Hydrogen storage in hydrofullerides

Highly reduced fullerenes containing nearly 5 wt. % of dihydrogen can be synthesized using readily available reagents. Hydrides prepared from C-60 by dissolving metal reductions give complex mixtures of unstable isomers of C60H36. High temperature syntheses using transfer hydrogenation reagents such as dihydroanthracene provide mainly two stable isomers of C60H36 that have been characterized spectroscopically. Dihydrogen can be removed thermally from these materials at 500 degreesC. The experimentally determined activation energy for the thermal removal of dihydrogen from C60H2 is 61.4 kcal/mol. This value is in good agreement with the value determined computationally for a multi step radical reaction. The 92 kcal/mol barrier determined computationally for the concerted loss of dihydrogen reflects the symmetry-imposed barrier to dehydrogenation.