Thermodynamics of substituted rhodanine III: Potentiometric and spectrophotometric studies of complexes of some transition metals with 3-phenylsulfonamidorhodanine

摘要

The dissociation constants of 3-phenylsulfonamidorhodanine (PSR) were determined potentiometrically in 0.1 M KCI and 20% (v/v) ethanol-water. The stepwise stability constants of the complexes of Mn2+, Co2+, Ni2+, Cu2+, Zn2+, La3+, Ce3+, Gd3+, UO22+ and Th4+ with PSR were determined. The stabilities of the complexes were found as follows: Th4+ > UO22+ > Gd3+ > Ce3+ > La3+ > Mn2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The thermodynamic parameters for PSR and its complexes were evaluated and discussed. The dissociation process is non-spontaneous, endothermic, and entropically unfavourable. The formation of the complexes was found to be spontaneous, exothermic or endothermic (depending on the metal), and entropically favourable. The stoichiometries of the complexes were determined spectrophotometrically and indicate the formation of 1:1 and 1:2 (metal:ligand) complexes. [References: 22]