Synthesis and Photophysical Properties of α-Pyrone-fused-pyrido[3,2,1-jk]carbazolone Derivatives : DFT/TD-DFT Insights

The present paper discloses an interesting microwave-assisted solvent-free protocol for the synthesis of thermally stable, highly fluorescent pyrano[2,3:4,5]pyrido[3,2,1-jk]carbazole-5,8-diones in good to high yields with good quantum yields (empty set >= 0.70) through a [3+3] annulation reaction of aryl-substituted Morita-Baylis-Hillman acetates with a 4-hydroxy-6H-pyrido[3,2,1-jk]carbazol-6-one in the presence of Hunig's base. The solvatochromic properties of synthesized compounds have been determined which showed blue shifts in absorption and emission spectra with increasing the polarity of solvents. Similarly, the higher quantum yields were also observed in case of non-polar solvents as compared to polar ones. Interestingly, the experimental results of photophysical properties were in good agreement with theoretical data obtained using B3LYP/6-311G++(d,p) level of theory. Furthermore, the synthesized chromophoric scaffolds exhibited good thermal stability (342-387 degrees C) and average fluorescence lifetime in the range of 2.011-2.139ns for 408nm, 2.268-2.277ns for 428nm.