Electrochemical Reduction of AQ27DS in Aqueous Solution

摘要

It is known that anthraquinone derivatives act as aqueous sulphide oxidation catalysts, so the redox chemistry of the compound anthraquinone 2,7-disulphonate (AQ27DS) stimulated our interest, as reported here. AQ27DS was reduced in aqueous solution at pH 9.0 to give a deep red coloured air-sensitive solution. Cyclic voltammetry and exhaustive electrolysis indicated that the anthraquinone was reversibly reduced in a two electron, one proton process at a variety of electrode surfaces. From limiting current results at a rotating disc electrode, the diffusion coefficient of AQ27DS was calculated to be 3.37 × 10{sup}(-10) m{sup}2 s{sup}(-1). Spectroscopic results confirmed that AQ27DSH{sup}- was the major reduced species, but also indicated that the di-anion (AQ27DS{sup}(2-)) and radical species AQ27DS·{sup}- were also present. ESR spectroscopy showed that the radical was formed via a comproportionation reaction between the di-anion and the AQ27DS starting material. The peak separation from voltammetry enabled the comproportionation constant (K{sub}c) to be estimated, and it was found to be in the range of 0.4 to 4.