INTRAMOLECULAR ENERGY-TRANSFER MECHANISM BETWEEN LIGANDS IN TERNARY RARE-EARTH COMPLEXES WITH AROMATIC CARBOXYLIC-ACIDS AND 1,10-PHENANTHROLINE

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with aromatic acids and 1,10-phenanthroline have been synthesized. The lowe st triplet state energies of ligands have been obtained by measuring t he phosphorescence spectra of binary gadolinium complexes. By comparin g the phosphorescence spectra of binary complexes with those of ternar y ones, it is found that there exists another intramolecular energy tr ansfer process from the aromatic acids to 1,10-phenanthroline besides the intramolecular energy transfer process between the aromatic acids and the central rare earth ions. The intramolecular energy transfer ef ficiencies have been calculated by determining phosphorescence lifetim es of binary and ternary gadolinium complexes. The luminescence proper ties of corresponding europium and terbium complexes are in agreement with the prediction based on energy transfer mechanism. (C) 1998 Elsev ier Science S.A. All rights reserved.