  Many-electron wavepacket dynamics based on time-dependent configuration
interaction (TDCI) is a numerically rigorous approach to quantitatively model
electron-transfer across molecular junctions. TDCI simulations of cyanobenzene
thiolates---para- and meta-linked to an acceptor gold atom---show donor states
\emph{conjugating} with the benzene $\pi$-network to allow better
through-molecule electron migration in the para isomer compared to the meta
counterpart. For dynamics involving \emph{non-conjugating} states, we find
electron-injection to stem exclusively from distance-dependent non-resonant
quantum mechanical tunneling, in which case the meta isomer exhibits better
dynamics. Computed trend in donor-to-acceptor net-electron transfer through
differently linked azulene bridges agrees with the trend seen in low-bias
conductivity measurements. Disruption of $\pi$-conjugation has been shown to be
the cause of diminished electron-injection through the 1,3-azulene, a
pathological case for graph-based diagnosis of destructive quantum
interference. Furthermore, we demonstrate quantum interference of many-electron
wavefunctions to drive para- vs. meta- selectivity in the coherent evolution of
superposed $\pi$(CN)- and $\sigma$(NC-C)-type wavepackets. Analyses reveal that
in the para-linked benzene, $\sigma$ and $\pi$ MOs localized at the donor
terminal are \emph{in-phase} leading to constructive interference of electron
density distribution while phase-flip of one of the MOs in the meta isomer
results in destructive interference. These findings suggest that \emph{a
priori} detection of orbital phase-flip and quantum coherence conditions can
aid in molecular device design strategies.
