The adsorption conformation of chemisorbed pyridine on the Cu(110) surface

Abstract

The adsorption conformation of pyridine on the Cu(110) surface has been studied using temperature programmed desorption, low energy electron diffraction, and electron stimulated desorption ion angular distribution techniques. Pyridine adsorbs on Cu(110) via the nitrogen lone pair orbital. The molecular symmetry axis is perpendicular to the surface. At low coverage, the aromatic ring plane of adsorbed pyridine is oriented parallel to the 〈001〉 plane, which is perpendicular to the close-packed copper atom rows on Cu(110). At high coverage, the aromatic ring plane of pyridine is azimuthally rotated by 25 (±5)° away from the 〈001〉 direction as a result of an attractive contribution from nonparallel aromatic ring–aromatic ring interactions superimposed on the overall repulsive adsorbate–adsorbate interactions. The zero coverage desorption activation energy of pyridine on Cu(110) is 0.97 eV and the repulsive adsorbate–adsorbate interaction energy is 0.16 eV/monolayer. At near saturation coverage, (5×3) and (4×3) long-range ordered structures were observed. It is proposed that the adsorbed pyridine on the Cu(110) surface forms a chain structure of nonparallel normally-oriented pyridine rings arranged in a chevron pattern at monolayer saturation coverage.