Synthesis, Structure, and Physicochemical Properties of Doubly Fused Phenoxazine‐Embedded Dithiasapphyrins

Herein, we report the synthesis of a new class of doubly fused phenoxazine‐embedded dithiasapphyrins via (3 + 2) condensation of an appropriate phenoxazine‐based tripyrrane with bithiophene diol in CH 2 Cl 2 under BF 3 ·OEt 2 ‐catalyzed conditions. Single‐crystal X‐ray diffraction analysis of one representative macrocycle revealed an unusual structural rearrangement involving inversion of the two thiophene rings of the bithiophene unit, followed by fusion of the inner thiophene carbon atoms with adjacent pyrrolic nitrogen atoms to generate two tripentacyclic fused rings within the dithiasapphyrin framework. The resulting macrocycle adopts a highly distorted conformation, with the phenoxazine unit deviating by 66.97° from the mean plane defined by the four meso ‐carbon atoms. These doubly fused phenoxazine‐embedded dithiasapphyrins exhibit intense panchromatic absorption across the UV–visible region with pronounced bathochromic shifts relative to their previously reported phenothiazine‐fused analogues. Protonation with TFA further extends the absorption profile into the UV–visible‐near‐infrared region, affording strongly red‐shifted diprotonated species. Electrochemical studies revealed that the phenoxazine‐fused macrocycles are more electron‐rich than the corresponding phenothiazine derivatives. Density functional theory and time‐dependent density functional theory studies support the experimental observations.