π‐Expansion on a Polycyclic Stable Neutral Radical: Synthesis and Physical Properties of a Benz‐Annulated Trioxotriangulene

Abstract We report the synthesis of a benz‐annulated derivative of trioxotriangulene ( TOT ), a fused polycyclic organic neutral radical, and also the investigation on the electronic effects of π‐expansion. The neutral radical species was highly stable under air in both solution and solid states. Quantum chemical calculation suggested that the molecule has a completely planar molecular structure, and the electronic spin is widely delocalized throughout the π‐skeleton while maintaining three‐fold symmetry, which was experimentally supported by electronic spin resonance spectrum. The neutral radical also showed a strong π‐association ability comparable to that of TOT neutral radical derivatives.