Chiral V-shaped Pyrenes: Hexagonal Packing, Superhelix, and Amplified Chiroptical Performance

Here, we designed symmetric and dissymmetric chiral V-shaped pyrenes by linking achiral pyrenes to trans-1,2-cyclohexane diamine scaffolds with varied spacers to investigate their circular dichroism (CD) and circularly polarized excimer emission (CPEE). In molecular solution, the symmetric V-shaped molecules (P1, P2, P3) displayed spacerdependent CD and CPEE originating from the intramolecular excimers while the dissymmetric V-shaped B was silent in CD and CPEE. Upon self-assembly, the chiral V-shaped conformation guided a helical hexagonal packing. Notably, P1 self-assembled into delicate superhelices with optimum chiroptical activities and the largest gCD for pyrene derivatives to date. The dissymmetric B formed two distinct hexagonal aggregates as twists and rectangular nanotubes with greatly amplified CPEE. This work demonstrates unprecedented hexagonal superhelices from chiral V-shaped scaffolds and provides a deep insight into the relationship between molecular conformation, supramolecular architectures, and their chiroptical performance.

Automated summary

In this study, symmetric and dissymmetric chiral V-shaped pyrenes were designed and their circular dichroism (CD) and circularly polarized excimer emission (CPEE) were investigated. Symmetric V-shaped molecules exhibited spacer-dependent CD and CPEE in molecular solution, while dissymmetric V-shaped molecules were silent in CD and CPEE. Additionally, the chiral V-shaped conformation guided a helical hexagonal packing upon self-assembly.