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Single Molecule Conductance of Linear Dithioalkanes in the Liquid Phase:  Apparently Activated Transport Due to Conformational Flexibility

Author(s):

Daniel R. Jones, Alessandro Troisi

Journal:

The Journal of Physical Chemistry C

Year:

2007

Volume:

111

Pages

14567-14573

DOI:

10.1021/jp074351c

Abstract:

We computed the single molecule conductance of a series of linearR-ˆ-dithiolalkanes as a function of theirconformation, following experimental evidence (Haiss et al.Faraday Discuss.2006,131, 253) that eventhese simple molecules exhibit a thermal gating of electron transfer. After performing a conformational searchusing the MM3 empirical force-field, for each conformation, we evaluated the conductance using DFT singlepoint calculations and Green’s function theoretical approach. We analyzed the complex dependence of theconductance on the conformation, discussing its correlation with the conformational energy and the moleculeend-to-end distance. From this data, the temperature dependence of conductance was calculated. Our calculationsconfirm that the conformational flexibility of the alkylic chain led to a higher conductance at highertemperatures. Therefore, the electron transport in these junctions appears to be thermally activated even if ittakes place by pure tunneling.

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