Slow Intermolecular Complexation-Decomplexation Exchanges of Cyclodextrins in Fullerene and Its Derivative Complexes

摘要

abstract_textpFullerenes (C-60 and C-70) and several functionalized C-60 derivatives can be encapsulated in two gamma-cyclodextrins (gamma-CDxs). Although intermolecular complexation-decomplexation exchange of gamma-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 gamma-CDx(2)center dot C-70 complex were 4.3 and 0.6s(-1) at 23 degrees C, respectively. In contrast, the intermolecular exchange rates for the gamma-CDx(2)center dot C-60 and C-60 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 gamma-CDx(2)center dot C-60 derivative complex was shown to have different intermolecular exchange rates for the two gamma-CDxs depending on steric hindrance from the substituent on the C-60 derivative./p/abstract_text