  In our theoretical study where we combine a nonequilibrium Green's function
(NEGF) approach with density functional theory (DFT) we investigate branched
compounds containing ferrocene moieties in both branches which due to their
metal centers are designed to allow for asymmetry induced by local charging. In
these compounds the ferrocene moieties are connected to pyridyl anchor groups
either directly or via acetylenic spacers in a meta-connection where we also
compare our results with those obtained for the respective single-branched
molecules with both meta- and para-connections between the metal center and the
anchors. We find a destructive quantum interference (DQI) feature in the
transmission function slightly below the lowest unoccupied molecular orbital
(LUMO) which dominates the conductance even for the uncharged branched compound
with spacer groups inserted. In an analysis based on mapping the structural
characteristics of the range of molecules in our article onto tight-binding
models, we identify the structural source of the DQI minimum as the
through-space coupling between the pyridyl anchor groups. We also find that
local charging on one of the branches only changes the conductance by about one
order of magnitude which we explain in terms of the spatial distributions of
the relevant molecular orbitals for the branched compounds.
