Stereoelectronic switching in single-molecule junctions

Article metrics


A new intersection between reaction chemistry and electronic circuitry is emerging from the ultraminiaturization of electronic devices. Over decades chemists have developed a nuanced understanding of stereoelectronics to establish how the electronic properties of molecules relate to their conformation; the recent advent of single-molecule break-junction techniques provides the means to alter this conformation with a level of control previously unimagined. Here we unite these ideas by demonstrating the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behaviour in permethyloligosilanes with methylthiomethyl electrode linkers. The strong σ conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur–methylene σ bonds that terminate the molecule. Theoretical calculations support the existence of three distinct dihedral conformations that differ drastically in their electronic character. We can shift between these three species by simply lengthening or compressing the molecular junction, and, in doing so, we can switch conductance digitally between two states.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Structures of oligosilanes Si1, Si4, Si7 and Si10 calculated at the B3LYP/6-31G** level.
Figure 2: Iterative synthesis of oligosilanes terminated with methylthiomethyl end groups.
Figure 3: Conductance analysis of the oligosilane series.
Figure 4: DFT calculations describe the mechanism for switching as the oligosilanes are elongated in the junction.


  1. 1

    Reed, M. A. & Tour, J. M. Computing with molecules. Sci. Am. 282, 86–93 (2000).

  2. 2

    Song, H., Reed, M. A. & Lee, T. Single molecule electronic devices. Adv. Mater. 23, 1583–1608 (2011).

  3. 3

    Turro, N. J. Modern Molecular Photochemistry (University Science Books, 1991).

  4. 4

    Butenhoff, T. J. & Moore, C. B. Hydrogen atom tunneling in the thermal tautomerism of porphine imbedded in a n-hexane matrix. J. Am. Chem. Soc. 110, 8336–8341 (1988).

  5. 5

    Phelan, N. F. & Orchin, M. Cross conjugation. J. Chem. Educ. 45, 633–637 (1968).

  6. 6

    Van der Molen, S. J. et al. Light-controlled conductance switching of ordered metal–molecule–metal devices. Nano Lett. 9, 76–80 (2009).

  7. 7

    Auwärter, W. et al. A surface-anchored molecular four-level conductance switch based on single proton transfer. Nature Nanotechnol. 7, 41–46 (2012).

  8. 8

    Darwish, N. et al. Observation of electrochemically controlled quantum interference in a single anthraquinone-based norbornylogous bridge molecule. Angew. Chem. Int. Ed. 51, 3203–3206 (2012).

  9. 9

    Eliel, E. L. & Wilen, S. H. Stereochemistry of Organic Compounds (Wiley, 1994).

  10. 10

    Choi, B-Y. et al. Conformational molecular switch of the azobenzene molecule: a scanning tunneling microscopy study. Phys. Rev. Lett. 96, 156106 (2006).

  11. 11

    Donhauser, Z. J. et al. Conductance switching in single molecules through conformational changes. Science 292, 2303–2307 (2001).

  12. 12

    Moore, A. M. et al. Molecular engineering and measurements to test hypothesized mechanisms in single molecule conductance switching. J. Am. Chem. Soc. 128, 1959–1967 (2006).

  13. 13

    Blum, A. S. et al. Molecularly inherent voltage-controlled conductance switching. Nature Mater. 4, 167–172 (2005).

  14. 14

    Rahimi, M. & Troisi, A. Probing local electric field and conformational switching in single-molecule break junctions. Phys. Rev. B 79, 113413 (2009).

  15. 15

    Moresco, F. et al. Conformational changes of single molecules induced by scanning tunneling microscopy manipulation: a route to molecular switching. Phys. Rev. Lett. 86, 672–675 (2001).

  16. 16

    Franco, I., Solomon, G. C., Schatz, G. C. & Ratner, M. A. Tunneling currents that increase with molecular elongation. J. Am. Chem. Soc. 133, 15714–15720 (2011).

  17. 17

    Shibano, Y. et al. Conformation effect of oligosilane linker on photoinduced electron transfer of tetrasilane-linked zinc porphyrin–[60]fullerene dyads. J. Organomet. Chem. 692, 356–367 (2007).

  18. 18

    Ruehl, K. E. & Matyjaszewski, K. Dearylation of α,ω-diphenylpermethylated oligosilanes with triflic acid. J. Organomet. Chem. 410, 1–12 (1991).

  19. 19

    Kobayashi, T. & Pannell, K. H. A general, high-yield reaction for the formation of (chloromethyl)oligosilanes. Organometallics 9, 2201–2203 (1990).

  20. 20

    Kobayashi, T. & Pannell, K. H. Synthesis of (chloromethyl)silanes by the low-temperature reaction of chlorosilanes and in situ generated (chloromethyl)lithium in tetrahydrofuran. Organometallics 10, 1960–1964 (1991).

  21. 21

    Anklam, E. Synthese von α-Halogen-ω-alkylthio-alkanen und α,ω-Bisalkylthio-alkanen. Synthesis 1987, 841–843 (1987).

  22. 22

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

  23. 23

    Park, Y. S. et al. Contact chemistry and single-molecule conductance: a comparison of phosphines, methyl sulfides, and amines. J. Am. Chem. Soc. 129, 15768–15769 (2007).

  24. 24

    Agraït, N., Rodrigo, J. & Vieira, S. Conductance steps and quantization in atomic-size contacts. Phys. Rev. B 47, 12345–12348 (1993).

  25. 25

    Gonzalez, M. T. et al. Electrical conductance of molecular junctions by a robust statistical analysis. Nano Lett. 6, 2238–2242 (2006).

