Ring Reconstruction on a Trichalcogenasumanene Buckybowl: A Facile Approach to Donor–Acceptor‐Type [5‐6‐7] Fused Planar Polyheterocycles. Issue 1 (5th November 2014) - Li, Xuexiang
Abstract: The transformation of trichalcogenasumanene buckybowls into donor–acceptor‐type [5‐6‐7] fused polyheterocycles is disclosed. The strategy involves a highly efficient ring‐opening of the flanking benzene upon oxidation at room temperature, and facile ring closure by functional‐group transformation. Crystallographic studies indicate that the resulting [5‐6‐7] fused polyheterocycles possess a planar conformation owing to the release of ring strain by expansion of one of the six‐membered flanking rings to the seven‐membered one. Additionally, the [5‐6‐7] fused polyheterocycles bear electron‐withdrawing groups, which reduce the HOMO–LUMO energy gap, and display broad absorption bands extending to λ =590 nm. Consequently, these compounds show strong red emission with fluorescence quantum yields of up to 38 %. Abstract : Bowled over : Oxidation of the electron‐rich and bowl‐shaped trichalcogenasumanenes by Oxone resulted in highly efficient ring‐cleavage of the flanking benzene at room temperature. The successive ring‐closure led to the creation of a series of donor–acceptor‐type (D–A) [5‐6‐7] fused planar polyheterocycles, which show a strong red emission.