Metallacycle-cored supramolecular assemblies with tunable fluorescence including white-light emission

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Photophysics

Background:

• Controlling fluorescence in supramolecular assemblies is key for advanced materials.
• Post-synthetic modification via host-guest interactions offers a facile route to tune photophysical properties without complex synthesis.

Purpose of the Study:

• To construct functional metallacycles and supramolecular oligomers with tunable emission.
• To investigate the influence of metal-ligand coordination and host-guest interactions on fluorescence.
• To demonstrate concentration-dependent and white-light emission from supramolecular assemblies.

Main Methods:

• Synthesis of phenanthrene-21-crown-7 (P21C7) functionalized diplatinum(II) metallacycles.
• Incorporation of different fluorophores (triphenylamine, tetraphenylethene, pyrene) into metallacycle precursors.
• Formation of emissive supramolecular oligomers using a fluorescent bis-ammonium linker and P21C7 host-guest recognition.

Main Results:

• Three rhomboidal metallacycles (1-3) were synthesized, exhibiting orange, cyan, and green emissions.
• Supramolecular oligomers were formed, demonstrating host-guest interactions between P21C7 units and the ammonium linker.
• A 1:1 mixture of metallacycle 1 and linker 4 showed concentration-dependent emission, shifting from blue to orange.
• White-light emission was achieved at a specific concentration (29 µM).

Conclusions:

• Pendant P21C7 units on metallacycles enable post-synthetic modification via host-guest interactions.
• Supramolecular assemblies with controllable fluorescence colors, including white light, can be constructed.
• This strategy provides a pathway for developing novel light-emitting materials and chemosensors.