Thermodynamic relationships of complex formation: Part II. Enthalpy-entropy interdependence in hard-hard interactions in aqueous solution

Abstract

Thermodynamic data for hard-hard interactions in stepwise complex formation in aqueous solution between UO 2(II), Th(IV) or tervalent cations and carboxylate ligands are inspected for the occurrence of enthalpy-entropy relationships. Such relationships are found in the first complexation of UO 2(II) and in all the stepwise complex formations between Ln(III) (Ln = lanthanide) and acetate, propionate, isobutyrate, lactate, or α-hydroxyiso-butyrate. Weaker correlations occur in the Th(IV) complex formation and in the Ln(III)-glycolate systems. The enthalpy-entropy susceptibilities are different for the various complexation reactions.