Electroactive counter anions in conducting polypyrrole: hexacyanoferrate and heteropolytungstate ions

Summary form only given. Hexacyanoferrate ions [Fe(CN) /sub 6/,z-(z=3,4) and heteropolytungstate ions [SiW/sub 12/O/sub 40/]/sup 4-/, [P/sub 2/W/sub 18/O/sub 62/]/sup 6-/ were doped into conducting polymers of pyrrole. The polymers exhibited reversible redox properties inherent to the anions in addition to those of the polypyrrole moiety, resulting in enhanced electrochemical charge storage capability which may have potentially useful applications. Whereas the hexacyanoferrate ions were labile toward exchange with anions in the electrolyte solutions in contact, the heteropolytungstate ions were retained in the polymer matrix without being ion-exchanged after repeated potential cycles in electrolyte solutions containing no heteropoly anions. Charge compensation on reduction was accomplished by cation insertion instead of releasing of the anions. Spin density of polymer with [Fe(CN) /sub 6/]/sup z-/ or [P/sub 2/W/sub 18/O/sub 62/]/sup 6-/ as measured by ESR was small indicating bipolaron formation accelerated by the anions bearing multiple charges.