Red-emitting NLOphoric carbazole-coumarin hybrids - Synthesis, photophysical properties and DFT studies

•Synthesis of novel red emitting carbazole-coumarins.•DFT studies on the carbazole-coumarin dyes.•Photophysical and spectroscopic studies of novel coumarin dyes.•NLO properties of carbazole-coumarin dyes.

The carbazole core is known to be a very efficient donor and can assist the coumarin core in achieving the red emission by pushing electrons in the chromophoric system. 9-ethyl-9H-carbazole-3-carbaldehyde and 9-ethyl-9H-carbazole-3,6-dicarbaldehyde were reacted with 3-acetyl-4-hydroxy-coumarin and 7-(N,N-diethylamino)-3-acetyl-4-hydroxy-coumarin to give the corresponding hybrids. The BF2-complexes of the 4-hydroxy-3-acetyl-coumarin derivatives were reacted to give the coumarin-carbazole hybrids. The molecules synthesized emit in the red region. Their photophysical properties were studied in various solvents of different polarity. The solvent polarity function plots were studied and show linearity. The introduction of two units of coumarin core on carbazole improves the molar extinction co-efficient of the dye. The BF2-complexation has enhanced the quantum efficiency and non-linear optical properties of the molecules.

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