Superior electron-transport ability of π-conjugated redox molecular wires prepared by the stepwise coordination method on a surface

Electronic conductivity of molecular wires is a critical fundamental issue in molecular electronics. π-Conjugated redox molecular wires with the superior long-range electron-transport ability could be constructed on a gold surface through the stepwise ligand-metal coordination method. The β^d value, indicating the degree of decrease in the electron-transfer rate constant with distance along the molecular wire between the electrode and the redox active species at the terminal of the wire, were 0.008-0.07 Å^-1 and 0.002-0.004 Å^-1 for molecular wires of bis(terpyridine)iron and bis(terpyridi-ne)cobalt complex oligomers, respec- tively. The influences on β^d by the chemical structure of molecular wires and the terminal redox units, temperature, electric field, and electrolyte concentration were clarified. The results indicate that facile sequential electron hopping between neighboring metalcomplex units within the wire is responsible for the high electron-transport ability.