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, [<i>n</i>]cycloparaphenylene-(π-extended [5]helicene) <b>[</b><i>n</i><b>]CPP-E5H</b> (<i>n</i> = 7 and 8). Single-crystal X-ray diffraction analysis unambiguously confirms the well-defined hoop-shaped architecture of <b>[7]CPP-E5H</b>, wherein the incorporated helicene adopts a twisted conformation. The enantiomers of <b>[7-8]CPP-E5H</b>, corresponding to (<i>P</i>)- and (<i>M</i>)-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.