Electrochemical and Electron Transfer Behavior of o-Chloranil with the Presence of Mg2+ in Acetonitrile

Abstract

The reduction process of o-chloranil (o-CA) with the presence of Mg2+ was observed in acetonitrile on a platinum electrode to compare that of p-chloranil (p-CA) with Mg2+. Although the reduction potentials of o-CA and p-CA were not so different without Mg2+, apparent differences were recognized for both reduction processes in the presence of Mg2+. While the adsorption of a Mg2+ salt of p-CA dianion, Mg2+p-CA2−, was reported, no adsorption of the reduced forms of o-CA was observed. Alternatively, significant changes in the electrochemical responses were observed implying a rigid complexation between Mg2+ and o-CA2− in solution. In addition , using a stopped-flow technique, the occurrence of the electron transfer between ferrocene, whose formal oxidation potential is +0.26 V (vs. , I−), and o-CA, whose formal reduction potential is 0.00 V, was observed in the presence of Mg2+, though the spontaneous electron transfer did not occur without Mg2+. This indicates the effect of Mg2+ to make the redox potential of o-CA positive by complexing, while this is not the case of p-CA.