Fourier transform Raman and surface‐enhanced Raman spectroscopy of some quinoline derivatives

Fourier transform (FT) Raman and surface‐enhanced Raman spectroscopy (SERS) were applied to the vibrational characterization of isoquinoline and 4‐methylquinoline. The assignment of the vibrational modes was carried out on the basis of results obtained from density functional theory calculations. The comparison of SER spectra with the FT‐Raman spectra reveals remarkable changes attributed to the chemical interaction between the molecules and the silver substrate. The SER spectra of the adsorbed molecules depend strongly on the pH conditions. Variation in SER spectra with change of pH is attributed to a change in orientation of the absorbed isoquinoline molecules with respect to the silver surface and to a change in the chemical nature of the 4‐methylquinoline molecules.