Theoretical surface-enhanced Raman spectra study of substituted benzenes. II. Density functional theoretical SERS modelling of o-, m-, and p-methoxybenzonitrile

The SERS modelling of o-, m-, and p-methoxybenzonitrile has been performed following the same methodology that in Part I. Optimized structure obtained from DFT calculations in a B3LYP-LANL2DZ level of calculation shows different tilted positions for the isomers under study. From correlations obtained by comparison of Raman and SERS spectra concerning geometrical parameters, frequency shifting, change in band intensity, and force constants is possible to give insight about the different effect of the metal surface on these molecules and the structural reasons of this behaviour. Frontier orbital analysis gives further information and reveals a ligand to metal charge transfer mechanism for all isomers, as well as its relative importance.