Raman, infrared and n.m.r. studies of the graphite hydrofluorides CxF1-δ(HF)δ(2 ≤ x ≤ 5)

Raman spectra of CxF1-δ(HF)δ(x/δ ≈ 12) show bands at 1600, 1355 and 839 cm-1, which are attributed to graphite-like vibrational modes of the carbon atom sheets. The infrared spectra show, in addition to graphite-like bands, absorptions at 1270 and 1100 cm-1, which are attributed to C-F stretching. Variable contact-time cross-polarized magic-angle spinning 13C nuclear magnetic resonance spectra (c.p.m.a.s.13C n.m.r.) have been obtained for x = 2.05 and 3.70. In both spectra, two peaks ( + 135/106 and + 88/106 chemical shift from TMS) are seen, which are attributed, respectively, to graphitic and C-F carbons. The ratio of graphitic to C-F carbon atoms has been found to be 1.6(2) : 1 in C2.05F0.82(HF)0.18. The carbon atom sheets in CxF1-δ(HF)δ appear to be very similar to those in pristine graphite. The bonding of fluorine to carbon is highly ionic. Bonding models are discussed.