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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 7
BKCSDE 30(7)
July 20, 2009 

Solvent Effects on the Solvatochromism of 7-Aminocoumarin Derivatives in Neat and Binary Solvent Mixtures: Correlation of the Electronic Transition Energies with the Solvent Polarity Parameters
Jin Yeong Choi, Eun Ju Park, Seung Hyun Chang, Tai Jong Kang*
Solvent effects, Solvatochromism, Stokes’ shift, Solvent polarity parameters, ET (30)
The change in the electronic absorption and emission energy of 7-aminocoumarin derivatives in binary solvent mixtures has been studied. The electronic transition energy along with the Stokes' shift is correlated with the orientation polarizability of the solvent as well as the empirical solvent polarity parameters ET (30). It is observed that the emission peak shift traces the change of ET (30) value very closely in binary solvent mixtures. The emission transition more strongly depends on the solvent polarity than the absorption, which indicates the dipole moment gets larger on excitation. From the dependence of the Stokes’ shift of 7-aminocoumarins with the solvent polarity parameters and the ground state dipole moment obtained by the semi-empirical calculations, the excited state dipole moment was estimated. The fluorescence lifetime change of 7-aminocoumarins in binary solvent mixtures was measured and the results are explained in terms of molecular conformation and solvent polarity. The study indicates the empirical solvent polarity ET (30) is a good measure of microscopic solvent polarity and it probes in general the non-specific solvent interactions.
1452 - 1458
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