Abstract Photolysis of 1-benzyl-3-carbamoylpyridinium chloride (BNA+) in aqueous solution in the presence of diethylamine and/or ethylenediaminetetraacetate gives the 6,6′-dimer (1), a coupled product of the pyridyl radicals generated by one-electron transfer from alkylamine to photoexcited BNA+. Thermal one-electron reduction of BNA+ either with zinc dust/copper sulfate or with magnesium powder in aqueous alkaline medium yields the 4,6′-dimer (2) together with a small amount of 1. In the case of 3,5-bis(ethoxycarbonyl)2,6-dimethylpyridine (HEox), the 2,2′-dimer (3) is formed as an initial photoreduction product, which is converted into the 4,4′-dimer (4) and 1,2-dihydropyridine (5) upon prolonged irradiation.