Torsional dependence of the reactivity of diphenylamine-type antioxidants

The dependence of energy, geometry and electronic structure of dihenylamine Ph2NH, its aminyl radical Ph2N, cation radical Ph2NH+ and nitroxide radical Ph2NO on the phenyl ring torsion have been investigated using B3LYP treatment. Stable structures of these systems are non-planar. The most significant changes are related to the nitrogen spin density as well as lengths, strengths and π character of C-N bonds. The reactivity of the cation and aminyl radical exhibits the highest sensitivity on the C-N bond torsion as deduced from nitrogen spin density and C-N bonds non-equivalence.