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

Graphite monofluoride (CF)n was studied by solid-state NMR. 19F spin−lattice relaxation time T1 and second moment measurements of the 19F 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. 19F magic angle spinning (MAS) NMR and 13C MAS NMR with 19F to 13C cross-polarization allows the determination of CF and CF2 groups. Reintroduction of dipolar coupling by cross-polarization is used for C−F bond length determination (0.138 ± 0.001 nm).