Ring Reconstruction on a Trichalcogenasumanene Buckybowl: A Facile Approach to Donor–Acceptor‐Type [5‐6‐7] Fused Planar Polyheterocycles

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 %.