THERMODYNAMICS OF SUBSTITUTED RHODANINE-II - BINARY COMPLEXES OF TH(IV), UO2(II), CE(III), AND LA(III) WITH 3-BENZAMIDORHODANINE AND ITS DERIVATIVES

Th(IV), UO2(II), Ce(III) and La(III) chelates with 3-benzamidorhodanine and its derivatives have been investigated potentiometrically in 0.1 M KCl and 20% (v/v) ethanol-water medium. The stability of the formed complexes increases in the order Th(IV) > UO2(II) > Ce(III) > La(III). For the same metal ion, the stability of the chelates is found to increase with decreasing temperature, ionic strength, dielectric constant of the medium and by increasing the electron repelling property of the substituent. The thermodynamic parameters (Delta G, Delta H and Delta S) for complexation are evaluated and discussed. The formation of the complexes has been found to be spontaneous, exothermic and entropically favourable.