Chiral Cycloparaarylenes Incorporating Binaphthyl Units: Dramatic Effects of Peripheral Functionalization on (Chir)Optical Properties

ABSTRACT Axially chiral [12]cycloparaarylenes 1 and 2 , consisting of three each of 1,1′‐binaphthyl and biphenyl units, were synthesized. Their characteristics were distinct from those of [12]cycloparaphenylene and depended on whether the 2,2′‐substituents on the binaphthyls were methoxy groups or a methylenedioxy bridge. 1 with methoxy groups adopted a D 3 ‐symmetric structure with transoid binaphthyls, whereas 2 with methylenedioxy groups existed as an equilibrium mixture of C 3 ‐ and C 1 ‐symmetric structures with cisoid binaphthyls. This difference arises from modulation in binaphthyl dihedral angles and the intrinsic preference of cycloparaarylenes (CPAs) for cylindrical arene arrangements. 1 displayed strong aggregation‐induced emission enhancement (AIEE) with Φ fl of 0.85 at 5°C and blue emission in the solid state. 2 showed weaker but more redshifted AIEE and solid‐state green emission. Trifluoroacetic acid molecules stabilized the highly symmetric conformations of 1 in the excited state, leading to a ninefold enhancement in fluorescence (FL) and intense circularly polarized luminescence (CPL) with | g lum | of 0.028 and B CPL of 820 M −1 cm −1 at −60°C.