Nitroxyl radicals: electrochemical redox behaviour and structure–activity relationships

Comparative study of electrochemical redox behaviour of five different nitroxyl radicals leads to the direct correlation between one-electron redox potentials and group electronegativity of the β-substituent on the ring. β-Substituents with an electron-donating effect caused a negative shift in the one-electron oxidation and one-electron reduction potentials of the nitroxyl radicals. In a similar aspect, β-substituents with an electron-withdrawing effect behaved oppositely.