An N-Heterocyclic-Carbene-Derived Distonic Radical Cation.

We present the discovery of a novel radical cation formed through one-electron oxidation of an N-heterocyclic carbene-carbodiimide (NHC-CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox-flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox-active NHC-CDI adducts and their persistent radical ions for various applications.