Kinetics of Reduction of Eight Viologens by dithionite Ion

Article abstract of DOI:10.1021/ja00295a013

The rate constants are reported for reduction by dithionite of methyl viologen, diquat, and six other diquaternary salts of 4,4'-bipyridine, 2,2'-bipyridine, and 1,10-phenanthroline.The active reductant is the SO2(1-) radical, and rate constants vary from >5*10⁸, to 8.5*10³ M^-1s^-1 with increasing negative reduction potential of the viologen.It is concluded that self-exchange rate constants for the viologens (X^2+/+ couple) are ca. 10⁸ M^-1s^-1, and it is supported by the results of a cross-reaction involving two viologens, the second-oreder rate constant being measured by pulse radiolytic techniques.