework so as to obtain the electroluminescent material with a high g factor on the basis of ensuring high efficiency.
Despite the above-mentioned advantages, chiral Eu (II) complexes have not yet been availableThere are reports on the structure-activity relationship of the asymmetric factor of luminescence, therefore, the structure-activity relationship is not clear at present. Therefore, more efforts must be made to rationally design the Eu (II) complex and to understand the mechanism of circular polarization luminescence to improve the chiral properties of the material and the corresponding device. The inventor of the invention thinks that the multidentate N ligand has good modification property of the group while keeping the high efficiency of the Eu (II) complex, and can effectively synthesize the Eu (II) complex with point chirality, axial chirality and surface chirality. Thus, in a particular embodiment of the invention, the inventors have selected the ligand (R/S) -MeN 8 And (R/S) -i-PrN 8 For designing four articles named (R/S) -Men 8 -EuI 2 And (R/S) -i-PrN 8 -EuI 2 The Eu (II) -containing azamacrocycle complex of (1). A series of crystal analyses, spectra, chiralities and theoretical studies were carried out to reveal the photophysical and circularly polarised luminescent properties of these Eu (II) complexes. Then, due to their high efficiency, high emission asymmetry factor and good thermal/air stability, such complexes are exemplarily selected as the light emitting layer material of CP-OLEDs. The optimized device has excellent performance, the maximum EQE is 15.6%, and the maximum brightness is 23000 cd.m -2 The maximum electroluminescence asymmetry factor is 3.9 × 10 -3 The material can perform as well as the CP-OLED device which takes the most advanced phosphorescent metal complex or TADF molecule as the luminescent material.
Embodiments of the present invention provide an electroluminescent material including a complex (R/S) -RN 8 -EuI 2 It has the following structure:
wherein X is a monovalent anion, such as F, cl, br, I, OCN, SCN, CN, CF 3 SO 3 、BF 4 Or PF 6 R is independently selected from H and C 1 -C 18 Alkyl, halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S-containing heteroaryl, O, N, S-containing coordinationThe metal ions with d-f transition luminescence such as Eu (II), ce (III), yb (II), sm (II) and the like are arranged on the alkyl of the dots, and the position of the "+" is provided with at least one chiral site; preferably, all "+" sites are chiral sites;
alternatively, the electroluminescent material comprises a complex EuX 2 -N 4 It has the following structure:
wherein X is a monovalent anion, such as F, cl, br, I, OCN, SCN, CN, CF 3 SO 3 、BF 4 Or PF 6 R is independently selected from H and C 1 -C 18 The compound is an alkyl, halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S heteroaryl, alkyl containing coordination sites of O, N and S, M is Eu (II), ce (III), yb (II), sm (II) and other metal ions with d-f transition luminescence, and the position of "+" is provided with at least one chiral site; preferably, all "+" sites are chiral sites;
alternatively, the electroluminescent material comprises a complex EuX 2 -cycloN 4 It has the following structure:
wherein X is a monovalent anion, such as F, cl, br, I, OCN, SCN, CN, CF 3 SO 3 、BF 4 Or PF 6 Each R is independently selected from H and C 1 -C 18 The "x" position has at least one chiral site; preferably, all "sites" are chiral sites.
According to one embodiment of the invention, for example, the luminescent material comprises (a) (R/S) -MeN 8 -EuI 2 ，(b)(R/S)-i-PrN 8 -EuI 2 ，(c)(R/S)-MeN 8 -Ce(OTf) 3 ，(d)(R/S)-N 4 Me 4 -EuI 2 ，(e)(R/S)-N 4 Me 6 -EuI 2 ，(f)(R/S)-N 4 Me 2 Et 4 -EuI 2 ，(g)(R/S)-cycloMeN 4 -EuI 2 ，(h)(R/S)-hexcycloN 4 -EuI 2 The corresponding structural formula of the complex is shown as follows:
embodiments of the present invention also provide an 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 an electroluminescent material as described above.
According to one embodiment of the invention, for example, the light-emitting layer is a mixture of a guest material and a host material, wherein the guest material comprises an electroluminescent material as described above, and the host material comprises m-MTDATA, mCP, mCBP, czSi, DCPPO, PCzAc, CBP, TCTA, TAPC, DPEPO, mCPCN, BCPO and the like, with a doping concentration of 1wt% to 99wt%, preferably 7wt% to 10wt%, most preferably 10wt%, the doping concentration being the mass of guest material as a percentage of the total mass of guest material and host material.
According to an embodiment of the present invention, for example, the electroluminescent device further comprises an electron transport layer between the cathode and the light-emitting layer, the electron transport layer comprising TmPyPB, DPEPO, TSPO1, bphen and/or TPBi.
According to an embodiment of the present invention, 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.
According to an embodiment of the present invention, for example, the electroluminescent device further includes 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.
Preferably, the hole transport layer comprises TAPC and the electron transport layer comprises Bphen.
According to one embodiment of the invention, the thickness of the light emitting layer is, for example, 10-40nm, preferably 15-30nm, preferably 20-25nm, most preferably 25nm.
According to an embodiment of the present invention, 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 TSPO1.
Preferably, the electroluminescent device further comprises a second hole transport layer located between the anode and the hole transport layer; preferably, the material of the second hole transport layer is NPB.
According to one embodiment of the present invention, for example, the electroluminescent device has a structure in which: ITO/MoO 3 (2 nm)/cyclohexylidenebis [ N, N' -bis (p-tolyl) aniline](TAPC，50nm)/(R/S)-MeN 8 -EuI 2 :4,4',4 "-Tris [ phenyl (m-tolyl) amino group]Triphenylamine (m-MTDATA, 10wt%,20 nm)/1, 3, 5-tris [ (3-pyridyl) -3-phenyl]Benzene (TmPyPB, 50 nm)/LiF (1 nm)/Al (100 nm).
