Vibrational spectroscopic studies on the dyes cresyl violet and coumarin 152

Infrared, Raman and SERS spectra of two cationic dyes-cresyl violet perchlorate and coumarin 152-were measured. Density function theory calculations were performed in order to support the vibrational spectra assignment. The data obtained indicate that cresyl violet is weakly physisorbed on the silver surface. The molecule is attached to the metal in a "vertical" configuration with its molecular plane perpendicular to the surface. Both amino groups of the molecule are in proximity to the metal surface. Coumarin 152 interacts with the silver surface through the carbonyl group. The C=O bond is weakened by the adsorption. The interaction with the metal also influences the adjacent double bonds in the lactone ring. Coumarin 152 is bonded to silver in a "vertical" configuration with its molecular plane perpendicular to the surface as well. (C) 2000 Elsevier Science B.V. All rights reserved.