  We derive an explicit expression for the quantum conductivity of a molecular
wire containing a redox center, which is embedded in an electrochemical
environment. The redox center interacts with the solvent, and the average over
the solvent configurations is performed numerically. Explicit calculations have
been performed for a chain of three atoms. When the redox center interacts
strongly with neighboring electronic levels, the current-potential curves show
interesting features like rectification, current plateaus and negative
differential resistance. Electronic spectroscopy of intermediate states can be
performed at constant small bias by varying the electrochemical potential of
the wire.
