U. V. irradiation of N-alkylphenothiazines (la—c) in carbon tetrachloride produced 3-(phenothiazin-N’-yl-carbonyl)-N’-alkylphenothiazine (2a—b) and/or 3-(N’-alkylphenothiazin-3’-yl-carbonyl) -N-alkylphenothiazine (3b—c) together with the radical cation carbon tetrachloride saltl +·CCl-· 4 (4a—c), presumably via a photoinduced electron transfer mechanism.
Electron transfer reactions take place readily between 2, 2, 6, 6-tetramethylpiperidine oxoammonium ions (la,lb) and phenothiazines (2a—2g), giving corresponding nitroxides (3a,3b) and phenothiazine radical cations (4a—4g). The rate constants for the electron self-exchange reactions between1 and3, as well as between2 and4, are determined by EPR and1HNMR line-broadening effect in acetonitrile. By application of the Marcus theory, the kinetics of the cross exchange reactions between1 and2 is studied.
