2 mm Electron paramagnetic resonance studies of the new types of imidazoline nitroxide radicals

The 2 mm band spectra have been obtained for imidazoline nitroxides, nitronyl and imino nitroxides, containing various substituents in different positions of a radical cycle in frozen toluene solutions. The spectra allowed the determination of all g tensor principal values and the A_zz component of the hyperfine interaction tensor with the nitrogen nucleus of 2 bonds on the lefthand side signN-̇O. The changes in the determined resonance parameters with the nature and position of substituents have been analysed. Additional hyperfine splittings induced by the ¹⁹F nucleus have been observed. Dimerization of imidazoline nitroxides, containing alcohol groups in the second position, has been observed in frozen toluene.