| Literature DB >> 20025266 |
Artem Mishchenko1, David Vonlanthen, Velimir Meded, Marius Bürkle, Chen Li, Ilya V Pobelov, Alexei Bagrets, Janne K Viljas, Fabian Pauly, Ferdinand Evers, Marcel Mayor, Thomas Wandlowski.
Abstract
The conductance of a family of biphenyl-dithiol derivatives with conformationally fixed torsion angle was measured using the scanning tunneling microscopy (STM)-break-junction method. We found that it depends on the torsion angle phi between two phenyl rings; twisting the biphenyl system from flat (phi = 0 degrees ) to perpendicular (phi = 90 degrees ) decreased the conductance by a factor of 30. Detailed calculations of transport based on density functional theory and a two level model (TLM) support the experimentally obtained cos(2) phi correlation between the junction conductance G and the torsion angle phi. The TLM describes the pair of hybridizing highest occupied molecular orbital (HOMO) states on the phenyl rings and illustrates that the pi-pi coupling dominates the transport under "off-resonance" conditions where the HOMO levels are well separated from the Femi energy.Entities:
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Year: 2010 PMID： 20025266 DOI： 10.1021/nl903084b
Source DB: PubMed Journal: Nano Lett ISSN： 1530-6984 Impact factor: 11.189