Nor[7]circulenyl Neutral Radical and Its Charged Species: Synthesis, Structures, and Efficient NIR‐II Photothermal Conversion for Imaging and Laser Ignition

Abstract [ n ]Circulenes have attracted considerable research interest; however, open‐shell [ n ]circulene‐type structures remain elusive. In this study, we report the synthesis of a highly stable nor[7]circulenyl radical (nor[7]CR) and its isolation in the crystalline phase. nor[7]CR exhibits a distinct four‐stage amphoteric redox behavior, as revealed by cyclic voltammetry. The stable cation (nor[7]CR + ) was obtained via chemical oxidation and isolated in crystalline form, and the corresponding anionic species were characterized spectroscopically. Remarkably, nor[7]CR + exhibits strong NIR‐II absorption at 1105 nm with a high photothermal conversion efficiency (PCE) of 93%, as well as a high maximum photothermal temperature ( T max ) under low optical power density. The applications of nor[7]CR + in photothermal imaging and laser ignition were demonstrated, highlighting its great potential as a photothermal material.