Abstract
The proton-ligand dissociation constant and metal-ligand stability constants of 7-sulfamerazine-azo-5-chloro-8-hydroxyquinoline (H2L) with some transition metal ions were calculated. The stability constants of the complexes with divalent transition metal ions such as Mn2+, Co2+, Ni2+ and Cu2+ are determined potentiometrically in 0.1 M KCl containing 40% (v/v) ethanol-water mixture. The order of the stability constants of the complexes was found to be Mn2+ < Co2+ < Ni2+ < Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters such as free energy change (DeltaG), enthalpy change (DeltaH) and entropy change (DeltaS) were determined and discussed. The dissociation process of the ligand was found to be non-spontaneous, endothermic and entropically unfavourable. The formation of the metal-ligand complexes has been found to be spontaneous, endothermic and entropically favourable at higher temperatures.