The electroreduction of 4,4'-azobispyridine-l,l'-dioxide (APDO) in dimethylformamide solutions was studied by polarography, cyclic voltammetry, controlled potential coulometry, and electron spin resonance, Voltammetric reduction showed two well-defined, reversible one-electron transfers. Coulometric reduction at a potential corresponding to the plateau of the first wave gave evidence of chemical reactions following the initial electron transfer producing intermediates which were also

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... ve at the same potentials. Coulometry at the second wave gave an over-all value of six Faradays per mole for the complete reduction of APDO to the dianion of azopyridine (A_P), identified by electrochemical and electron spin resonance techniques. A mechanism for the reduction process consistent with the experimental evidence is presented.