Site-Specific Assembly Of Fullerene Nanorings Guided By Two-Dimensional Gold Clusters

Molecules can self-assemble rather easily into straight one-dimensional wires-via covalent or noncovalent bonding. To organize molecules into cyclic structures such as rings or loops where the number of molecules forming each structure is accurately controlled is a much more challenging task. Here we demonstrate the construction of fullerene nanorings on the (111) plane of gold using single-atomic layer-high gold islands as the seeding agent. C-60 molecules are trapped by the step edges of the seeding Au island leading to the formation of molecular rings. The smallest ring consists of six C-60 molecules encircling 19 Au atoms. Scanning tunneling microscopy imaging reveals that the rings are formed at specific locations on the reconstructed Au(111) surface with the diameter of the ring controlled by the size of the gold island. Molecular mechanics modeling provides a detailed understanding of the relationship between the number of molecules in the ring and the number of gold atoms within the Au island.