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Humidity-controlled rectification switching in ruthenium-complex molecular junctions


Although molecular rectifiers were proposed over four decades ago1,2, until recently reported rectification ratios (RR) were rather moderate2,3,4,5,6,7,8,9,10,11 (RR ~ 101). This ceiling was convincingly broken using a eutectic GaIn top contact12 to probe molecular monolayers of coupled ferrocene groups (RR ~ 105), as well as using scanning tunnelling microscopy-break junctions13,14,15,16 and mechanically controlled break junctions17 to probe single molecules (RR ~ 102–103). Here, we demonstrate a device based on a molecular monolayer in which the RR can be switched by more than three orders of magnitude (between RR ~ 100 and RR ≥ 103) in response to humidity. As the relative humidity is toggled between 5% and 60%, the current–voltage (IV) characteristics of a monolayer of di-nuclear Ru-complex molecules reversibly change from symmetric to strongly asymmetric (diode-like). Key to this behaviour is the presence of two localized molecular orbitals in series, which are nearly degenerate in dry circumstances but become misaligned under high humidity conditions, due to the displacement of counter ions (PF6 ). This asymmetric gating of the two relevant localized molecular orbital levels results in humidity-controlled diode-like behaviour.

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Fig. 1: Experimental set-up and molecular systems studied.
Fig. 2: Experimental current–voltage characteristics of the 1-Ru-N and 2-Ru-N molecular junctions.
Fig. 3: RR data for all molecular junctions and tip-radius dependent data for 2-Ru-N.
Fig. 4: Theoretical model of the electronic states of the 2-Ru-N molecule for dry and humid conditions.
Fig. 5: Theoretical IV characteristics for 1-Ru-N and 2-Ru-N molecules.


  1. Aviram, A. & Ratner, M. Molecular rectifiers. Chem. Phys. Lett. 29, 277–283 (1974).

    Article  Google Scholar 

  2. Metzger, R. M. Unimolecular electrical rectifiers. Chem. Rev. 103, 3803–3834 (2003).

    Article  Google Scholar 

  3. McCreery, R. L. & Bergren, A. J. Progress with molecular electronic junctions: meeting experimental challenges in design and fabrication. Adv. Mater. 21, 4303–4322 (2009).

    Article  Google Scholar 

  4. Yasuda, S., Nakamura, T., Matsumoto, M. & Shigekawa, H. Phase switching of a single isomeric molecule and associated characteristic rectification. J. Am. Chem. Soc. 125, 16430–16433 (2003).

    Article  Google Scholar 

  5. Kitagawa, K., Morita, T. & Kimura, S. Molecular rectification of a helical peptide with a redox group in the metal-molecule-metal junction. J. Phys. Chem. B 109, 13906–13911 (2005).

    Article  Google Scholar 

  6. Loertscher, E. et al. Transport properties of a single-molecule diode. ACS Nano 6, 4931–4939 (2012).

    Article  Google Scholar 

  7. Diez–Perez, I. et al. Rectification and stability of a single molecular diode with controlled orientation. Nat. Chem. 1, 635–641 (2009).

    Article  Google Scholar 

  8. Batra, A. et al. Tuning rectification in single-molecular diodes. Nano Lett. 13, 6233–6237 (2013).

    Article  Google Scholar 

  9. Elbing, M. et al. A single-molecule diode. Proc. Natl Acad. Sci. USA 102, 8815–8820 (2005).

    Article  Google Scholar 

  10. Guo, C. et al. Molecular rectifier composed of DNA with high rectification ratio enabled by intercalation. Nat. Chem. 8, 484–490 (2016).

    Article  Google Scholar 

  11. Terada, K., Kobayashi, K., Hikita, J. & Haga, M.-A. Electric conduction properties of self-assembled monolayer films of Ru complexes with disulfide/phosphonate anchors in a Au-(molecular ensemble)-(Au nanoparticle) junction. Chem. Lett. 38, 416–417 (2009).

    Article  Google Scholar 

  12. Chen, X. et al. Molecular diodes with rectification ratios exceeding 105 driven by electrostatic interactions. Nat. Nanotech. 12, 797–803 (2017).

    Google Scholar 

  13. Capozzi, B. et al. Single-molecule diodes with high rectification ratios through environmental control. Nat. Nanotech. 10, 522–527 (2015).

    Article  Google Scholar 

  14. Aragonès, A. C. et al. Single-molecule electrical contacts on silicon electrodes under ambient conditions. Nat. Commun. 8, 15056 (2017).

    Article  Google Scholar 

  15. Cheung, K. C. M., Chen, X. Y., Albrecht, T. & Kornyshev, A. A. Principles of a single-molecule rectifier in electrolytic environment. J. Phys. Chem. C 120, 3089–3106 (2016).

