Physico-chemical Studies on the Complexes

Azosulfonamide rhodanines are widely used as analytical reagents. They are capable of forming chelates with many of metal ions. The formed chelates are distinguished by their stability due to the formation of chelate ring. From the structural point of view, these were considered as metal indicators since they posses functional groups capable of chelate formation joined directly to the central metal ions.In the present investigation, proton-ligand stability constant, pKH, of azosulfonamide rhodanine compounds will be determined potentiometrically in 20% (v/v) DMF-water mixture. The metal-ligand stability constantsof the compounds with Fe2+, Cd2+, Fe3+,UO2 2+ and Zr4+ will be determined potentiometrically. Stoichiometeries of the complexes formed in solution will be determined potentiometrically. The enthalpy change, the entorpy change, and the free energy change, of the compounds and their complexes will be evaluated and discussed. The structure of these chelates will be elucidated from the study of their elementalanalyses, infrared spectra, 1H-NMR spectrum, electronic spectra, magnetic measurements and ESR.