Mobility of Long-Lived Fullerene Radical in Solid State and Nonlinear Temperature Dependence

A singly bonded fullerene dimer [C₆₀R]₂ in the solid state thermally generates a pair of fullerene radicals C₆₀R^• that dissociate reversibly and irreversibly upon heating and cooling of the solid. The temperature dependence of the electron mobility of the solid shows striking nonlinearity, caused by the dissociation of a strongly interacting radical pair into two free radicals, which interact with the neighboring fullerene molecules to increase the mobility 10 times to a value of 1.5 × 10^–3 cm² V^–1 s^–1. The nonlinearity is due to the plastic crystalline nature of fullerene crystals