Photophysical characteristics of three novel benzanthrone derivatives: Experimental and theoretical estimation of dipole moments

Abstract

The effect of solvents on absorption and fluorescence spectra and dipole moments of novel benzanthrone derivatives such as 3-N-(N',N'-Dimethylformamidino) benzanthrone (1), 3-N-(N',N'-Diethylacetamidino) benzanthrone (2) and 3-morpholinobenzanthrone (3) have been studied in various solvents. The fluorescence lifetime of the dyes (1-3) in chloroform were also recorded. Bathochromic shift observed in the absorption and fluorescence spectra of these molecules with increasing solvent polarity indicates that the transitions involved are ??*. Using the theory of solvatochromism, the difference in the excited-state (?e) and the ground-state (?e) dipole moments was estimated from Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet, and McRae equations by using the variation of Stokes shift with the solvent's relative permittivity and refractive index. AM1 and PM6 semiempirical molecular calculations using MOPAC and ab-initio calculationsat B3LYP/6-31 G* level of theory using Gaussian 03 software were carried out to estimate the ground-state dipole moments and some other physicochemical properties. Further, the change in dipole moment value (? ?) was also calculated by using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter (ETN). The excited-state dipole moments observed are larger than their ground-state counterparts, indicating a substantial redistribution of the ?-electron densities in a more polar excited state for all the systems investigated. © 2010 Elsevier Ltd.