Substituent effect on structure and surface activity of N-methylpyridinium salts studied by FT-IR, FT-RS, SERS and DFT calculations

The substituent effect on structure and surface activity of mono- and disubstituted N-methylpyridinium salts was investigated by means of Raman, infrared and surface-enhanced Raman spectroscopy (SERS). The signi fi cant differences observed in Raman and infrared spectra have been correlated with marker bands assigned to in-plane and out-of-plane vibrations, respectively. This vibrational analysis, complemented by quantum chemical calculations (B3LYP/6-311++G(d,p)) was a basis for investigation of the surface activity of the studied compounds. Signi fi cant differences in their SERS spectra related to the enhancement mechanism and adsorbate orientation have been observed and analyzed.