DETECTION OF FULLEROID SITES IN FULLERENE-60 BY HIGH-RESOLUTION SOLID-STATE H-1-NMR

H-1 solid-state NMR with magic-angle spinning (MAS NMR) detects dilute H-containing species in chromatographically purified C-60 Because of the weakness of the H-1-H-1 dipolar couplings, the spectral peaks are very sharp and the T-1 values are not averaged by spin diffusion. On the basis of chemical shifts and peak connectivities as revealed by COSY, we have identified various fulleroids, as well as toluene and dioctyl phthalate (DOP) impurities. The fulleroids contain HC=CHCH2CH3, HC=CHCH3, and HC=CH groups. DOP is probably complexed to C-60 via the aromatic moiety. Laboratory and rotating-frame spin-diffusion experiments show that the H-containing species are so diluted by bulk C-60 that they cannot communicate by intermolecular spin diffusion. The intramolecular spin-diffusion paths suggest that the alkyl chains of DOP are folded back toward the aromatic ring. We have found that two-dimensional H-1 NMR techniques work well in the solid state without a multiple-pulse homonuclear decoupling, provided that the species under study are sufficiently dilute by a nondipolar medium.