Heptagon-Containing Nanographene Embedded into [10]Cycloparaphenylene

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Development of novel macrocyclic compounds with tailored properties is crucial for advanced molecular recognition.
• Polycyclic Aromatic Hydrocarbons (PAHs) offer unique electronic and structural features for designing functional materials.
• Fullerenes (C60, C70) are important electron acceptors with applications in organic electronics and photochemistry.

Purpose of the Study:

• To synthesize and characterize a new nanohoop incorporating a curved, π-extended polycyclic aromatic hydrocarbon (PAH) unit.
• To investigate the supramolecular receptor properties of the novel nanohoop towards curved π-systems like fullerenes.
• To explore the photochemical behavior and charge transfer dynamics within the host-guest complexes.

Main Methods:

• Synthesis of a novel nanohoop featuring a heptagon-containing PAH unit.
• Characterization of the nanohoop using spectroscopic techniques.
• Binding studies with fullerenes (C60, C70) using fluorescence measurements to determine binding constants.
• Ultrafast spectroscopic analysis (nanosecond and femtosecond) to probe charge transfer dynamics.

Main Results:

• Successful synthesis and characterization of a novel nanohoop macrocycle.
• Demonstration of the nanohoop as a potent supramolecular receptor for C60 and C70 fullerenes, with binding constants around 10^7 M^-1.
• Observation of quasi-instantaneous charge separation in photoexcited host-guest complexes, attributed to ultrafast charge transfer from the nanohoop to the fullerene.

Conclusions:

• Saddle-shaped PAHs with dibenzocycloheptatrienone motifs are effective building blocks for new macrocycles.
• These macrocycles exhibit significant molecular receptor abilities for curved π-systems.
• The resulting host-guest complexes display versatile photochemical responses and promising electron-donor properties.