Conformationally Locked Cyclo[<i>2</i>]Dipyrrins Linked with Anthracene Subunits: Synthesis and Chiroptical Properties
Anjana Prasad Nambiar, Probal Nag, Ruth Mariam Ipe, Sivaranjana Reddy Vennapusa, Sabapathi Gokulnath
Abstract
Abstract Herein, 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 | g abs | in the order of 10 −3 , and luminescence dissymmetry factors | g lum | of 3.8×10 −3 and 2.9×10 −3 at 702 nm, respectively.