A Compact Circularly Polarized Luminescence Emitter–Chirality of a [2.2]‐Paracyclophane Macrocycle

Chiral organic molecules with pronounced chiroptical responses are of significant interest for applications ranging from bioimaging to optoelectronic devices. Herein, we report comprehensive chiroptical investigations of a compact [2.2]paracyclophane (PCP)- based macrocycle and its open precursor. While the synthesis of the structure was reported by the group of Michael Haley, chiroptical investigations were still missing. The rigid PCP core acts as a chiral template, inducing helical twisting within the conjugated diacetylene framework. Owing to its low atomic count, the compact macrocycle represents an attractive model system for combined experimental and computational studies, enabling fast DFT and TD-DFT calculations. The macrocycle and its open synthetic precursor were synthesized, structurally characterized, and, in both cases, enantiomers were separated on a chiral stationary phase HPLC. Absolute configurations were assigned through TD-DFT calculations. Optical measurements reveal enhanced conjugation and redshifted emission upon macrocyclization. Electric circular dichroism (ECD) spectra exhibit multiple intense cotton bands. ... mehrBoth macrocycle and open precursor display exceptionally high circularly polarized luminescence (CPL) dissymmetry factors, with glum around 10$^{−2}$. Despite moderate CPL brightness, limited by the compounds’ quantum yields, these results demonstrate the strong chiral amplification imparted by the PCP. The presented scaffold provides a versatile platform for probing structure–property relationships in chiral conjugated macrocycles.