N‐Heterocyclic Carbene Monolayers on Nickel, Iron, and Steel by a Radical‐to‐Carbene Strategy

Abstract

Abstract N‐Heterocyclic carbenes (NHCs) have recently emerged as the next‐generation surface ligands with improved stability and molecular flexibility. Despite these premises, research on NHC‐enriched flat surfaces is mainly limited to noble metals, while formation of free NHCs often requires the use of vacuum, bases, or strictly air‐ and moisture‐free conditions. We hereby report an unprecedented radical‐to‐carbene‐based approach for fabricating NHC monolayers on earth‐abundant and naturally oxidized metal surfaces of nickel, iron, and stainless steel. Following an open‐cell electrografting approach, 2‐azolyl radicals are firstly formed and immobilized on the metal to then rearrange into NHC monolayers apparently composed of flat‐lying NHCs, as corroborated by X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), sum‐frequency generation (SFG), and cyclic voltammetry (CV) measurements. Density functional theory (DFT) calculations highlighted the role of metal adatoms in facilitating the radical‐to‐carbene transition. A surface stability test was conducted to assess the tolerance of the NHC‐enriched surfaces toward physical, chemical, and electrochemical stress. Ultimately, this work expands the application field of carbenes‐on‐surfaces to cost‐effective and widely used materials, while offering an agile and, until now, mechanistically unknown approach to their generation.