ELECTROPOLYMERIZATION OF BIS(4-CYANO-1-PYRIDINIO) DERIVATIVES FOR THEPREPARATION OF POLYVIOLOGEN FILMS ON ELECTRODES

Six bis(4-cyano-1-pyridinio) derivatives have been synthesized and dep osited onto electrodes by cathodic electropolymerization (E(Red) = -0. 64--0.74 V vs. SCE) under basic conditions. The deposited films were c onstructed of polyviologens that showed characteristic electrochromism s with colorless or slightly yellow to blue- or red-violet. The deriva tive was reduced to 4-cyano-1,4-dihydro-4-pyridyl radicals, which were coupled successively to form a polyviologen film on the electrode wit h an elimination of cyanide ions. Characteristically, the polyviologen films deposited by this electropolymerization were insoluble in water and common organic solvents with a spontaneous cross-linking. Especia lly, a polyanion as a supporting electrolyte forced the polyviologen t o form a polyelectrolyte complex in situ. The current efficiency of su rface coverage with the polyanion electrolyte (23% in the typical case ) was about four-times larger than those with monomeric anions.