Thermodynamic Study of Complexation of (2-Mercapto-4-Methyl Phenyl)-2-Benzamido-3-Ethoxy Thiopropenate with Cu2+, Co2+, and Hg2+in Binary Dimethylsulphoxide–Acetonitrile Solutions

The complexation of a newly synthesized mercapto compound, (2-mercapto-4-methyl phenyl)-2-benzamido-3-ethoxy thiopropenate, with Co 2+ , Cu 2+ , and Hg 2+ have been studied in binary dimethylsulphoxide-acetonitrile (DMSO-AN) mixtures at different temperatures by a conductometric technique. Stoichiometry and stability of the resulting complexes were evaluated by KINFIT program and from molar conductivity-mol ratio (ligand to metal) data were found to vary in the sequence Co 2+ > Cu 2+ > Hg 2+ . In all cases, evidence for the formation of both 1:1 and 2: 1 (ligand to metal) complexes were obtained. The stability of these complexes increases with decreasing temperature. The enthalpy and entropy of complexation were determined from the temperature dependence of the formation constants. In all cases, the complexes were found to be enthalpy and entropy stabilized. Furthermore, in all of the complexes which were studied, not only an increase in the percentage of dimethylsulfoxide in DMSO-AN solvents mixtures would drastically decrease the stability of the resulting complexes, but also enthalpy and entropy would be more positive and negative respectively (decrease of stability).