State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
Phys Chem Chem Phys. 2009 Nov 14;11(42):9687-95. doi: 10.1039/b912243e.
In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10]phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'-c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions. The larger secondary ligands DPPz, MDPz, DDPz and BDPz lead to incomplete energy transfer from the triplet states of ligands to the (5)D(0) of the Eu(3+) ion compared with smaller ones (PyPhen and MPP) due to their lower S(1) or T(1) state energy levels than that of TTA or (5)D(0) of Eu(3+). "Small polaron" stabilization energy (SPE) results reveal that electron trapping is the dominant electroluminescence (EL) mechanism in these materials due to their lower LUMO energies than 4,4'-N,N'-dicarbazolebiphenyl (CBP). Reorganization energy (l) values show that these materials have better electron than hole transporting properties. In addition, the reasons for the origin of the 500 nm emission in Eu-PyPhen- and Eu-MPP-based OLED devices were investigated, and we suppose this emission may result from 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), not from Alq(3).
本文采用量子化学方法研究了不同取代位的菲咯啉对一系列 Eu(TTA)(3)L（L=[1,10]菲咯啉（Phen）、吡嗪并[2,3-f][1,10]菲咯啉（PyPhen）、2-甲基吡嗪并[2,3-f][1,10]菲咯啉（MPP）、二吡啶并[3,2-a:2',3'-c]吩嗪（DPPz）、11-甲基二吡啶并[3,2-a:2',3'-c]吩嗪（MDPz）、11,12-二甲基二吡啶并[3,2-a:2',3'-c]吩嗪（DDPz）和苯并[i]二吡啶并[3,2-a:2',3'-c]吩嗪（BDPz））配合物的吸收、能量转移和电致发光性能的影响。吸收光谱计算表明，不同大小的辅助配体对跃迁性质、强度和吸收峰位置有不同的影响。较大的辅助配体 DPPz、MDPz、DDPz 和 BDPz 由于其 S(1)或 T(1)态能级低于 TTA 或 Eu(3+)的 (5)D(0)，导致配体三重态到 Eu(3+)的 (5)D(0)的能量转移不完全，而较小的辅助配体（PyPhen 和 MPP）则导致能量转移不完全。“小极化子”稳定能（SPE）结果表明，由于这些材料的 LUMO 能量低于 4,4'-二咔唑联苯（CBP），电子俘获是这些材料主导的电致发光（EL）机制。重组能（l）值表明，这些材料具有更好的电子输运性能，而非空穴输运性能。此外，还研究了 Eu-PyPhen-和 Eu-MPP 基 OLED 器件中 500nm 发射的起源原因，我们推测该发射可能来自 2,9-二甲基-4,7-二苯基-1,10-菲咯啉（BCP），而不是来自 Alq(3)。
