Three‐Component Synthesis and Photophysical Properties of Novel Coumarin‐Based Merocyanines

Novel E ‐configured coumarin‐based merocyanines were efficiently synthesized by a one‐pot, three‐component Sonogashira coupling–Michael addition starting from triflyl coumarins, terminal alkynes and secondary amines. The photophysical properties of the synthesized yellow to orange merocyanines were studied by UV/Vis and fluorescence spectroscopy and rationalized by Hammett–Taft correlations and DFT and TD‐DFT calculations. Most compounds were only weakly fluorescent in solution; however, two compounds were investigated in more detail with respect to their aggregation behavior. The system for R 2 =H and NR 2 3 =pyrrolidinyl shows aggregation induced emission at a water content of 40–60 % in methanol, while the chromophore with R 2 = p ‐Me 2 NC 6 H 4 and NR 2 3 =morpholinyl displays considerable aggregation induced emission enhancement with a concomitant redshift at increasing water contents in THF.