Polarography and solvatochromism. Part 1.—Polarographic reduction of 5′-methoxy-2′-hydroxy-N-methyl-4-stilbazolium iodide and related compounds

Abstract

2′-Hydroxy-N-methyl-4-stilbazolium iodide (IIa), its 5′-chloro-(IIc) and 5′-nitro-(IIb) derivatives are strongly adsorbed at the surface of the dropping mercury electrode (d.m.e.). 5′-Methoxy-2-hydroxy-N-methyl-4-stilbazolium (IId) iodide proved to be less strongly adsorbed and is reduced in the protonated form at lower pH-values in two one-electron steps. The product of reduction in the first step can undergo protonation, and protonated and unprotonated radicals undergo reduction at different potentials. When the properties of the betaine form of compound (IId) are to be studied, the half-wave potentials must be measured at pH 13–14, as at lower pH-values reduction of the phenolic form predominates.