Carbazole-containing push–pull chromophore with viscosity and polarity sensitive emissions: Synthesis and photophysical properties

• Synthesis of carbazole based extended styryls having better photophysical properties.
• Synthesized extended styryl act as florescent molecular rotors.
• The photophysical properties of the extended styryl were investigated in different solvent polarity.

Carbazole based D-π-A extended styryl dyes with intramolecular charge transfer characteristics were synthesized. The intramolecular charge transfers of these D-π-A extended styryls have been examined with the study of photophysical properties like absorption, emission and quantum yield in various solvents of different polarities. All the dyes demonstrated positive solvatochromism. They showed largely improved photophysical properties and large Stokes shifts due to twist geometry. Oscillator strengths and transition state dipole moments have been studied to understand charge transfer within the molecules. The fluorescence molecular rotors properties of the series of extended styryls have been evaluated. The dyes having good charge transfer characteristics showed better FMR properties. Sensitivity of the fluorescence emission towards solvent polarity and viscosity has been investigated using fluorescence emission spectra.

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