Probes of Nonreactive Environment. II. Molecular Association Effects with Methylviologen

摘要

The purpose of this investigation was to learn more about the discovery that the epr (electron paramagnetic resonance) spectra of methylviologen cation radical chloride vary markedly depending on the environment in which the radical was produced. Methylviologen cation radical chloride was formed by allowing 0.5,0,025 and 0.00135 M aqueous solutions of 1,1'-dimethyl-4'-bipyridinium dichloride to react with either zinc or diethylamine. The radical formed in the presence of the highest concentration of the bipyridinium dichloride exhibited a single epr line, whereas that formed at the lower concentrations showed a multiline pattern. The single epr line is attributed to a molecular association between methylviologen cation radical chloride and 1,1'-dimethyl-4,4'-bipyridinium dichloride (methylviologen dication dichloride). Rapid exchange in the complex explains the loss of hyperfine structure in the epr spectra. This finding may be useful in designing studies involving electron transfer in many chemical and biochemical systems. Viologen complexes may be helpful as chain carriers of electrons between molecular sites. (Author)