Photophysical characteristics of three novel benzanthrone derivatives: Experimental and theoretical estimation of dipole moments B. Siddlingeshwar a , S.M. Hanagodimath a,n , E.M. Kirilova b , Georgii K. Kirilov c a Department of Physics, Gulbarga University, Gulbarga 585 106, Karnataka, India b Department of Chemistry, Daugavpils University, Vienibas 13, Daugavpils, Latvia c Department of Physics, Daugavpils University, Parades 1, Daugavpils, Latvia article info Article history: Received 7 February 2010 Received in revised form 14 June 2010 Accepted 5 September 2010 Keywords: Dipole moments Solvatochromic method Ab-initio AM1 PM6 E T N parameter abstract The effect of solvents on absorption and fluorescence spectra and dipole moments of novel benzanthrone derivatives such as 3-N-(N 0 ,N 0 -Dimethylformamidino) benzan- throne (1), 3-N-(N 0 ,N 0 -Diethylacetamidino) benzanthrone (2) and 3-morpholinobenzan- throne (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 p-p n . Using the theory of solvatochromism, the difference in the excited-state (m e ) and the ground-state (m 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 calculations at B3LYP/6-31 G n 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 (Dm) was also calculated by using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter (E T N ). The excited-state dipole moments observed are larger than their ground-state counterparts, indicating a substantial redistribution of the p-electron densities in a more polar excited state for all the systems investigated. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction Compounds containing donor and acceptor functional- ities in conjugation are called push–pull systems. Substituted benzanthrone derivatives bearing electron-withdrawing groups on one carbon atom and electron-donating groups on the other also form a part of push–pull systems. The molecular structures and IUPAC names of the molecules under study are presented in Fig. 1. In present systems, the electron-donating substituent is at a C-3 position and the carbonyl group of the chromophorous system is an electron- accepting group. These systems have interesting chemical and spectral properties. It is well-known, that for such systems electronic excitation is often accompanied by considerable charge redistribution. Intramolecular charge redistribution upon electronic excitation is a fundamental physicochemical process. A very fruitful and widely used method to study this process is the determination of electric dipole moments in different electronic states [1]. A dipole moment represents a direct measure of electron distribution in a molecule of known geometry. It is a physical constant which can be obtained by experimental and theoretical methods. A number of excellent texts, monographs, and reviews devoted to Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jqsrt Journal of Quantitative Spectroscopy & Radiative Transfer 0022-4073/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jqsrt.2010.09.001 n Corresponding author. Tel.: + 91 8472245252; fax: + 91 8472222039 E-mail address: smhmath@rediffmail.com (S.M. Hanagodimath). Journal of Quantitative Spectroscopy & Radiative Transfer 112 (2011) 448–456