Chiral Nanohoops with π-Extended Helicene Units: Synthesis, Crystal Structure, and Chiroptical Properties

Herein, we report the synthesis, structural characterization, and physical properties of two helicene-embedded chiral nanohoop enantiomers, [n]cycloparaphenylene-(π-extended [5]helicene) [n]CPP-E5H (n = 7 and 8). Single-crystal X-ray diffraction analysis unambiguously confirms the well-defined hoop-shaped architecture of [7]CPP-E5H, wherein the incorporated helicene adopts a twisted conformation. The enantiomers of [7-8]CPP-E5H, corresponding to (P)- and (M)-helical configurations, were successfully resolved via high-performance liquid chromatography. Their chiroptical properties were studied using circular dichroism, circularly polarized luminescence spectroscopy, and theoretical calculations.