Heteroaryl-Fused Triazapentalenes: Synthesis and Aggregation-Induced Emission.

A pyridine-fused triazapentalene shows weak fluorescence in solution and is readily accessible via nitrene-mediated cyclization. In this study, a modified Cadogan reaction was used to synthesize . Palladium-catalyzed reactions have been used as post-functionalization methods. Interestingly, modified Suzuki cross-couplings with various boronic acids resulted in poor to moderate yields of - which were arylated at the azole moiety. Direct CH arylation of gave the products with the same regiochemistry in satisfactory yields. The structures of - were confirmed using NMR analysis. In addition, the photophysical properties of - were studied under various conditions. Particularly, the emission of - is enhanced in the solid and aggregate state.