How plutonium "brown" peroxo complex emerges from electrolysis experiments.

An original spectroelectrochemical approach was employed to probe redox reactions with plutonium. Monitoring Pu electrolysis under aerated conditions revealed the formation of a transient species. Using chemometric methods, the associated spectroscopic signature was found to correspond with a dimeric peroxo-bridged Pu complex described 70 years ago, often referred to as the plutonium "brown" complex. A separate synthesis of this complex confirmed the presence of the transient species during electrolysis, challenging conventional concepts of Pu electrochemistry. The mechanistic role of the Pu "brown" complex during Pu electrolysis is also discussed.