Electron spin resonance spectra of an irradiated single crystal of difluoromalonamide and hyperfine tensors of ?-fluorine couplings

Abstract

The principal values of the ¹⁹F hyperfine tensor for the ·CF(CONH₂)₂ radical in a γ-irradiated single crystal of difluoromalonamide have been determined to be 200, -1, -10 g perpendicular to the radical plane, parallel to the C-F bond, and perpendicular to the C-F bond in the radical plane, respectively. The deviation from axial symmetry of the hyperfine tensor is discussed in comparison with that in other related compounds and it is concluded that the spin polarization of 2pσ electrons in the C-F bond plays an important role. The polarization factors, Q cf ^f and Q fc ^f , for the 2pσ electrons have been estimated to be -45 and +233 g so as to account for the hyperfine tensors of a series of compounds.