First Synthesis and Characterization of CH @C.

The endohedral fullerene CH @C , in which each C fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/ benzene solvate shows no significant distortion of the carbon cage, relative to the C analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The H spin-lattice relaxation times (T ) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C cage. The synthesis of CH @C opens a route to endofullerenes incorporating large guest molecules and atoms.