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Thermodynamics and the structural aspects of the ternary complexes of Am(III), Cm(III) and Eu(III) with Ox and EDTA + Ox.

Thakur P, Mathur JN, Dodge CJ, Francis AJ, Choppin GR

Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.

The stability constants and the associated thermodynamic parameters of formation of the binary and the ternary complexes of Am(3+), Cm(3+) and Eu(3+) were determined by a solvent extraction to measure the variation in the distribution coefficient with temperature (0-60 degrees C) for aqueous solutions of I = 6.60 m (NaClO(4)). The formation of ternary complexes is favored by both the enthalpy (exothermic) and the entropy (endothermic) values. (13) C NMR, TRLFS and EXAFS spectral data was used to study the coordination modes of the ternary complexes. In the formation of the complex M(EDTA)(Ox)(3-), the EDTA retained all its coordination sites with Ox binding via two carboxylates and with one water of hydration remaining attached to the M(3+). In the complex M(EDTA)(Ox)(2)(5-), one carboxylate, either from EDTA or Ox, is not bounded to M(3+) and there were no water of hydration attached to these cations.

Published 11 October 2006 in Dalton Trans.
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