Chemical Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, California 94720, USA.
Inorg Chem. 2009 Oct 5;48(19):9316-24. doi: 10.1021/ic901161z.
The efficiency of Eu(3+) luminescence by energy transfer from an antenna ligand can be strongly dependent on the metal ion coordination geometry. The geometric component of the Eu(III) sensitization has been probed using series of tetradentate 1,2-HOPO derivatives that are connected by bridges of varying length and geometry. The ligands are N,N'-(1,2-phenylene)bis(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamide) for the ligand (L(1)), 1-hydroxy-N-(2-(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamido)benzyl)-6-oxo-1,6-dihydropyridine-2-carboxamide (L(2)) and N,N'-(1,2-phenylenebis(methylene))bis(1-hydroxy-6-oxo-1,6-dihydropyridine-2-carboxamide) (L(3)). Spectroscopic characterization of both the Gd(III) and the Eu(III) metal complexes, time-dependent density functional theory (TD-DFT) analysis of model compounds and evaluation of the kinetic parameters for the europium emission were completed. Some striking differences were observed in the luminescence quantum yield by altering the bridging unit. The Eu(L(2))(2) derivative shows efficient sensitization coupled with good metal centered emission. For Eu(L(3))(2), the large quenching of the luminescence quantum yield compared to Eu(L(2))(2) is primarily a result of one inner sphere water molecule bound to the europium cation while for Eu(L(1))(2), the low luminescence quantum yield can be attributed to inefficient sensitization of the europium ion.
从天线配体向金属离子转移能量的 Eu(3+) 荧光效率可以强烈依赖于金属离子的配位几何形状。通过一系列具有不同长度和几何形状桥接的四齿 1,2-HOPO 衍生物，探测了 Eu(III)敏化的几何成分。配体为 N,N'-(1,2-亚苯基)双(1-羟基-6-氧代-1,6-二氢吡啶-2-甲酰胺)(配体 L(1))、1-羟基-N-(2-(1-羟基-6-氧代-1,6-二氢吡啶-2-甲酰胺基)苄基)-6-氧代-1,6-二氢吡啶-2-甲酰胺(L(2))和 N,N'-(1,2-亚苯基双(亚甲基))双(1-羟基-6-氧代-1,6-二氢吡啶-2-甲酰胺)(L(3))。完成了 Gd(III)和 Eu(III)金属配合物的光谱特性、模型化合物的时间依赖密度泛函理论(TD-DFT)分析以及铕发射的动力学参数评估。通过改变桥接单元，观察到了在荧光量子产率方面的一些显著差异。Eu(L(2))(2)衍生物表现出高效的敏化作用，同时具有良好的金属中心发射。对于Eu(L(3))(2)，与Eu(L(2))(2)相比，荧光量子产率的大量猝灭主要是由于一个内球水分子与铕阳离子结合，而对于Eu(L(1))(2)，荧光量子产率低可归因于铕离子的敏化效率低下。
