Stimulus-Mediated Ultrastable Radical Formation

Summary Organic radicals are reactive and often short-lived species typically formed through either the addition of a chemical agent or photochemical means. On account of their open-shell electronic structure, they have attracted attention based upon their magnetic properties and desirable spectroscopic behavior. Redox-sensitive molecules, such as viologen (V), undergo one-electron reductions to form radical species. These species hold significant potential in myriad applications but are limited because they are rapidly quenched by oxygen in air. Using methyl viologen (MV) as an example, we show that the MV radical (MV+⋅) can be formed through electrochemical, chemical, and photochemical stimuli as well as a novel thermal stimulus in various deep eutectic solvents (DESs) and was found to be exceptionally stable. The conductive properties of DESs allowed for the fabrication of an aerobic electrochromic device through a straightforward, economical approach. Our report represents a unique approach to extending reactive radical lifetimes in air without altering the parent structure.