Switching the Conductance of a Single Molecule by Photoinduced Hydrogen Transfer

A new mechanism for optical switching of nanoscale single-molecule junctions between different conductance
states is proposed. The mechanism is based on photoinduced excited state hydrogen transfer in the molecular
bridge. Employing first principles electronic structure and transport calculations for prototype examples it is shown that the keto and enol tautomeric forms of the molecular bridge exhibit very different conductance
properties, which realize the ‘on’ and ‘off’ states of the molecular switch. The feasibility and robustness of
the mechanism is analyzed in some detail.