Wardman P
Cancer Research Campaign, Mount Vernon Hospital, Northwood, Middlesex, U.K.
Free Radic Res Commun. 1991;14(1):57-67. doi: 10.3109/10715769109088942.
Bipyridinium compounds such as the viologens (V2+) have been used extensively as redox indicators, but radical dimerization leads to reduction potentials of the oxidant/radical one-electron couple, E(V2+/V2+) varying with radical concentration: a particular problem with benzyl viologen. Pulse radiolysis has been used to characterize the one-electron transfer equilibria between methyl (MV2+) or benzyl (BV2+) viologen and a 2-nitroimidazole (misonidazole), and between methyl and benzyl viologens directly. Total radical concentrations were typically approximately 0.4 mumol dm-3 to minimize dimerization. Based on E(MV2+/MV2+) = -450 mV, a value of E(BV2+/BV2+) = -374 mV is now recommended. The implications for other 'reference' redox couples are discussed.
联吡啶化合物如紫精（V2+）已被广泛用作氧化还原指示剂，但自由基二聚化导致氧化剂/自由基单电子偶合的还原电位，即E(V2+/V2+)随自由基浓度而变化：这是苄基紫精的一个特殊问题。脉冲辐解已用于表征甲基紫精（MV2+）或苄基紫精（BV2+）与2-硝基咪唑（米索硝唑）之间以及甲基紫精和苄基紫精之间的单电子转移平衡。总自由基浓度通常约为0.4 μmol dm-3，以尽量减少二聚化。基于E(MV2+/MV2+) = -450 mV，现推荐E(BV2+/BV2+) = -374 mV的值。还讨论了对其他“参考”氧化还原偶合的影响。
