An sp-sp2-hybridized molecular carbon allotrope C16 flake

The molecular carbon allotropes have an enduring attraction to chemists and physicists for their elusive structures and extraordinary properties. Cyclo16carbon has been produced on the surface and is well characterized, while it is interesting that molecular carbon allotrope, like C16, referring to molecules composed of 16 carbon atoms, presents a fascinating realm of isomeric possibilities. Except for cyclo16carbon, C16 isomers with other structures have been predicted only by theory. Here, we report the synthesis and structural characterization of a graphene-shaped isomer, i.e., C16 flake on a bilayer NaCl surface grown on Au(111), using an atom-manipulation strategy by eliminating chlorine from a fully chlorinated pyrene molecule, C16Cl10. The sp- and sp2-hybridized structure of C16 flake is well characterized by bond-resolved atomic force microscopy. Theoretical calculations reveal an open-shell singlet ground state of C16 flake. While cyclo16carbon has been produced on the surface and is well characterized, C16 isomers with other structures have been predicted only by theory. Here, the authors report the synthesis and structural characterization of a graphene-shaped C16 flake on a bilayer NaCl surface grown on Au(111).