Solvation of an excess electron in pyrrolidinium dicyanamide based ionic liquids.

Abstract

In a recent article [J. Am. Chem. Soc. 2011, 133, 20186], we described the nature of the "dry" excess electron in a variety of different ionic liquids. We found that this could delocalize over cations or anions depending on the nature of the ions involved. A second article [J. Am. Chem. Soc. 2013, 135, 17528] explored the nature of the "dry to trapped" excess electron transition, the early localization dynamics, and associated spectroscopic signatures in alkylamonium and pyrrolidinium bis(trifluoromethylsulfonyl)amide based ionic liquids. In this study we predicted that the trapped electron localizes on an anion, resulting in fragmentation that is undesirable for photochemical, electrochemical, and radiation chemistry applications. The current work focuses instead on an ionic liquid based on the dicyanamide anion that on a time scale relevant to electron transfer and solvation dynamics does not appear to undergo facile fragmentation. Although electrochemical cathodic and anodic limits were correctly predicted by our recent study, it is unclear whether the reaction channels explored are necessarily those responsible for the observed near-infrared (NIR) band typical of excess electrons at long time. Could it be possible that the electrochemically relevant reaction channel is not necessarily the one giving rise to the NIR signal? This work attempts to approach such structural and dynamical aspects relevant to photodegradation, radiation chemistry, and electrochemistry in the case of pyrrolidinium dicyanamide based ionic liquids.