Synthesis and Spectral–Luminescent Properties of 2-Amino-6-chloro-4-(4-(dimethylamino)phenyl)pyridine-3,5-dicarbonitrile and Compounds Based on It

A series of new donor–acceptor chromophores based on pyridine derivatives was synthesized by substituting the chlorine atom in 2-amino-4-(4-(dimethylamino)phenyl)-6-chloropyridine-3,5-dicarbonitrile with a variety of N-, C-, O-, and S-nucleophiles. The spectral and luminescent properties of the resulting compounds in DMSO were examined. The absorption spectra featured intense bands with maxima in the range of 345–380 nm. In the case of compounds bearing an exocyclic double bond, pronounced shoulders were observed in the longer-wavelength region, extending up to 400 nm. Quantum chemical calculations based on density functional theory (DFT) made it possible to assign the observed absorption bands to specific electronic transitions and to attribute the appearance of shoulders to the presence of multiple tautomeric forms of the chromophores in solution. All synthesized compounds displayed photoluminescence with emission maxima in the range of 467–546 nm, depending on the nature of the introduced nucleophile.