作者:B.S Santos、C de Mello Donegá、G.F de Sá、L.F.C de Oliveira、P.S Santos
DOI:10.1016/s1386-1425(98)00143-7
日期:1998.11
Complexes of Eu3+, Gd3+, and Tb3+ with tropolone (tropolone = 2-hydroxy-2,4,6-cycloheptatrien-1-one) were synthesized and characterized by C and H elemental analysis, infrared vibrational spectroscopy, X-ray powder diffraction analysis and Raman vibrational spectroscopy. The results show that the complexes are isostructural and have the formula [Ln(trop)(3)], where Ln = Eu3+, Gd3+ or Tb3+ and trop = tropolone. The characteristic luminescence of the Eu3+ and Tb3+ ions was not observed either upon ligand excitation (300-380nm) or upon direct f-f excitation, not even at 4.2 K. In order to understand this phenomenon the spectroscopic properties of the Gd(trop)(3) complex (absorption spectra at 298 K, excitation and emission spectra from 4.2 to 298 K and decay time measurements from 20 to 298 K) were investigated. The emission spectra show three distinct bands, which are ascribed to ligand electronic states: a singlet state, S-1 (pi-pi*), at 24270 cm(-1), and two triplet states, T-1 and T-2, at 15630 cm(-1) and 16610 cm(-1), respectively. Both triplet states are situated below the emitting states of the Eu3+ and Tb3+ ions (D-5(o) and D-5(4), respectively), thus suppressing the luminescence from these states by back-transfer. (C) 1998 Elsevier Science B.V. All rights reserved.