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

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(center dot-), then Q(center dot-) reacts with Q to produce dimer Q(2)(center dot-). What's more, both the g-dimer and sigma-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.