    Article  Google Scholar 

  16. Sherif, S. et al. Current rectification in a single molecule diode: the role of electrode coupling. Nanotechnology 26, 291001 (2015).

    Article  Google Scholar 

  17. Perrin, M. L. et al. A gate-tunable single-molecule diode. Nanoscale 8, 8927–8931 (2016).

    Article  Google Scholar 

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

    Article  Google Scholar 

  19. Guedon, C. M. et al. Observation of quantum interference in molecular charge transport. Nat. Nanotech. 7, 304–308 (2012).

    Article  Google Scholar 

  20. Luo, L. et al. Length and temperature dependent conduction of ruthenium-containing redox-active molecular wires. J. Phys. Chem. C 115, 19955–19961 (2011).

    Article  Google Scholar 

  21. Kaliginedi, V. et al. Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond. Nanoscale 7, 17685–17692 (2015).

    Article  Google Scholar 

  22. Nagashima, T. et al. Photoresponsive molecular memory films composed of sequentially assembled heterolayers containing ruthenium complexes. Chem. Eur. J. 22, 1658–1667 (2016).

    Article  Google Scholar 

  23. Mohos, M. et al. Breaking force and conductance of gold nanojunctions: effect of humidity. J. Phys. Chem. Lett. 5, 3560–3564 (2014).

    Article  Google Scholar 

  24. Perrin, M. L. Large negative differential conductance in single molecule break junctions. Nat. Nanotech. 9, 830–834 (2014).

    Article  Google Scholar 

  25. te Velde, G. et al. Chemistry with ADF. J. Comp. Chem. 22, 931–967 (2001).

    Article  Google Scholar 

  26. Guerra, C. F., Snijders, J. G., te Velde, G. & Baerends, E. J. Towards an order-N DFT method. Theor. Chem. Acc. 99, 391–403 (1998).

    Google Scholar 

  27. Poot, M. et al. Temperature dependence of three-terminal molecular junctions with sulfur end-functionalized tercyclohexylidenes. Nano Lett. 6, 1031–1035 (2006).

    Article  Google Scholar 

  28. Bergren, A. J., McCreery, R. L., Stoyanov, S. R., Gusarov, S. & Kovalenko, A. Electronic characteristics and charge transport mechanisms for large area aromatic molecular junctions. J. Phys. Chem. C 114, 15806–15815 (2010).

    Article  Google Scholar 

  29. Schwarz, F. et al. Field-induced conductance switching by charge-state alternation in organometallic single-molecule junctions. Nat. Nanotech. 11, 170–176 (2016).

    Article  Google Scholar 

  30. Allnat, A. R. & Lidiard, A. B. Atomic Transport in Solids 180–185 (Cambridge Univ., Cambridge 1993).

  31. Terada, K. et al. Memory effects in molecular films of free-standing rod-shaped ruthenium complexes on an electrode. Angew. Chem. Int. Ed. 50, 6287–6291 (2011).

    Article  Google Scholar 

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

    Article  Google Scholar 

  33. Mowbray, D. J., Jones, G. & Thygesen, K. S. Influence of functional groups on charge transport in molecular junctions. J. Chem. Phys. 128, 111103 (2008).

    Article  Google Scholar 

  34. Pye, C. C., Ziegler, T., van Lenthe, E. & Louwen, J. N. An implementation of the conductor-like screening model of solvation within the Amsterdam density functional package: Part II. COSMO for real solvents (1). Can. J.Chem. 87, 790–797 (2009).

    Article  Google Scholar 

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We thank F. Galli for technical support and advice. We acknowledge financial support from the Swiss National Science Foundation (grant no. 200020-144471), as well as from the JSPS KAKENHI (grant no. JP17H05383; Coordination Asymmetry, Japan) and the Science Research Promotion Fund from the Promotion and Mutual Aid Corporation for Private Schools of Japan, and from the Netherlands Organisation for Scientific Research (NWO) via FOM programme no. 141.

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H.O. and M.H. designed and synthesized the molecules. H.A., V.K., P.B., H.O. and M.H. characterized the SAMs. H.A. and V.K. performed the C-AFM measurements. H.A., V.K. and S.J.v.d.M. designed the experiment and performed data analysis. J.A.C.G. and J.M.T. performed the calculations. H.A., V.K., J.A.C.G., J.M.T. and S.J.v.d.M. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Veerabhadrarao Kaliginedi or Sense Jan van der Molen.

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Atesci, H., Kaliginedi, V., Celis Gil, J.A. et al. Humidity-controlled rectification switching in ruthenium-complex molecular junctions. Nature Nanotech 13, 117–121 (2018).

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