Precise Monoselective Aromatic C–H Bond Activation by Chemisorption of <i>Meta</i>-Aryne on a Metal Surface

Aromatic C–H bond activation has attracted much attention due to its versatile applications in the synthesis of aryl-containing chemicals. The major challenge lies in the minimization of the activation barrier and maximization of the regioselectivity. Here, we report the highly selective activation of the central aromatic C–H bond in <i>meta</i>-aryne species anchored to a copper surface, which catalyzes the C–H bond dissociation. Two prototype molecules, i.e., 4′,6′-dibromo-<i>meta</i>-terphenyl and 3′,5′-dibromo-<i>ortho</i>-terphenyl, have been employed to perform C–C coupling reactions on Cu(111). The chemical structures of the resulting products have been clarified by a combination of scanning tunneling microscopy and noncontact atomic force microscopy. Both methods demonstrate a remarkable weakening of the targeted C–H bond. Density functional theory calculations reveal that this efficient C–H activation stems from the extraordinary chemisorption of the <i>meta</i>-aryne on the Cu(111) surface, resulting in the close proximity of the targeted C–H group to the Cu(111) surface and the absence of planarity of the phenyl ring. These effects lead to a lowering of the C–H dissociation barrier from 1.80 to 1.12 eV, in agreement with the experimental data

London Dispersion Directs On-Surface Self-Assembly of [121]Tetramantane Molecules

London dispersion (LD) acts between all atoms and molecules in nature, but the role of LD interactions in the self-assembly of molecular layers is still poorly understood. In this study, direct visualization of single molecules using atomic force microscopy with CO-functionalized tips revealed the exact adsorption structures of bulky and highly polarizable [121]­tetramantane molecules on Au(111) and Cu(111) surfaces. We determined the absolute molecular orientations of the completely sp³-hybridized tetramantanes on metal surfaces. Moreover, we demonstrate how LD drives this on-surface self-assembly of [121]­tetramantane hydrocarbons, resulting in the formation of a highly ordered 2D lattice. Our experimental findings were underpinned by a systematic computational study, which allowed us to quantify the energies associated with LD interactions and to analyze intermolecular close contacts and attractions in detail