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

Area of Science:

• Supramolecular Chemistry
• Organic Self-Assembly
• Chirality Studies

Background:

• Understanding the origins of homochirality in nature is crucial.
• Aqueous self-assembly of chiral molecules presents significant challenges.
• Supramolecular host-guest chemistry offers a platform for controlled assembly.

Purpose of the Study:

• To develop a chiral amplification system in an aqueous medium.
• To investigate the formation of hierarchical supramolecular aggregates.
• To explore the stimuli-responsive behavior and fluorescence properties of these aggregates.

Main Methods:

• Synthesis of a C3-symmetric complex between protonated benzoylated melamine (PBM) and beta-cyclodextrin (β-CD).
• Characterization using UV-vis, PXRD, FT-IR, NMR, DLS, SEM, and AFM.
• Circular dichroism (CD) spectroscopy to assess chirality.
• Theoretical optimization of the monomeric complex structure.
• Nucleation-elongation modeling to elucidate cooperativity.

Main Results:

• Formation of concentration-dependent, asymmetric hierarchical columnar H-aggregates stabilized by π-π interactions and hydrogen bonding.
• Maximum chiral amplification (∼50-fold) observed at 0.9 mM PBM@3β-CD.
• Light irradiation induced transformation to distorted J-aggregates with retained chirality.
• Exhibited brilliant aggregation-induced fluorescence (AIF) with a quantum yield of 0.11 at 390 nm.
• Cooperativity explained by a nucleation-elongation model.

Conclusions:

• Successfully developed a novel multicomponent, stimuli-responsive supramolecular system in water.
• Demonstrated significant chiral amplification and aggregation-induced fluorescence.
• Provided valuable insights into the formation of conformationally asymmetric superstructures and host-guest self-assembly.