Single and double reduction of C60 in 2:1 γ-cyclodextrin/[60]fullerene inclusion complexes by cyclodextrin radicals

Spectroscopic and chemical properties of gamma-CD center dot radicals, resulting from the abstraction by HO center dot radicals of hydrogen atoms, have been investigated using pulse radiolysis. The reactions of gamma-CD center dot radicals with C-60 in 2:1 gamma-CD/C-60 inclusion complexes have been Studied in aqueous solutions. It has been demonstrated that the gamma-CD center dot radicals are reducing species producing C-60(center dot-) monoanion radicals, as well as doubly reduced C-60(2-). well characterised by their absorption spectra in the near IR. The oxidation potential of gamma-CD center dot radical is estimated to be more negative than -390 mV vs. NHE. The kinetics of the C-60 reduction by gamma-CD center dot radicals have been determined and compared with kinetics by other reducing species including the solvated electron (e(aq)(-)) and CO2 center dot- radicals. It was observed that the method of preparation of the 2:1 gamma-CD/C-60 inclusion complexes modifies the C-60 reduction mechanism. (C) 2008 Elsevier B.V. All rights reserved.