Conversion between the two spin-isomers of hydrogen (ortho- and para-hydrogen) requires a paramagnetic catalyst. Nitroxide radicals bound to C60 serve as covalently attached spin-catalysts for a hydrogen molecule trapped inside the fullerene. We have measured the spin-conversion rates of two endohedral nitroxofullerene systems (1 and 2) at various temperatures.  These molecules have either one or two TEMPO moieties at a favorable distance from the center of the C60 cage for ortho/para conversion of the guest inside (~10.1 �). At liquid helium temperatures, the nitroxides generate an excess (>75%) of para-hydrogen within the fullerene with lifetimes of 26 and 13 days, respectively. Once warmed to room temperature, these non-equilibrium polarizations persist for many hours (lifetime= 30 and 17 hours, respectively).

Measurement and control of spin-flipping rates in endohedral hydrogen via covalently-bound nitroxides

241st National Meeting (2011)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.