Effect of structures of bipyridinium salts on redox potential and its application to CO2 fixation

Abstract

The relation between the structures and the redox potentials in electron carriers, 1,1′-dialkyl-4,4′-bipyridinium salts (4,4′-BP) and 1,1′-dialkyl-2,2′-bipyridinium salts (2,2′-BP), is theoretically analyzed by AM1 calculation. Relatively good linearity is obtained between the Gibbs free energies and the redox potentials. These electron carriers are used in a CO₂ fixation reaction using enzyme (formate dehydrogenase), in which formic acid is obtained as a final product. It is found that the efficiency of CO₂ fixation is dominated by the relative magnitude of redox potentials of the electron carriers, a photosensitizer and CO₂.