Drawings
FIG. 1 is a chemical structural formula of a complex in which (a) (R/S) -MeN 8 -EuI 2 ，(b)(R/S)-i-PrN 8 -EuI 2 ，(c)(R/S)-MeN 8 -Ce(OTf) 3 ，(d)(R/S)-N 4 Me 4 -EuI 2 ，(e)(R/S)-N 4 Me 6 -EuI 2 ，(f)(R/S)-N 4 Me 2 Et 4 -EuI 2 ，(g)(R/S)-MeN 4 -EuI 2 ，(h)(R/S)-cyclohexN 4 -EuI 2
FIG. 2 is a schematic diagram of a crystal structure of a complex in an example of the present invention, wherein (a) (R/S) -MeN 8 -EuI 2 ，(b)(R/S)-i-PrN 8 -EuI 2 ，(c)(S)-MeN 8 -Ce(OTf) 3 ，(d)(R)-N 4 Me 4 -EuI 2 ，(e)(S)-N 4 Me 6 -EuI 2 ，(f)(S)-N 4 Me 2 Et 4 -EuI 2 。
Detailed Description
The chiral d-f transition rare earth complex and its application as electroluminescent material of the present invention will be further described with reference to the following specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention. Abbreviations the corresponding compounds are full names:
m-MTDATA 4,4' -tris [ phenyl (m-tolyl) amino ] triphenylamine
mCP N, N-diazoxide-3, 5-benzene
mCBP 3, 3-di (9H-carbazol-9-yl) biphenyl
CzSi 9- (4-tert-butylphenyl) -3, 6-bis (triphenylsilyl) -9H-carbazole
DCPPO bis (9H-carbazol-9-yl) (phenyl) phosphine oxide
PCzAc 9, 9-dimethyl-10- (9-phenyl-9H-carbazol-3-yl) -9, 10-dihydroacridine
CBP 4,4' -bis (9-carbazolyl) -1, 10-biphenyl
TCTA Tris (4- (9 carbazolyl) phenyl) amine
TAPC 4,4' -Cyclohexylbis [ N, N-bis (4-methylphenyl) aniline ]
DPEPO bis [2- ((oxo) diphenylphosphino) phenyl ] ether
mCPCN 9- (3- (9H-carbazol-9-yl) phenyl) -9H-carbazole-3-carbonitrile
BCPO bis-4- (N-carbazolyl) phenyl) phenylphosphine oxide
Bphen 4, 7-diphenyl-1, 10-phenanthroline
TSPO1 Diphenyl [4- (triphenylsilyl) phenyl ] phosphine oxide
NPB N, N '-di (1-naphthyl) -N, N' -diphenyl-1, 1 '-biphenyl-4, 4' -diamine
PEDOT PSS Poly (ethylenedioxythiophene) -poly (styrenesulfonate)
Preparation method and test method.
All chemicals used in the synthesis were commercially available and used as received unless otherwise indicated. 1 H-NMR was measured on Bruker-400 MHz NMR. Tetramethylsilane (TMS) was used as an internal reference for chemical shift correction, where δ TMS Equal to 0. Elemental analysis was performed on a VARIO EL analyzer. Eu (Eu) 2+ All syntheses of the complexes were carried out in a glove box. Solid Eu 2+ All spectral tests of the complexes were carried out after paraffin encapsulation between two quartz plates, the solution being in N 2 The test was carried out in a cuvette with a stopcock under an atmosphere. By using KMnO 4 Commercial paraffin was purified by oxidation and column chromatography to remove the optical brightener.
Synthesis of N-p-toluenesulfonyl-2-methylazepine (Me-Azi): into a 1L three-necked flask, 700mL of Dichloromethane (DCM) was charged, followed by sequentially adding 2-aminopropanol (0.133mol, 10.00g), p-toluenesulfonyl chloride (TsCl) (0.277mol, 52.80g) and catalyst 4-Dimethylaminopyridine (DMAP) (0.013mol, 1.58g) and stirring. Triethylamine (TEA) (0.40mol, 40.49g) was slowly added dropwise to the reaction solution under nitrogen at 0 ℃ over about 1 hour. After the dropwise addition, the reaction mixture was allowed to return to room temperature and reacted overnight. The reaction solution on the next day was saturated with 260mL of NH 4 The organic phase was separated after washing with Cl solution and the aqueous phase was washed 3 times with 100mL of DCM. The organic phases were combined and washed with anhydrous Na 2 SO 4 After drying, the solvent was spin-dried to give the crude product as an orange-yellow oil. The colorless needle crystal which is easy to be supercooled is obtained after column chromatography separation (eluent: 1: mixed solution of ethyl acetate and petroleum ether of 8), and the yield is 56.9%. 1 H NMR(400MHz,CDCl 3 ):δ1.15(d,3H,J＝5.6Hz)；1.93(d,1H,J＝4.6Hz)；2.34(s,3H)；2.50(d,1H,J＝7.0Hz)；2.72(m,1H)；7.24(d,2H,J＝8.0Hz)；7.73(d,2H,J＝8.0Hz).
Synthesis of N-p-toluenesulfonyl-2-isopropylazetidine (i-Pr-Azi): 13.72g of valinol (0.133 mol) were used as preproininol instead of 2-aminopropanolThe reaction conditions and the post-treatment of the material are the same as those of Me-Azi, the yellow viscous solid obtained by rotary evaporation is recrystallized by Petroleum Ether (PE), the supernatant is separated by decantation, and fluffy colorless needle crystals are separated out after cooling, and the yield is 50.3%. 1 H NMR(400MHz,CDCl 3 ):δ0.80(d,J＝6.8Hz,3H),0.90(d,J＝6.8Hz,3H),1.41(m,1H),2.10(d,J＝4.4Hz,1H),2.45(s,3H),2.51(m,1H),2.62(d,J＝6.8Hz,1H),7.33(d,J＝8.0Hz,2H),7.83(d,J＝8.0Hz,2H).
