Heptagon-Containing Nanographene Embedded into [10]Cycloparaphenylene.

Abstract

We report the synthesis and characterization of a novel type of nanohoop, consisting of a cycloparaphenylene derivative incorporating a curved heptagon-containing p-extended polycyclic aromatic hydrocarbon unit. We demonstrate that this new macrocycle behaves as a supramolecular receptor of curved p-systems such as fullerenes C60 and C70, with remarkably large binding constants (ca. 107 M-1), as estimated by fluorescence measurements. Nanosecond and femtosecond spectroscopic analysis show that these host-guest complexes are capable of quasi-instantaneous charge separation upon photoexcitation, due to the ultrafast charge transfer from the macrocycle to the complexed fullerene. These results demonstrate saddle-shaped polycyclic aromatic hydrocarbons (PAHs) with dibenzocycloheptatrienone motifs as structural components for new macrocycles displaying molecular receptor abilities and versatile photochemical responses with promising electron-donor properties in host-guest complexes.