CHARGE-TRANSFER IN SERS - SPECTRA OF 3,5-DIMETHYLPYRIDINE AT A SILVERELECTRODE

The SERS spectra of 3,5-dimethylpyridine recorded at different electro de potentials were analysed. Their most characteristic feature is the enhancement of the band assigned to mode 8a as the electrode potential becomes more negative. This behaviour is different to that observed i n the SERS spectra of pyridine where all four modes 6a, 1, 9a and 8a a re enhanced in spite of the fact that both molecules belong to the sam e molecular point group. These differences were explained on the basis of a resonant charge transfer mechanism (CT). The band assigned to th e fundamental nu(s)(CH3) was used to estimate the electromagnetic mech anism contributions to SERS intensities, which allowed the direct corr elation of the theoretical SERS-CT intensities calculated on the basis of Peticolas' equation with experimental results. (C) 1998 John Wiley & Sons, Ltd.