Redox reactions of basic fuchsin in homogeneous aqueous media

Abstract

The pulse-radiolysis technique has been employed to understand the reaction mechanism and to characterize the transient species involved in the redox processes taking place in the radiation chemistry of basic fuchsin (BF+). One-electron reduction and oxidation reactions of BF+ have been carried out in homogeneous aqueous solutions employing various reducing (eaq−, (CH3)2C•OH, CO2•−) and oxidizing (N•3, Br•, Cl2•− Br2•−) radicals. The absorption spectra of the transients formed in the above reactions have been attributed to semi-reduced and semi-oxidized species of BF+, respectively. The kinetic and spectroscopic properties of these transients have been evaluated. The reaction with H• and •OH radicals have also been performed and compared with those of specific one-electron reducing and oxidizing radicals. These reactions have been inferred predominantly by addition to BF+. Protolytic equilibria involving semi-reduced species of basic fuchsin have been studied over the pH range from 2 to 10 and the pKa has been determined to be 3.9.