Synthesis of tris (N-p-toluenesulfonyl-2-aminopropyl) amine (Me-Ts-NTEA): me-Azi (33.51mmol, 7.094g) is added to a 100mL pressure-resistant reaction flask at room temperature, then 1.55mL of 7M ammonia-methanol solution and 3.87mL of ultra-dry methanol are sequentially added, a cover is closed, the temperature is raised to 45 ℃ after the sealing, the oil bath is carried out for reaction for 4 days, 40mL of methanol (MeOH) is added for refluxing for 2 hours after the reaction is finished, and the white solid is obtained after the solvent is dried by the spinning and is separated by column chromatography (eluent: ethyl acetate of 1 1 H NMR(400MHz,CDCl 3 ):δ0.96(d,J＝6.4Hz,9H),2.13(dd,J＝13.0and 3.8Hz,3H),2.38(s,9H),2.51(dd,J＝12.9and 11.1Hz,3H),3.64-3.67(m,3H),5.74(br d,J＝5.6Hz,3H),7.23(d,J＝7.9Hz,6H),7.83(d,J＝8.2Hz,6H).
Synthesis of tris (N-p-toluenesulfonyl-2-amino-3-methylbutyl) amine (i-Pr-Ts-NTEA): the synthesis method is similar to that of Me-Ts-NTEA, white powdery solid separated out by cooling after oil bath reaction at 50 ℃ for 4 days is filtered, and reactants are washed out by methanol to obtain the product, wherein the yield is 69.5%. 1 H NMR(400MHz,CDCl 3 ):δ0.78(d,J＝6.9Hz,9H),0.80(d,J＝6.9Hz,10H),.1.70(pd,J＝6.9,4.2Hz,3H),2.13(td,J＝12.0,11.3,4.6Hz,3H),2.38(s,9H),2.96(t,J＝12.1Hz,3H),3.82(ddt,J＝11.5,8.6,4.5Hz,3H),6.20(d,J＝7.0Hz,3H),7.23(d,J＝8.1Hz,6H),7.80–7.87(m,7H).
Synthesis of tris (2-aminopropyl) amine (Me-NTEA): to a 250mL single-neck flask were added Me-Ts-NTEA (7.682mmol, 5.018g) and phenol (74.13mmol, 6.976g), followed by 100mL 48% hydrobromic acid, and the mixture was refluxed under nitrogen for 2 days, during which time the solution changed from colorless to orange-red to dark-red. After the reaction, when the reaction solution naturally cooled to room temperature, the system was observed to separate into black oil and dark orange redA colored aqueous phase. The aqueous phase was separated, adjusted to a pH of about 1 with 4M sodium hydroxide (NaOH) solution, and washed with Ethyl Acetate (EA) to pale yellow to colorless. Then NaOH solution was added, pH of the aqueous phase was adjusted to above 13 and product was extracted with DCM. Anhydrous Na for organic phase 2 SO 4 Drying, filtering, spin-drying the filtrate to obtain light yellow oily liquid, distilling under reduced pressure, collecting 104-107 deg.C fraction to obtain colorless transparent oily liquid, standing to solidify to obtain transparent feather-like crystals with a yield of 50.5%. 1 H NMR(400MHz,CDCl 3 ):δ0.95–1.05(m,3H),1.71(s,6H),2.13–2.29(m,6H),3.10(dqd,J＝9.7,6.3,3.3Hz,3H).
Synthesis of tris (2-amino-3-methylbutyl) amine (i-Pr-NTEA): to a 250mL single-neck flask were added i-Pr-Ts-NTEA (6.167mmol, 4.533g) and phenol (59.51mmol, 5.601g), followed by 100mL of 40% hydrobromic acid, and refluxed under nitrogen for 2 days. The work-up after the end of the reaction was similar to Me-NTEA, but the DCM phase was dried by rotary drying to give a pale yellow oily liquid which was pure without distillation, 87.6% yield. 1 H NMR(400MHz,CDCl 3 ):δ0.90(d,J＝6.7Hz,9H),0.91(d,J＝6.7Hz,9H),1.50(octet,J＝6.6Hz,3H),1.89(br.s,6H),2.26–2.29(m,6H),2.67–2.72(m,3H).
3,8,12,17,20, 25-hexamethyl-1, 4,7,10,13,16,21, 24-octaazabicyclo [8.8.8 ] s]Hexacosane (Men) 8 ) The synthesis of (2): under the condition of a dry ice-acetone bath at-78 ℃, 1g of Me-NTEA (5.310 mmol), 38mL of isopropanol and 1.52mL of TEA are added into a 100mL three-neck flask, and mechanical stirring is started to uniformly mix the three components. 1.14g of 40% aqueous glyoxal solution diluted with 7.6mL of isopropyl alcohol was added to the dropping funnel, and then the glyoxal solution was slowly dropped into the flask under a nitrogen atmosphere at a rate of 2 s/drop. After the completion of the dropwise addition, the reaction system was gradually returned to room temperature, and transferred to a 250mL flask, and 1.52g of sodium borohydride (40.10 mmol, excess) was added in portions, followed by addition of 20mL of methanol, and the mixture was stirred overnight under a nitrogen atmosphere. After overnight, the solvent of the reaction system was spin dried, the resulting solid was soaked in DCM for 20min under nitrogen atmosphere and filtered, and the filtrate was spin dried to give a pale yellow solid. Drying the crude product in a vacuum drying oven at 100 deg.C overnight, and placing in a sublimator at 185 deg.C and 0.1PaSublimating for 24 hours under the condition to obtain colorless flaky transparent crystals with the yield of 18.3 percent. 1 H NMR(400MHz,CDCl 3 ):δ1.02(q,J＝3.9,3.5Hz,18H),1.21(d,J＝6.1Hz,6H),1.84(d,J＝12.8Hz,6H),2.37–2.71(m,6H),2.69–3.05(m,12H).
3,8,12,17,20,25-hexaisopropyl-1,4,7,10,13,16,21,24-octaazabicyclo [8.8.8 ] c]Hexacosane (i-PrN) 8 ) The synthesis of (2): synthetic method and N 8 Me 6 Similarly, 1g of i-Pr-NTEA (3.670 mmol) was transferred into a single-neck flask, and 2g of sodium borohydride (52.76 mmol) was added in portions, followed by addition of 13mL of methanol and stirring for 2 days. Post-treatment with N 8 Me 6 Similarly, the crude product after vacuum drying is put into a sublimator to be sublimed for 24 hours under the condition of 160 ℃ and 0.1Pa, colorless granular transparent crystals are obtained, and the yield is 8.7 percent. 1 H NMR(400MHz,CDCl 3 ):δ0.86(d,J＝6.8Hz,18H),0.91(d,J＝6.9Hz,18H),1.71(pd,J＝7.0,4.4Hz,6H),2.18(dd,J＝13.1,10.1Hz,6H),2.26(dd,J＝13.0,7.3Hz,12H),2.52–2.69(m,6H),2.92(q,J＝8.5,6.4Hz,6H).
