Synthesis of Armchair and Chiral Carbon Nanobelts

Carbon nanobelts that consist of a loop of fully fused benzene rings are long-standing and challenging targets of organic synthesis and are key steps toward the ultimate synthesis of uniform carbon nanotubes (CNTs) of single chirality and predefined diameter. Herein, we report the synthesis of an unprecedented armchair carbon nanobelt and the first chiral carbon nanobelt, which represent sidewall segments of armchair and chiral CNTs, (12,12) CNT and (18,12) CNT, respectively. These carbon nanobelts were synthesized from 2,5-di(benzyloxy)-1,4-benzoquinone in six steps by pi-expansion of the corresponding polyarylated carbon nanorings through Scholl reactions. Scanning tunneling microscopy revealed these nanobelts to be nanoparticles of roughly uniform size. In contrast to earlier unsuccessful attempts to synthesize carbon nanobelts from the corresponding carbon nanorings, the belt-forming step reported herein is accompanied by either a small increase or even a decrease in strain energy, as found from the theoretical calculations.