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Abstract:
N-Heterocyclic olefins (NHOs), possessing highly polarizable and remarkably electron-rich double bonds, have been effectively utilized as exceptional anchors for surface modifications. Herein, the adsorption, orientation, and electronic properties of NHOs on a metal surface are investigated. On Cu(111), the sterically low-demanding IMe-NHO is compared to its analogous IMe-NHC counterpart. High-resolution electron energy-loss spectroscopy (HREELS) measurements show for both molecules a flat-lying ring adsorption configuration. While the NHC adopts a dimer configuration including a Cu adatom, the NHO chemisorbs over a C–Cu bond perpendicular to the surface. This distinct difference leads for the IMe-NHOs to have a higher thermal stability on the surface. Moreover, IMe-NHOs introduce a higher net electron transfer to the surface compared to the IMe-NHCs, which results in a stronger effect on the work function. These results highlight the role of NHOs in surface science as they extend the functionalization capabilities of NHCs into stronger electronic modification.
