Complexation thermodynamics and the structure of the binary and the ternary complexes of Am3+, Cm3+ and Eu3+ with IDA and EDTA + IDA

The stability and the associated thermodynamic parameters of the binary and the ternary complexes of trivalent Am, Cm, and Eu with IDA and with EDTA + IDA, were determined by using a solvent extraction technique for aqueous solutions of I = 6.60 m (NaClO4) at temperatures of 0–60 °C. The endothermic enthalpy and the positive entropy reflect the significant effect of dehydration in the formation of these complexes at high ionic strength. TRLFS and NMR (1H and 13C) data helped to establish the structure of the ternary complexes in solution. In the ternary complex M(EDTA)(IDA)3−, EDTA binds via four carboxylates and two nitrogens, and IDA via two carboxylates and one nitrogen to the central Eu3+.