Current-voltage characteristics of tunneling molecular junctions for off-resonance injection

An analytical expression is obtained for the I-V curves for a tight-binding model of a molecule-metal junction for off-resonance injection. The derivation takes into account a self-consistent determination of the voltage that leads to a spatial pattern where the voltage drop occurs at the molecule-wire interface. The relevance of this model for electron transfer reactions and molecular conductance is assessed. It leads to a striking power law dependence of the current on the voltage, while preserving the exponential length dependence of either the conductance or the reaction rate.