Quantitative treatment of the effect of solvent on the electronic absorption and fluorescence spectra of substituted coumarins: Evaluation of the first excited singlet-state dipole moments |
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Authors: | Jean-Jacques Aaron Mihaela Buna Cyril Parkanyi Maged Shafik Antonious Alphonse Tine Lamine Cisse |
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Affiliation: | (1) Institut de Topologie et de Dynamique des Systèmes, associé au CNRS URA 34, Université Paris 7, Denis Diderot, 1 rue Guy de la Brosse, 75005 Paris, France;(2) Department of Chemistry, Florida Atlantic University, 777 Glades Road, P.O. Box 3091, 33431-0991 Boca Raton, Florida;(3) Present address: Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt;(4) Départment de Chimie, Faculté des Sciences, Université C. A. Diop, Dakar, Sénégal |
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Abstract: | The electronic absorption and fluorescence spectra of coumarin and 11 substituted coumarins were measured in several solvents (dioxane, ethyl ether, ethyl acetate, ethanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide). Ground-state dipole moments were determined in dioxane at 298 K. The results were used to obtain the first excited singlet-state dipole moments of the coumarins under study by the solvatochromic shift method (Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan correlations). Also, the ground- and the first excited singlet-state dipole moments were calculated using a combination of the PPP method (-contribution) and the vector sum of the -bond and group moments (-contribution). In general, the first excited singlet-state dipole moments of the coumarins are noticeably higher than the corresponding ground-state values, indicating a substantial redistribution of the-electron densities resulting in a more polar excited state. There is a reasonably good agreement between the calculated and the experimental dipole moments.Presented, in part, at the 2nd International Conference on Solar Energy Storage and Applied Photochemistry, Cairo, Egypt, January 6–11, 1993. For a preliminary communication, see Ref. 1. |
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Keywords: | Electronic absorption fluorescence coumarins solvent first excited singlet-state dipole moments |
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