Halogen Interaction Effects on Chiral Self‐Assemblies on Cyclodipeptide Scaffolds Across Hierarchy

Abstract

AbstractHow halogenation affects protein or peptide folding and self‐assembly hierarchically? This study tries to answer this question by using the halogen bonding mediated self‐assemblies on cyclodipeptide scaffolds. Single‐functionalized cyclodipeptides (Cyclo‐GX) based on para‐halogenated phenylalanine in the solid state form homochiral helical nanotubes via consecutive X···O bonds (X = Cl, Br, and I) independent of halogen kinds. In contrast, double‐functionalized cyclodipeptides (Cyclo‐XX) feature versatile self‐assembly architectures depending on the para‐substituents (X = H, F, Cl, Br, and I), affording nanotubular, lamellar, and triple helical nanotubular architectures. Cyclo‐BrBr exclusively adopts intramolecular Type‐IV X···X interaction that alters the molecular folding and packing, which also gives rise to opposite chirality at molecular folding (secondary structure), stacking (tertiary structure), and self‐assembled nanohelices (quarternary structure) at macroscopic scale. It unveils how halogenation impacts on the self‐assembly and chirality at hierarchical levels in specific peptides. Clusteroluminescence is found for the cyclodipeptides, achieving high quantum yield up to 71%, whereby circularly polarized luminescence is realized with tunable handedness by controlling halogen substituents.