Spin-labeled fulleropyrrolidines

We describe the synthesis and properties of a series of fulleropyrrolidines bearing stable nitroxide free radical moieties covalently linked to the [60]fullerene cage. The nitroxide electron spin functions as a weakly interacting probe for the investigation of radical anions and paramagnetic excited states of functionalized fullerenes. Electron transfer processes, spin coupling in polyradical adducts, and interactions between radical and fullerene excited triplet unpaired electrons have been studied through electron paramagnetic resonance. Photogenerated quartet and quintet high spin species, obtained from the spin coupling of the fullerene triplet with the nitroxide spins, have been observed for the first time at room temperature.