Experimental observations and mechanistic interpretation

Our published studies [18, 19] of poly(thionine) redox switching showed that, in acetic acid buffer, the leuco (reduced) form (L) is oxidized, losing two electrons and two protons, to generate the oxidised form (7 ). Furthermore, acetic acid is coordinated only to the 7-form so that reduction causes 7 to lose an acetic acid molecule. However, reduction of 7 to L follows a different path than the reverse of the oxidation path. Water transfer is also involved in the redox cycle. We can (in simplified form) write the overall redox switching process as  

Our problem is to assign a mechanism to the implied combination of electron/proton, solvation and acetic acid coordination steps. The mechanistic details of this redox cycle were given in Figs. 6 and 7 of Ref. [19]. As we now show, the scheme of cubes is a vastly superior and more concise way to present the details of the complete redox cycle for this process. 

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