Electrochemical Characteristics of Some Purpurins in Aqueous and Nonaqueous Solutions

The Electrochemical Impedance Technique (EIS) and the Cyclic Voltammetric method (CV) were used to investigate the behavior of purpurin (P), Anthrapurpurin (AP) and Benzopurpurin (BP) in aqueous and in N, N-dimethylformamide (DMF) media. In the CV experiments, both the radical and the dianion of these substances were assumed to form of limited stability due to chemical protonation. In case of benzopurpurin, the CV measurements in DMF revealed a cis-trans isomerization changes of the molecule. The CV study includes also simulation of some responses using appropriate theoretical fitting models to confirm proposed reaction rates. The EIS experiments were carried out using a small AC amplitude and a relatively wide frequency range. The diagrams are characterized in the complex plane by the demonization of the Warburg impedance behavior at low frequencies and the appearance of two uncompleted semicircles in the Nyquist plot of the complex plane.