Electron-Transfer Reactions and Conformational Changes Associated with the Reduction of Bianthrone

Article abstract of DOI:10.1021/ja00394a018

The electrochemical reduction of the low-temperature A form of bianthrone (1A) at a platinum cathod in DMF proceeds in a two-electron, irreversible reaction, giving the dianion 3B which is structurally similar to the high-temperature B form of bianthrone (1B), having two planar ring system twisted about the central connecting bond.The overall reduction involves a large structural change.By contrast, 3B is rapidly and reversibly oxidized to a structurally similar anion radical, 2B, and then to 1B which is not stable at room temperature and converts to 1A as it diffuses away from the electrode.This scheme was confirmed by cyclic voltammetry and transmission-mode spectroelectrochemistry.Rate constants for both the 1A->1B and 1B->1A reactions were determined, and upper limits were put on the rate constants for the direct electrochemical reduction of 1A to 2B or 3B.