Regium-π bonds: An Unexplored Link between Noble Metal Nanoparticles and Aromatic Surfaces.

The ability of metal clusters involving elements from group 11 (Ag, Cu, Au) to favorably interact with π systems of different size and electronic nature was evaluated at the PBE0-D3/def2-TZVPP//PBE0-D3/def2-TZVP level of theory. The M9 clusters (M=Cu, Ag, Au) were used as σ-hole and σ-lump donors, and benzene, trifluorobenzene, and hexafluorobenzene as aromatic rings. In addition, the study was expanded to the analysis of extended π systems by using naphthalene and anthracene as well as their corresponding perfluorinated derivatives. Furthermore, Bader's theory of Atoms in Molecules as well as natural bonding orbital and spin-density calculations were used to further investigate and characterize the regium-π and σ-lump complexes described herein. Apparently, regium-π bonds have not previously been described in the literature and may be of great importance in the understanding of organocatalytic processes involving aromatic substrates as well as in the design of new materials based on this novel subclass of σ-hole bonding.