Measurement and analysis of formation constants of europium with carboxylates

Formation constants of a trivalent f-element, europium, with a series of carboxylates containing neutral donors such as amine and alcohol oxygen were determined by solvent extraction method in 0.1 M NaClO4 at 25degC. Thirteen carboxylates were adopted for a systematic study of the effect of the functional groups on the complex stabilization. In order to analyze the trend of formation constants, a simple model was developed in which these ligand molecules were considered as composed of a certain number of fragment components of functional groups and chemical bridges each of which differently contributes to the formation constant. All parameter values for electrostatic and steric effects of the fragments were successfully determined by using the formation constants obtained experimentally. The present model is useful for predicting the formation constants of similar multidentate ligands by combining the fragment components and parameter values. (author)