Atomic-Scale Evidence of Surface-Catalyzed Gold-Carbon Covalent Bonding

Surface-confined self-assembly and metal-ligand coordination is a versatile method for creating and tuning the properties of low-dimensional nanostructures. Here we study the interaction between gold (Au) atoms and dicyanoanthracene (DCA) molecules adsorbed on Ag(111), characterized at 5 K by means of scanning tunneling microscopy (STM) and spectroscopy (STS), and atomic force microscopies (ncAFM). We observed a crystalline two-dimensional self-assembly consisting of close-packed DCA-Au-DCA units, in which a single Au atom binds covalently to a carbon atom at the anthracene ends. This conclusion is based on submolecular resolution ncAFM imaging achieved with a carbon monoxide (CO) functionalized tip probe, combined with atomic-scale STM manipulation of the DCA-Au-DCA units. The formation of such covalently bonded organometallic units indicates a selective on-surface reaction with a relatively low activation barrier which could be exploited to synthesize future functional nanomaterials.