N-heterocyclic carbene-functionalized magic-number gold nanoclusters


Magic-number gold nanoclusters are atomically precise nanomaterials that have enabled unprecedented insight into structure–property relationships in nanoscience. Thiolates are the most common ligand, binding to the cluster via a staple motif in which only central gold atoms are in the metallic state. The lack of other strongly bound ligands for nanoclusters with different bonding modes has been a significant limitation in the field. Here, we report a previously unknown ligand for gold(0) nanoclusters—N-heterocyclic carbenes (NHCs)—which feature a robust metal–carbon single bond and impart high stability to the corresponding gold cluster. The addition of a single NHC to gold nanoclusters results in significantly improved stability and catalytic properties in the electrocatalytic reduction of CO2. By varying the conditions, nature and number of equivalents of the NHC, predominantly or exclusively monosubstituted NHC-functionalized clusters result. Clusters can also be obtained with up to five NHCs, as a mixture of species.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Synthesis and characterization of NHC-modified Au11 nanoclusters.
Fig. 2: DFT and UV–vis spectroscopic prediction of structure for NHC-modified nanoclusters.
Fig. 3: Spectroscopic and XRD characterization of NHC-substituted cluster 3a.
Fig. 4: Assessment of stability and ligand dissociation by CID mass spectrometry.
Fig. 5: Nanocluster stability and activity in the electrocatalytic reduction of CO2 to CO.

Data availability

Spectral and purity data are available for all new compounds, along with original NMR, MS, XPS, UV–vis, DFT, TGA–MS and electrochemical data. Single-crystal X-ray crystallographic data are included for cluster 3a, while crystallographic data for cluster 3a have been deposited at the Cambridge Crystallographic Data Centre under deposition no. CCDC 1878623. Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. All other data supporting the findings of this study are available within the Article and its Supplementary Information, or from the corresponding author upon reasonable request.


  1. 1.

    Bürgi, T. Properties of the gold–sulphur interface: from self-assembled monolayers to clusters. Nanoscale 7, 15553–15567 (2015).

  2. 2.

    Häkkinen, H. The gold–sulfur interface at the nanoscale. Nat. Chem. 4, 443–455 (2012).

  3. 3.

    Yamazoe, S., Koyasu, K. & Tsukuda, T. Nonscalable oxidation catalysis of gold clusters. Acc. Chem. Res. 47, 816–824 (2014).

  4. 4.

    Jadzinsky, P. D., Calero, G., Ackerson, C. J., Bushnell, D. A. & Kornberg, R. D. Structure of a thiol monolayer-protected gold nanoparticle at 1.1 Å resolution. Science 318, 430–433 (2007).

  5. 5.

    Häkkinen, H., Walter, M. & Grönbeck, H. Divide and protect: capping gold nanoclusters with molecular gold–thiolate rings. J. Phys. Chem. B 110, 9927–9931 (2006).

  6. 6.

    Qian, H., Zhu, M., Wu, Z. & Jin, R. Quantum sized gold nanoclusters with atomic precision. Acc. Chem. Res. 45, 1470–1479 (2012).

  7. 7.

    Hesari, M., Workentin, M. S. & Ding, Z. NIR electrochemiluminescence from Au25 nanoclusters facilitated by highly oxidizing and reducing co-reactant radicals. Chem. Sci. 5, 3814–3822 (2014).

  8. 8.

    Jensen, K. M. Ø. et al. Polymorphism in magic-sized Au144(SR)60 clusters. Nat. Commun. 7, 11859 (2016).

  9. 9.

    Chevrier, D. M., Yang, R., Chatt, A. & Zhang, P. Bonding properties of thiolate-protected gold nanoclusters and structural analogs from X-ray absorption spectroscopy. Nanotechnol. Rev. 4, 193–206 (2015).

  10. 10.

    Chevrier, D. M., Zeng, C. J., Jin, R. C., Chatt, A. & Zhang, P. Role of Au4 units on the electronic and bonding properties of Au28(SR)20 nanoclusters from X-ray spectroscopy. J. Phys. Chem. C 119, 1217–1223 (2015).

  11. 11.

    Jin, R. Quantum sized, thiolate-protected gold nanoclusters. Nanoscale 2, 343–362 (2010).

  12. 12.

    Tsukuda, T. & Häkkinen, H. Protected Metal Clusters: From Fundamentals to Applications (Elsevier, Amsterdam, 2015).

  13. 13.

    Wang, Y. et al. Atomically precise alkynyl-protected metal nanoclusters as a model catalyst: observation of promoting effect of surface ligands on catalysis by metal nanoparticles. J. Am. Chem. Soc. 138, 3278–3281 (2016).

  14. 14.

    Wang, Y. et al. Site preference in multimetallic nanoclusters: incorporation of alkali metal ions or copper atoms into the alkynyl-protected body-centered cubic cluster [Au7Ag8(C≡CtBu)12]+. Angew. Chem. Int. Ed. 55, 15152–15156 (2016).

  15. 15.

    Wang, Y. et al. An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands. J. Am. Chem. Soc. 137, 4324–4327 (2015).

