Aggregation induced emissive and NLOphoric coumarin thiazole hybrid dyes: Synthesis, photophysics and TD-DFT studies

Three novel coumarin thiazole hybrid dyes 2-((4-(4-hydroxy-2-oxo-2H-chromen-3-yl)-2-morpholinothiazol-5-yl)methylene)malononitrile (CSM), (E)-2-(benzo[d]thiazol-2-yl)-3-(4-(4-hydroxy-2-oxo-2H-chromen-3-yl)-2-morpholinothiazol-5-yl)acrylonitrile (CSB), (E)-2-(3-(4-(4-hydroxy-2-oxo-2H-chromen-3-yl)-2-morpholinothiazol-5-yl)-1-phenylallylidene)malononitrile (CSA) were synthesized. The newly synthesized dyes and previously reported dyes (E)-2-(3-(2-(4-(4-hydroxy-2-oxo-2H-chromen-3-yl)-2-morpholinothiazol-5-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (CSI) and (E)-2-(3-(2-(4-(4-methoxy-2-oxo-2H-chromen-3-yl)-2-morpholinothiazol-5-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (MeOCSI) were studied for their photophysical properties in selected solvents of varying polarity. CSM, CSB, CSA and CSI were studied for their aggregation studies, absolute quantum yield, lifetime studies in selected solvents. In aggregation induced emission studies, remarkable enhancement of 9 folds for CSM, 10 folds for CSB, 6 folds for CSA and 20 folds for CSI was observed at concentrations 50% of H2O in THF. All the dyes showed twisted intramolecular charge transfer (TICT) phenomenon which was evaluated using Rettig's equation. DFT and TD-DFT studies were carried out to understand their structural aspects, linear and non-linear optical properties. Experimental and computational data show good correlation with each other. (C) 2017 Elsevier B.V. All rights reserved.