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-benzamidorhodanin e 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 in crease with decreasing temperature, ionic strength, dielectric constan t of the medium and by increasing the electron repelling property of t he substituent. The thermodynamic parameters (Delta G, Delta H and Del ta S) for complexation are evaluated and discussed. The formation of t he complexes has been found to be spontaneous, exothermic and entropic ally favourable.