Pulse radiolysis studies on the redox reactions of aqueous solutions of .gamma.-cyclodextrine/C60 complexes

Abstract

Pulse radiolytical studies on the water-soluble [gamma]-cyclodextrine/C[sub 60] ([gamma]-CD/C[sub 60]) complex with primary radiolytic species, such as [sup [sm bullet]]OH, [sup [sm bullet]]H, and e[sub aq][sup [minus]] have been carried out in aqueous solution. Rare constant for the formation of the transient products are determined by following the build-up kinetics of the species at the respective absorption maxima and the bleaching of the ground state C[sub 60] at 330 nm. [sup [sm bullet]]OH- and [sup [sm bullet]]H-induced reactions lead to a transient with [lambda][sub max] at 290 nm showing identical formation kinetics as the concurrent bleaching at 330-335 nm. Studies on [gamma]-CD/C[sub 60] complexes and uncomplexed [gamma]-CD indicated that [sup [sm bullet]]OH is mainly reacting with the host ([gamma]-CD) by hydrogen abstraction (employing competition kinetics with KSCN as reference standard). The resulting radical subsequently reacts with C[sub 60] to yield a radical adduct which absorbs at 290 nm. Reaction of the Cl[sub 2][sup [minus]] with [gamma]-CD/C[sub 60] produces a transient species that shows a broad absorption maximum at 380-430 nm. This species is assigned to be the radical adduct (C[sub 60]Cl)[sup [sm bullet]]. 27 refs., 5 figs.