Synthesis and Photophysical Properties of 4-Aroyl-2,6-diaminopyridine-3,5-dicarbonitriles

Three complementary methods were developed for the synthesis of novel 4-aroyl-2,6-diaminopyridine-3,5-dicarbonitriles based on selective nucleophilic substitution of chlorine, reduction of azide derivatives, and ANRORC recyclization of furan precursors. A comprehensive study of the photophysical properties of the obtained series of compounds revealed dual fluorescence caused by an equilibrium between monomer emission and excimer emission. It was found that the position and intensity of the excimer band are effectively governed by the electronic nature of substituents in the aroyl fragment, solvent polarity, and solution concentration.