Solvent effects on the nπ* transition of pyrimidine in aqueous solution |
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Authors: | Jiali Gao Kyoungrim Byun |
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Institution: | (1) Department of Chemistry, State University of New York, Buffalo, NY 14260, USA, US |
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Abstract: | A hybrid quantum mechanical and molecular mechanical potential is used in Monte Carlo simulations to examine the solvent
effects on the electronic excitation energy for the n→π* transition of pyrimidine in aqueous solution. In the present study,
the pyrimidine molecule is described by the semi-empirical AM1 model, while the solvent molecules are treated classically.
Two sets of calculations are performed: the first involves the use of the pairwise three-point charge TIP3P model for water,
and the second computation employs a polarizable many-body potential for the solvent. The latter calculation takes into account
the effect of solvent polarization following the solute electronic excitation, and makes a correction to the energies determined
using pairwise potentials, which neglects such fast polarization effects and overestimates the solute-solvent interactions
on the Franck-Condon excited states. Our simulation studies of pyrimidine in water indicate that the solvent charge redistribution
following the solute electronic excitation makes modest corrections (about −130␣cm−1) to the energy predicted by using pairwise potentials. Specific hydrogen bonding interactions between pyrimidine and water
are important for the prediction of solvatochromic shifts for pyrimidine. The computed n→π* blue shift is 2275±110 cm−1, which may be compared with the experimental value (2700 cm−1) from isooctane to water.
Received: 14 January 1997 / Accepted: 21 February 1997 |
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Keywords: | : Solvent effect Pyrimidine Hybrid quantum mechanical and molecular mechanical potential |
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