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Solid-state Na and C NMR characterization of Na3C60
Authors:Robert W Schurko  Mathew J Willans  Boris Skadtchenko  David M Antonelli
Institution:Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Ave. Windsor, Ont., Canada, N9B 3P4
Abstract:Two separate samples of Na3C60 were prepared by direct reaction of C60 with sodium metal vapor, and subjected to different annealing times of 10 days and 16 days. Solid-state 13C and 23Na NMR, along with elemental analysis, powder X-ray diffraction (XRD) and Raman spectroscopy, were used to characterize both samples. The Raman spectra of both materials have a single peak at 1447 cm−1 which correspond to the Ag peak of C603−, consistent with the stoichiometry of NaxC60 with x=3. The powder XRD patterns are also virtually identical for both samples. However, solid-state 23Na and 13C NMR spectra of the two samples are significantly different, suggesting a relationship between annealing times and the final structure of the alkali fulleride. Variable-temperature 23Na magic-angle spinning (MAS) NMR experiments reveal the existence of two or three distinct sodium species and reversible temperature-dependent diffusion of sodium ions between octahedral and tetrahedral interstitial sites. 13C MAS NMR experiments are used to identify resonances corresponding to free C60 and fulleride species, implying that the samples are segregated-phase materials composed of C60 and non-stoichiometric Na3C60. Variable-temperature 13C MAS NMR experiments reveal temperature-dependent motion of the fullerides.
Keywords:Solid-state NMR  23Na NMR  Fullerenes  Fullerides  Solid-state chemistry
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