Enantiopure synthesis of uniform [<i>n</i>]cycloparaphenylene-pillar[5]arene multi-macrocycles and their chiroptical properties

Chiral conjugated nanohoops are attractive based on their potential circularly polarized luminescence (CPL) activity. Using an approach of merging chiral pillar[5]arene (P[5]A) macrocycles with a conjugated nanohoop architecture, we report the enantioselective synthesis of [n]cycloparaphenylene ([n]CPP)–P[5]A conjugates, [n]CPP-PAn/3 (n = 9, 12 and 15), using a Pt-mediated macrocyclization of enantiopure phenylene-extended P[5]A. The three multi-macrocycles exhibit photophysical behavior closely related to their parent [n]CPPs. Their high fluorescence quantum yield (ΦF = 56–81%) and circularly polarized luminescence (CPL) with dissymmetry factors glum of 4.2 × 10−4–3.0 × 10−3 lead to CPL brightnesses BCPL of up to 96 M−1 cm−1 in [15]CPP-PA3. This study presents the selective synthesis of statistically disfavored isomers to obtain high-symmetry chiral nanohoops suitable for chiroptical applications.