Chiroptical Response of Carbon Nanocages Enhanced by Achiral Guests

Opening up [60]fullerene makes itself inherently chiral without loss of congenital π-conjugation. An immoderately large aperture on [60]fullerene, however, renders the molecule less rigid and therefore it would reduce dissymmetry factors. Herein, we examined supramolecular technique in geometrical reinforcement of chiral open-[60]fullerenes by encasing achiral guests such as Ar, CO₂, and CH₃CN. At a lowest-energy transition, we confirmed a guest-dependency on chiroptical responses with increasing a dissymmetry factor by nearly twice to three times. It should be noted that the guests play a negligible role in electronic structures of the carbon cages. Instead, they are engaged in preclusion of an orifice shrinking not to reduce chiroptical response.