LUMINESCENCE STUDY OF EUROPIUM(III) COMPLEXES WITH SEVERAL DICARBOXYLIC-ACIDS IN AQUEOUS-SOLUTION

Luminescence lifetimes of Eu(III) in complexes with dicarboxylate ligands and N, O or S donors have been measured in H2O and D2O solutions of varying pH and europium-ligand ratio. The ligands were iminodiacetate (IDA), diglycolate (DGA), thiodiglycolate (TDA), dipicolinate (DPA), benzene-1, 2-bis(oxyacetate) (BDODA), ethylenediaminediacetate (EDDA) and ethylene-1, 2-dithiodiacetate (EDTDA). The lifetimes have been used to measure the number of water molecules coordinated to the Eu(III) ion in each complex. The results show that in the 1:1 and 1:2 complexes the ligands: IDA, DGA and DPA are tridentate whereas the TDA complexes are bidentate. BDODA and EDDA form tetradentate 1:1 and bidentate 1:2 complexes, while EDTDA is bidentate in both the 1:1 and 1:2 complexes. These results indicate that the nitrogen and oxygen donors are bonded to lanthanide ions in the DGA, IDA, DPA and EDDA complexes, whereas the sulfur donors are not bonded in the TDA and EDTDA complexes.