One-dimensional self-assembled molecular chains on Cu(100): Interplay between surface-assisted coordination chemistry and substrate commensurability

The surface-assisted self-assembly of one-dimensional chains using linear, rigid bipyridyl molecules of different lengths on the Cu(100) surface is presented. The chains are assembled from a stable 2-fold coordination of the terminal pyridyl groups of the molecules with Cu adatoms which diffuse from the substrate step edges. This type of interaction is selective and reversible, allowing for effective self-assembly. We observe several partially dynamic aspects of chain growth which highlight critical considerations for growth of the present system as well as other molecular nanostructures on solid substrates. The steric and electronic templating of the metal substrate leads to strictly one-dimensional bonding geometries and unusually low (2-fold) coordination. The epitaxial relation of the molecular structure with the substrate lattice has profound effects on the growth kinetics and stability of the structures. Additionally, the substrate-mediated interactions influence the stability and structure over longer ranges than can be influenced by bonding interactions, manifested here as specific interchain distances at high molecule coverages.