Synthesis and fluorescence properties of carbazole and fluorene-based compounds

Three donor–acceptor (D–A) conjugated compounds consisted of carbazole and fluorene (Scheme 1) were synthesized via Wittig-Horner, Ullmann or Sonogashira reaction. Their photoluminescence properties were investigated in solution and solid state, respectively. Luminescence in various solvents revealed the intramolecular charge transfer (ICT) process exists in these D–A molecules. Correlation between the Stokes’ shifts and solvent polarity parameters indicated that moderate large dipole moments exist in the excited states.