An Electrochemical Investigation of the Redox Properties of Murexide in Aqueous and Non-Aqueous Media

Abstract

Knowledge of solvent effects on the redox properties of Murexide (Mu) is important for understanding its role as an electron acceptor in analytical and inorganic chemistry. In the present study, an investigation of the electrochemical behavior of the compound by both Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) in both aqueous and non-aqueous solutions was undertaken. It is suggested that, the reaction mechanism proceeds according to an Erev CE-rev-route. This reaction mechanism is confirmed by the CV behavior for barbituric acid, which is essentially represent a main part of murexide, under the same conditions. In DMSO, the one-electron reduction potential peak of murexide was found to shift positively by 223 mV to the value of the corresponding wave obtained in DMF under the same conditions. The shift is most readily explained by the presence of murexide aggregates in DMF. The one-electron oxidation potential position is relatively unaffected by aggregation. The data has also revealed that murexide decomposes in the level of radical anion at the N = C bond into two approximately equal units. In aqueous sodium perchlorate (NaClO₄) solutions, it is suggested that the decomposion of murexide is relatively slow, leading to nearly a reversible 1e-transfer process (E-mechanism). In both KNO₃ and KCl solutions, the one-electron transfer step of murexide was found to be an adsorption wave. The Electrochemical Impedance (EIS) response of murexide is either low-frequency Warburg impedance or a capacitive semicircle behavior at high frequencies, depending on the medium.