Conformationally Locked Cyclo[2]Dipyrrins Linked with Anthracene Subunits: Synthesis and Chiroptical Properties

Abstract

AbstractHerein, we report the synthesis of anthracene‐containing twisted cyclo[2]dipyrrin 1 by utilizing a non‐planar building block, 1,5‐dipyrrylanthracene (1,5‐DPA). The non‐planar nature of the macrocycle enhanced the solubility and helped in structural characterization. Macrocycle 1 adopts a twisted ‘figure of eight’ conformation stabilized by strong intramolecular H‐bonding interactions and exists as a pair of helical enantiomers, as revealed by X‐ray crystallographic analysis. More importantly, the sterically locked structure enabled facile optical resolution using chiral HPLC. The (P,P) and (M,M) enantiomers show moderate chiroptical properties, such as absorption dissymmetry factors |gabs| in the order of 10−3, and luminescence dissymmetry factors |glum| of 3.8×10−3 and 2.9×10−3 at 702 nm, respectively.