Semiempirical molecular orbital calculations of anisotropic 1H, 13C and 19F hyperfine coupling constants in hydrocarbon and fluorocarbon radicals

The anisotropic hyperfine coupling constants (AHCC) from the electron spin resonance (E.S.R.) spectra of a variety of atoms in organic radicals have been calculated by means of semiempirical molecular orbital wavefunctions in the INDO approximation. Hyperfine tensors involving ¹H, ¹³C and ¹⁹F nuclei are obtained for the ?H, ?H₃, CH₃?H₂, (CH₃)₃? hydrocarbon radicals, malonic acid radical, ?H₂F, ?F₂H, ?F₃ and CF₃?H₂ radicals. The calculated values are compared with available experimental, non-empirical and semiempirical values for these radicals. All integrals of the operator entering the electronic contributions have been evaluated over Slater type orbitals. The introduction of deorthogonalized wavefunctions gives generally better calculated results. In particular, the tensor components of the ¹⁹F AHCC are in good agreement with the experimental results without the necessity of readjusting the effective nuclear charges.