(R/S)-MeN 8 -EuI 2 The synthesis of (2): at room temperature, under a nitrogen atmosphere, to a solution containing 52mg of EuI 2 (0.128 mmol) of tetrahydrofuran was added dropwise thereto a solution containing 59mg of (R/S) -MeN 8 (0.128 mmol) tetrahydrofuran, wherein the solution turns from colorless to yellow, and orange red powder is separated out at the same time, and the product is obtained after filtration and draining. Calculated value of elemental analysis C 24 H 54 EuI 2 N 8 (860.52) C,33.50; h,6.33; n,13.02; found in elemental analysis of 33.55; h,6.39; n,12.77.
(R/S)-i-PrN 8 -EuI 2 The synthesis of (2): to a solution containing 52mg of EuI at room temperature under a nitrogen atmosphere 2 (0.128 mmol) of tetrahydrofuran solution, 80mg of (R/S) -i-PrN is added dropwise 8 (0.128 mmol) of tetrahydrofuran, whereby the solution changed from almost colorless to pale green and had bright green color under UV excitation. And (3) with stirring, the solution becomes dark in color, meanwhile, light green powder is separated out, and the product is obtained after filtration and pumping. The complex can be purified by vacuum sublimation at 280 ℃. Calculated value of elemental analysis C 36 H 78 EuI 2 N 8 (1028.85) C,42.03; h,7.64; n,10.89; yuanFound in the assay of C,41.57; h,7.41; n,10.63.
(S)-MeN 8 -Ce(OTf) 3 The synthesis of (2): at room temperature, under a nitrogen atmosphere, to a solution containing 59mg of Ce (OTf) 3 (0.1 mmol) of a methanol solution containing 45mg of (R/S) -i-PrN is added dropwise 8 (0.1 mmol) in methanol, the solution remained colorless at all times and had bright blue light under UV excitation. As the stirring proceeded, the solution turned slightly brown, drained and recrystallized from DCM/n-hexane to give the pure product. Calculated value of elemental analysis C 27 H 54 CeF 9 N 8 O 9 S 3 C,31.12; h,5.22; n,10.75; found in elemental analysis of 31.48; h,5.67; n,10.43.
(R/S) -N, N' -1, 2-Cyclohexanedibis (2-chloroacetamide) ((R/S) -N) 2 O 2 Cl 2 ) The synthesis of (2): (R/S) -cyclohexanediamine (3.42g, 30.0mmol) and potassium carbonate (10.3g, 75.0mmol) were added to a solvent in which 23mL of Dichloromethane (DCM) and 18mL of water were mixed, chloroacetyl chloride (6.72g, 60.0mmol) was slowly added dropwise in an ice-water bath, and after completion of the addition, the temperature was returned to room temperature, and stirring was carried out for 12 hours, at which time a white solid precipitated. Removing DCM by rotary evaporation, filtering, and placing the obtained white solid at 60 ℃ for vacuum drying for 12h to obtain the product. Yield 9.42g, 93%. 1 H NMR(CDCl 3 ):δ1.36(m,4H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),1.82–2.10(m,4H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),3.77(m,2H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),4.01(br s,4H,-CH 2 -Cl),6.82(br s,2H,NH-CO)。
(R/S) -N, N' -1, 2-Cyclohexanedibis (2- (dimethylamino) acetamide) ((R/S) -N 4 O 2 Me 4 ) The synthesis of (2): will (R/S) -N 2 O 2 Cl 2 (4.33g, 16.5 mmol) was added to an ethanol solution of dimethylamine (33 wt%,160mL,0.860 mol), and the mixture was stirred at room temperature for 2 days. After the reaction was complete, the solvent was pumped off, the solid was dissolved in 100mL DCM, washed 3 times with water (3X 100 mL), dried over potassium carbonate, filtered and the solvent was pumped off to give the product. Yield: 1.50g, yield: 32 percent. 1 H NMR(CDCl 3 ):δ1.22-1.38(m,4H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),1.72–2.05(m,4H,NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),2.24(s,12H,-N-(CH 3 ) 2 ),2.84-2.94(m,4H,NH-CO-CH 2 -),3.75(m,2H,NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-)。
(R/S)-N 1 ,N 1 ' -dimethyl-1, 2-cyclohexanedibis (N) 2 ,N 2 -dimethylethane-1, 2-diamine ((R/S) -N) 4 Me 4 ) The synthesis of (2): taking LiAlH in a glove box 4 (810mg, 21.3mmol) was slowly dispersed in 20mL of Tetrahydrofuran (THF), and then slowly added dropwise to a solution containing (R/S) -N 2 O 2 Me 4 (1.50g, 5.28mmol) in 20mL THF in a 100mL round bottom flask. Taken out after sealing, at N 2 And refluxing for 24 hours under protection. After the reaction, 2mL of water was used to quench the excess LiAlH 4 Filtering, and spin-drying the filtrate to obtain a yellow oily crude product. Sublimation purification at 90 ℃ gave the product as a colorless oil. Yield: 528mg, yield: 39 percent. 1 H NMR(400MHz,CDCl 3 ):δ1.03(m,2H,NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),1.23(m,2H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),1.73(m,2H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),2.05(m,2H,NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),2.16(m,2H,-NH-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-NH-),2.23(s,12H,-N-(CH 3 ) 2 ),2.25(br s,2H,-NH),2.40(m,4H,-CH 2 -N-(CH 3 ) 2 ),2.53(dt,-CH 2 -CH 2 -N-(CH 3 ) 2 ),2.82(dt,CH 2 -CH 2 -N-(CH 3 ) 2 )。
(R/S)-N 4 Me 4 -EuI 2 The synthesis of (2): in the glove box, take (R/S)N 4 Me 4 (66.0mg, 0.250mmol) and EuI 2 (101mg, 0.250mmol) were each dissolved in 20mL THF, and EuI was then added 2 Is slowly added dropwise to N 4 Me 4 In THF to obtain a green clear solution, which emits blue-green light under 365nm excitation. Stirred at room temperature for 24h. And after the reaction is finished, adding 20mL of n-hexane into the solution, separating out green solids, and filtering to obtain the product. Yield 90mg, 54% yield. Calculated value of elemental analysis C 14 H 32 EuI 2 N 4 0.5THF: c,27.54; h,5.13; n,8.03; found in elemental analysis C,27.69; h,5.51; and N,7.84.
