Estimation of dipole moments of some biologically active coumarins by solvatochromic shift method based on solvent polarity parameter, E(T)(N).

The electronic absorption and fluorescence spectra of three newly synthesized coumarin derivatives viz., 4-(5-methyl-3-furan-2-yl-benzofuran-2-yl)-7-methyl-chromen-2-one (MFBMC), 4-(5-chloro-3-furan-2-yl-benzofuran-2-yl)-6-methyl-chromen-2-one (ClFBMC) and 4-(5-methyl-3-phenyl-benzofuran-2-yl)-6-chloro-chromen-2-one (MPBClC) have been recorded at room temperature (296 K) in solvents of different polarities. The effects of the solvents upon the spectral properties are discussed. Solvatochromic correlations were used to estimate the ground-state (mu(g)) and excited-state (mu(e)) dipole moments. The excited-state dipole moments for all the three molecules are found to be larger than their corresponding ground-state dipole moments. Further, the changes in dipole moment (Delta mu) were calculated both from solvatochromic shift method and on the basis of microscopic empirical solvent polarity parameter (E(T)(N)), and the values are compared.