Push–pull fluorophores with viscosity dependent and aggregation induced emissions insensitive to polarity

• Synthesis and characterization of carbazole based extended styryl with morpholine thiazole as π-conjugated bridge.
• Photophysical properties of extended styryls have been studied extensively by using spectroscopic methods.
• Synthesized extended styryls showed aggregation induced emission and viscosity sensitive emission.
• The aggregation induced emission and viscosity sensitive emission were carried out using spectroscopic methods.

A series of push–pull chromophoric extended styryls from 5,5′-(9-ethyl-9H-carbazole-3,6-diyl)bis(2-morpholinothiazole-4-carbaldehyde) were synthesized by Knoevenagal condensation reaction with active methylene compounds. The intermediate carbaldehyde was synthesized from carbazole through multistep reactions. The intramolecular charge transfer of synthesized highly conjugated symmetrical D–π–A (D-donor, A-acceptor) extended styryls with rigid structure have been investigated by means of photophysical properties. The photophysical properties like absorption, emission and quantum yield of styryl derivatives were evaluated in various solvents of different polarities. All these synthesized extended styryls have exhibited aggregation induced emission with enhanced fluorescence intensity. This series of compounds can also be used as fluorescence molecular rotors for viscosity sensing. The sensitivity of viscosity towards UV absorption as well as fluorescence emission has also been investigated.

Figure optionsDownload as PowerPoint slide