Voltammetric reduction of perinaphthenone in aqueous and non-aqueous media: An electrochemical ESR investigation

The electrochemical reduction of perinaphthenone on solid electrodes in aqueous and non-aqueous media is reported and paramagnetic species formed are characterised by use of electrochemical ESR, employing a tubular flow cell. In aqueous ethanol a single electron reduction process generates the radical anion which is protonated at pH < 9, as indicated by the shift of the voltammetric wave with pH. Observed ESR spectra are presented and signal intensity measurements show that the neutral radical has a lifetime close to 1 min. In acetonitrile, the reduction occurs in two waves. The first corresponds to the reversible electrogeneration of radical anions and these are found to be stable on the experimental timescale, whereas the second wave is attributed to the formation of the dianion, which undergoes a chemical reaction with the solvent. The behaviour of benzanthrone in acetonitrile is found to be similar to that of perinaphthenone.