(R/S) -N, N' -dimethyl-1, 2-cyclohexanebis (2-chloro-N-methylacetamide) ((R/S) -N 2 O 2 Me 2 Cl 2 ) The synthesis of (2): (R/S) -N, N' -dimethyl-1, 2-cyclohexanediamine (8.52g, 60.0mmol) and potassium carbonate (20.7g, 150mmol) were added to a solvent comprising a mixture of 46mL of DCM and 36mL of water, chloroacetyl chloride (13.4 g, 120mmol) was slowly added dropwise in an ice-water bath, and after completion of the addition, the temperature was returned to room temperature, and stirring was carried out for 12 hours, whereupon a white solid precipitated. DCM was removed by rotary evaporation and filtration, and the resulting white solid was dried in vacuo at 60 ℃ for 12h to give the product in 14.5g, 91% yield. 1 H NMR(400MHz,CDCl 3 ):δ1.35(m,4H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),1.72–1.87(m,4H,N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),2.90(s,6H,CO-N-CH 3 ),4.00-4.08(m,4H,-N-CO-CH 2 -),4.56-4.64(m,2H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-)。
(R/S) -N, N' -dimethyl-1, 2-cyclohexanebis (2- (dimethylamino) -N-methylacetamide) ((R/S) -N 4 Me 6 O 2 ) The synthesis of (2): will (R/S) -N 2 O 2 Me 2 Cl 2 (2.56g, 8.72mmol) was added to an ethanol solution of dimethylamine (33 wt%,86mL, 0.460mol), and stirred at room temperature for 2 days. After the reaction was complete, the solvent was pumped off, the solid was dissolved in 100mL DCM, washed 3 times with water (3X 100 mL), dried over potassium carbonate, filtered and the solvent was pumped off to give the product. Yield:1.40g, yield: 51 percent. 1 H NMR(400MHz,CDCl 3 ):δ1.35(m,4H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),1.48–1.80(m,4H,N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),2.28(s,12H,-N-(CH 3 ) 2 ),2.85(s,6H,CO-N-CH 3 ),2.96-3.12(m,4H,-N-CO-CH 2 -),4.62(m,2H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-)。
(R/S)-N 1 ,N 1 ' -dimethyl-1, 2-cyclohexanedibis (N) 1 ,N 2 ,N 2 -trimethylethane-1, 2-diamine ((R/S) -N) 4 Me 6 ) The synthesis of (2): taking LiAlH in a glove box 4 (855mg, 22.5 mmol) was slowly dispersed in 20mL of Tetrahydrofuran (THF), and then slowly added dropwise to a solution containing (R/S) -N 4 Me 6 O 2 (1.40g, 4.50mmol) in 20mL THF in a 100mL round bottom flask. Taken out after sealing, at N 2 And refluxing for 24 hours under protection. After the reaction, 2mL of water was used to quench the excess LiAlH 4 Filtering, and spin-drying the filtrate to obtain a yellow oily crude product. Sublimation purification at 90 ℃ gives the product as a colorless oil. Yield: 630mg, yield: and 55 percent. 1 H NMR(400MHz,CDCl 3 ):δ1.06-1.26(m,4H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),1.65–1.86(m,4H,N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),2.24(s,12H,-N-(CH 3 ) 2 ),2.25(s,6H,CH 2 -N-CH 3 ),2.32-2.45(m,8H,-N-CH 2 -CH 2 -N-),2.61-2.65(m,2H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-)。
(R/S)-N 4 Me 6 -EuI 2 The synthesis of (2): in glove box, (R/S) -N 4 Me 6 (71.0mg, 0.250mmol) and EuI 2 (101mg, 0.250mmol) were each dissolved in 20mL THF, and EuI was then added 2 Is slowly added dropwise to the (R/S) -N solution 4 Me 6 In THF solution to obtain a pale green clear solutionClear solution, continue to stir and separate out light green solid, emit blue light under 365nm excitation. Stirred at room temperature for 24h. After the reaction is finished, filtering to obtain the product. Yield 120mg, yield 70%. Calculated value of elemental analysis C 16 H 36 EuI 2 N 4 : c,27.84; h,5.26; n,8.12; found in elemental analysis C,27.97; h,5.30; and N,8.10.
