Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments |
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| Authors: | Abebe Belay Ermias Libnedengel Hyung Kook Kim Yoon‐Hwae Hwang |
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| Affiliation: | 1. Department of Nanomaterial Engineering and Nanoconvergence Technology, Pusan National University, Miryang, Korea;2. Department of Physics, School of Natural Sciences, Adama Science and Technology University, Adama, Ethiopia |
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| Abstract: | The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV‐vis electronic absorption spectra. From solvatochromic theory the ground and excited‐state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski–Chamma–Viallet and Reichardt equations are quite similar. The ground and excited‐state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO‐LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | Dipole moment chlorogenic acid caffeic acid solvatochromic effect DFT |
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