Tailored functional monolayers made from mesoionic carbenes.

• Mesoionic carbenes (MICs) are used for the first time to modify surfaces. In comparison to NHCs, MICs offer more versatility to immobilize functional groups since they are covalently grafted by click chemistry. • We demonstrate the approach by presenting results with 5 molecules bearing different functional groups, including 3 electroactive ones (no study in this domain features that many substrates). • A wide range of spectroscopic techniques are used: X-ray photoelectron Spectroscopy, infrared Spectroscopy, and even Tip-Enhanced Raman Spectroscopy which provides a local analysis of the surface (once again, no corresponding study has included such a variety of analyses for surface characterization). • The monitoring of MIC grafting as a function of electrode immersion time could be simply performed by cyclic voltammetry. • We demonstrate that reversible exchange reactions are possible between MICs and dodecanethiol on gold surfaces, opening the route for mixed assemblies. Significant progress has been made over the last decades in surface functionalization of coinage metals using thiols and more recently N-heterocyclic carbenes. As shown in this work, mesoionic carbenes (MICs) provide straightforward access to a novel class of surface ligands including electroactive ones and thus materials. Importantly, MICs are easily accessed from triazolium salts (TS) onto which functional groups may be attached with little synthetic effort. Here, we present a library of TS that were further converted, in situ , into MICs and grafted onto gold surfaces. The modified surfaces were thoroughly characterized by advanced spectroscopic methods such as XPS, infrared and Tip-Enhanced Raman Spectroscopy. Through cyclic voltammetry at 100 Vs-1, we could evaluate the surfacic concentration of the grafted molecules for electroactive MICs. We also prepared mixed MIC/thiol self-assembled monolayers, which opens the route to multifunctional surfaces. Triazolium salts bearing redox active or Raman responsive pendant functional arms are easily synthesized through Click Chemistry followed by N3-quaternization. These salts are applied as mesoionic carbene (MIC) precursors for the formation of active self-assembled monolayers (SAMs) on gold surfaces. Ligand grafting on gold was confirmed by cyclic voltammetry (CV), XPS, Raman and TERS spectroscopies. [Display omitted] [ABSTRACT FROM AUTHOR]