"Dependence of single-molecule junction conductance on molecular
conformation," by Latha Venkataraman,
Jennifer E. Klare, Colin Nuckolls, Mark S. Hybertsen, & Michael L.
Steigerwald, Nature, 442(7105): 904-7,
24 August 2006.
Abstract: "Since it was first suggested that a single
molecule might function as an active electronic component, a number of
techniques have been developed to measure the charge transport properties
of single molecules. Although scanning tunnelling microscopy observations
under high vacuum conditions can allow stable measurements of electron
transport, most measurements of a single molecule bonded in a
metal-molecule-metal junction exhibit relatively large variations in
conductance. As a result, even simple predictions about how molecules
behave in such junctions have still not been rigorously tested. For
instance, it is well known that the tunnelling current passing through a
molecule depends on its conformation; but although some experiments have
verified this effect, a comprehensive mapping of how junction conductance
changes with molecular conformation is not yet available. In the simple
case of a biphenyl--a molecule with two phenyl rings linked by a single C-C
bond--conductance is expected to change with the relative twist angle
between the two rings, with the planar conformation having the highest
conductance. Here we use amine link groups to form single-molecule
junctions with more reproducible current-voltage characteristics. This
allows us to extract average conductance values from thousands of
individual
measurements on a series of seven biphenyl molecules with different ring
substitutions that alter the twist angle of the molecules. We find that the
conductance for the series decreases with increasing twist angle,
consistent with a cosine-squared relation predicted for transport through
pi-conjugated biphenyl systems."
This 2006 report from Nature was cited 16
times in current journal articles indexed by Clarivate
during March-April 2008. Thanks to that latest two-month tally, this is
currently the second-most-cited chemistry paper published in the last two
years (not counting reviews). Prior to the most recent bimonthly count,
citations to the paper have accrued as follows:
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