Conductance study of some transition and heavy metal complexes with 1,10-diaza-18-crown-6 in binary acetonitrile-dimethylsulfoxide mixtures

A conductance study of the interaction between cobalt, nickel, copper, zinc, cadmium, and lead ions with 1,10-diaza-18-crown-6 in different acetonitrile-dimethylsulfoxide mixtures has been carried out at various temperatures. The formation constants of the resulting 11 complexes were determined from the molar conductance-mole ratio data and found to vary in the order Zn²⁺2+2+2+2+2+. The enthalpy and entropy of complexation reactions were determined from the temperature dependence of the formation constants. A linear relationship is observed between the log K_f of different complexes and mole fraction of acetonitrile in the solvent mixtures. The TS vs. H plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of an enthalpy-entropy compensation in the complexation reactions.