Ru(II)-Based Multitopic Hosts for Fullerene Binding: Impact of the Anion in the Recognition Process

The development of multitopic hosts for fullerene recognition based on nonplanar corannulene (C₂₀H₁₀) structures presents challenges, primarily due to the requirement for synergistic interactions with multiple units of this polycyclic aromatic hydrocarbon. Moreover, increasing the number of corannulene groups in a single chemical structure while avoiding the cost of increasing flexibility has been scarcely explored. Herein, we report the synthesis of a family of multitopic Ru(II)-polypyridyl complexes bearing up to six units of corannulene arranged by pairs, offering a total of three molecular tweezers. All of them are fixed by the central atom and organized in an octahedral structure. Their fullerene recognition capabilities have been thoroughly demonstrated toward C₆₀ and C₇₀ showing that they can reasonably accommodate up to three fullerenes per host in a noncooperative manner. There are, however, some features that diverge from comparable hosts in the literature, such as the low value of several association constants. This behavior, supported by theoretical studies, is attributed to the presence of two noninnocent BAr₄^F anions that interfere with the supramolecular binding through ion pair formation. These findings highlight the crucial role of selecting compatible ionic species in supramolecular host design as they can significantly influence the recognition process.