article published yes Taekyeong Kim author Pierre Darancet author Jonathan R. Widawsky author Michele Kotiuga author Su Ying Quek author Jeffrey B. Neaton author Latha Venkataraman author 9ebb78a5-cc0d-11ee-8322-fae086a32caf0000-0002-6957-6089 We measure conductance and thermopower of single Au–4,4′-bipyridine–Au junctions in distinct low and high conductance binding geometries accessed by modulating the electrode separation. We use these data to determine the electronic energy level alignment and coupling strength for these junctions, which are known to conduct through the lowest unoccupied molecular orbital (LUMO). Contrary to intuition, we find that, in the high-conductance junction, the LUMO resonance energy is further away from the Au Fermi energy than in the low-conductance junction. However, the LUMO of the high-conducting junction is better coupled to the electrode. These results are in good quantitative agreement with self-energy corrected zero-bias density functional theory calculations. Our calculations show further that measurements of conductance and thermopower in amine-terminated oligophenyl–Au junctions, where conduction occurs through the highest occupied molecular orbitals, cannot be used to extract electronic parameters as their transmission functions do not follow a simple Lorentzian form. American Chemical Society2014 eng 1530-6984 1530-6992 2444658510.1021/nl404143v 142794-798 yes Kim T, Darancet P, Widawsky JR, Kotiuga M, Quek SY, Neaton JB, Venkataraman L. 2014. Determination of energy level alignment and coupling strength in 4,4′-bipyridine single-molecule junctions. Nano Letters. 14(2), 794–798. Kim T, Darancet P, Widawsky JR, et al. Determination of energy level alignment and coupling strength in 4,4′-bipyridine single-molecule junctions. <i>Nano Letters</i>. 2014;14(2):794-798. doi:<a href="https://doi.org/10.1021/nl404143v">10.1021/nl404143v</a> T. Kim <i>et al.</i>, “Determination of energy level alignment and coupling strength in 4,4′-bipyridine single-molecule junctions,” <i>Nano Letters</i>, vol. 14, no. 2. American Chemical Society, pp. 794–798, 2014. Kim, Taekyeong, Pierre Darancet, Jonathan R. Widawsky, Michele Kotiuga, Su Ying Quek, Jeffrey B. Neaton, and Latha Venkataraman. “Determination of Energy Level Alignment and Coupling Strength in 4,4′-Bipyridine Single-Molecule Junctions.” <i>Nano Letters</i>. American Chemical Society, 2014. <a href="https://doi.org/10.1021/nl404143v">https://doi.org/10.1021/nl404143v</a>. Kim, T., Darancet, P., Widawsky, J. R., Kotiuga, M., Quek, S. Y., Neaton, J. B., &#38; Venkataraman, L. (2014). Determination of energy level alignment and coupling strength in 4,4′-bipyridine single-molecule junctions. <i>Nano Letters</i>. American Chemical Society. <a href="https://doi.org/10.1021/nl404143v">https://doi.org/10.1021/nl404143v</a> T. Kim, P. Darancet, J.R. Widawsky, M. Kotiuga, S.Y. Quek, J.B. Neaton, L. Venkataraman, Nano Letters 14 (2014) 794–798. Kim, Taekyeong, et al. “Determination of Energy Level Alignment and Coupling Strength in 4,4′-Bipyridine Single-Molecule Junctions.” <i>Nano Letters</i>, vol. 14, no. 2, American Chemical Society, 2014, pp. 794–98, doi:<a href="https://doi.org/10.1021/nl404143v">10.1021/nl404143v</a>. 179882024-09-09T11:24:55Z2025-01-03T07:44:13Z