Synthesis and Photophysical Properties of Ethyl 3,6-Diamino-4-aryl-5-cyanothieno[2,3-b]pyridine-2-carboxylates

A new method was developed for the synthesis of ethyl 3,6-diamino-4-aryl-5-cyanothieno[2,3-b]pyridine-2-carboxylates by the reaction of 4-aryl-2-amino-6-chloropyridine-3,5-dicarbonitriles with ethyl 2-mercaptoacetate. The synthesized compounds exhibit fluorescence both in solution and in the solid state. The emission maxima in benzene solution depend on the substituent and are in the range of 503–531 nm or from 498 to 541 nm in the solid state. For photoluminescence of ethyl 3,6-diamino-4-aryl-5-cyanothieno[2,3-b]pyridine-2-carboxylates, large Stokes shifts were observed: from 214 nm (13106 cm^–1) in chloroform to 251 nm (14433 cm^–1) in methanol.