Role of proton-coupled electron transfer in the redox interconversion between benzoquinone and hydroquinone.

Benzoquinone/hydroquinone redox interconversion by the reversible Os(dmb)33+/2+ couple over an extended pH range with added acids and bases has revealed the existence of seven discrete pathways. Application of spectrophotometric monitoring with stopped-flow mixing has been used to explore the role of PCET. The results have revealed a role for phosphoric acid and acetate as proton donor and acceptor in the concerted electron–proton transfer reduction of benzoquinone and oxidation of hydroquinone, respectively.