The structure of phenoxyl radicals as studied by 2 mm band ESR

The g-tensor components of a number of phenoxyl radicals including Coppinger's radicals have been measured by ESR spectroscopy in the 2 mm band (140 GHz). Assuming that the g-tensor anisotropy arises mainly from spin-orbit interaction on the oxygen atom, the geometrical structure of Coppinger's radical was determined. Some additional assumptions for nitrogen contributions to the g-tensor allowed the estimation of the geometrical structure of N-Coppinger's radical as well. The validity of such assumptions was confirmed by quantum chemical calculations using the unrestricted Hartree-Fock method.