Characterization and spectroscopic studies of Eu3+ and Tb3+ complexes with 2,2′-bipyridine-4,4′-dicarboxylic acid

This work reports on the synthesis of the ligand 2,2'-bipyridine-4,4'-dicarboxylic acid (bpc), the characterization and photophysical properties of Ln(2)(bpc)(3).nH(2)O (Ln=Eu,Tb,Gd). The compounds were synthesized by the addition of LnCl(3) aqueous solution to an aqueous ligand (bpc) solution (pH similar to7.0). The characteristic transitions D-5(0) --> F-7(J) (J = 0, 1, 2, 3 and 4) of the Eu3+ and D-5(4) --> F-7(J) (J=6, 5, 4 and 3) of Tb3+ were observed. The lifetime measurements of the D-5(0) and D-5(4) excited levels (0.37 and 0.90+/-0.01 ms) are in agreement with three to four coordinated water molecules. The monoexponential decay curves reveal only one type of site for each ion in the complexes. The complexes were also characterized by thermogravimetric analyses and infrared spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.