Synthesis and Surface Assembly of Ruthenium Bipyridine Complexes

Disulfide-functionalized bipyridine and the corresponding thiol derivative were prepared starting from xanthogenate-functionalized bipyridine. The reduction of the xanthogenate by hydrazine led to the formation of a mixture of thiol and disulfide-functionalized bipyridines that could be separated by size exclusion chromatography. The chelating properties of the bipyridine units were used to prepare fluorescent heteroleptic ruthenium complexes, whereas the thiol or disulfide group on the other end of the molecule was used to anchor the individual ligands as well as the formed complexes to solid substrates. Scanning tunnelling microscopy was used to visualize the assembly of these species on a flat gold(111) substrate.