Journal of Physical Chemistry, Vol.98, No.38, 9565-9569, 1994
Pulse-Radiolysis Studies on the Redox Reactions of Aqueous-Solutions of Gamma-Cyclodextrine C-60 Complexes
Pulse radiolytical studies on the water-Soluble gamma-cyclodextrine/C60 (gamma-CD/C-60) complex with primary radiolytic species, such as (OH)-O-., H-., and e(aq)(-) have been carried out in aqueous solution. Rate constants 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-60 at 330 nm. (OH)-O-.- and H-.-induced reactions lead to a transient with lambda(max) at 290 nm showing identical formation kinetics as the concurrent bleaching at 330-335 nm. Studies on gamma-CDIC60 complexes and uncomplexed y-CD indicated that (OH)-O-. 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-60 to yield a radical adduct which absorbs at 290 nm. Reaction of the Cl-2.- with gamma-CD/C60 produces a transient species that shows a broad absorption maximum at 380-430 nm. This species is assigned to be the radical adduct (C60Cl)(.). Studies regarding the reaction of the e(aq)(-) with gamma-CD/C-60 indicates the formation of gamma-CD complexed C-60(.-), as has been confirmed by monitoring its characteristic absorption spectrum in the near IR with lambda(max) at 950 and 1080 nm.
Keywords:LASER FLASH-PHOTOLYSIS;EXCITED-STATE BEHAVIOR;ONE-ELECTRON REDUCTION;PHOTOPHYSICAL PROPERTIES;GAMMA-CYCLODEXTRIN;RATE CONSTANTS;C-60;RADICALS;FULLERENES;C-70