title: Surface-enhanced Raman scattering of picolinamide, nicotinamide, and isonicotinamide: unusual carboxamide deprotonation under adsorption on silver nanoparticles.
abstract: Surface-Enhanced Raman Scattering (SERS) of picolinamide, nicotinamide, and isonicotinamide has been studied on silver colloids at pH⩾7. The wavenumbers of the SERS bands assigned to 1; νring and ν(C-X) vibrational modes show important blue-shifts (ca. +50cm(-1)) with respect to the Raman spectra, whereas the Amide III bands undergo red-shifts up to -50cm(-1). We demonstrate that these shifts are originated by the deprotonation of the carboxamide groups which link to the metal through the nitrogen and oxygen atoms of the respective azanion groups. In order to support this conclusion, theoretical DFT force field calculations have been carried out, confirming that the pyridinecarboxamides interact with the metallic surface in their deprotonated forms as benzamide does.
authors: Department of Physical Chemistry, Faculty of Science, University of Málaga, Málaga, Spain. jcastro@uma.es
authors: Jose L
authors: JL
authors: Castro
authors: Juan F
authors: JF
authors: Arenas
authors: Maria R
authors: MR
authors: Lopez-Ramirez
authors: Juan
authors: J
authors: Soto
authors: Juan C
authors: JC
authors: Otero
mesh_terms: D000327:Adsorption; D000577:Amides / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009536:Niacinamide / Q000737:chemistry*; D010848:Picolinic Acids / Q000737:chemistry*; D011522:Protons; D012834:Silver; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D000577:Amides; D003102:Colloids; D010848:Picolinic Acids; D011522:Protons; D009536:Niacinamide; D012834:Silver; C027681:isonicotinamide; C003142:picolinamide