Detailed Electrochemical Probing of the pH Dependent Redox Behavior of 1-methoxyphenazine

Abstract

The electrochemical behavior of a biologically important phenazine derivative, 1-methoxyphenazine (MPZ) was scrutinized over a pH range 1.2–12.8 by cyclic, square wave and differential pulse voltammetry. The results of cathodic peak potential shift as a function of pH demonstrated that 1-methoxy phenazine is reduced by a 1e−, 1H+ diffusion controlled process. Epc − Epc/2 values, scan rate dependent deviation of peak potential, heterogeneous electron transfer rate constant and inequality of the components of total current proved the quasi-reversible nature of the redox process. MPZ was found to oxidize in the pH range 5–12.8 by the loss of a single electron without proton involvement. The pKa of MPZ with a value of 11.2 was determined from the intersection of the two segments of Ep vs. pH plot. The pKa values of MPZ obtained from all the three electrochemical techniques were found in very good agreement. The limits of detection and quantification of 1-methoxyphenazine were determined as 2.6 μM and 8.6 μM respectively. On the basis of the results obtained redox mechanism was proposed with the objective of emphasizing imperative aspects of structure-activity relationships and understanding the unexplored pathways by which this class of compounds exert its biochemical actions.