  16. 16.

    Wan, X. K., Tang, Q., Yuan, S. F., Jiang, D. E. & Wang, Q. M. Au19 nanocluster featuring a V-shaped alkynyl-gold motif. J. Am. Chem. Soc. 137, 652–655 (2015).

  17. 17.

    Maity, P., Tsunoyama, H., Yamauchi, M., Xie, S. H. & Tsukuda, T. Organogold clusters protected by phenylacetylene. J. Am. Chem. Soc. 133, 20123–20125 (2011).

  18. 18.

    Weidner, T. et al. NHC-based self-assembled monolayers on solid gold substrates. Aust. J. Chem. 64, 1177–1179 (2011).

  19. 19.

    Zhukhovitskiy, A. V., Mavros, M. G., Voorhis, T. V. & Johnson, J. A. Addressable carbene anchors for gold surfaces. J. Am. Chem. Soc. 135, 7418–7421 (2013).

  20. 20.

    Crudden, C. M. et al. Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold. Nat. Chem. 6, 409–414 (2014).

  21. 21.

    Crudden, C. M. et al. Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing. Nat. Commun. 7, 12654 (2016).

  22. 22.

    Zhukhovitskiy, A. V., MacLeod, M. J. & Johnson, J. A. Carbene ligands in surface chemistry: from stabilization of discrete elemental allotropes to modification of nanoscale and bulk substrates. Chem. Rev. 115, 11503–11532 (2015).

  23. 23.

    Larrea, C. R. et al. N-heterocyclic carbene self-assembled monolayers on copper and gold: dramatic effect of wingtip groups on binding, orientation and assembly. ChemPhysChem 18, 3536–3539 (2017).

  24. 24.

    MacLeod, M. J. & Johnson, J. A. Pegylated N-heterocyclic carbene anchors designed to stabilize gold nanoparticles in biologically relevant media. J. Am. Chem. Soc. 137, 7974–7977 (2015).

  25. 25.

    Kim, H. K. et al. Reduction of the work function of gold by N-heterocyclic carbenes. Chem. Mater. 29, 3403–3411 (2017).

  26. 26.

    Wang, G. et al. Ballbot-type motion of N-heterocyclic carbenes on gold surfaces. Nat. Chem. 9, 152–156 (2016).

  27. 27.

    Engel, S., Fritz, E. C. & Ravoo, B. J. New trends in the functionalization of metallic gold: from organosulfur ligands to N-heterocyclic carbenes. Chem. Soc. Rev. 46, 2057–2075 (2017).

  28. 28.

    Moller, N. et al. Stabilization of high oxidation state upconversion nanoparticles by N-heterocyclic carbenes. Angew. Chem. Int. Ed. 56, 4356–4360 (2017).

  29. 29.

    Salorinne, K. et al. Water-soluble N-heterocyclic carbene-protected gold nanoparticles: size-controlled synthesis, stability and optical properties. Angew. Chem. Int. Ed. 56, 6198–6202 (2017).

  30. 30.

    Man, R. W. Y. et al. Ultrastable gold nanoparticles modified by bidentate N-heterocyclic carbene ligands. J. Am. Chem. Soc. 140, 1576–1579 (2018).

  31. 31.

    Rühling, A. et al. Modular bidentate hybrid NHC–thioether ligands for the stabilization of palladium nanoparticles in various solvents. Angew. Chem. Int. Ed. 55, 5856–5860 (2016).

  32. 32.

    Crudden, C. M. & Allen, D. A. Stability and reactivity of N-heterocyclic carbene complexes. Coord. Chem. Rev. 248, 2247–2273 (2004).

  33. 33.

    Hopkinson, M. N., Richter, C., Schedler, M. & Glorius, F. An overview of N-heterocyclic carbenes. Nature 510, 485–496 (2014).

  34. 34.

    Polgar, A. M., Weigend, F., Zhang, A., Stillman, M. J. & Corrigan, J. F. A N-heterocyclic carbene-stabilized coinage metal–chalcogenide framework with tunable optical properties. J. Am. Chem. Soc. 139, 14045–14048 (2017).

  35. 35.

    Azizpoor Fard, M., Levchenko, T. I., Cadogan, C., Humenny, W. J. & Corrigan, J. F. Stable -ESiMe3 complexes of CuI and AgI (E = S, Se) with NHCs: synthons in ternary nanocluster assembly. Chem. Eur. J 22, 4543–4550 (2016).

  36. 36.

    Robilotto, T. J., Bacsa, J., Gray, T. G. & Sadighi, J. P. Synthesis of a trigold monocation: an isolobal analogue of [H3]+. Angew. Chem. Int. Ed. 51, 12077–12080 (2012).

  37. 37.

    Jin, L. et al. Trinuclear gold clusters supported by cyclic (alkyl)(amino)carbene ligands: mimics for gold heterogeneous catalysts. Angew. Chem. Int. Ed. 53, 9059–9063 (2014).

  38. 38.

