jp501122n_si_001.pdf (2.79 MB)
Conductance of Well-Defined Porphyrin Self-Assembled Molecular Wires up to 14 nm in Length
journal contribution
posted on 2014-04-03, 00:00 authored by Quirina Ferreira, Ana M. Bragança, Luís Alcácer, Jorge MorgadoWe show that molecular wires up to
14 nm in length composed by zinc-porphyrins bridged by bipyridines
stand efficient electrical transport. Self-assembled molecular wires
were prepared step-by-step, alternating up to 13 units of zinc-octaethylporphyrin
with axially coordinated 4,4′-bipyridine, on highly oriented
pyrolytic graphite (HOPG). A combination of molecular resolution imaging
and scanning tunneling spectroscopy allowed us to follow molecules
self-assembly in real time during wire fabrication and to measure
wires current, respectively. A statistical analysis of hundreds of
current–voltage curves was carried out to determine the conductance
of individual porphyrin/bipyridine wires. From the conductance dependence
on the wires length an ultra low attenuation factor (β = 0.015
± 0.006 Å–1) was obtained for shorter
wires, with a transition in conduction regime occurring at ca. 6.5
nm long wires.