Diverse Proton-Conducting Nanotubes via a Tandem Macrocyclization and Assembly Strategy

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Macrocycles assembling into nanotubes exhibit unique properties due to their structure and environment.
• Developing efficient synthetic strategies for diverse nanotube structures is crucial for exploring their potential applications.

Purpose of the Study:

• To report a versatile strategy for synthesizing diverse nanotube structures using a conserved pyridine-containing building block.
• To investigate the self-assembly mechanism and proton conductivity of the synthesized pyridine-containing macrocycles and nanotubes.

Main Methods:

• Imine condensation reaction between a 2,4,6-triphenylpyridine-based diamine and various aromatic dialdehydes.
• Characterization of macrocycle and nanotube structures using atomic force microscopy and in-solvo X-ray diffraction.
• Measurement of proton conductivity using electrochemical impedance spectroscopy.

Main Results:

• A single, efficient reaction yielded diverse macrocycles (pentagonal, hexagonal, diamond-shaped) based on dialdehyde substitution.
• Protonation of macrocycles under mild conditions drove self-assembly into high-aspect ratio nanotubes.
• Pyridine-containing nanotube assemblies exhibited measurable proton conductivity up to 10^-3 S m^-1, varying with pore size.

Conclusions:

• The developed synthetic strategy provides a general method for accessing robust, pyridine-containing nanotube assemblies.
• This approach enables systematic investigations into the emergent properties of nanotubes, such as proton conductivity.
• The tunable pore sizes of these nanotubes offer potential for applications in areas requiring controlled ion transport.