Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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

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.

Your institute does not have access to this article

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

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.

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.

References

  1. Davis, W. B., Svec, W. A., Ratner, M. A. & Wasielewski, M. R. Molecular-wire behaviour in p-phenylenevinylene oligomers. Nature 396, 60–63 (1998).

    CAS  Article  Google Scholar 

  2. Nitzan, A. & Ratner, M. A. Electron transport in molecular wire junctions. Science 300, 1384–1389 (2003).

    CAS  PubMed  Article  Google Scholar 

  3. Choi, S. H., Kim, B. & Frisbie, C. D. Electrical resistance of long conjugated molecular wires. Science 320, 1482–1486 (2008).

    CAS  Article  Google Scholar 

  4. Lafferentz, L. et al. Conductance of a single conjugated polymer as a continuous function of its length. Science 323, 1193–1197 (2009).

    CAS  PubMed  Article  Google Scholar 

  5. Sedghi, G. et al. Long-range electron tunnelling in oligo-porphyrin molecular wires. Nat. Nano. 6, 517–523 (2011).

    CAS  Article  Google Scholar 

  6. Nacci, C. et al. Conductance of a single flexible molecular wire composed of alternating donor and acceptor units. Nat. Commun. 6, 7397 (2015).

  7. Zhou, Y. et al. Quantum length dependence of conductance in oligomers: first-principles calculations. Phys. Rev. B 75, 245407 (2007).

    Article  CAS  Google Scholar 

  8. Reimers, J. & Hush, N. Electron transfer and energy transfer through bridged systems. I. Formalism. Chem. Phys. 134, 323–354 (1989).

    CAS  Article  Google Scholar 

  9. Joachim, C. Ligand-length dependence of the intramolecular electron transfer through-bond coupling parameter. Chem. Phys. 116, 339–349 (1987).

    CAS  Article  Google Scholar 

  10. Tsuji, Y., Movassagh, R., Datta, S. & Hoffmann, R. Exponential attenuation of through-bond transmission in a polyene: theory and potential realizations. ACS Nano 9, 11109–11120 (2015).

    CAS  PubMed  Article  Google Scholar 

  11. Li, S., Gan, C. K., Son, Y.-W., Feng, Y. P. & Quek, S. Y. Anomalous length-independent frontier resonant transmission peaks in armchair graphene nanoribbon molecular wires. Carbon 76, 285–291 (2014).

    CAS  Article  Google Scholar 

  12. Gil-Guerrero, S., Peña-Gallego, Á., Ramos-Berdullas, N., Martin Pendas, A. & Mandado, M. Assessing the reversed exponential decay of the electrical conductance in molecular wires: the undeniable effect of static electron correlation. Nano Lett. 19, 7394–7399 (2019).

    CAS  PubMed  Article  Google Scholar 

  13. Heeger, A. J., Kivelson, S., Schrieffer, J. & Su, W.-P. Solitons in conducting polymers. Rev. Mod. Phys. 60, 781–850 (1988).

    CAS  Article  Google Scholar 

  14. Cirera, B. et al. Tailoring topological order and π-conjugation to engineer quasi-metallic polymers. Nat. Nano. 15, 437–443 (2020).

    CAS  Article  Google Scholar 

  15. Su, W. P., Schrieffer, J. & Heeger, A. J. Solitons in polyacetylene. Phys. Rev. Lett. 42, 1698–1701 (1979).

    CAS  Article  Google Scholar 

  16. Stuyver, T., Zeng, T., Tsuji, Y., Geerlings, P. & De Proft, F. Diradical character as a guiding principle for the insightful design of molecular nanowires with an increasing conductance with length. Nano Lett. 18, 7298–7304 (2018).

    CAS  PubMed  Article  Google Scholar 

  17. Hernangómez-Pérez, D., Gunasekaran, S., Venkataraman, L. & Evers, F. Solitonics with polyacetylenes. Nano Lett. 20, 2615–2619 (2020).

    PubMed  Article  CAS  Google Scholar 

  18. Gunasekaran, S. et al. Near length-independent conductance in polymethine molecular wires. Nano Lett. 18, 6387–6391 (2018).

