Ballistic Conductance through Porphyrin Nanoribbons

Abstract

High Resolution Image Download MS PowerPoint Slide The search for long molecular wires that can transport charge with maximum efficiency over many nanometers has driven molecular electronics since its inception. Single-molecule conductance normally decays with length and is typically far below the theoretical limit of G 0 (77.5 μS). Here, we measure the conductances of a family of edge-fused porphyrin ribbons (lengths 1–7 nm) that display remarkable behavior. The low-bias conductance is high across the whole series. Charging the molecules in situ results in a dramatic realignment of the frontier orbitals, increasing the conductance to 1 G 0 (corresponding to a current of 20 μA). This behavior is most pronounced in the longer molecules due to their smaller HOMO–LUMO gaps. The conductance-voltage traces frequently exhibit peaks at zero bias, showing that a molecular energy level is in resonance with the Fermi level. This work lays the foundations for long, perfectly transmissive, molecular wires with technological potential.