On the feasibility of reactions through the fullerene wall: a theoretical study of NH x @C 60 .

We propose a new approach to the synthesis of AHx @fullerene structures via reactions through the fullerene wall. To investigate the feasibility of the approach, the step-by-step hydrogenation of the template endofullerene N@C60 up to NH4 @C60 has been studied using DFT and MP2 calculations. Protonation of the endohedral guest through the fullerene wall is competitive with escape of the guest, whereas reaction with a hydrogen atom is less favorable. Each protonation step is highly exothermic, so that less active acids can also protonate the guest with less accumulation of energy. The final product, NH4 @C60 is a novel concentric ion pair NH4 + @C60 ˙- in which the charge-centers of the two ions coincide.