ABSTRACT
We found that anthraquinone diffuses along a straight line across a flat, highly symmetric Cu111 surface. It can also reversibly attach one or two CO2 molecules as "cargo" and act as a "molecule carrier," thereby transforming the diffusive behavior of the CO2 molecules from isotropic to linear. Density functional theory calculations indicated a substrate-mediated attraction of approximately 0.12 electron volt (eV). Scanning tunneling microscopy revealed individual steps of the molecular complex on its diffusion pathway, with increases of approximately 0.03 and approximately 0.02 eV in the diffusion barrier upon attachment of the first and second CO2 molecule, respectively.
ABSTRACT
Para-halosubstituted thiophenols (X-TPs, where X is Br, Cl, or F) form ordered islands and monolayers on Cu(111) at temperatures as low as 81 K. At incomplete coverages, all X-TPs adsorb with the dehydrogenated thiol group attached to the substrate and the substituted ring inclined toward the surface, as verified experimentally and theoretically. The structure of ordered islands has a pronounced dependence on the nature of the halogen substituent: while unsubstituted TP and pentafluoro-TP molecules do not self-assemble into extended ordered patterns at 81 K, X-TP molecules form a range of different structures which depend both on the size and electronegativity of the substituent, as well as on the coverage.
