Heteronuclear dipolar recoupling using Hartmann–Hahn cross polarization: A probe for 19F– 13C distance determination of fluorinated carbon materials

Abstract

A NMR determination of the C–F bond length in fluorinated carbon materials using dipolar recoupling is described. To this end Hartmann–Hahn cross polarization with magic angle spinning (inverse cross polarization sequence) is used. A description of the corresponding 13C magnetization evolution as a function of the evolution time and its simulation for typical fluorinated samples are realized. The procedure is applied to 15 different materials having different bonding (semi-covalent or covalent) and from various carbon allotropic varieties. The distance evolves from 0.138 ± 0.002 nm for covalent bonding to 0.1445 ± 0.002 nm for semi-covalent bonding. Other parameters may affect the C–F bond length e.g. steric hindrance which leads for fluorinated fullerenes to an increase of this distance up to 0.146 ± 0.002 nm .