On the Synthesis and Electrochemical Properties of Some New Bipyridinium and Related Compounds

Z. Naturforsch. 43b, 475-482 (1988); received February 13/October 22, 1987 Electron Transfer Relays, Viologen Derivatives, Bipyridinium Compounds, Stable Cation Radicals, Photoinduced Water Splitting The synthesis of some new bipyridinium salts is described. Their behavior upon reduction is studied by cyclovoltammetry, coulometry and spectroscopically. Halfwave potentials range from —0.28 V to —0.59 V and e values of the reduced viologens lie around 104 MT'cm-1. In addition two relay compounds (4,4'-pyridine-2,4-diyl)-bis-(l-methylpyridinium methylsulfate), 4.4',4"(pyridine-2,4,6-triyl)-tris-(l-methylpyridiniumchloride) that are not viologens are described. These substances also form a colored radical upon reduction, but with exceptional stability towards oxidation with dioxygen. From coulometric measurements it is inferred that three electrons are transferred in one step. Spectral changes observed in the course of the electrochemical reduction are explained by dimer formation.