期刊
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
卷 79, 期 3, 页码 428-436出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.saa.2011.02.053
关键词
Coumarins; Ground-state dipole moments; Excited singlet-state dipole moments; Fluorescence spectra; Solvatochromic methods; AM1 approach
类别
资金
- Agence Universitaire pour la Francophonie (AUF)
- Ministry of biocarburants, sustainable energies and scientific research of Senegal
- Third World Academy of Sciences
The solvent effects on the electronic absorption and fluorescence emission spectra of several coumarins derivatives, containing amino, N,N-dimethyl-amino, N,N-diethyl-amino, hydroxyl, methyl, carboxyl, or halogen substituents at the positions 7, 4, or 3, were investigated in eight solvents with various polarities. The first excited singlet-state dipole moments of these coumarins were determined by various solvatochromic methods, using the theoretical ground-state dipole moments which were calculated by the AM1 method. The first excited singlet-state dipole moment values were obtained by the Bakhshiev, Kawski-Chamma-Viallet, Lippert-Mataga, and Reichardt-Dimroth equations, and were compared to the ground-state dipole moments. In all cases, the dipole moments were found to be higher in the excited singlet-state than in the ground state because of the different electron densities in both states. The red-shifts of the absorption and fluorescence emission bands, observed for most compounds upon increasing the solvent polarity, indicated that the electronic transitions were of pi-pi* nature. (C) 2011 Elsevier B.V. All rights reserved.
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