(R/S) -N, N' -dimethyl-1, 2-cyclohexanebis (2- (diethylamino) -N-methylacetamide) ((R/S) -N 4 Me 2 Et 4 O 2 ) The synthesis of (2): will (R/S) -N 2 O 2 Me 2 Cl 2 (2.56g, 8.72mmol) was added to a solution of diethylamine in ethanol (33 wt%,86mL, 0.460mol) and stirred at room temperature for 2 days. After the reaction was complete, the solvent was pumped off, the solid was dissolved in 100mL DCM, washed 3 times with water (3X 100 mL), dried over potassium carbonate, filtered and the solvent was pumped off to give the product. Yield: 1.88g, yield: 59 percent. 1 H NMR(400MHz,DMSO):δ1.08(t,12H,-N-(CH 2 -CH 3 ) 2 ),1.10-1.21(m,4H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),1.48–1.80(m,4H,N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),2.65(m,8H,-N-(CH 2 -CH 3 ) 2 ),3.25(s,4H,-N-CO-CH 2 -),3.27(s,6H,CO-N-CH 3 ),4.16(m,2H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-)。
(R/S)-N 1 ,N 1 ' -dimethyl-1, 2-cyclohexanedibis (N) 2 ,N 2 -dimethyl-N 1 -methylpropane-1, 2-diamine ((R/S) -N) 4 Me 2 Et 4 ) The synthesis of (2): taking LiAlH in a glove box 4 (855mg, 22.5mmol) was slowly dispersed in 20mL of Tetrahydrofuran (THF), and then slowly added dropwise to a solution containing (R/S) -N 4 Me 2 Et 4 O 2 (1.66g, 4.50mmol) in 20mL THF in a 100mL round bottom flask. Taken out after sealing is completed, at N 2 And refluxing for 24 hours under protection. After the reaction, 2mL of water was used to quench the excess LiAlH 4 Filtering, and spin-drying the filtrate to obtain a crude product of a light yellow oil. 90 deg.CPurification by sublimation gave the product as a colorless oil. Yield: 756mg, yield: 49 percent. 1 H NMR(400MHz,DMSO):δ0.95(t,12H,-N-(CH 2 -CH 3 ) 2 ),1.10-1.26(m,4H,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),1.33-1.60(m,4H,N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-),2.24(s,6H,-N-CH 3 ),2.41-2.55(m,18H,-N-(CH 2 -CH 3 ) 2 ,-N-CH 2 -CH 2 -N-,-N-(CH-CH 2 -(CH 2 ) 2 -CH 2 -CH)-N-)。
(R/S)-N 4 Me 2 Et 4 -EuI 2 The synthesis of (2): in a glove box, (R/S) -N is taken 4 Me 2 Et 4 (85.0mg, 0.250mmol) and EuI 2 (101mg, 0.250mmol) were each dissolved in 20mL THF, and EuI was then added 2 Is slowly added dropwise to the (R/S) -N solution 4 Me 2 Et 4 The solution of (2) in THF to obtain a light green clear solution, and stirring is continued to separate out a light green solid which emits blue light under the excitation of 365 nm. Stirred at room temperature for 24h. After the reaction is finished, filtering to obtain the product. Yield 115mg, 62% yield. Calculated value of elemental analysis C 16 H 36 EuI 2 N 4 : c,32.18; h,5.94; n,7.51; the measured value of elemental analysis is C,32.00; h,5.77; and N,7.26.
And (3) photo-physical measurement: the UV-visible absorption spectrum was obtained using a UV-3100 spectrometer from Shimadzu, japan. Steady state/transient PL spectra were recorded on an edinburg analysis instrument FLS980 spectrophotometer (edinburg limited) equipped with a pulsed laser. The photoluminescence quantum yield (PLQY) of the crystalline powder was measured by an absolute PLQY measurement system on C9920-02 of Hamamatsu corporation.
And (3) thermal stability analysis: use of Q600SDT Instrument at fixed N 2 Thermogravimetric analysis was recorded at a ramp rate of 15 °/min from room temperature to 700 ℃.
Preparation and testing of OLEDs: indium Tin Oxide (ITO) anodes are commercially available with a sheet resistance of 14 Ω/gauge (Ω square) -1 ) The thickness is 80nm. In thatBefore preparation, the ITO substrate was cleaned with deionized water, acetone and ethanol. The organic and metal layers are deposited in separate vacuum chambers at a pressure of less than 1X 10 -4 Pa. The thickness of each layer and the evaporation rate of all materials were monitored using a quartz crystal monitor. For organic materials, the deposition rates are respectively maintained at
For the cathode, the deposition rate is maintained at
The effective area of each device is 4mm 2 . All electrical and optical measurements were performed under atmospheric ambient conditions and the devices were packaged in a glove box. EL spectra, current density-voltage-luminance (J-V-L) and EQE data were measured by a computer controlled Keithley 2400 source meter, absolute EQE measurement system (C9920-12) and photon multichannel Analyzer (PMA-12, hamamatsu Photonics).
Example 1 Structure of the Complex
By mixing EuI in methanol or tetrahydrofuran 2 And corresponding ligands, four complexes (R/S) -MeN are synthesized in a glove box 8 -EuI 2 And (R/S) -i-PrN 8 -EuI 2 The product was confirmed by elemental analysis. The coordination geometry was studied by single crystal X-ray diffraction (SCXRD) (see figure 2 of the specification). Compared with (R) -Men 8 -EuI 2 ，(R/S)-i-PrN 8 -EuI 2 The introduction of the middle isopropyl increases the steric hindrance, so that the average bond length of Eu-N bond is increased ((R) -Men) 8 -EuI 2 Average bond length of
(R)-i-PrN 8 -EuI 2 Has an average bond length of
). The bond length is increased so thatThe interaction force of the ligand and the central metal is reduced, namely the ligand field is weakened, the split of the 5d orbit of Eu (II) is reduced, and the 4f orbit is in the inner layer, so that the energy level is not interfered by the external ligand field. The energy difference for the electron to jump from the lowest energy level of the 5d orbital (LUMO) back to the 4f orbital (HOMO) increases, thereby blue-shifting the emission spectrum.
Example 2 photophysical Properties of the Complex
To systematically study chiral Eu 2+ The inventors determined the steady state spectrum, transient spectrum and circularly polarized emission spectrum of the complex by its photophysical properties. (R/S) -MeN 8 -EuI 2 The methanol solution of (A) shows orange-yellow emission with a maximum wavelength (. Lamda.) max ) 587nm. The Eu-N bond length is increased due to the steric hindrance effect of the isopropyl group when the methyl group is changed into the isopropyl group, and the (R/S) -i-PrN 8 -EuI 2 λ of max Is 560nm. The excited state lifetime of these complexes is one thousand or more nanoseconds (table 1). The full width at half maximum (FWHM) of these complexes in solid powders is relatively narrow (only 51nm at the narrowest) compared to luminescent materials characterized by a Charge Transfer (CT) mechanism. The excitation bandwidths of these complexes are uncharacterized and range from 230nm to 500nm (EuX) 2 -N 8 And EuX 2 -N 8 M 6 ) And 230nm-600nm (EuX) 2 -N 4 ) In the meantime. According to the above photo-physical studies, and considering that the ligand in the complex system is a saturated organic compound having an extremely high energy level, the possibility of ligand-metal charge transfer (LMCT) is excluded. Thus, the excitation and emission process can be regarded as Eu 2+ Electron transition in an ion in which the ground state is 4f 7 [ 8 S 7/2 ]Excited state of 4f 6 [ 7 F 0 ]5s 1 。
The ultraviolet visible spectrum shows (R/S) -Men 8 -EuI 2 And (R/S) -i-PrN 8 -EuI 2 Having a high energy absorption (. Epsilon.) at 250nm>1000L·mol -1 ·cm -1 ) And low energy absorption peaks at 413 and 404nm (epsilon =747L mol) -1 cm -1 ,(R/S-MeN 8 -EuI 2 ) And ε =771L mol -1 cm -1 ，(R/S)-i-PrN 8 -EuI 2 ) Consistent with their excitation bands. Due to f-The d-transition is Laporte and spin allowed, and the molar absorption will be larger.
