Room-Temperature Synthesis of Carbon Nanochains via the Wurtz Reaction.

Abstract

In the field of surface synthesis, various reactions driven by the catalytic effect of metal substrates, particularly the Ullmann reaction, have been thoroughly investigated. The Wurtz reaction facilitates the coupling of alkyl halides through the removal of halogen atoms with a low energy barrier on the surface; however, the preparation of novel carbon nanostructures via the Wurtz reaction has been scarcely reported. Here, we report the successful synthesis of ethyl-bridged binaphthyl molecular chains on Ag(111) at room temperature via the Wurtz reaction. However, this structure was not obtained through low-temperature deposition followed by annealing even above room temperature. High-resolution scanning tunneling microscopy combined with density functional theory calculations reveal that the rate-limiting step of C-C homocoupling exhibits a low-energy barrier, facilitating the room-temperature synthesis of carbon nanochain structures. Moreover, the stereochemical configuration of adsorbed molecules hinders the activation of the C-X (X = Br) bond away from the metal surface and, therefore, critically influences the reaction pathways and final products. This work advances the understanding of surface-mediated reactions involving precursor molecules with stereochemical structures. Moreover, it provides an optimized approach for synthesizing novel carbon nanostructures under mild conditions.