Synthesis of new efficient fluorophores of thieno[2,3-<i>b</i>]pyridine series

Abstract

The reaction of 4-amino-6-aryl-2-halopyridine-3,5-dicarbonitriles with thioglycolic acid ethyl ester was used to synthesize a series of new efficient fluorophores of thieno[2,3- b ]pyridine series. The long-wavelength absorption bands of DMSO solutions of the prepared compounds are at the boundary of the UV and visible regions of the spectrum (λabs 375-388 nm) and show an ambiguous influence of the substituent electronic effect, that was explained by quantum chemical calculations. The emission maxima are in the yellow-green region (λem 490- 510 nm) and they are blue-shifted in the presence of electron donor groups with slightly increasing intensity (Φem 37.8-60.6%). It was found that the nitro group presence causes a complete photoluminescence quenching both in solution and in the solid state. In addition, the position of the emission maximum (λem 473-505 nm) and its intensity (Φem 3.6-72.7%) strongly depend on the polarity and the basic properties of the medium, that was established using the Catalan empirical model.