Direct Formation of C-C Triple-Bonded Structural Motifs by On-Surface Dehalogenative Homocouplings of Tribromomethyl-Substituted Arenes

On-surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied in recent years. The formation of acetylenic scaffolds provides an important route to the fabrication of emerging carbon nanostructures, including carbyne, graphyne, and graphdiyne, which feature chemically vulnerable sp-hybridized carbon atoms. Herein, we designed and synthesized a tribromomethyl-substituted compound. By using a combination of high-resolution scanning tunneling microscopy, non-contact atomic force microscopy, and density functional theory calculations, we demonstrated that it is feasible to convert these compounds directly into C-C triple-bonded structural motifs by on-surface dehalogenative homocoupling reactions. Concurrently, sp(3)-hybridized carbon atoms are converted into sp-hybridized ones, that is, an alkyl group is transformed into an alkynyl moiety. Moreover, we achieved the formation of dimer structures, one-dimensional molecular wires, and two-dimensional molecular networks on Au(111) surfaces, which should inspire further studies towards two-dimensional graphyne structures.