An NMR investigation on the adducted hydrogen in weak ferromagnetic rhombohedral C60 polymers

The fact that a magnetic hysteresis loop is observed only in polymerized C60 and is absent in both pristine and depolymerized C60 establishes a close link between the weak ferromagnetism and the underlying structure. Furthermore, the correlation between the weak ferromagnetism and hydrogen presence has been explored by 1H NMR and 1H–13C cross-polarization NMR, whereby strong bonding between the H adducts and C60 has been verified. The adducted hydrogens most likely form bonds with the carbon atoms of inter-C60 four-membered rings. This conclusion is further supported by the formation energy of adducted H and the exchange energy among adducted H obtained from first-principle calculations on Rh-C60.