A graphyne spoked wheel

Abstract

<h2>Summary</h2> γ-Graphyne is an emerging carbon allotrope, and synthesis of large-size atomically precise γ-graphyne fragments would be crucial to understand its distinctive properties. Herein, a long-sought-after graphyne spoked wheel with 6-fold symmetry was synthesized mainly through cobalt(0)-catalyzed cyclotrimerization of a triyne intermediate followed by 12-fold intramolecular Stille coupling reactions. Its structure was unambiguously confirmed by X-ray crystallographic analysis, which revealed a closely stacked dimer structure. NMR and theoretical analysis disclosed that fusion of six anti-aromatic hexadehydro[12]annulene units led to a decrease in local aromaticity of all seven benzenoid rings (particularly, the central one), which is quite different from a graphene analog, hexa-<i>peri</i>-hexabenzocoronene (HBC). Its optical and electrochemical properties are also different from those of HBC, showing allowed HOMO → LUMO electronic transition and facile electrochemical reduction. This study provided a new method for the synthesis of even larger γ-graphyne fragments and demonstrated the unique electronic properties and packing structure of γ-graphyne as compared with those of graphene.