N-Heterocyclic Carbenes as a Robust Platform for Surface-Enhanced Raman Spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) underpins a wide range of commercial and fundamental applications. SERS often relies on ligands, usually thiols, bound to a noble metal surface. The difficulty of straightforward thiol synthesis combined with their instability on surfaces highlights the need for alternative ligand design. We present the first example of SERS utilizing N-heterocyclic carbene ligands. A general three step synthesis is presented for functionalized NHC-CO2 adducts. These ligands are deposited on SERS-active gold film-over-nanosphere substrates (AuFONs) in solvent-free and base-free conditions, which prevents fouling. The resulting films are found to be robust and capable of postsynthetic modifications.