VOLTAMMETRIC STUDY OF THE 2-DIMENSIONAL PHASE FORMED BY THE CATION-RADICAL OF METHYL VIOLOGEN ON MERCURY IN THE PRESENCE OF IODIDE-IONS

Methyl viologen (MV(2+)) gives a very narrow, sharp, tailless reversib le peak by cyclic voltammetry at a mercury electrode. The peak arises from the one-electron reduction of the molecule to its cation radical (MV .(+)), which forms a two-dimensional (2D) phase over the electrode . In this work, we tested various analytical criteria in order to vali date this assignation and fit the voltammetric peak numerically to the theoretical model developed for this purpose. The formation ofthe two -dimensional condensed phase of MV .(+) over mercury was found to depe nd on temperature. Like three-dimensional phases, 2D phases are not fo rmed above a given, critical temperature. Thus, the voltammetric peak disappeared abruptly above 67 degrees C, which can therefore be adopte d as the critical temperature for the 2D phase of methyl viologen.