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 1:1 complexes were determined from the molar conductance-mole ratio data and found to vary in the order Zn2+ < Co2+ < Ni2+ < Cu2+ < Cd2+ < Pb2+. 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 T Delta S vs. Delta 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.