The Aggregation-Induced Emission Enhancement Properties of Heteroaryl Fused Triazapentalens Synthesis and Fluorescence Characteristics

A pyridine-fused triazapentalene shows weak fluorescence in solution, and is readily accessible via nitrene-mediated cyclization. In this research, a modified Cadogan reaction was used to synthesize HetATAP1. Palladium-catalyzed reactions have been demonstrated as post-functionalization methods. Interestingly, Suzuki cross-coupling with various boronic acids resulted in poor to moderate yields of the products HetATAP2-5 arylated on the azole moiety. Direct CH arylation of HetATAP1 gave the products with the same regiochemistry in satisfactory yields. The structures of HetATAP2-5 were confirmed using NMR analysis. In addition, the fluorescence properties of HetATAP2-5 were studied in the solid-state and solution at room temperature, and the photophysical properties of HetATAP3 and 4 in the aggregated state were both measured in ACN/water and THF/water mixtures, respectively.