resumo
New lanthanide complexes of 2-hydroxynicotinic acid (H(2)nicO) [Ln(HnicO)(2)(mu-HnicO)(H2O)] (.) nH(2)O (Ln = Eu, Gd, Tb, Er, Tm) were prepared. The crystal structures of the [Tb(HnicO)(2)(g-HnicO)(H2O)] (.) 1.75H(2)O(1) and [Eu(HniCO)(2)(mu-HnicO)(H2O)] (.) 1.25H(2)O (2) complexes were determined by X-ray diffraction. The 2-hydroxynicotinate ligand coordinates through O,O-chelation to the lanthanide(III) ions as shown by X-ray diffraction and the infrared, Raman and NMR spectroscopy results. Photoluminescence measurements were performed for the Eu(III) and Tb(III) complexes. Lifetimes of 0.592 +/- 0.007 and 0.113 +/- 0.002 ms were determined for the Eu3+ and Tb3+ emitting states D-5(0) and D-5(4), respectively. A value around 30% was found for the D-5(0) quantum efficiency. The energy transfer mechanisms between the lanthanide ions and the ligands are discussed and compared with those observed in similar complexes involving the 3-hydroxypicolinate ligand based on the luminescence of the respective Gd3+-based complexes. (C) 2003 Published by Elsevier Ltd.
palavras-chave
TRANSITION-METAL COMPLEXES; EMISSION QUANTUM YIELDS; PYRIDINECARBOXYLIC ACIDS; 3-HYDROXYPICOLINIC ACID; SPECTROSCOPIC PROPERTIES; SOLUTION EQUILIBRIA; COORDINATION MODES; ENERGY-TRANSFER; NICOTINIC-ACID; ALUMINUM(III)
categoria
Chemistry; Crystallography
autores
Soares-Santos, PCR; Nogueira, HIS; Rocha, J; Felix, V; Drew, MGB; Ferreira, RAS; Carlos, LD; Trindade, T
nossos autores
Helena Isabel Seguro Nogueira
Professor Auxiliar com Agregação
João Rocha
Prof. Catedrático
Luís Carlos
Professor Catedrático
Maria Rute de Amorim e Sá Ferreira André
Professor Catedrático
Paula Cristina Ramos Soares e Santos
Técnico de Laboratório
Tito Trindade
Professor Catedrático