Abstract
The proton-ligand dissociation constants of 4-(1H-indol-3-yl)butanoic acid and the stability constants of its metal-ligand complexes with (Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and UO22+) have been determined potentiometrically in 0.1 mol . dm(-3) (KCl) and 10% (by volume) ethanol-water mixture and at (298, 308, and 318) K. The order of the stability constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Cu2+, and UO22+. The effect of temperature was studied, and the corresponding thermodynamic parameters (Delta G, Delta H, and Delta S) were derived and are discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic, and entropically favorable.