Surface-enhanced Raman scattering of zinc tetrakis(4-N-methylpyridyl)porphyrin

The surface‐enhanced Raman spectra of zinc tetrakis(4‐N‐methylpyridyl)porphyrin in silver sol using various excitation wavelengths are reported. On the basis of comparison of the patterns of the relative enhancement between SERS and normal Raman bands and using previous theoretical calculations, this molecule is found to be anchored on the silver surface with ‘flat‐on’ geometry. Generally, out‐of‐plane porphyrin and pyridyl modes are relatively strongly enhanced relative to the in‐plane porphyrin skeletal modes in SERS as compared with normal Raman spectra. The mode assignment for this molecule was attempted based on the enhancement pattern of Raman modes depending on the geometry of the adsorbed molecule and the mode character. The selective enhancement of some modes would be helpful in the vibrational mode assignments of porphyrins having peripheral phenyl groups.