Ilmi Rashid, Yin Jiaxuan, Dutra José D L, Al Rasbi Nawal K, Oliveira Willyan F, Zhou Liang, Wong Wai-Yeung, Raithby Paul R, Khan Muhammad S
Department of Chemistry, Sultan Qaboos University, P. O. Box 36, Al Khod 123, Oman.
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, People's Republic of China.
Dalton Trans. 2022 Sep 26;51(37):14228-14242. doi: 10.1039/d2dt01873j.
Two new organo-europium complexes (OEuCs) [Eu(tfac)(TB-Im)] (Eu1) [Eu(hfac)(TB-Im)] (Eu2) incorporating fluorinated (hexafluoroacetylacetone; Hhfaa) or hemi-fluorinated (trifluoroacetylacetone; Htfac) β-diketones together with the large bite angle N^N ligand (2-(4-thiazolyl)benzimidazole; TB-Im) have been synthesized and characterized. The structure of the complexes has been established by single crystal X-ray diffraction (SC-XRD) analysis and shows that the coordination sphere is composed of a EuON core (octacoordinated). Continuous shape measures (CShMs) revealed that the geometry around Eu(III) is trigonal dodecahedral with approximate -symmetry. Efficient red emission is observed for both the complexes in solution with a fairly large photoluminescence quantum yield (PLQY (LEu) = 39.00-47.00%). Furthermore, by utilizing the experimental photoluminescence (PL) data and theoretical modelling employing density functional theory (DFT) in conjunction with LUMPAC, energy transfer (ET) and back energy transfer rates were calculated, and an ET mechanism for the sensitized PL is proposed and discussed in detail. Finally, the complexes were used as an emitting layer (EML) to fabricate 20 organic light emitting diodes (OLEDs) by varying the doping concentration. Interestingly, both the complex-based OLEDs at 4 wt% doping concentration display white electroluminescence (EL) with the brightness () = 100.5-364.1 cd m at very low turn-on voltage () = 3.9-4.6 V. The overall electroluminescence performance of Eu1 and Eu2 is higher than that of the reported europium based single component white-OLEDs.
合成并表征了两种新型有机铕配合物（OEuC）[Eu(tfac)(TB-Im)]（Eu1）和[Eu(hfac)(TB-Im)]（Eu2），它们分别包含氟化（六氟乙酰丙酮；Hhfaa）或半氟化（三氟乙酰丙酮；Htfac）的β-二酮以及大咬角N^N配体（2-(4-噻唑基)苯并咪唑；TB-Im）。通过单晶X射线衍射（SC-XRD）分析确定了配合物的结构，结果表明其配位球由一个EuON核心（八配位）组成。连续形状测量（CShM）显示，Eu(III)周围的几何形状为具有近似 - 对称性的三角十二面体。两种配合物在溶液中均观察到高效的红色发射，且具有相当高的光致发光量子产率（PLQY(LEu) = 39.00 - 47.00%）。此外，利用实验光致发光（PL）数据以及结合LUMPAC采用密度泛函理论（DFT）的理论建模，计算了能量转移（ET）和反向能量转移速率，并详细提出并讨论了敏化PL的ET机制。最后，通过改变掺杂浓度，将这些配合物用作发光层（EML）来制备20个有机发光二极管（OLED）。有趣的是，两种掺杂浓度为4 wt%的基于配合物的OLED在非常低的开启电压（= 3.9 - 4.6 V）下均显示出白色电致发光（EL），亮度（）= 100.5 - 364.1 cd m 。Eu1和Eu2的整体电致发光性能高于已报道的基于铕的单组分白色OLED。
