Fullerene Dianions Research Articles

Anion radicals of [60]-fullerene and its ortho-quinodimethane adducts generated by cathodic reduction and photochemical electron transfer: an EPR and vis—near-IR study

Abstract [60]-Fullerene and its four ortho-quinodimethane adducts, one of them in oligomeric form, were reduced by three different methods, (a) by cathodic reduction, (b) in photoexcited TiO2 suspension, and (c) quenching photoexcited fullerene by triethylamine donor. The radicals obtained were mainly investigated by EPR and also characterized by vis—near-IR measurements. All three methods of generation gave two identical radical products: the primary radical A, which is a fullerene mono-anion, with EPR spectral parameters gA = 2.0000 and peak-to-peak width ppA = 0.09 mT for [60]-fullerene, ppA = 0.105 for its adducts and ppA = 0.19 mT for the fullerene oligomer. The near-IR band of A at 1077 nm for [60]-fullerene shiftd into the region of 1010 nm for its ortho-quinodimethane adducts. As a consecutive product of A, radical B was found with gB = 2.0006 and ppB = 0.07 mT for all [60]-fullerene adducts. The EPR signal of B converts to A after stopping photogeneration, resulting in a total increase of the spin susceptibility in the form of fullerene mono-anion A. The formation of fullerene di-anion or fullerene associates is considered as an alternative.