“Janus-type” Ruthenium Complex Bearing Both Phosphonic Acids and Pyrene Groups for Functionalization of ITO and HOPG Surfaces

Abstract A novel Janus-type ruthenium complex bearing both phosphonic acid and pyrene groups was tethered to both ITO and HOPG surfaces in different tethering modes. On the ITO surface, the phosphonic groups were selectively attached to the ITO, resulting in the hydrophobic surface because of the exposed pyrene groups on the top. On the other hand, on the HOPG surface, pyrene groups interacted with the HOPG surface through noncovalent interaction, resulting in a hydrophilic surface exposing phosphonic acid groups. This selectivity makes it possible to fabricate redox-active ruthenium complex and graphene composite by layer-by-layer growth of molecular units.