Benzothiazole- and Benzoxazole-Substituted Pyridine-2-Carboxylates as Efficient Sensitizers of Europium Luminescence
详细信息 查看全文
- 作者：Nail M. Shavaleev ; Rosario Scopelliti ; Frdric Gumy ; Jean-Claude G. Bnzli
- 刊名：Inorganic Chemistry
- 出版年：2009
- 出版时间：July 6, 2009
- 年：2009
- 卷：48
- 期：13
- 页码：6178-6191
- 全文大小：1019K
- 年卷期：v.48,no.13(July 6, 2009)
- ISSN：1520-510X
文摘
A facile synthesis of benzothiazole- and benzoxazole-substituted pyridine-2-carboxylic acids has been developed. These ligands form mononuclear nine-coordinate complexes [Ln(κ3-ligand)2(κ1-ligand)(H2O)2] with light and heavy trivalent lanthanides, as established from the X-ray analysis of 11 complexes. A crystal structure of a minor product, the anhydrous nine-coordinate complex [Eu(κ3-L)3], has also been determined. Photophysical studies of gadolinium chelates indicate that the triplet states of the new ligands are located at 20400−21400 cm−1. The ligands are good sensitizers of the europium luminescence with ligand-to-metal energy transfer efficiency in the range 60−100%. The overall quantum yields of the europium emission are substantial, 12−14% in the solid state, and increase to 29−39% upon replacement of two metal-coordinated water molecules with dimethylsulfoxide in solution. The luminescence of near-infrared emitting lanthanides is also sensitized, but quantum yields are much smaller, reaching 0.17% for neodymium and 1.25% for ytterbium in DMSO, while energy transfer efficiencies for these two ions are below 50%.