The bonding of acetonitrile and CH2CN on Ag(110) determined by near edge x-ray absorption fine structure: Evidence for π-donor bonding and azimuthal ordering
Abstract
Carbon K edge near edge x-ray absorption fine structure (NEXAFS) spectra of adsorbed acetonitrile and reactive intermediates derived therefrom on Ag(110) were studied in order to determine their orientation and bonding to the surface. For both the multilayer and the adsorbed monolayer there is excellent agreement between the spectra of the adsorbed acetonitrile and the gas phase species. For the multilayer coverage the orientation of the acetonitrile molecules is not completely random; the molecules prefer an orientation with their bond axes closer to parallel than perpendicular to the surface. At monolayer coverage acetonitrile bound to the surface is unrehybridized. It is bound with its linear molecular skeleton parallel to the surface and randomly oriented azimuthally. Annealing molecular CH3CN to 325 K in the presence of coadsorbed atomic oxygen produces a linear CH2CN surface intermediate, the molecular axis of which is parallel to the surface and perpendicular to the close-packed direction. The C-C and C-N bond lengths are essentially unperturbed from their values in gas phase CH3CN. Bonding appears to occur between the methylene carbon and the metal, as expected. A broadening of the π* resonance for transition into the π* orbital perpendicular to the surface is interpreted in terms of π-donor bonding. © 1989 American Institute of Physics.