Synchrotron far-infrared RAIRS studies of complex molecules on Cu(110)

Synchrotron Far-IR RAIRS data for atomic O and a range of complex oxygen-containing molecular species on Cu(110) and Cu(100) surfaces are presented. For the latter group of adsorbates, it can be seen that instrument upgrades have enabled the monitoring of low intensity bands with high resolution. Atomic oxygen adsorbed in the long-bridge position in the (2×1) reconstructed phase on Cu(110) gives rise to a νCu–O stretching vibration at 389 cm−1. The adsorption of the diketones, methylacetoacetate and acetylacetone, on Cu(110) yields a pure νCu–O vibration at ∼300 cm−1 for the νCu–OC unit of a delocalised keto-enol chelate. The monotartrate form of (R,R)-tartaric acid adsorbed via its carboxylate group on Cu(110) shows a νCu–O stretching vibration at 378 cm−1. This is almost identical to the νCu–O stretching frequency of formate adsorbed via its carboxylate unit at Cu(100) and Cu(110) surfaces. For formate, the high resolution of the IR technique has enabled the asymmetry of the absorption band to be detected, suggesting the presence of heterogeneity in the adlayer. Finally, even with this limited data set, the νCu–O stretching frequency seems to be a very sensitive indicator of bonding mode, with the atomic species, the OCO unit and the OCCCO unit, giving rise to frequencies in defined regions of the spectrum.