Synthesis of Positional Isomers and Photophysical Properties of Pyridines with Tricyanobutadiene Fragment Containing Aryl and Trifluoromethyl Substituents

A method was developed for obtaining positional isomers—2-[6-aryl-4-trifluoromethyl-3-cyanopyridin-2(1H)-ylidene]malononitriles and 2-[4-aryl-6-trifluoromethyl-3-cyanopyridin-2(1H)-ylidene]malononitriles, which differ in the opposite positioning of the aryl and trifluoromethyl substituents. These compounds exhibit photoluminescence in solutions ranging from the violet to the yellow region of the visible spectrum (λ_em^max = 418–577 nm). The strongest photoluminescence was observed in low-polarity solvents, where the quantum yield of photoluminescence reached 46%. It was shown that a basic medium leads to a significant red shift due to the formation of the anionic form.