Study of Complex Formation between 5,7-Diiodo-8-hydroxyquinoline and Zn2+, Cd2+, Pb2+and Tl+Cations in Binary Non-Aqueous Solvents Using Square Wave Polarography Technique (SWP)

The complexation reaction between Zn 2+ , Pb 2+ , Cd 2+ and T 1+ cations by 5,7-diiodo-8-hydroxyquinoline (IQN) was studied in the Dimethylformamide /Acetonitril (DMF-AN) binary system using square wave polarography technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-wave or peak potential of the polarographic waves of metal ions against the ligand concentration. The stoichiometry of the complexes was found to be 1:1. The results obtained show that there is an inverse relationship between the formation constant of the complexes and the donor number of solvent base on the Guttmann donocity scale. In all cases the formation constants increased with increasing amounts of AN in these binary systems. The selectivity order for IQN complexes with the cations is Zn 2+ > Pb 2+ > Cd 2+ > T1 + .