Chiral Amplification in Dynamic Supramolecularly Tailored Aggregates with Enhanced Stimuli-Responsive Fluorescence...

Chiral amplification of supramolecular aggregates in a completely aqueous medium is a treasure trove to realize the origins of homochirality in nature. Here, we report the development of a concentration-dependent asymmetric hierarchical columnar H-aggregate from the repeated cooperative stacking of a propeller shaped complex between C₃ symmetric protonated benzoylated melamine (PBM) and beta-cyclodextrin (β-CD) in water governed by π-π interaction and 3-fold H-bonding as evidenced by UV-vis, PXRD, FT-IR, 1D and 2D NMR, DLS, SEM, AFM, etc. Circular dichroism spectra demonstrated the overall intrinsic conformational chirality. A 0.9 mM aqueous solution of PBM@3β-CD exhibited the maximum expression of chirality (∼50 folds). Light irradiation has transformed it into distorted J-aggregate with retention of chirality with an effective coherence length (N ≈ 5). It showed brilliant aggregation induced fluorescence (AIF) with fluorescence quantum yield Φ_F = 0.11 at 390 nm. The structure of the monomeric PBM@3β-CD was theoretically optimized. The expression of cooperativity from the synergistic interactions among the monomeric repeating units is elucidated by a nucleation-elongation model. Our results thus open new routes to understand multicomponent stimuli-responsive supramolecular host-guest self-assembly, offering valuable insights into the formed conformationally asymmetric superstructures.