TABLE 1 summary of photophysical properties of four europium-emitting complexes 1
1 R/S is two materials with different chirality, and their luminescence properties are identical except the chirality direction.
The inventors tested the luminescent properties of the four complex doped films by Circular Dichroism (CD) and circular polarization spectroscopy (CPL). All four complexes were doped in m-MTDATA (doping concentration 10 wt%). Their CD spectra show a clear mirror symmetry. This strong Cotton effect, which can be attributed to the d-f transition, indicates that the introduced chiral group successfully introduces chirality into the Eu (II) center. An almost symmetric emission spectrum is also observed from the CPL spectrum. The light-emitting asymmetric factors of the four complexes are respectively as follows: 4.6X 10 -3 ((R)-MeN 8 -EuI 2 ),-5.7×10 -3 ((S)-MeN 8 -EuI 2 ),6.4×10 -3 ((R)-i-PrN 8 -EuI 2 ) and-5.6X 10 -3 ((S)-i-PrN 8 -EuI 2 ) Further confirming the chiral nature of the excited state.
(R/S)-N 4 Me 4 -EuI 2 The crystal powder emits bright sky blue light under the excitation of 365nm ultraviolet light, and the maximum emission wavelength of the crystal powder is at 488 nm; in contrast, (R/S) -N 4 Me 6 -EuI 2 The emission spectrum of the crystal powder under the excitation of ultraviolet light generates blue shift, and the maximum emission wavelength is 481nm; (R/S) -N 4 Me 2 Et 4 -EuI 2 Further blue-shifted to a maximum peak of 465nm, a deep blue emission with CIE of (0.13, 0.08) is exhibited. Corresponding to (R/S) -N 4 Me 4 -EuI 2 ，(R/S)-N 4 Me 6 -EuI 2 ，(R/S)-N 4 Me 2 Et 4 -EuI 2 The excited state life of the three complex powders is 584ns and 665ns respectively,724ns, which is consistent with previous literature reports on excited state lifetimes of D-f transition Eu (II) complexes, PLQY is 46%,93%,97%, respectively. The experimentally measured emission peak width (32-35 nm) and excited state lifetime as short as several hundred nanoseconds indicate that the emission process is likely to be the excited state (4 f) of central Eu (II) with Laporte allowance 6 5d 1 ) And the ground state (4 f) 7 ) 5d-4f transitions in between.
From (R/S) -N 4 Me 4 -EuI 2 ，(R/S)-N 4 Me 6 -EuI 2 To (R/S) -N 4 Me 2 Et 4 -EuI 2 The emission spectrum of the complex is in turn blue-shifted. This is associated with the susceptibility of the Eu (II) complex 5d orbital to ligand field effects. With reference to the crystal structure, from N 4 Me 4 -EuI 2 To N 4 Me 6 -EuI 2 The introduction of methyl increases steric hindrance, so that Eu (II) has small surrounding space and can not accommodate one molecule of THF coordination, the coordination number is reduced from 7 to 6, the ligand field is finally weakened, the split of the 5d orbital is reduced, the energy level of the lowest orbital of the 5d orbital (namely LUMO of the ligand) is increased, and finally, the energy gap (E) of the electron which is transited from the lowest energy level of the 5d orbital to the ground state (namely HOMO) is increased g ) Becomes larger and the light emission is blue shifted. From N 4 Me 6 -EuI 2 To N 4 Me 2 Et 4 -EuI 2 The increase of the alkyl chain enables the Eu-N bond and the Eu-I bond to have longer lengths, the acting force of the ligand on the 5d orbit is reduced, the ligand field is weakened, the 5d orbit split is also reduced, and the luminescence blue shift is achieved.
EXAMPLE 3 thermal and air stability of the Complex
The thermal stability of the four compounds was investigated by thermogravimetric analysis (TGA). (R/S) -MeN 8 -EuI 2 And (R/S) -i-PrN 8 -EuI 2 (T d Corresponding to a 5% weight loss) were 410 deg.c, 415 deg.c and 415 deg.c, respectively. The residual weight percentage of these compounds at 550 ℃ is not changed and should theoretically be the mass percentage of the metal halide relative to the total mass, since the decomposition process is temporarily due to the breaking of coordination bonds and volatilization of the organic ligands.
Then at 10 -5 These compounds were tested for sublimation characteristics under high vacuum at Pa and gradient heating. Discovery of (R/S) -Men 8 -EuI 2 And (R/S) -i-PrN 8 -EuI 2 Complete sublimation in the small range of 50mg was possible around 300 ℃ and 320 ℃ (test tube temperature, different from sample temperature). It is noteworthy that significant decomposition occurs in the bulk sublimation, which may be due to uneven heating in the sublimation boat.
EXAMPLE 4 electroluminescent device
Photophysics according to example 2 and stability study of example 3, euX 2 -N 8 The complexes are good candidates for luminescent materials for OLEDs. Due to the lack of experience with Eu (II) complex devices for OLEDs, efforts are made to optimize the device structure. First, select (R/S) -Men 8 -EuI 2 Device optimization, including screening of host materials in subsequent examples, finding the best combination of Hole Transport Layer (HTL) and Electron Transport Layer (ETL), adjusting the emissive layer thickness, and then further following the optimization conditions, adjusting (R/S) -Men 8 -EuI 2 Doping concentration of the device and thickness of the emitting layer, material used.
