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

Abstract

A cyclophane is reported incorporating two units of a heptagon-containing extended polycyclic aromatic hydrocarbon (PAH) analogue of the hexa-peri-hexabenzocoronene (HBC) moiety (hept-HBC). This cyclophane represents a new class of macrocyclic structures that incorporate for the first time seven-membered rings within extended PAH frameworks. The saddle curvature of the hept-HBC macrocycle units induced by the presence of the nonhexagonal ring along with the flexible alkyl linkers generate a cavity with shape complementarity and appropriate size to enable π interactions with fullerenes. Therefore, the cyclophane forms host-guest complexes with C₆₀ and C₇₀ with estimated binding constants of K_a =420±2 m^-1 and K_a =(6.49±0.23)×10³ m^-1 , respectively. As a result, the macrocycle can selectively bind C₇₀ in the presence of an excess of a mixture of C₆₀ and C₇₀ .

Keywords: fullerenes; host-guest systems; macrocycles; nanographenes; nanostructures.