Calculated hyperfine coupling constants of some sigma-type radicals

Abstract

The hyperfine coupling constants of some type radicals were calculated by using the DFT(B3LYP) method with LanL2DZ basic set. These are phenyl, naphthyl, pyridyl, and quinolyl radicals. Also, the study was enriched by the calculations of the spin densities for all the radicals. From the results it was concluded that the spin density of the unpaired electron is mainly in one sp-hybrid orbital of the carbon atom from which hydrogen is removed. The electron paramagnetic resonance (EPR) spectra of all the radicals are generally based on the hyperfine splittings belonging to only the close hydrogen or azote atoms of the benzene ring to the unpaired electron since the effect of the other atoms is disappeared in the linewith of the EPR spectrum lines. The EPR spectra were also simulated by using their calculated isotropic hyperfine coupling constants and, compared with the experimental data. It was found a good agreement beetwen them.