Synthesis, characterisation, estimation of ground-and excited-state dipole moments using solvatochromic shift and theoretical studies of new iminocoumarin derivatives

The study on the fluorescence and UV–Vis absorption of some iminocoumarins at ambient temperature in several solvents showed a bathochromic shift with the increase of the solvent polarity. The use of the solvathochromic method allowed us to determine the dipole moment in both ground and excited states. The studied molecules exhibit much higher dipole moments in the excited state than in the ground state, which can be due to the redistribution of π-electron densities in the excited state making molecules more polar with higher dipole moments. Furthermore, HOMO–LUMO gap were also estimated theoretically using B3LYP/6–311 + G (d,p) level of theory; the low energy gap indicated the eventual charge transfer interaction occurring in the molecules, and responsible for their light emitting properties.publishe