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Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold

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A Corrigendum to this article was published on 20 June 2014

An Erratum to this article was published on 21 May 2014

This article has been updated

Abstract

Since the first report of thiol-based self-assembled monolayers (SAMs) 30 years ago, these structures have been examined in a huge variety of applications. The oxidative and thermal instabilities of these systems are widely known, however, and are an impediment to their widespread commercial use. Here, we describe the generation of N-heterocyclic carbene (NHC)-based SAMs on gold that demonstrate considerably greater resistance to heat and chemical reagents than the thiol-based counterparts. This increased stability is related to the increased strength of the gold–carbon bond relative to that of a gold–sulfur bond, and to a different mode of bonding in the case of the carbene ligand. Once bound to gold, NHCs are not displaced by thiols or thioethers, and are stable to high temperatures, boiling water, organic solvents, pH extremes, electrochemical cycling above 0 V and 1% hydrogen peroxide. In particular, benzimidazole-derived carbenes provide films with the highest stabilities and evidence of short-range molecular ordering. Chemical derivatization can be employed to adjust the surface properties of NHC-based SAMs.

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Figure 1: Reaction of NHCs with bare and sulfide-protected Au surfaces, and reaction of thiols and sulfides with 1-protected Au(111) surfaces.
Figure 2: Molecular-scale ordering and high stability of NHC–Au(111) surfaces.
Figure 3: Chemical derivatization of Au(111) surfaces and film stability under repeated electrochemical cycling.

Change history

  • 10 April 2014

    In the version of this Article originally published, J. Hugh Horton should also have been denoted a corresponding author. This error has now been corrected in the online versions of the Article.

  • 21 May 2014

    In the version of this Article originally published, ref. 40 was incorrect, it should have read: Rodríguez-Castillo, M. et al. Reactivity of gold nanoparticles towards N-heterocyclic carbenes. Dalton Trans. 43, 5978–5982 (2014). This has been corrected in the online versions of the Article.

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Acknowledgements

C.M.C., J.H.H., A.B.M., N.J.M., G.W. and H-B.K. acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding in terms of Discovery and Research Tools and Instruments grants. C.M.C. acknowledges NSERC for Discovery Accelerator Supplements funding. C.M.C., J.H.H., A.B.M. and G.W. acknowledge the Canada Foundation for Innovation for infrastructure funding. E.C.K. acknowledges NSERC for a Postgraduate Scholarship (Doctoral) fellowship. J.D.L. and A.R-W. acknowledge NSERC for Undergraduate Student Research Awards funding. E.C.K. and T.S. acknowledge the Queen's Chemistry Department for Queen's Graduate Awards. P. McBreen, K. Itami and H-P. Loock are thanked for useful discussions.

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Contributions

C.M.C. conceived the concept, and J.H.H. and C.M.C. equally designed the experiments and prepared the manuscript using feedback from the other authors. Synthetic studies were carried out in C.M.C.'s lab, and surface studies in J.H.H.'s lab. A.B.M. and B.D. carried out STM studies, G.W. carried out solid-state MAS NMR studies, N.J.M. carried out computational studies, I.I.E., E.C.K. and T.S. worked on the syntheses of NHCs 6 and 7. O.V.Z., J.D.L. and A.R-W. worked on the synthesis and adsorption of carbenes 1–5 on surfaces. O.V.Z. and I.I.E. carried out the stability studies. I.I.E. carried out surface characterizations. Z.S. and H.B.K. carried out electrochemical measurements.

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Correspondence to Cathleen M. Crudden or J. Hugh Horton.

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Crudden, C., Horton, J., Ebralidze, I. et al. Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold. Nature Chem 6, 409–414 (2014). https://doi.org/10.1038/nchem.1891

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