On the so-called "semi-ionic" C-F bond character in fluorine-GIC

The short-range structures of fluorine-graphite intercalation compounds with stage-1 structures, CxF (x = 2.47, 2.84, 3.61), were analyzed by means of neutron diffraction. It has been shown that the so-called "semi-ionic" C-F bond character in CxF is essentially covalent with the bond length of 0.140nm, and the original planar graphene sheets are buckled at the sp(3)-hybridized carbon atoms bound to fluorine atoms. Conjugated C-C double bonds with the bond length of 0.142 nm are preserved between the carbon atoms unbound to fluorine atoms in CxF, while other C-C bonds are single bonds with the bond lengths of 0.153nm. The C-F bond order in CxF is slightly lower than those in poly(carbon monofluoride) ((CF)(n)) and poly(dicarbon monofluoride) ((C2F)(n)), which is explained by the hyperconjugation involving the C-C bonds on the carbon sheets and C-F bond. (C) 2004 Elsevier Ltd. All rights reserved.