Optimizing bidentate N-heterocyclic carbene ligands for the modification of late transition metal surfaces – new insights through theory

Börner MC, Neugebauer J

Abstract

The functionalization of metal surfaces with N-heterocyclic carbenes (NHCs) has gained much interest in the past decade{,} since the modified materials are highly suitable for the development of specialized applications{,} for example in heterogeneous catalysis. More recently{,} multidentate NHC-ligands have been utilized to further improve the properties of the modified materials. However{,} the influence of the linker{,} which connects the NHC units{,} on the adsorption behavior of multidentate NHC-ligands has not been investigated so far. This knowledge is essential in order to access the full potential of applications. Here{,} we provide a thorough computational study{,} which compares the performance of bidentate NHC-ligands with twelve different linkers on the Cu(111){,} Pd(111) and Au(111) surfaces. It is shown that{,} on the Cu(111) and Au(111) surfaces{,} linkers should most importantly allow for a favorable arrangement of all NHC units{,} while aromatic linkers lead to stronger adsorption than aliphatic ones on Pd(111) surfaces. As a consequence{,} bidentate NHCs with aromatic linkers on Pd(111) surfaces tolerate larger deviations from the optimum single-NHC adsorption mode.