Structurally Tunable pH-Responsive Luminescent Assemblies from Halogen Bonded Supra-π-amphiphiles

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Stimuli-responsive self-assembled nanostructures are crucial for advanced functional materials.
• Nonsymmetrical amphiphiles offer unique properties for supramolecular assembly.
• Halogen (X)-bonding is an effective noncovalent interaction for molecular recognition and self-assembly.

Purpose of the Study:

• To develop emissive supra-π-amphiphiles in water using X-bonding interactions.
• To investigate the role of X-bonding in the formation and morphology of nanostructures.
• To explore the stimuli-responsive disassembly of these self-assembled materials.

Main Methods:

• Synthesis of pyridyl functionalized naphthalene monoimide (NMI-Py) as X-bond acceptor.
• Synthesis of iodotetrafluorophenyl functionalized polyethylene glycol (PEG-I) and triethylene glycol (TEG-I) as X-bond donors.
• Characterization of self-assembled nanostructures using SCXRD and DFT calculations.
• Investigation of pH-responsive behavior through acid-triggered disassembly.

Main Results:

• Successful construction of emissive supra-π-amphiphiles in water via X-bonding.
• Defined nanostructures (fibers and vesicles) formed, dependent on X-bond donor chain length (PEG-I vs. TEG-I).
• X-bonding was confirmed as essential for nanostructure formation, with control molecules failing to assemble.
• Acid-triggered disassembly demonstrated pH responsiveness and thermal robustness of the nanostructures.

Conclusions:

• A unique supramolecular strategy utilizing X-bonding enables the facile fabrication of luminescent supra-π-amphiphiles.
• The self-assembly process is governed by X-bonding, orthogonal dipole-dipole interactions, and π-stacking.
• This approach allows for tunable morphology and stimuli-responsive disassembly, offering a platform for smart materials.