Lemniscular carbon nanohoops with contiguous conjugation from planar chiral [2.2]paracyclophane: influence of the regioselective synthesis on topological chirality

Abstract

We report herein the regioselective synthesis of all-carbon lemniscular nanohoops <i>bis-po</i>-CC and <i>bis-pm</i>-TC by the rational control of ring closures at the different positions of planar chiral tetrasubstituted [2.2]paracyclophane. Topological analyses reveal that <i>bis-pm</i>-TC is topologically chiral while <i>bis-po</i>-CC is topologically achiral. X-ray crystal analysis demonstrates that <i>bis-pm</i>-TC adopts a lemniscular conformation with a contiguous conjugation. CD and CPL measurements further reveal that the chiroptical properties of <i>bis-pm</i>-TC are obviously different from those of <i>bis-po</i>-CC due to their different topological chiralities.