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Bipyridine-Based Molecular Wire Conducts Easily

Robust conductor may enable molecular electronic devices

by Jyllian Kemsley
February 25, 2013 | A version of this story appeared in Volume 91, Issue 8

Molecular electronic devices require robust molecular wires to conduct charge over long distances. A new wire based on a repeating bipyridine structure shows unprecedented conductance and maintains it over longer distances compared with other carbon-based wires (J. Phys. Chem. Lett., DOI: 10.1021/jz302057m). A team led by Magdaléna Hromadová of the Academy of Sciences of the Czech Republic synthesized the wires with repeating units of a substituted viologen, or 4,4'-bipyridine, with an aryl group inserted between the pyridine units. The wires were tethered to a gold-coated scanning tunneling microscope tip on one end and a gold substrate on the other. As the wire lengthens from one to six repeating units, or 2.4 nm to 11.0 nm, the conductance drops minimally. The longest wire has a conductance of 2.9 nanosiemens, nearly three orders of magnitude higher than that of other carbon-based wires of comparable length. The wires withstand repeated cycling between oxidized and reduced states. Hromadová and colleagues suggest that the longer wires work through a hopping mechanism in which the viologen units are each reduced with two one-electron transfer steps.


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