Properties of strongly oxidizing radicals in organic media are important for understanding charge transport in organic solar cells, mechanistic studies of electron transfer in solutions, and probing chemical transformations in nuclear fuel processing. However, investigation of such high energy species is challenging due to their transient nature and limited availability of methods for their generation. Conventional electrochemical techniques, such as cyclic or pulsed voltammetry only yield approximate values of reduction potentials of highly oxidizing radicals due to irreversibility of electron transfer. In this work we employed pulse radiolysis (PR) to generate radical cations of substituted triphenyl amines (TPA) and biphenyls (BP) and measured their reduction potentials using redox equilibrium ladder approach. Potentials of TPA and methoxy-substituted biphenyl radicals in 1,2-dichloroethane containing 0.1M TBA PF<sub>6</sub> show good correlation thus validating PR equilibrium method. Potentials of <i>p</i>-substituted biphenyls increase from R = OMe to R = CN, but the trend shows saturation at higher sigma values. This study has explored the effects of inter- and intramolecular charge delocalization, solvent media, added electrolyte and ion pairing on measured potentials of biphenyl derivatives.

Redox properties of strongly oxidizing radicals in organic solvents probed by pulse radiolysis

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