Abstract
Electron transfer through molecules is an ubiquitous process underlying the function of biological systems and synthetic devices. The electronic coupling between components varies with the structure of the molecular bridge, often in classically unintuitive ways, as determined by its quantum electronic structure. Considerable efforts in electron-transfer theory have yielded models that are useful conceptually and provide quantitative means to understand transfer rates in terms of local contributions. Here we show how a description of the local currents within a bridging molecule bound to metallic electrodes can provide chemical insight into current flow. In particular, we show that through-space, as opposed to through-bond, terms dominate in a surprising number of instances, and that interference effects can be characterized by the reversal of ring currents. Together these ideas have implications for the design of molecular electronic devices, in particular for the ways in which substituent effects may be used for maximum impact.
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Acknowledgements
The authors would like to thank David Q. Andrews for very helpful comments. This work was funded by NSF-Chemistry, NSF-MRSEC, and ONR-Chemistry. C.H. would like to thank the German Research Foundation (DFG) for generous support through a postdoctoral research fellowship. T.H. thanks the Carlsberg foundation (Carlsbergfondet) for generous support.
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G.C.S. performed calculations and analysis for the paper and Supplementary Information and wrote the paper. C.H. performed calculations and analysis for the Supplementary Information. T.H. wrote the theory section of the Supplementary Information. V.M. assisted in project design. M.A.R. edited the paper and provided supervision.
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Solomon, G., Herrmann, C., Hansen, T. et al. Exploring local currents in molecular junctions. Nature Chem 2, 223–228 (2010). https://doi.org/10.1038/nchem.546
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DOI: https://doi.org/10.1038/nchem.546
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