Imidazolinium N-Heterocyclic Carbene Ligands for Enhanced Stability on Gold Surfaces

Abstract

N-heterocyclic carbenes (NHCs) have emerged as versatile and robust ligands for noble metal surface modifications due to their ability to form compact, self-assembled monolayers. Despite a growing body of research, previous NHC surface modification schemes have employed just two structural motifs: the benzimidazolium NHC and the imidazolium NHC. However, different NHC moieties, including saturated NHCs, are often more effective in homogenous catalysis chemistry than these aforementioned motifs and may impart numerous advantages to NHC surfaces, such as increased stability and access to chiral groups. This work explores the preparation and stability of NHC-coated gold surfaces using imidazolium and imidazolinium NHC ligands. X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy demonstrate the attachment of NHC ligands to the gold surface and show enhanced stability of imidazolinium compared to the traditional imidazolium under harsh acidic conditions.