“…N-heterocyclic carbenes (NHCs) are an emerging class of ligands for functionalizing extended metal surfaces, nanoparticles and nanoclusters. − The ability of NHCs to produce self-assembled monolayers on a range of metallic, non-metallic, and metalloid substrates has attracted considerable interest with potential applications in multiple fields including catalysis, microelectronics, biosensing, surface protection, and 3D MOF architectures. ,,,,,− In such applications, it is critical to control the orientation and packing of NHC monolayers to fine-tune surface density, metal accessibility, and ligand orientation. Although the factors dictating binding orientation and self-assembly are not fully elucidated, several studies have pointed toward the important effect of exocyclic nitrogen substituents (wingtips). ,,,− Sterically congested N-substituents, such as iPr, tBu, Mes, and Dipp (wingtip groups), allow access to geometries whereby the heterocycle is perpendicular to the surface. As summarized in Scheme , top, regardless of their backbone structures, NHCs with primary substituents including Me, Et, and Bu give ordered overlayers composed of flat-lying M(NHC) 2 species resulting from the abstraction of a metal atom (M) from the surface. ,,− …”