A. Bakker, A. Timmer, E. Kolodzeiski, M. Freitag, H.-Y. Gao, H. Mönig, S. Amirjalayer, F. Glorius, H. Fuchs
Elucidating the binding modes of N-heterocyclic carbenes on a gold surface
J. Am. Chem. Soc., 2018, 140 (38), pp 11889–11892
Tuning the binding mode of N-heterocyclic carbenes (NHCs) on metal surfaces is crucial for the development of new functional materials. To understand the impact of alkyl sidegroups on the formation of NHCs species at the Au(111) surface, we combined scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. We reveal two significantly different binding modes depending on the alkyl length. In case of the short alkyl-substituent an up-standing configuration with one Au adatom is preferred, whereas the longer alkyl groups result exclusively in NHC-Au- NHC complexes lying flat on the surface. Our study highlights how well-defined structural modifications of NHCs allow to control the local binding motif on surfaces, which is important to design designated catalytic sites at interfaces.