Electrochemistry of the 9‐phenyl‐10‐methyl‐acridan/acridinium redox system; a high‐potential NADH/NAD⁺ analogue

Abstract

Abstract Cyclic voltammetry and preparative controlled potential electrolysis show that the 9‐phenyl‐10‐methyl‐acridinium/acridan (AcPh + /AcPhH) redox couple can be cycled electrochemically between the oxidized (AcPh + ) and reduced states (AcPhH) without any apparent side‐reaction. The 9‐phenyl‐10‐methyl‐acridanyl radical (AcPh • ) was identified as a first intermediate in the electrochemical reduction of AcPh + by cyclic voltammetry as well as by electronic absorption and ESR spectroscopy. In contrast to other acridanyl and related dihydropyridyl radicals, AcPh • shows no tendency to undergo dimerization. In aprotic media, AcPh • is shown to undergo a second reversible one‐electron reduction to yield AcPh − , which is, even in these media readily protonated to give AcPhH. The stability of these intermediates seems to be the major factor responsible for the clean electrochemical interconversion of the AcPh + /AcPhH redox couple. The implementation of this redox couple as part of photo‐electrochemical energy conversion systems is discussed.