Long-Range Electron Transport of Ruthenium-Centered Multilayer Films <i>via</i> a Stepping-Stone Mechanism

We studied electron transport of Ru complex multilayer films, whose structure resembles redox-active complex films known in the literature to have long-range electron transport abilities. Hydrogen bond formation in terms of pH control was used to induce spontaneous growth of a Ru complex multilayer. We made a cross-check between electrochemical measurements and <i>I–V</i> measurements using PEDOT:PSS to eliminate the risk of pinhole contributions to the mechanism and have found small β values of 0.012–0.021 Å^–1. Our Ru complex layers exhibit long-range electron transport but with low conductance. On the basis of the results of our theoretical–experimental collaboration, we propose a modified tunneling mechanism named the “stepping-stone mechanism”, where the alignment of site potentials forms a narrow band around <i>E</i>_F, making resonant tunneling possible. Our observations may support Tuccito <i>et al</i>.’s proposed mechanism