Ion Exchange of Ferro(ferri)cyanide in Polyvinylferrocene Films

Ion exchange of ferro/ferricyanide into oxidized polyvinylferrocene (PV-Fc) films occurs upon repetitious cycling of a PV-Fc film between its oxidized and reduced forms in the presence of either Fe(CN)₆^3-and Fe(CN)₆^4-. The ion exchange is evident from cyclic voltammetry and the response of a quartz crystal microbalance coated with a PV-Fc film. Insertion of the multiply charged anions appears to result in deactivation of polyvinylferrocene sites, with the exchanged films initially exhibiting voltammetric waves due to confined ferro(ferri)cyanide. Prolonged cycling of the exchanged films causes complete passivation of the films towards redox species in the film, as well as solution species, suggesting extensive electrostatic cross-linking by the multiply charged anions. Coulometric experiments suggest that approximately one ferro(ferri)cyanide exchanges for three PV-Fc redox sites. The visible spectra of the exchanged films after prolonged cycling suggests the presence of Prussian blue-like species in the polymer film which presumably arise from decomposition of the polymer.