Electronic isomerism (electromerism) of 6,8-di-tert-butyl-3H-phenoxazin-3-one oxime radical

Abstract

A radical stable at room temperature was prepared by the oxidation of a toluene solution of 6,8-di-(tert-butyl)-3H-phenoxazin-3-one oxime with lead oxide PbO2. The DFT/B3LYP/6-311++G**, ab initio MP2/def2-svp, and CASSCF (15,15)/def2svp calculations showed the ground structure of the radical in which the spin density is concentrated on the heterocyclic nitrogen atom and energetically close electromeric form in which the spin density is predominantly localized on the exocyclic nitroso group. Two forms of the radical are the first example of electronic isomerism in the series of electroneutral organic structures.