In our recent research, we have been able to measure and characterize the impact of intrinsic molecular properties on the conductance of single molecule circuits formed with amine-gold linkages 1-4. Experiments are carried out by repeatedly forming and breaking a gold point contact in a solution containing the target molecule. This is repeated thousand of times while measuring the junction current at fixed bias resulting in a large number of independent measurements of the conductance for each target molecule. Amine link groups result in a clear conductance signature that we use to study trends with molecule length, conjugation and structure. The hypothesis that the nitrogen atom from the amine group bonds to a coordinatively unsaturated gold atom in the junction through a donor-acceptor mechanism has successfully explained the observed trends. Each molecule has been analyzed using quantum chemistry techniques based on Density Functional Theory, applied to the molecule bonded to a gold fragment to represent each electrode. In this talk, I will review the experiments and the physical picture of the junction based on the calculations. I will then focus on three recent studies: (i) the impact of substituents on the conductance through diaminobenzene 3; (ii) the trends in conductance through diaminonaphthalene and diaminoanthracene as a function of the location of the amine link groups 4; and (iii) comparison of junctions formed with amine links to those formed with methylthiol and dimethylphosphine links.
- L. Venkataraman, J.E. Klare, I.W. Tam, C. Nuckolls, M.S Hybertsen and M. Steigerwald, Nano Letters, vol. 5, pp. 458-462, 2006.
-  L. Venkataraman, J.E. Klare, C. Nuckolls, M.S Hybertsen and M. Steigerwald, Nature, vol. 442, pp. 904-907, 2006.
-  L. Venkataraman, Y.S. Park, A.C. Whalley, C. Nuckolls, M.S Hybertsen and M.L. Steigerwald, Nano Letters, vol. 7, pp. 502-506, 2007.
-  J.R. Quinn, F.W. Foss, Jr., L. Venkataraman, M.S. Hybertsen, and R. Breslow, Journal of the American Chemical Society, vol. 129, pp. 6714-6715, 2007.
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