The OLED structure obtained by final optimization is ITO/MoO 3 (2 nm)/4, 4' -cyclohexylbis [ N, N-bis (4-methylphenyl) aniline](TAPC,50nm)/(R/S)-MeN 8 -EuI 2 Or (R/S) -i-PrN 8 -EuI 2 4,4' -tris [ phenyl (m-tolyl) amino group]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 most preferred (R/S) -Men 8 -EuI 2 The device has a light-on voltage (V) of 4.7V on )，23000cd·m -2 Maximum luminance (L) max )，56.9cd·A -1 Maximum Current Efficiency (CE) max ) And excellent performance up to an EQE of 15.6%. (R/S) -i-PrN 8 -EuI 2 The device as a luminescent material is represented by V on ，L max ，CE max And EQE are respectively 4.5V, 19000cd.m -2 、41.0cd·A -1 And 10.0%. The device results of the embodiment of the invention can be compared with most mainstream OLEDs (phosphorescent metal complexes or TADF molecules as luminescent materials)And (5) beautifying.
By testing the spectrums of the circular polarization electroluminescence of the four complex devices, the electroluminescence asymmetry factors are respectively as follows: 3.9X 10 -3 ((R)-MeN 8 -EuI 2 ),-3.7×10 -3 ((S)-MeN 8 -EuI 2 ),3.1×10 -3 ((R)-i-PrN 8 -EuI 2 ) and-2.6X 10 -3 ((S)-i-PrN 8 -EuI 2 ). Due to the fact that the asymmetric factor is high, the device is expected to replace a traditional physical optical filter method in the field of 3D display light sources, and the purposes of simplifying the structure of the device and increasing the brightness of the device are achieved while circularly polarized light is obtained.
EXAMPLE 10 electroluminescent device-solution method for preparing OLED
In view of EuX 2 -N 4 And EuX 2 -N 8 M 6 The europium complex series has poor thermal stability, and the OLED device adopting the compound as a light-emitting layer is prepared by a solution method in the embodiment, and the structure of the device is ITO/PEDOT: PSS (20 nm)/EuX 2 -N 4 Or EuX 2 -N 8 M 6 (20 nm)/TPBi (60 nm)/LiF (0.7 nm)/Al (100 nm). The device performance results are shown in table 2. Although the performance of these devices is not good at present, it is expected that the performance of the devices will be significantly improved when the film forming process is improved and the appropriate charge transport material and host material are selected.
TABLE 2 EuX-based solution Process preparation 2 -N n And EuX 2 -N 8 M 6 Device parameters of light-emitting OLEDs
The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An electroluminescent material, characterized in that the electroluminescent material comprises a complex (R/S) -RN 8 -EuI 2 It has the following structure:
alternatively, the electroluminescent material comprises a complex EuX 2 -N 4 It has the following structure:
alternatively, the electroluminescent material comprises a complex EuX 2 -cycloN 4 It has the following structure:
wherein X is a negative valence ionRadicals, e.g. F, cl, br, I, OCN, SCN, CN, CF 3 SO 3 、BF 4 Or PF 6 R is independently selected from H and C 1 -C 18 The compound is an alkyl, halogen-substituted alkyl, halogen atom, aryl, halogen-substituted aryl, alkyl-substituted aryl, O, N, S heteroaryl, alkyl containing coordination sites of O, N and S, M is Eu (II), ce (III), yb (II), sm (II) and other metal ions with d-f transition luminescence, and the position of "+" is provided with at least one chiral site; preferably, all "+" sites are chiral sites; .
2. The electroluminescent material of claim 1, wherein the luminescent material comprises (a) (R/S) -MeN 8 -EuI 2 ，(b)(R/S)-i-PrN 8 -EuI 2 ，(c)(R/S)-MeN 8 -Ce(OTf) 3 ，(d)(R/S)-N 4 Me 4 -EuI 2 ，(e)(R/S)-N 4 Me 6 -EuI 2 ，(f)(R/S)-N 4 Me 2 Et 4 -EuI 2 ，(g)(R/S)-MeN 4 -EuI 2 ，(h)(R/S)-cyclohexN 4 -EuI 2 The corresponding structural formula of the complex is shown as follows:
3. an electroluminescent device comprising a cathode, an anode, and a light-emitting layer between the cathode and the anode, wherein the light-emitting layer comprises an electroluminescent material as claimed in claim 1 or 2.
4. An electroluminescent device according to claim 3, characterized in that the light-emitting layer is a mixture of a guest material and a host material, wherein the guest material comprises an electroluminescent material according to claim 1 or 2, and the host material comprises m-MTDATA, mCP, mCBP, czSi, DCPPO, PCzAc, CBP, TCTA, TAPC, DPEPO, mCPCN, BCPO, with a doping concentration of 1wt% to 99wt%, preferably 7wt% to 10wt%, most preferably 10wt%, the doping concentration being the mass of guest material as a percentage of the total mass of guest material and host material.
5. An electroluminescent device according to claim 3 or 4, characterized in that the electroluminescent device further comprises an electron transport layer between the cathode and the light-emitting layer, the electron transport layer comprising TmPyPB, DPEPO, TSPO1, bphen and/or TPBi.
6. An electroluminescent device according to claim 3 or 4, characterized in that it 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.
7. An electroluminescent device according to claim 5 or 6, characterized in that it 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;
preferably, the hole transport layer comprises TAPC and the electron transport layer comprises Bphen.
8. An electroluminescent device according to any of claims 3 to 7, characterized in that the thickness of the light-emitting layer is 10-40nm, preferably 15-30nm, preferably 20-25nm, most preferably 25nm.
9. The electroluminescent device of claim 5, further comprising a hole blocking layer between the light-emitting layer and the electron transport layer; preferably, the material of the hole blocking layer is TSPO1;
preferably, the electroluminescent device further comprises a second hole transport layer located between the anode and the hole transport layer; preferably, the material of the second hole transport layer is NPB.
10. An electroluminescent device as claimed in claim 3, characterized in that the electroluminescent device has the structure: ITO/MoO 3 (2 nm)/4, 4' -Cyclohexylbis [ N, N-bis (4-methylphenyl) aniline](TAPC,50nm)/(R/S)-MeN 8 -EuI 2 Or (R/S) -i-PrN 8 -EuI 2 4,4' -tris [ phenyl (m-tolyl) amino group]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).
Priority Applications (1)
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