A spectroelectrochemical study of the electrosorption of 4-isopropylsulfanylmethyl-1,2,3-triazole on gold

The electrosorption of 4-isopropylsulfanylmethyl-1,2,3-triazole (ISMT) on a polycrystalline gold electrode has been studied with cyclic voltammetry and surface enhanced Raman spectroscopy (SERS). Vibrational wavenumbers were calculated for the conceivable tautomers with density function theory (DFT) at the B3LYP level using the 6-31G* basis set. The data obtained from vibrational frequency calculations are used to assign vibrational bands obtained in infrared and Raman spectroscopy as well as in surface enhanced Raman spectroscopy of the molecule adsorbed on a roughened gold electrode surface. Results imply a gold–sulfur interaction with ISMT adsorbed intact (i.e. without C–S bond cleavage) onto the gold surface from neutral solution. Beyond a gold–sulfur stretching mode, this suggestion is supported by significantly enhanced internal modes of the methyl groups in the isopropyl substituent and an almost complete lack of shift of band positions of the triazole ring itself being expected in case of a gold–nitrogen interaction. With an acidic electrolyte solution, a gold–sulfur vibrational mode typical of a thiolate-like adsorbate is found, this indicates dissociative adsorption.