Surface-enhanced Raman spectroscopic studies of 2-mercaptobenzoxazole on silver sols

Surface-enhanced Raman spectra of 2-mercaptobenzoxazole (MBO) adsorbed on silver hydrosol were obtained. From the comparison of the SER and normal Raman spectra, both in the solid state and in NaOH solution, it can be deduced that the molecule is dissociatively adsorbed on the silver sol. The similarity between SER and normal Raman spectra of the corresponding silver complex is diagnostic of chemisorption of MBO on the metal surface. The SERS data were interpreted with the help of the results of RHF ab initio calculations both of the MBO anion, in which the 6-31 + G** basis set was used, and of the corresponding silver complex AgMBO, performed with the LANL2DZ basis set. On the basis of the description provided by the potential energy distribution of the vibrational normal modes related to the most enhanced bands in the SER spectra, it can be deduced that MBO interacts with the silver sol via the lone pairs of the sulphur and of the nitrogen atoms and, to some extent, also through the ring-pi system, assuming a tilted orientation with respect to the metal surface. Copyright (C) 2001 John Wiley & Sons, Ltd.