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Highly conducting single-molecule topological insulators based on mono- and di-radical cations

Nature Chemistry volume 14, pages 1061–1067 (2022)Cite this article

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Abstract

Single-molecule topological insulators are promising candidates as conducting wires over nanometre length scales. A key advantage is their ability to exhibit quasi-metallic transport, in contrast to conjugated molecular wires which typically exhibit a low conductance that decays as the wire length increases. Here, we study a family of oligophenylene-bridged bis(triarylamines) with tunable and stable mono- or di-radicaloid character. These wires can undergo one- and two-electron chemical oxidations to the corresponding mono-cation and di-cation, respectively. We show that the oxidized wires exhibit reversed conductance decay with increasing length, consistent with the expectation for Su–Schrieffer–Heeger-type one-dimensional topological insulators. The 2.6-nm-long di-cation reported here displays a conductance greater than 0.1G0, where G0 is the conductance quantum, a factor of 5,400 greater than the neutral form. The observed conductance–length relationship is similar between the mono-cation and di-cation series. Density functional theory calculations elucidate how the frontier orbitals and delocalization of radicals facilitate the observed non-classical quasi-metallic behaviour.

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Fig. 1: Chemical characteristics of the Bn molecular wires.
Fig. 2: Conductance measurements of the Bn, Bn+ and Bn2+ series.
Fig. 3: Transmission calculations of the neutral Bn series.
Fig. 4: Transmission calculations of the oxidized Bn+ and Bn2+ series.

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Data availability

The data that support the findings of this study are available only on request from the corresponding authors. Prior to making the data available, the data need to be converted from a binary format to a text format, which we are happy to do on request.

Code availability

The data that support the findings were acquired using a custom instrument controlled by custom software (Igor Pro, Wavemetrics). The software is available from the corresponding authors upon reasonable request.

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Acknowledgements

This work was supported in part by the National Science Foundation under grant DMR-1807580. J.Z.L. thanks the A*STAR Graduate Academy in Singapore for a graduate fellowship. S.G. was supported by a National Science Foundation Graduate Research Fellowship under grant DGE-1644869. C.R.P. was supported by a National Defense Science and Engineering Graduate Fellowship. X.Y. and G.L. acknowledge the Analysis and Testing Center of Beijing Institute of Technology for characterization in NMR and high-resolution mass spectrometry. X.Y. acknowledges the Beijing Institute of Technology Research Fund Program for Young Scholars. G.L. thanks the Project of the Science Funds of Jiangxi Education Office (GJJ180629) and the Project of Jiangxi Science and Technology Normal University (2016XJZD009) for financial support. J.W. and F.E. thank M. Camarasa-Gomez for helpful discussions. J.W. and F.E. acknowledge the Gauss Centre for Supercomputing for providing computational resources on SuperMUC-NG at the Leibniz Supercomputing Centre under project ID pn72pa. The work in Regensburg was supported by the Deutsche Forschungsgemeinschaft (German Research Foundation) through project ID 314695032 (SFB 1277, subprojects A03 and B01).

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  1. These authors contributed equally: Liang Li, Jonathan Z. Low.

Authors and Affiliations

  1. Department of Chemistry, Columbia University, New York, NY, USA

    Liang Li, Jonathan Z. Low, Suman Gunasekaran, Claudia R. Prindle, Rachel L. Starr, Colin Nuckolls, Michael L. Steigerwald, Luis M. Campos & Latha Venkataraman

  2. Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany

    Jan Wilhelm & Ferdinand Evers

  3. Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, P. R. China

    Guanming Liao & Xiaodong Yin

  4. Technische Universität Dresden, Dresden, König-Bau, Germany

    Dorothea Golze

  5. Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA

    Latha Venkataraman

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Contributions

L.L. and J.Z.L. performed all scanning tunnelling microscopy measurements. J.W., L.L. and D.G. performed all DFT calculations. G.L., R.L.S., C.R.P. and X.Y. performed all the synthesis. L.L., J.Z.L, J.W., X.Y., F.E., L.M.C. and L.V. wrote the paper with contributions from all authors. L.V., X.Y., F.E. and L.M.C. oversaw the project.

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Correspondence to Ferdinand Evers, Luis M. Campos, Xiaodong Yin or Latha Venkataraman.

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Nature Chemistry thanks Marcos Mandado and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–15, Tables 1 and 2 and Discussion.

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Li, L., Low, J.Z., Wilhelm, J. et al. Highly conducting single-molecule topological insulators based on mono- and di-radical cations. Nat. Chem. 14, 1061–1067 (2022). https://doi.org/10.1038/s41557-022-00978-1

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