Two-Dimensional Hierarchical Supramolecular Assembly of a Silole Derivative and Surface-Assisted Chemical Transformations

The bonding and organization of 1,1,2,3,4,5-hexaphenysilole (HPS) molecules adsorbed on Cu(111) and Ag(111) surfaces has been investigated using low-temperature scanning tunneling microscopy and X-ray photoelectron spectroscopy. In room-temperature-prepared samples, HPS molecules form extended networks that exhibit hierarchical organization stabilized by π–π interaction between exocyclic phenyl groups. After 430 K annealing on Cu(111), the compound is chemically altered as evidenced by Si 2p core level shift. This change is accompanied by a different adsorption configuration and a transformation of the assembled structures from networks to uniformly sized chiral clusters. The clusters, each composed of three molecules, are dispersively distributed on the surface. Monte Carlo simulations signal that this new phase can be understood as a result of competing long-range repulsions and short-range attractions. After even higher annealing at 520 K, the clusters dissolve and the exocyclic phenyl moieties undergo...