THERMODYNAMIC AND VOLTAMMETRIC STUDIES OF SALICYLALDEHYDE-4-(2-PYRIDYL)-3-THIOSEMICARBAZONE

UV spectra, de polarograms, cyclic voltammetry and coulometry measurem ents of salicylaldehyde-4-(2-pyridyl)-3-thiosemicarbazone (H2SPT) were recorded in Britton-Robinson buffer solutions of pH 2-12. The dissoci ation constants of H2SPT evaluated spectrophotometrically and potentio metrically in a 5% (v/v) DMF-water mixture are concordant. The dc-pola rograms in solutions of pH < 8.5 exhibit a single 4-electron diffusion -controlled polarographic wave, whereas in solutions of pH > 8.5 two w aves are observed. The cyclic voltammograms give a single cathodic pea k in acidic and neutral solutions, whereas two cathodic peaks can be i dentified in alkaline ones. An electrode mechanism is proposed and dis cussed. The effect of temperature on the dissociation constants and th e polarographic data was also investigated; the corresponding thermody namic parameters were derived and are discussed.