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

Abstract

Abstract:The electrochemical behavior of some sulpha drug-Schiff 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, diffusion-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 coefficient (α) of the electrode reaction and the diffusion coefficient (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.