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

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