  26. 26

    Klausen, R. S., Widawsky, J. R., Steigerwald, M. L., Venkataraman, L. & Nuckolls, C. Conductive molecular silicon. J. Am. Chem. Soc. 134, 4541–4544 (2012).

  27. 27

    Hybertsen, M. S. et al. Amine-linked single-molecule circuits: systematic trends across molecular families. J. Phys. Condens. Matter 20, 374115 (2008).

  28. 28

    Sandorfy, C. LCAO MO calculations on saturated hydrocarbons and their substituted derivatives. Can. J. Chem. 33, 1337–1351 (1955).

  29. 29

    Schepers, T. & Michl, J. Optimized ladder C and ladder H models for sigma conjugation: chain segmentation in polysilanes. J. Phys. Org. Chem. 15, 490–498 (2002).

  30. 30

    Salomon, A. et al. Comparison of electronic transport measurements on organic molecules. Adv. Mater. 15, 1881–1890 (2003).

  31. 31

    Temirov, R., Lassise, A., Anders, F. B. & Tautz, F. S. Kondo effect by controlled cleavage of a single-molecule contact. Nanotechnology 19, 065401 (2008).

  32. 32

    Bruot, C., Hihath, J. & Tao, N. Mechanically controlled molecular orbital alignment in single molecule junctions. Nature Nanotechnol. 7, 35–40 (2012).

  33. 33

    González, M. T. et al. Stability of single- and few-molecule junctions of conjugated diamines. J. Am. Chem. Soc. 135, 5420–5426 (2013).

  34. 34

    Trouwborst, M., Huisman, E., Bakker, F., van der Molen, S. & van Wees, B. Single atom adhesion in optimized gold nanojunctions. Phys. Rev. Lett. 100, 175502 (2008).

  35. 35

    Chang, S., He, J., Zhang, P., Gyarfas, B. & Lindsay, S. Gap distance and interactions in a molecular tunnel junction. J. Am. Chem. Soc. 133, 14267–14269 (2011).

  36. 36

    Lin, J. & Beratan, D. N. Tunneling while pulling: the dependence of tunneling current on end-to-end distance in a flexible molecule. J. Phys. Chem. A 108, 5655–5661 (2004).

  37. 37

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

  38. 38

    Fan, F-R. F. et al. Charge transport through self-assembled monolayers of compounds of interest in molecular electronics. J. Am. Chem. Soc. 124, 5550–5560 (2002).

  39. 39

    Piqueras, M. C., Crespo, R. & Michl, J. The transoid, ortho, and gauche conformers of decamethyl-n-tetrasilane, n-Si4Me10: electronic transitions in the multistate complete active space second-order perturbation theory description. J. Phys. Chem. A 107, 4661–4668 (2003).

  40. 40

    George, C. B., Ratner, M. A. & Lambert, J. B. Strong conductance variation in conformationally constrained oligosilane tunnel junctions. J. Phys. Chem. A 113, 3876–3880 (2009).

  41. 41

    Michl, J. & West, R. Conformations of linear chains. Systematics and suggestions for nomenclature. Acc. Chem. Res. 33, 821–823 (2000).

  42. 42

    Goddard, W. A. & Harding, L. B. The description of chemical bonding from ab initio calculations. Annu. Rev. Phys. Chem. 29, 363–396 (1978).

  43. 43

    Jaguar, version 8.3 (Schrodinger, Inc., New York, 2014).

  44. 44

    Parameswaran, R. et al. Reliable formation of single molecule junctions with air-stable diphenylphosphine linkers. J. Phys. Chem. Lett. 1, 2114–2119 (2010).

  45. 45

    McConnell, H. M. Intramolecular charge transfer in aromatic free radicals. J. Chem. Phys. 35, 508–515 (1961).

  46. 46

    Woitellier, S., Launay, J. P. & Joachim, C. The possibility of molecular switching: theoretical study of [(NH3)5Ru-4,4′-bipy-Ru(NH3)5]5+. Chem. Phys. 131, 481–488 (1989).

  47. 47

    Venkataraman, L. et al. Electronics and chemistry: varying single-molecule junction conductance using chemical substituents. Nano Lett. 7, 502–506 (2007).

  48. 48

    Venkataraman, L., Klare, J. E., Nuckolls, C., Hybertsen, M. S. & Steigerwald, M. L. Dependence of single-molecule junction conductance on molecular conformation. Nature 442, 904–907 (2006).

  49. 49

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

  50. 50

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

Download references


We thank the National Science Foundation (NSF) for the primary support of these studies under Grant No. CHE-1404922. T.A.S. is supported by the NSF Graduate Research Fellowship under Grant No. 11-44155. H.L. is supported by the Semiconductor Research Corporation and New York Center for Advanced Interconnect Science and Technology program. L.V. thanks the Packard Foundation for support. We thank R. S. Klausen, P. Mortimer and Y. Itagaki for mass spectrometry assistance and O. Adak, E. J. Dell and J. L. Leighton for insightful discussions.

Author information

T.A.S. synthesized all the molecules. H.L. carried out all the STM-BJ measurements. T.A.S. and M.L.S. carried out all the computations. All the authors conceived the idea, designed the experiments, analysed the data and co-wrote the manuscript.

Correspondence to Michael L. Steigerwald or Latha Venkataraman or Colin Nuckolls.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 5824 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Su, T., Li, H., Steigerwald, M. et al. Stereoelectronic switching in single-molecule junctions. Nature Chem 7, 215–220 (2015) doi:10.1038/nchem.2180

Download citation

Further reading