title: Revisiting the photophysical properties and excited singlet-state dipole moments of several coumarin derivatives.
abstract: 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 π-π* nature.
authors.affiliation: Laboratoire de Photochimie et d'Analyse, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP, Dakar, Senegal.
authors.forename: Lamine
authors.initials: L
authors.lastname: Cisse
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Djande
authors.forename: Martine
authors.initials: M
authors.lastname: Capo-Chichi
authors.forename: François
authors.initials: F
authors.lastname: Delatre
authors.forename: Adama
authors.initials: A
authors.lastname: Saba
authors.forename: Alphonse
authors.initials: A
authors.lastname: Tine
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Aaron
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D004583:Electrons; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D003374:Coumarins; D012997:Solvents