NEXAFS studies of halobenzenes and phenyl groups on Cu(111)

The orientations of halobenzenes (C6H5Cl and C6H5I) and phenyl (C6H5) groups adsorbed on a Cu(111) surface have been studied by the near edge X-ray absorption fine structure (NEXAFS) method. For near-monolayer coverages, both chlorobenzene (C6H5Cl) and iodobenzene (C6H5I) bond with the plane of their aromatic π-rings tilted away from the surface plane by 45 ± 5°. Phenyl groups, generated by thermal dissociation of iodobenzene on the surface at T > 180 K, bond with their π-rings tilted away from the surface plane by an average angle of 43 ± 5° at near-saturation coverages. This geometry is analogous to the η1 structure found for pyridine adsorption on metal surfaces.