Stabilities and reactivities of buckminsterfullerene radicals, (ButO)nC60˙, towards dioxygen, nitric oxide and spin trapping agents

Abstract

(Bu^tO)_nC₆₀˙ radicals have been conveniently produced by addition of photochemically generated ButO' radicals to buckminsterfullerene (C₆₀). Radical adducts (where n > 2) are very persistent under N₂ at room temperature and can be observed for as long as nine days. Reactions between the radical adducts and dioxygen (O₂) are slow and reactivities vary among (Bu^tO)_nC₆₀˙ radicals. However, nitric oxide (˙NO) reacts more rapidly with (Bu^tO)_nC₆₀˙ radicals. Among the product components are stable dibuckminsterfullerene aminoxyl (nitroxide) radicals, [(Bu^tO)_nC₆₀]₂N–O˙, which have been observed by EPR spectroscopy at concentrations of ca. 10^–7 M for the first time. Surprisingly, (Bu^tO)_nC_6O˙ radicals are riot reactive towards several typical radical-trapping agents (spin traps), e.g. DMPO (5,5-dimethyl-1-pyrroline N-oxide), PBN (C-phenyl N-tert-butylnitrone), NB (nitrosobenzene) and MNP (2-methyl-2-nitrosopropane), when used at typical concentrations (10–100 mM) at room temperature.