Stretching Livens Up Electron Transport | Chemical & Engineering News
Volume 89 Issue 39 | p. 28 | Concentrates
Issue Date: September 26, 2011

Stretching Livens Up Electron Transport

Molecular dynamics simulation shows boost in electron tunneling for elongated designer molecule
Department: Science & Technology
Keywords: electron tunneling, molecular dynamics, molecular electronics
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This cyclophane, when pulled between a gold AFM tip and a gold electrode in a simulation, increases its electron conductance.
Credit: J. Am. Chem. Soc.
A cyclophane, when pulled between an AFM tip and electrode in simulation, increases its electron conductance.
 
This cyclophane, when pulled between a gold AFM tip and a gold electrode in a simulation, increases its electron conductance.
Credit: J. Am. Chem. Soc.

As some molecules elongate, it turns out that they have an easier time transporting electrons along their frameworks, according to a molecular simulation study (J. Am. Chem. Soc., DOI: 10.1021/ja205908q). This counterintuitive behavior—longer molecules usually have poor conductance compared with shorter ones—could open the door to mechanically activated molecular electronic devices, says the research team led by Mark A. Ratner and George C. Schatz of Northwestern University. Using molecular dynamics and electronic structural methods, the researchers simulated passing current along a cyclophane molecule they designed (shown) as it was stretched between the gold tip of an atomic force microscope and a gold electrode surface. The team found that the molecule’s electrical resistance decreased when stretched, especially taking a dive once the compound’s bulky tert-butyl groups moved out of the way to allow π-stacking between its aromatic rings. “What makes this so exciting,” says David N. Beratan, a theoretical chemist at Duke University, “is that the authors find applied force may strongly remodel electron tunneling pathways,” a result that bolsters earlier simulation work on electron transport in DNA and proteins.

 
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