THERMODYNAMIC RELATIONSHIPS OF COMPLEX-FORMATION .2. ENTHALPY ENTROPY INTERDEPENDENCE IN HARD HARD INTERACTIONS IN AQUEOUS-SOLUTION

Thermodynamic data for hard-hard interactions in stepwise complex formation in aqueous solution between UO2(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 UO2(II) and in all the stepwise complex formations between Ln(III) (Ln = lanthanide) and acetate, propionate, isobutyrate, lactate, or alpha-hydroxyisobutyrate. 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.