Fullerenes (C60 and C70) and several functionalized C60 derivatives can be encapsulated in two γ-cyclodextrins (γ-CDxs). Although intermolecular complexation–decomplexation exchange of γ-CDx is known to be very slow, the exchange rates have yet to be quantitatively measured. Herein, we determined that the pseudo-first-order association and dissociation rate constants for the γ-CDx2•C70 complex were 4.3 and 0.6 s−1 at 23 °C, respectively. In contrast, the intermolecular exchange rates for the γ-CDx2•C60 and C60 derivative complexes were slower than the time scale of exchange spectroscopy NMR experiments and the exchange rate constants were in the order of 10−4 s−1. Furthermore, a γ-CDx2•C60 derivative complex was shown to have different intermolecular exchange rates for the two γ-CDxs depending on steric hindrance from the substituent on the C60 derivative.
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