SPECTROSCOPIC STUDY OF THE ISOMERIZATION OF Z-PYRIDINE-2-FORMYL TO E-PYRIDINE-2-FORMYL THIOSEMICARBAZONE

Pyridine-2-formyl thiosemicarbazone (PATS2) was synthesized in the E ( anti) and Z (syn) configurations. Raman spectra were obtained in the s olid state, and in DMSO and aqueous solutions. The SER spectra of PATS 2 adsorbed on a silver electrode in DMSO and in aqueous solutions show ing striking differences. The comparison of Raman data revealed that P ATS2 is present on the silver electrode surface in the same configurat ion as the predominant isomer of the corresponding parent solutions. T he prevalence of the E (anti) isomer in DMSO solutions was confirmed b y Raman and H-1 NMR spectroscopies, and by means of the latter techniq ue, the anti configuration is also proved to be predominant in aqueous solutions of different pHs, even starting with Z-PATS2 solutions. A s trong interaction of E-PATS2 with water molecules by hydrogen bonding accounts for marked differences in Raman spectra of this isomer in DMS O and water solutions, and for the corresponding E-PATS2 species adsor bed on the silver electrode surface.