NMR investigation of the azafullerene (C59N)2 and the alkali fullerides NaxC60 with X = 2, 4 and 6

We present C-13 MAS NMR measurements on the (C59N)(2) dimer. The room temperature NMR spectrum obtained by spinning the sample at 10 kHz shows a weak line at 90 ppm and a group of lines around 140 ppm. The simulation of the obtained spectra allows us to attribute the line at 90 ppm to the sp(3) carbons forming the expected interball single bond and the other lines to the sp(2) carbons of the dimer molecules. The distortion of the C59N molecules due to the introduction of the nitrogen atom into the C-60 cage and the C-13-N-14 dipolar coupling must be at the origin of the observed group of resonances. We also report on C-13 NMR measurements on NaxC60 (x = 2, 4 and 6) compounds. The NMR spectrum of the Na2C60 sample presents a narrow isotropic line at 172 ppm. The Na6C60 resonance appears at 176 ppm and is 20 ppm more shifted down field than the resonances of A(6)C(60) compounds with heavier alkalis, reflecting a strong polarization of the transferred electrons to the C-60 molecules. The Na4C60 polymer phase shows several isotropic resonances with the corresponding side bands in the region from 100 to 250 ppm and a single line at 76 ppm. We attribute the former group of lines to the inequivalent sp(2) carbons on the C-60 molecules and the latter line to the sp(3) carbons of the single interball bondings. (C) 1998 Elsevier Science Ltd. All rights reserved.