Synthesis and voltammetry of [bmim]4[α-S2W 18O62] and related compounds: Rapid precipitation and dissolution of reduced surface films

Abstract

1-n-Butyl-3-methylimidazolium (bmim) salts of [α-SiM 12O40]4- and [α-S2M 18O62]4- (M = Mo, W) were synthesized and characterized. In sharp contrast to the multiple one-electron diffusion-controlled reduction processes expected in solution at a glassy carbon electrode, reduction of these salts beyond the one-electron level in CH 3CN (0.1 M [bmim][PF6]) led to rapid precipitation of arrays of microdroplets or microcrystals onto the surface. Upon oxidation these arrays dissolved on the electrochemical time scale, resulting in voltammograms displaying both diffusion-controlled and surface-confined behavior. These novel observations appear to be related to the ability of the [bmim]+ cations and p..