Semiempirical molecular orbital calculations of anisotropic1H,13C and19F hyperfine coupling constants in hydrocarbon and fluorocarbon radicals

Abstract

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 ĊH, ĊH3, CH3ĊH2, (CH3)3Ċ hydrocarbon radicals, malonic acid radical, ĊH2F, ĊF2H, ĊF3 and CF3ĊH2 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.