Adsorption of some benzohydroxamic acid derivatives on copper oxide: assignment and interpretation of SERS spectra

The general aim of this work is to obtain information about the adsorption geometry of several benzohydroxamic acid (BHA) derivatives deposited on copper oxide. The investigation is done by means of surface enhanced Raman spectroscopy (SERS). In order to interpret the experimental information, an assignment of the SERS spectra is carried out. The process of assignment is supported by theoretical spectra derived from quantum‐chemical calculations. As the size of the molecules and the overall lack of symmetry of the adsorbate‐substrate system hinder the transparent description of the molecular vibrations, the local symmetry of the benzene is used as a basic classification feature. Such an approach is justified because, according to the theoretical spectra, the vibrations typical for the free benzene ring are conserved in the studied molecules. The deformations of the substituent and hydroxamic groups are added as a secondary descriptive element. On the basis of the spectrum assignment, the common vibrations typical for all investigated compounds and those used for identification that are pertinent to each of them, are classified. The surface selection rule is then qualitatively applied in order to derive information about the adsorption geometry. Copyright © 2006 John Wiley & Sons, Ltd.