W. Kolodziejski et al., DETECTION OF FULLEROID SITES IN FULLERENE-60 BY HIGH-RESOLUTION SOLID-STATE H-1-NMR, Journal of physical chemistry, 99(10), 1995, pp. 3365-3370
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 t
he basis of chemical shifts and peak connectivities as revealed by COS
Y, we have identified various fulleroids, as well as toluene and dioct
yl phthalate (DOP) impurities. The fulleroids contain HC=CHCH2CH3, HC=
CHCH3, and HC=CH groups. DOP is probably complexed to C-60 via the aro
matic moiety. Laboratory and rotating-frame spin-diffusion experiments
show that the H-containing species are so diluted by bulk C-60 that t
hey cannot communicate by intermolecular spin diffusion. The intramole
cular spin-diffusion paths suggest that the alkyl chains of DOP are fo
lded back toward the aromatic ring. We have found that two-dimensional
H-1 NMR techniques work well in the solid state without a multiple-pu
lse homonuclear decoupling, provided that the species under study are
sufficiently dilute by a nondipolar medium.