    CAS  PubMed  Article  Google Scholar 

  19. Zang, Y. et al. Cumulene wires display increasing conductance with increasing length. Nano Lett. 20, 8415–8419 (2020).

    CAS  PubMed  Article  Google Scholar 

  20. Xu, W. et al. Unusual length dependence of the conductance in cumulene molecular wires. Angew. Chem. Int. Ed. 58, 8378–8382 (2019).

    CAS  Article  Google Scholar 

  21. Leary, E. et al. Bias-driven conductance increase with length in porphyrin tapes. J. Am. Chem. Soc. 140, 12877–12883 (2018).

    CAS  PubMed  Article  Google Scholar 

  22. Meier, E. J., An, F. A. & Gadway, B. Observation of the topological soliton state in the Su–Schrieffer–Heeger model. Nat. Commun. 7, 13986 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  23. Montgomery, L. K., Huffman, J. C., Jurczak, E. A. & Grendze, M. P. The molecular structures of Thiele’s and Chichibabin’s hydrocarbons. J. Am. Chem. Soc. 108, 6004–6011 (1986).

    CAS  PubMed  Article  Google Scholar 

  24. Su, Y. et al. Tuning ground states of bis(triarylamine) dications: from a closed‐shell singlet to a diradicaloid with an excited triplet state. Angew. Chem. Int. Ed. 126, 2901–2905 (2014).

    Article  Google Scholar 

  25. Heeger, A. J. Semiconducting and metallic polymers: the fourth generation of polymeric materials (Nobel lecture). Angew. Chem. Int. Ed. 40, 2591–2611 (2001).

    CAS  Article  Google Scholar 

  26. Joubert-Doriol, L. & Izmaylov, A. F. Molecular “topological insulators”: a case study of electron transfer in the bis(methylene) adamantyl carbocation. Chem. Comm. 53, 7365–7368 (2017).

    CAS  PubMed  Article  Google Scholar 

  27. Lambert, C. & Nöll, G. The class II/III transition in triarylamine redox systems. J. Am. Chem. Soc. 121, 8434–8442 (1999).

    CAS  Article  Google Scholar 

  28. Low, P. J. et al. Crystal, molecular and electronic structure of N,N′‐diphenyl‐N,N′‐bis(2,4‐dimethylphenyl)‐(1,1′‐biphenyl)‐4,4′‐diamine and the corresponding radical cation. Chem. Eur. J. 10, 83–91 (2004).

    CAS  PubMed  Article  Google Scholar 

  29. Xu, B. & Tao, N. J. Measurement of single-molecule resistance by repeated formation of molecular junctions. Science 301, 1221–1223 (2003).

    CAS  PubMed  Article  Google Scholar 

  30. Venkataraman, L. et al. Single-molecule circuits with well-defined molecular conductance. Nano Lett. 6, 458–462 (2006).

    CAS  PubMed  Article  Google Scholar 

  31. Park, Y. S. et al. Frustrated rotations in single-molecule junctions. J. Am. Chem. Soc. 131, 10820–10821 (2009).

    CAS  PubMed  Article  Google Scholar 

  32. Zang, Y. et al. Electronically transparent Au–N bonds for molecular junctions. J. Am. Chem. Soc. 139, 14845–14848 (2017).

    CAS  PubMed  Article  Google Scholar 

  33. Low, J. Z. et al. The environment-dependent behavior of the Blatter radical at the metal–molecule interface. Nano Lett. 19, 2543–2548 (2019).

    CAS  PubMed  Article  Google Scholar 

  34. Lu, Q. et al. From tunneling to hopping: a comprehensive investigation of charge transport mechanism in molecular junctions based on oligo (p-phenylene ethynylene)s. ACS Nano 3, 3861–3868 (2009).

    CAS  PubMed  Article  Google Scholar 

  35. Fatemi, V., Kamenetska, M., Neaton, J. & Venkataraman, L. Environmental control of single-molecule junction transport. Nano Lett. 11, 1988–1992 (2011).

    CAS  PubMed  Article  Google Scholar 

  36. Choi, B. et al. Solvent-dependent conductance decay constants in single cluster junctions. Chem. Sci. 7, 2701–2705 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  37. Capozzi, B. et al. Tunable charge transport in single-molecule junctions via electrolytic gating. Nano Lett. 14, 1400–1404 (2014).

