Synthesis and Dual-State Emission of Highly Functionalized Thieno[2,3-b]pyridines

Abstract

An efficient method for the synthesis of highly functionalized thieno[2,3-b]pyridine derivatives, namely ethyl 3-amino-4-aryl-6-(dimethylaminomethylideneamino)-5-cyanothieno[2,3-b]pyridine-2-carboxylates, was developed starting from 4-aryl-2-(dimethylaminomethylideneamino)-6-chloropyridine-3,5-dicarbonitriles and ethyl mercaptoacetate. Study of the photophysical properties of the synthesized compounds revealed a rare dual-state emission (DSE) behavior, observed both in solution and in the solid state. Fluorescence maxima in DMSO solution depend on the nature of the substituent and lie in the range of 494–508 nm, whereas in the solid state the emission is observed in the 494–516 nm region.