"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 Thomson Reuters 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:

January-February 2008: 12 citations
November-December 2007: 10
September-October 2007: 15
July-August 2007: 3
May-June 2007: 4
March-April 2007: 4
January-February 2007: 2
November-December 2006: 2

Total citations to date: 68

SOURCE: Hot Papers Database (Included with a subscription to the print newsletter Science Watch^®, available from the Research Services Group of Thomson Reuters. Packaged on a CD that is mailed with each Science Watch issue, the Hot Papers Database contains data on hundreds of highly cited papers published during the last two years. User interface permits searching by author, organization, journal, field, and more. Total citations, as well as citations accrued during successive bimonthly periods, can be assessed and graphed. An updated CD containing the most recent bimonthly data is mailed with every new issue of Science Watch, six times a year. The CD also includes an electronic version of the Science Watch issue in HTML format, for personal desktop access.