Direct Formation of C–C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of <i>gem</i>-Dibromomethyl Molecules

Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal <i>gem</i>-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C–C double-bonded structural motifs <i>via</i> on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp³-hybridized state to an sp²-hybridized state of carbon atoms, <i>i</i>.<i>e</i>., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly­(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale