  The study of electron transport through single molecules is essential to the
development of molecular electronics. Indeed, trends in electronic conductance
through organic nanowires have emerged with the increasing reliability of
electron transport measurements at the single-molecule level. Experimental and
theoretical work has shown that tunneling distance, HOMO-LUMO gap and molecular
conformation influence electron transport in both saturated and pi-conjugated
nanowires. However, there is relatively little experimental data on electron
transport through fused aromatic rings. Here we show using diaminoacenes that
conductivity depends not only on the number of fused aromatic rings in the
molecule, which defines the molecular HOMO-LUMO gap, but also on the position
of the amino groups on the rings. Specifically, we find that conductance is
highest with minimal disruption of aromaticity in fused aromatic nanowires.
