Highly Ordered N-Heterocyclic Carbene Monolayers on Cu(111)

Eloise Angove; Federico Grillo; Herbert A Früchtl; Alex J Veinot; Ishwar Singh; J Hugh Horton; Cathleen M Crudden; Christopher J Baddeley

doi:10.1021/acs.jpclett.1c04073

Highly Ordered N-Heterocyclic Carbene Monolayers on Cu(111)

J Phys Chem Lett. 2022 Mar 3;13(8):2051-2056. doi: 10.1021/acs.jpclett.1c04073. Epub 2022 Feb 24.

Authors

Eloise Angove¹, Federico Grillo¹, Herbert A Früchtl¹, Alex J Veinot², Ishwar Singh², J Hugh Horton², Cathleen M Crudden^{2

3}, Christopher J Baddeley¹

Affiliations

¹ EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom.
² Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario Canada, K7L 3N6.
³ Institute of Transformative Bio-Molecules, ITbM-WPI, Nagoya University, Nagoya, Chikusa 464-8601, Japan.

Abstract

The benzannulated N-heterocyclic carbene, 1,3-dibenzylbenzimidazolylidene (NHC^DBZ) forms large, highly ordered domains when adsorbed on Cu(111) under ultrahigh vacuum conditions. A combination of scanning tunnelling microscopy (STM), high-resolution electron energy loss spectroscopy (HREELS), and density functional theory (DFT) calculations reveals that the overlayer consists of vertical benzannulated NHC moieties coordinating to Cu adatoms. Long-range order results from the placement of the two benzyl substituents on opposite sides of the benzimidazole moiety, with their aromatic rings approximately parallel to the surface. The organization of three surface-bound benzyl substituents from three different NHCs into a triangular array controls the formation of a highly ordered Kagome-like surface lattice. By comparison with earlier studies of NHCs on Cu(111), we show that the binding geometry and self-assembly of NHC^DBZ are influenced by intermolecular and adsorbate-substrate interactions and facilitated by the flexibility of the methylene linkage between the N-heterocycle and the aromatic wingtip substituents.