  Redox molecular junctions are molecular conduction junctions that involve
more than one oxidation state of the molecular bridge. This property is derived
from the ability of the molecule to transiently localize transmitting
electrons, implying relatively weak molecule-leads coupling and, in many cases,
the validity of the Marcus theory of electron transfer. Here we study the
implications of this property on the non-linear transport properties of such
junctions. We obtain an analytical solution of the integral equations that
describe molecular conduction in the Marcus kinetic regime and use it in
different physical limits to predict some important features of nonlinear
transport in metal-molecule-metal junctions. In particular, conduction,
rectification and negative differential resistance can be obtained in different
regimes of interplay between two different conduction channels associated with
different localization properties of the excess molecular charge, without
specific assumptions about the electronic structure of the molecular bridge.
The predicted behaviors show temperature dependences typically observed in the
experiment. The validity of the proposed model and ways to test its predictions
and implement the implied control strategies are discussed
