Anion radicals of mono- and bisfunctionalized [60]fullerene derivatives. Evidence for <SUP>13</SUP>C satellites in their EPR spectra

Upon photo- and electrochemical in situ reduction of [60]fullerene derivatives, C<INF>60</INF>[C(COOEt)<INF>2</INF>]<INF>n</INF> (n=1, 2), characteristic single-line EPR spectra are observed which are attributable to the corresponding radical anions. Monofunctionalized C<INF>60</INF>[C(COOEt)<INF>2</INF>] shows a reduction behavior similar to pristine C<INF>60</INF>, i.e. formation of a primary radical A which converts with time into B with a peak-to-peak width of pp<INF>A</INF>≈0.1 mT and g<INF>A</INF>=2.0000, pp<INF>B</INF>≈0.05 mT and g<INF>B</INF>=2.0006. In contrast, the EPR spectra of the four bis-adducts-{equatorial, trans-1, trans-2 and trans-3 C<INF>60</INF>[C(COOEt)<INF>2</INF>]<INF>2</INF>} are dominated by only one narrow line with pp ranging from 0.007 to 0.03 mT and g values between 2.0002 and 2.0004. Their relative width changes with the regiosteric positioning of the functionalizing addends. Well resolved spectra reveal ¹³C satellites, originating from 12–20 carbon nuclei. Slightly higher splittings (a<INF>13C</INF>≈0.2 mT) for four carbon nuclei suggest higher spin density at the keto group carbons of the bis(ethoxycarbonyl)methylene substituents. © 1997 John Wiley & Sons, Ltd.