A Macrocycle Based on a Heptagon-Containing Hexa-peri-hexabenzocoronene

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are crucial building blocks in materials science.
• Hexa-peri-hexabenzocoronene (HBC) derivatives are known for their unique electronic and structural properties.
• Macrocyclic chemistry offers platforms for selective molecular recognition and encapsulation.

Purpose of the Study:

• To synthesize and characterize a novel cyclophane incorporating heptagon-containing PAH units (hept-HBC).
• To investigate the host-guest complexation capabilities of the new cyclophane with fullerenes (C60 and C70).
• To explore the potential for selective fullerene binding and separation using these macrocyclic structures.

Main Methods:

• Synthesis of a novel cyclophane featuring two hept-HBC units linked by flexible alkyl chains.
• Spectroscopic characterization of the synthesized cyclophane.
• Binding studies to determine host-guest complex formation constants with C60 and C70 fullerenes.
• Evaluation of selective binding of C70 in the presence of mixed fullerenes.

Main Results:

• A new class of cyclophane incorporating heptagon-containing PAH analogues (hept-HBC) was successfully synthesized.
• The hept-HBC cyclophane forms stable host-guest complexes with both C60 and C70 fullerenes.
• Binding constants were determined, showing a preference for C70 (Ka = (6.49±0.23)×10^3 M^-1) over C60 (Ka = 420±2 M^-1).
• The cyclophane demonstrated selective binding of C70 from a mixture of C60 and C70.

Conclusions:

• The incorporation of seven-membered rings into extended PAH frameworks leads to unique macrocyclic structures.
• The saddle curvature and cavity of the hept-HBC cyclophane enable effective pi-pi interactions with fullerenes.
• This novel macrocycle shows significant potential for the selective recognition and separation of C70 fullerene.