Investigation on the π-Dimer/σ-Dimer of 1,8-Dihydroxy-9,10-anthracenedione in the Process of Electrochemical Reduction by Using IR Spectroelectrochemical Cyclic Voltabsorptometry and Derivative Cyclic Voltabsorptometry

Abstract

The electrochemical reduction of 1,8-dihydroxy-9,10-anthracenedione (Q) has been investigated by cyclic voltammetry (CV). Both 9,10-anthroquinone (AQ) and 1,8-methoxy-9,10-anthracenedione (DMeAQ) are reduced in two steps. First, they are reduced to the anion radical. Next, the anion radicals are reduced to the dianion. However, the CV of Q shows more cathodic and anodic peaks, which suggests the formation of a neutral- anion radical complex. To study the reaction mechanism of Q, in situ infrared (IR) spectroelectrochemistry, IR cyclic voltabsorptometry (CVA), and derivative cyclic voltabsorptometry (DCVA) spectroelectrochemical techniques are used to track the electrochemical reduction process. It is found that Q is reduced to Q•–, then Q•– reacts with Q to produce dimer Q2•–. What’s more, both the π-dimer and σ-dimer can be observed during the electrochemical process by an IR spectroelectrochemical technique. As a result, a new reaction mechanism of Q has been proposed by this powerful approach.