A Mesoionic Platform for Persistent Anionic Nitrogen‐Centered Radicals

Persistent anionic N‐centered radicals are exceptionally rare, as the coexistence of negative charge and unpaired electron density typically promotes protonation, aggregation, and irreversible redox chemistry. Here we introduce mesoionic 1,2,3‐triazines as a platform for stabilizing such elusive open‐shell anions. These compounds undergo clean and reversible one‐electron reduction to generate negatively charged nitrogen‐centered radicals, and suitable substitution enables their isolation as crystalline salts. EPR spectroscopy, single‐crystal x‐ray diffraction, and computational analysis reveal dominant nitrogen spin localization together with reduction‐induced structural changes consistent with occupation of a parent triazine antibonding orbital. The resulting anionic radicals display chemically clean electron‐transfer behavior and are reversibly oxidized to their zwitterionic precursors. These findings further highlight the potential of mesoionic 1,2,3‐triazines as redox‐active molecular platforms for applications in complex electrochemical environments.