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

UV spectra, de polarograms, cyclic voltammetry and coulometry measurements of salicylaldehyde-4-(2-pyridyl)-3-thiosemicarbazone (H2SPT) were recorded in Britton-Robinson buffer solutions of pH 2-12. The dissociation constants of H2SPT evaluated spectrophotometrically and potentiometrically in a 5\% (v/v) DMF-water mixture are concordant. The dc-polarograms in solutions of pH < 8.5 exhibit a single 4-electron diffusion-controlled polarographic wave, whereas in solutions of pH > 8.5 two waves are observed. The cyclic voltammograms give a single cathodic peak in acidic and neutral solutions, whereas two cathodic peaks can be identified in alkaline ones. An electrode mechanism is proposed and discussed. The effect of temperature on the dissociation constants and the polarographic data was also investigated; the corresponding thermodynamic parameters were derived and are discussed.