Investigation on bonding interaction of benzonitrile with silver nano particles probed by surface enhanced Raman scattering and quantum chemical calculations

The Raman spectra of benzonitrile (Bz) in silver colloidal solution have been recorded at different millimolar concentrations of benzonitrile in the spectral range, 400-2300 cm-1 and the spectral parameters of prominent bands in the region are discussed as a function of concentration. The binding interactions between the benzonitrile and one/two silver atom complexes, [Bz + 1(2)Ag]0 and [Bz + 1(2)Ag]+1 have been investigated using DFT calculations at B3LYP level employing three basis sets, Lanl2DZ, SDD and CEP-31G. The Bz molecule seems to be adsorbed in end-on orientation. The binding energy of [Bz + 2Ag]0 complex is greater than that of [Bz + 1Ag]0 complex. Some bands of benzonitrile show red shift upon surface coordination while some are blue shifted. The red shift in ν(C≡N) vibrational mode is discussed in terms of shortening of C-CN bond due to metal-adsorbate back donation