Synthesis and study of optical application of organic dyes based on substituted 4-oxo-2-(thiophen-2-yl)aminobut-2-enoic acids

Highly photoluminescent organic dyes are key materials for organic optoelectronics and photonics. In this paper, we report on the rational design of organic dyes based on substituted 2-(thiophen-2-yl)amino-4-oxobut-2-enoic acids, which are synthesised by a sequential multistep method from substituted 2-hydroxy-4-oxobut-2-enoic acids and the ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophen-3-carboxylate. The ability of modification of the chemical structure of the dyes during synthesis allows the introduction of different structural fragments that have a significant effect on the optical properties of the target materials. The obtained organic dyes possess effective photoluminescence (PL) in the orange-red region of the spectrum from 596 to 635 nm in powdered form. At the same time, solvents convert them to a non-luminescent state, and a red shift of the main absorption maximum occurs during the transition from nonpolar to polar solvents, which suggests a significant influence of the formed hydrogen bonds inside the molecule during the formation of a rigid crystal structure.