    CAS  PubMed  Article  Google Scholar 

  38. Delaney, P., Nolan, M. & Greer, J. Symmetry, delocalization, and molecular conductance. J. Chem. Phys. 122, 044710 (2005).

    CAS  Article  Google Scholar 

  39. Blum, V. et al. Ab initio molecular simulations with numeric atom-centered orbitals. Comp. Phys. Comm. 180, 2175–2196 (2009).

    CAS  Article  Google Scholar 

  40. Arnold, A., Weigend, F. & Evers, F. Quantum chemistry calculations for molecules coupled to reservoirs: formalism, implementation, and application to benzenedithiol. J. Chem. Phys. 126, 174101 (2007).

    CAS  PubMed  Article  Google Scholar 

  41. Bagrets, A. Spin-polarized electron transport across metal–organic molecules: a density functional theory approach. J. Chem. Theory Comp. 9, 2801–2815 (2013).

    CAS  Article  Google Scholar 

  42. Quek, S. Y. et al. Amine−gold linked single-molecule circuits: experiment and theory. Nano Lett. 7, 3477–3482 (2007).

    CAS  PubMed  Article  Google Scholar 

  43. Evers, F., Korytár, R., Tewari, S. & van Ruitenbeek, J. M. Advances and challenges in single-molecule electron transport. Rev. Mod. Phys. 92, 035001 (2020).

    CAS  Article  Google Scholar 

  44. Klausen, R. S. et al. Evaluating atomic components in fluorene wires. Chem. Sci. 5, 1561–1564 (2014).

    CAS  Article  Google Scholar 

  45. Yoshizawa, K. An orbital rule for electron transport in molecules. Acc. Chem. Res. 45, 1612–1621 (2012).

    CAS  PubMed  Article  Google Scholar 

  46. Garner, M. H., Bro-Jørgensen, W., Pedersen, P. D. & Solomon, G. C. Reverse bond-length alternation in cumulenes: candidates for increasing electronic transmission with length. J. Phys. Chem. C 122, 26777–26789 (2018).

    CAS  Article  Google Scholar 

  47. Gil-Guerrero, S., Ramos-Berdullas, N., Pendás, Á. M., Francisco, E. & Mandado, M. Anti-ohmic single molecule electron transport: is it feasible? Nano. Adv. 1, 1901–1913 (2019).

    CAS  Article  Google Scholar 

  48. Asmar, M. M., Sheehy, D. E. & Vekhter, I. Topological phases of topological-insulator thin films. Phys. Rev. B 97, 075419 (2018).

    CAS  Article  Google Scholar 

  49. Brédas, J.-L., Chance, R. & Silbey, R. Comparative theoretical study of the doping of conjugated polymers: polarons in polyacetylene and polyparaphenylene. Phys. Rev. B 26, 5843–5854 (1982).

    Article  Google Scholar 

  50. Madrid, P. B., Polgar, W. E., Toll, L. & Tanga, M. J. Synthesis and antitubercular activity of phenothiazines with reduced binding to dopamine and serotonin receptors. Bioorg. Med. Chem. Lett. 17, 3014–3017 (2007).

    CAS  PubMed  Article  Google Scholar 

  51. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  PubMed  Article  Google Scholar 

  52. Lenthe, E. V., Baerends, E.-J. & Snijders, J. G. Relativistic regular two‐component hamiltonians. J. Chem. Phys. 99, 4597–4610 (1993).

    Article  Google Scholar 

  53. Wilhelm, J., Walz, M., Stendel, M., Bagrets, A. & Evers, F. Ab initio simulations of scanning-tunneling-microscope images with embedding techniques and application to C58-dimers on Au(111). Phys. Chem. Chem. Phys. 15, 6684–6690 (2013).

    CAS  PubMed  Article  Google Scholar 

  54. Balasubramani, S. G. et al. TURBOMOLE: modular program suite for ab initio quantum-chemical and condensed-matter simulations. J. Chem. Phys. 152, 184107 (2020).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

Download references

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).

Author information

Authors and Affiliations

Authors

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.

Corresponding authors

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

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

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

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

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

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

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

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1038/s41557-022-00978-1

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing