  In our theoretical study where we combine a nonequilibrium Green's function
(NEGF) approach with density functional theory (DFT) we investigate compounds
containing a ferrocene moiety which is connected to i) thiol anchor groups on
both sides in a para-connection, ii) a pyridyl anchor group on one side in a
meta-connection and a thiol group on the other side in a para-connection, in
both cases with acetylenic spacers in between the Ferrocene and the anchors. We
predict possible single molecule junction geometries within a scanning
tunneling microscopy (STM) setup where we find that the conductance trend for
the set of conformations are intriguing in the sense that the conductance does
not decrease while the junction length increases which we analyze and explain
in terms of Fermi level alignment. We also find a pattern for the
current-voltage (IV) curves within the linear-response regime for both
molecules we study, where the conductance variation with the molecular
configurations is surprisingly small.
