Structural aspects of the low-temperature deprotonation of benzoic acid on Cu(110) surfaces

Exposure of Cu(110) at 90 K to a sub-monolayer amount of benzoic acid gives rise to both benzoate and undissociated acid species. Low coverage STM shows the diffusion and re-arrangement of molecules on the edge of clusters, while higher coverage images show one-dimensional dimeric features, assigned to benzoic acid dimers, growing anisotropically in the 〈001〉 direction. At higher temperature, a different dimer chain along the (± 4, 3) directions can be observed. From temperature-dependent FTIR, the deprotonation of the flat-lying species takes place between 120 and 170 K. Further annealing shows crystallization at 183 K, which results in the periodic α-phase. In contrast, for the multilayer surface, the desorption of multilayer starts at 200 K and results in all molecules being upright in the c(8 × 2) structure.