On the so-called “semi-ionic” C–F bond character in fluorine–GIC Original Research Article

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 0.140 nm, and the original planar graphene sheets are buckled at the sp3-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 0.153 nm. 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.