High Molecular Conductance\nand Inverted Conductance\nDecay over 3 nm in Aminium-Terminated Carbon-Bridged Oligophenylene-Vinylenes

With the progressing miniaturization of electronic device\ncomponents\nto improve circuit density while retaining or even reducing spatial\nrequirements, single molecules employed as electric components define\nthe lower limit of accessible structural width. To circumvent the\ntypical exponential conductance decay for increasing length in molecule-based\nwires, topological states, which describe the occurrence of discontinuities\nof a bulk material’s electronic structure confined to its surface,\ncan be realized for molecules by the introduction of unpaired spins\nat the molecular termini. The resulting high conductance and reversed\nconductance decay are typically only observed for shorter molecules,\nas the terminal spins must be within the electronic coupling range\nto produce the desired effects. We expand the realm of long and exceptionally\nconductive molecular wires by employing highly conjugated, planarized\ncarbon-bridged oligo­(phenylene-vinylene)­s as conduits between readily\noxidizable diarylamine termini. This yields molecular wires of already\ndecent conductance values and small conductance decay in the neutral\nstate. Upon the introduction of topological states, the conductance\ncan be increased by a factor of up to 1800 for a 3 nm long molecule,\nand the conductance decay becomes inverted, together with an excellent\nsignal intensity at concentrations as low as 0.01 mM.