Enantiopure synthesis of uniform [n]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 (Φ F = 56-81%) and circularly polarized luminescence (CPL) with dissymmetry factors g lum of 4.2 × 10-4-3.0 × 10-3 lead to CPL brightnesses B CPL 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.