ELECTROCHEMICAL REDUCTION OF 1,1'-ETHYLENEBIS(3-CARBAMIDOPYRIDINIUM BROMIDE)

1,1ʹ-Ethylenebis(3-carbamidopyridinium bromide) undergoes a 2-electron reduction at a cathode of controlled potential to yield a product in which the two pyridine rings are linked by a new bond between the 6 positions. The original pyridinium salt is regenerated upon electrochemical oxidation at controlled anode potential, but partial oxidation with oxygen yields a stable, deep red free radical. The same radical is obtained in better yield by exhaustive oxidation with oxygen followed by a 1-electron electrochemical reduction. The esr spectrum of the radical is similar to that obtained upon reduction of 1,1ʹ-ethylene-2,2'dipyridylium dibromide (“Diquat”); differences between the spectra can be explained by the absence of carbamide groups in the “Diquat” case. Reasonable structures may be advanced for the various species on the basis of ultraviolet and esr spectra. © 1969, American Chemical Society. All rights reserved.