Insights into the surface chemistry of N-heterocyclic carbenes

N-heterocyclic carbenes (NHCs) have emerged as a versatile and powerful class of ligands in surface chemistry, offering remarkable stability and tunability when bound to surfaces, including metals, metal oxides, and semiconductors. Understanding their surface and interfacial mechanisms at the atomic-level is essential for precise control of molecule-surface interaction, as well as intermolecular interactions, which directly influence material performance and functionalities. Research in surface chemistry focusing on molecular binding modes, self-assembly, on-surface reactions, and electronic properties is crucial for the rational design of efficient catalysts, customized materials, and high-performance devices. This review highlights these critical aspects of NHCs on surfaces, beginning with their robust and multiple binding modes, which underpin their stability and versatility. The covalent NHC-surface bonds allow NHCs to form stable attachments, often surpassing the strength of traditional thiol-based modifiers, promoting robust anchoring across diverse materials. Another focus is the self-assembly of NHCs into highly ordered monolayers, which facilitates the design of functional nanostructures. Emerging topics also include on-surface reactions, surface electronic properties, and interfacial charge transfer of NHCs, emphasizing their dependence on the substrate and NHC molecular structure. By consolidating recent advancements in the study of NHCs on surfaces, we aim to provide a comprehensive overview of their transformative potential in surface chemistry at the atomic scale, while also identifying key challenges and future directions in the field.