Extraordinarily high reduction states of rullerenes produced by intercalation with divalent metals

Intercalation of divalent alkaline earth metals produces extraordinary high reduction states of fullerenes in the solid state. Ba₆C₆₀ and Ba₉C₇₀ are found as the saturation phases of Ba intercalation into C₆₀ and C₇₀, respectively. The nominal valence states of these compounds are C₆₀ ^12- and C ₇₀ ^18-. We have systematically investigated the Raman spectra of alkaline earth metals doped C₇₀, and found that the tangential mode shows a continuous downshift, indicating that such high reduction states are realized.