Stimuli-responsive luminescent coumarin thiazole hybrid dye: Synthesis, aggregation induced emission, thermochromism and DFT study

•CS-Azine show ESIPT phenomenon between thiazole and not with azomethine linkage.•AIEE was observed at 60% DMF-H2O mixture.•CS-Azine show thermochromism at 285 °C.•Non-linear optical values observed were found higher than urea.

Novel coumarin thiazole hybrid dye with azomethine linkage was synthesized. The dye is very sparingly soluble in DMF and insoluble in other solvents. The dye shows 2 fold increase in emission enhancement on aggregation caused at 60% DMF-H2O mixture. Differential thermal analysis revealed a change from one polymorph to the other polymorph at 285 °C leading to emission in the red region. Excited State Intramolecular Proton Transfer takes place with thiazole nitrogen atom and not with N atom of azomethine linkage contrary to Pigment Yellow 101. High color value (K/S = 10.42) and light fastness (rating = 8) properties were found as compared to Pigment Yellow 101. The computed absorption and emission values were found closer to the experimental values. The pigment exhibits higher first and second order hyperpolarizabilities (24 times more α0, 248 times more β0 and 756 times more γ value than urea).

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