A Kinetically Stabilized Nitrogen‐Doped Triangulene Cation: Stable and NIR Fluorescent Diradical Cation with Triplet Ground State

Abstract

AbstractA kinetically‐stabilized nitrogen‐doped triangulene cation derivative has been synthesized and isolated as the stable diradical with a triplet ground state that exhibits near‐infrared emission. As was the case for a triangulene derivative we previously synthesized, the triplet ground state with a large singlet‐triplet energy gap was experimentally confirmed by magnetic measurements. In contrast to the triangulene derivative, the nitrogen‐doped triangulene cation derivative is highly stable even in solution under air and exhibits near‐infrared absorption and emission because the alternancy symmetry of triangulene is broken by the nitrogen cation. Breaking the alternancy symmetry of triplet alternant hydrocarbon diradicals by a nitrogen cation would therefore be an effective strategy to create stable diradicals possessing magnetic properties similar to the parent hydrocarbons but with different electrochemical and photophysical properties.