Abstract
One-electron oxidation of thionine has been studied using specific oxidizing radicals such as Cl−Tl(II) and N3 generated by pulse radiolysis of aqueous solutions. The semioxidized thionine exhibited threepK’s indicating four conjugate acid-base forms. N3 radicals were found to be less efficient in oxidizing thionine as compared to Cl 2 − , Tl2+ and Tl(OH)+. The rate constants for electron abstraction from thionine by Cl 2 − , Tl2+, Tl(OH)+, Tl(OH)2 and N3 were evaluated. The spectra of different protonated forms of semioxidized thionine and the extinction coefficients at λmax are presented. Reaction of OH radicals with thionine gave transient products whose spectra and acid-base properties were different from those of semioxidized thionine. The rate constant for formation of the product transient agrees well with competition kinetic value for reaction of OH with thionine reported earlier.
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