Bottom-up synthesis of finite models of helical (n,m)-single-wall carbon nanotubes

The bottom-up synthesis of hoop-shaped aromatic hydrocarbons is currently attracting interest, because they can serve as finite models of single-wall carbon nanotubes (SWNTs). Models for chiral (n,m)-SWNTs, particularly those with optical activity, have not been synthesized but are of special interest owing to their anomalous helical network of sp(2)-carbons. Here we show that finite model compounds for (12,8)-, (11,9)- and (10,10)-SWNTs are synthetically accessible by a stepwise macrocyclization of [4]phenacene, a compound that bears fused benzene rings in a zigzag arrangement, and we can isolate and identify all the isomers including the enantiomers with (P)- and (M)-helicity. The complete isolation and identification of the model compounds led to the first examination of the stereo-disproportionation of chiral SWNT models, which encourages the future studies on asymmetric induction for the synthesis.