Solid-state NMR (19F and 13C) study of graphite monofluoride (CF)n: 19F spin-lattice magnetic relaxation and 19F/13C distance determination by Hartmann-Hahn cross polarization |
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Authors: | Giraudet Jérôme Dubois Marc Hamwi André Stone William E E Pirotte Pascal Masin Francis |
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Institution: | Matière Condensée et Résonance Magnétique, Université Libre de Bruxelles, CP 232, Boulevard du Triomphe, B-1050 Bruxelles, Belgium. |
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Abstract: | Graphite monofluoride (CF)(n) was studied by solid-state NMR. (19)F spin-lattice relaxation time T(1) and second moment measurements of the (19)F line are presented. A "chair" conformation structure is found to be compatible with the experimental data. Relaxation is shown to be mainly due to paramagnetic oxygen. The presence of a molecular motion with an activation energy of 1.685 kJ.mol(-1) (202.7 K) is also evidenced. (19)F magic angle spinning (MAS) NMR and (13)C MAS NMR with (19)F to (13)C cross-polarization allows the determination of CF and CF(2) groups. Reintroduction of dipolar coupling by cross-polarization is used for C-F bond length determination (0.138 +/- 0.001 nm). |
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