Introducing Prism[4]arene: A Macrocycle with Enantiomerically Resolvable Inherent Chirality and Intriguing Chiroptical Properties
Paolo Della Sala, Carmen Talotta, Margherita De Rosa, Stefano Superchi, Ernesto Santoro, Silvano Geremia, Neal Hickey, Marco Fusè, Sergio Abbate, Giuseppe Mazzeo, Giovanna Longhi, Carmine Gaeta
Abstract
High Resolution Image Download MS PowerPoint Slide This study presents the first report of an inherently chiral prismarene with resolved enantiomers. Prism[4]arenes, synthesized via a thermodynamic template approach using a tailor-made selective cation, effectively maintain their chirality due to their strained macrorings and narrow annuli, which prevent the flipping of naphthalene rings. The solid-state structure of the synthesized PrS[4] iPe revealed a racemic crystal composed of all-p R and all-p S enantiomeric pairs, forming supramolecular polymeric chains of homochiral molecules interlinked by intermolecular host–guest interactions. Both enantiomers were resolved by using chiral high-performance liquid chromatography (HPLC), and their chiroptical properties were thoroughly investigated. Configurational assignment was achieved through time-dependent density functional theory (TDDFT) computations alongside electronic circular dichroism/ultraviolet–visible (ECD/UV–vis) spectral analysis. Notably, the circularly polarized luminescence (CPL) properties exhibited a significant dissymmetry ratio of 0.008 for these prism[4]arenes, due to electric and magnetic dipole transition moments both directed along the cylinder axis. Furthermore, the ability of PrS[4] iPe to achieve enantioselective recognition with chiral ammonium guests was demonstrated.