ORDERED OVERLAYERS OF ANILINE AND PHENOL ON PD(110) - SURFACE-STRUCTURE AND BONDING

The surface structure and bonding of aniline and phenol on Pd(110) has been studied by angle resolved UV photoemission (ARUPS) using synchrotron radiation, LEED, and thermal desorption spectroscopy (TDS). Both molecules form ordered c(4 × 2) surface structures on Pd(110), and ARUPS and TDS results suggest that aniline and phenol split off an H atom from the functional group to form C6H5NH and C6H5O species in the monolayer phases. The molecules coordinate to the surface via the it electrons of the aromatic rings and via the heteroatoms as indicated by the stabilisation of the π states and of the N or O lone pair electrons in the ARUPS spectra; thus they adopt an adsorption geometry with the ring plane in close proximity to the metal surface. The results do not, however, rule out some tilting of the molecules which would be expected from steric considerations. There is preferential azimuthal orientation in the densely packed adlayers of the monolayer phases, and the molecules align with their functional groups along the [001] azimuth. © 1990.