Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

摘要

The electrochemical behavior of some sulpha drug-Schif bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values(2.5-11.7)containing 20% (v/v)of ethanol using DC-polarography,cyclic voltammetry and controlled-potential electrolysis.The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single,2-electron, irreversible,di?usion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N-to-CH_2-NH-.The symmetry transfer coeffcient(alpha)of the electrode reaction and the diffusion coeffcient(D_0)of the reactant species were determined.The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence:H~+,e~-,e~-,H~+.The dissociation constant of the sulpha drug-Schiff bases,the stability constant and stoichiometry of their complexes with various divalent transition metal ions(Mn~(2+),Co~(2+), Ni~(2+),Cu~(2+) and Zn~(2+))were determined potentiometrically at room temperature.