Hydrogenation of C ₆₀ in peapods: Physical chemistry in nano vessels

Hydrogenation of C ₆₀ molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C ₆₀ hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution ¹³C and ¹H NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp ³ carbon resonances. We estimate that approximately 78% of the C ₆₀ molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C ₆₀ molecule. As a consequence, the rotational dynamics of the encapsulated C ₆₀H _x molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale.