Toward Larger Cyclo-9,10-Anthryleneparaphenylenes.

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Aromatic building blocks are crucial for constructing complex molecular architectures.
• Nanohoops, or cyclic aromatic molecules, offer unique structural and electronic properties.
• Developing scalable synthesis methods for well-defined nanohoops remains a challenge.

Purpose of the Study:

• To synthesize and characterize nanohoops of varying sizes based on diphenylanthracene units.
• To investigate the three-dimensional structures of these synthesized nanohoops.
• To study the reactivity and stability of the nanohoops, particularly their susceptibility to oxidation.

Main Methods:

• Utilizing a cross-coupling strategy involving an anthracene-based kinked precursor and 9,10-diborylated anthracene.
• Synthesizing and isolating nanohoops up to the nonameric stage.
• Employing X-ray diffraction for three-dimensional structural elucidation.
• Conducting reactivity studies, focusing on oxidation resistance.

Main Results:

• Successful synthesis and isolation of diphenylanthracene-based nanohoops up to the nonamer (36 aromatic rings).
• Detailed three-dimensional structural information obtained via X-ray diffraction.
• The trimeric macrocycle, upon rearomatization to cyclo-9,10-anthryleneparaphenylene (CAPP), demonstrated significant susceptibility to oxidation.

Conclusions:

• The cross-coupling strategy provides a viable route to synthesize well-defined, multi-ring aromatic nanohoops.
• Structural characterization confirms the precise arrangement of aromatic units in the nanohoops.
• The inherent instability of the rearomatized CAPP form towards oxidation highlights limitations for certain applications and suggests areas for future molecular design improvements.