VOLTAMMETRIC, SPECTROSCOPIC AND COMPUTATIONAL STUDY OF THREE BIOLOGICALLY ACTIVE ORGANIC COMPOUNDS

Abstract

In the present work, an endeavor has been made to study the redox mechanism of three biologically active organic compounds namely 1-methoxyphenazine (MPZ), 2-benzoyl-7methoxy-2,3-dihydroisoquinoline-4(1H)-one (IQN) and1-hydroxy-2-(hydroxymethyl) anthracene-9,10-dione (HAQ) in a wide pH using three different voltammetric techniques (cyclic, differential pulse and square wave voltammetry), UV-Visible spectroscopy and computational study. Phenazines, isoquinolines and anthraquinones are known to have strong potency of antibacterial, antifungal, hypertension, antiparasitic and anti cancer activities. Therefore, the detailed electrochemistry of three novel derivatives of these classes was carried out in different pH media with the objective to understand the mechanism of their redox behavior. These mechanistic pathways are expected to present a key in considering the hidden routes by which such compounds exert its biochemical action. In the present work, voltammetry was performed for the three mentioned compounds in buffered ethanolic aqueous media. Cyclic voltammetry was used to determine diffusion coefficient and heterogeneous electron transfer rate constant from scan rate and concentration effect respectively. The involvement of protons in redox mechanism was confirmed from a shift in peak potential as a function of medium pH. Differential pulse voltammetry was used to verify the exact number of electrons involved in the redox process. Similarly the nature of the redox process was decided from the results of square wave voltammetry. The redox mechanism proposed on the basis of CV, DPV and SWV investigations was supported by theoretical calculations. Furthermore, a detailed UV-Visible spectroscopy was performed in a wide pH range to investigate the effect of medium on the absorption response of these compounds. Pka values were also determined from spectroscopic experiments. IQN and HAQ exhibited pH dependent reduction and oxidation while MPZ underwent pH dependent reduction and pH independent oxidation