Redox Chemistry of the Superoxide Ion in a Phosphonium-Based Ionic Liquid in the Presence of Water

Stable electrogenerated superoxide ion has been observed for the first time in a phosphonium-based ionic liquid in the presence of water, leading to a chemically reversible O-2/O-2(center dot-) redox couple instead of the disproportionation reaction that is usually observed. It appears that the cation solvates the superoxide anion, stabilizing it against the disproportionation reaction. The electrogeneration is studied at various levels of water or other diluents including toluene to explore the limits of stability of the superoxide ion under these conditions.