    McKenzie, L. C., Zaikova, T. O. & Hutchison, J. E. Structurally similar triphenylphosphine-stabilized undecagolds, Au11(PPh3)7Cl3 and [Au11(PPh3)8Cl2]Cl, exhibit distinct ligand exchange pathways with glutathione. J. Am. Chem. Soc. 136, 13426–13435 (2014).

  39. 39.

    Enkovaara, J. et al. Electronic structure calculations with GPAW: a real-space implementation of the projector augmented-wave method. J. Phys. Condens. Matter 22, 253202 (2010).

  40. 40.

    Zhang, P. & Sham, T. K. X-ray studies of the structure and electronic behavior of alkanethiolate-capped gold nanoparticles: the interplay of size and surface effects. Phys. Rev. Lett. 90, 245502 (2003).

  41. 41.

    Lopez-Cartes, C. et al. Gold nanoparticles with different capping systems: an electronic and structural XAS analysis. J. Phys. Chem. B 109, 8761–8766 (2005).

  42. 42.

    Tang, Q. & Jiang, D.-E. Comprehensive view of the ligand–gold interface from first principles. Chem. Mater. 29, 6908–6915 (2017).

  43. 43.

    Rodríguez-Castillo, M. et al. Reactivity of gold nanoparticles towards N-heterocyclic carbenes. Dalton Trans. 43, 5978–5982 (2014).

  44. 44.

    Tang, Q. et al. Lattice-hydride mechanism in electrocatalytic CO2 reduction by structurally precise copper-hydride nanoclusters. J. Am. Chem. Soc. 139, 9728–9736 (2017).

  45. 45.

    Cao, Z. et al. A molecular surface functionalization approach to tuning nanoparticle electrocatalysts for carbon dioxide reduction. J. Am. Chem. Soc. 138, 8120–8125 (2016).

  46. 46.

    Cao, Z. et al. Chelating N-heterocyclic carbene ligands enable tuning of electrocatalytic CO2 reduction to formate and carbon monoxide: surface organometallic chemistry. Angew. Chem. Int. Ed. 57, 4981–4985 (2018).

  47. 47.

    Gray, H. B. Powering the planet with solar fuel. Nat. Chem. 1, 7 (2009).

  48. 48.

    Liu, M. et al. Enhanced electrocatalytic CO2 reduction via field-induced reagent concentration. Nature 537, 382–386 (2016).

  49. 49.

    Zhang, L., Zhao, Z.-J. & Gong, J. Nanostructured materials for heterogeneous electrocatalytic CO2 reduction and their related reaction mechanisms. Angew. Chem. Int. Ed. 56, 11326–11353 (2017).

Download references


C.M.C., J.H.H. and E.H.S. acknowledge support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) and the Ministry of Research Innovation (MRI) in terms of discovery grants and infrastructure grants, respectively. K.A. and P.J.G. thank NSERC for support through the awarding of USRA fellowships. M.R.N. thanks the Ontario Graduate Scholarship programme and Queen’s University for fellowship support. This work was supported by KAKENHI from the Japan Society for the Promotion of Science (JSPS; 17H03030 and 16K13962 to C.M.C. and 17H01182 to T.T.), Nanotechnology Platform (project no. 12024046) and the Elements Strategy Initiative for Catalysts & Batteries (ESICB). J.S.P.S. and N.U. acknowledge funding of this research through The World Premier International Research Center Initiative (WPI) programme. The computational work was supported by the Academy of Finland through the Academy Professorship of H.H. All computations were carried out at the Finnish CSC computer centre. S.K. thanks the Väisälä Foundation for a personal PhD study grant. K. Itami is thanked for assistance with the preparation of this manuscript.

Author information

C.M.C., P.J.U., M.R.N. and K.S. designed and carried out the synthesis of the nanoclusters, assisted by K.A., P.J.G., M.N., K.M.O. and R.W.Y.M. K.M.O. and R.W.Y.M. optimized the synthetic procedures and purifications and acquired TGA–MS data. MS analysis was performed and interpreted by S.T., R.T. and T.T., including CID MS. Crystallization of 3a was carried out by M.N. and S.T. on a sample prepared and purified by K.M.O. DFT studies, including prediction of structure and optical spectra, were carried out by S.K., S.M. and H.H. EXAFS and XANES studies were carried out and interpreted by J.H.H. and J.D.P. Electrocatalytic studies were performed and interpreted by C.-T.D. and E.H.S. The manuscript was written by C.M.C. with assistance from co-authors.

Correspondence to Hannu Häkkinen or Tatsuya Tsukuda or Cathleen M. Crudden.

Ethics declarations

Competing interests

The authors declare no competing interests.

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 experimental details, synthetic procedures, compound characterization data including spectral and purity data for all new compounds, along with original NMR, MS, XPS, UV-vis DFT, TGA–MS, single-crystal X-ray analysis and electrochemical data.

Crystallographic data

CIF for compound 3a; CCDC reference: 1878623.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Narouz, M.R., Osten, K.M., Unsworth, P.J. et al. N-heterocyclic carbene-functionalized magic-number gold nanoclusters. Nat. Chem. 11, 419–425 (2019). https://doi.org/10.1038/s41557-019-0246-5

Download citation

Further reading