Self-Assembled Monolayers of Nitron: Self-Activated and Chemically Addressable N-Heterocyclic Carbene Monolayers with Triazolone Structural Motif.

N-heterocyclic carbenes (NHCs) have emerged as a unique molecular platform for the formation of self-assembled monolayers (SAMs) on various surfaces. However, active carbene formation requires deprotonation of imidazolium salt precursors, which is mostly facilitated by exposure of the salt to exogenous base. Base residues were found to be adsorbed on the metal surface and hindered the formation of well-ordered carbene-based monolayers. Herein, we show that nitron, a triazolone-based molecule that freely tautomerizes into carbene, can spontaneously self-assemble into monolayers on Pt and Au surfaces, overcoming the necessity for base-induced deprotonation for active carbene formation. SAMs of nitron were found thermally stable and could not be displaced by thiols, demonstrating their high chemical stability. The addressable amine group in surface-anchored nitron was shown to be chemically available for SN2 reaction, making the surface-anchored nitron a chemically-addressable cross-linking reagent for surface modifications.