A Crystalline π‐Stack Containing Five Stereoisomers: Insights into Conformational Isomorphism, Chirality Inversion, and Disorder. (18th August 2017)

• Record Type: Journal Article
• Authors: Nowak‐Król, Agnieszka; Röhr, Merle I. S.; Schmidt, David; Würthner, Frank
• Is Part Of: Angewandte Chemie. Volume 129:Number 39(2017)
• Page Start: 11936
• Page End: 11940
• Publication Date: 2017-08-18
• Subjects: Chiralität -- Einkristalle -- Isomerisierungen -- Konformationsisomorphie -- Perylenbisimid; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201705445
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: An unprecedented crystal‐packing arrangement of a tetramethoxy‐bay‐substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, that is, an achiral (AC ) PBI of saddle‐shaped geometry along with two pairs of propeller‐like twisted ( P )‐ and ( M )‐enantiomeric PBI frameworks. All these five conformations are observed within a single π‐stack revealing an intriguing packing sequence with an inversion of chirality from P to M viaAC . Nudged elastic band calculations for the isolated molecule show thatAC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition‐state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is aided by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations.