Switching on the dipole: A new principle for the self-assembly of asymmetric monomers on metal surfaces

COLL 215

Owain P. H. Vaughan, ophv2@cam.ac.uk, Ali Alavi, Federico J. Williams, and Richard M. Lambert. Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
Self-assembly offers unique possibilities for the construction of nanometer scale structures on surfaces. Previously, by means of non-covalent interactions (primarily hydrogen bonding and metal coordination) a diverse range of two-dimensional assemblies have been fabricated, from isolated rows to extended networks. Here, by means of STM, we report the discovery of self-assembled discrete tetramers of styrene and styrene derivatives on the Ag(100) surface. Chirality defects, whose probability depends on monomer structure, can occur during tetramer growth leading to the formation of more complex structures. The phenomenon appears to be unprecedented and is due to metal-mediated coupling of the molecular p electron systems, an effect for which a general theoretical explanation is provided. This points the way to the ab initio design of finite self-assembled systems based on monomers that lack inversion symmetry.