Accurate computation of fluorescence spectra in solution: A time-dependent DFT study on the excited states of some uracil derivatives in water and acetonitrile solution

PHYS 598

Roberto Improta, robimp@unina.it, Istituto Biostrutture e Bioimmagini-IBB, Italian National Research Council, Via mezzocannone 16, I-80136 Napoli, Italy, Vincenzo Barone, Chemistry, University "Federico II" of Naples, Complesso Universitario Monte S. Angelo, I-80126 Napoli, Italy, Michael Frisch, Gaussian, Inc, 340 Quinnipiac St Bldg 40, Wallingford, CT 06492, Giovanni Scalmani, Gaussian Inc, 340 Quinnipiac St. Bldg 40, Wallingford, CT 06492, and Thomas Gustavsson, Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM - CNRS, URA 2453, CEA Saclay, F-91191 Gif-sur-Yvette, France.
We have studied the potential energy surface of the two lowest energy excited states of uracil and of some 5-substituted uracil derivatives, as, thymine (5,methyl-uracil), and 5,fluoro-uracil in water and in acetonitrile. As a first step we have localized and characterized at the PCM/TD-PBE0 level the minima associated to the weak n->π* transition and to the strong π->π* transition, taking into account both bulk effects and the cybotactic region. The computed spectra are in good agreement with the experimental one and we show that (i) the S1/S2 ordering strongly depends on the nature of the embedding medium, and (ii) only by taking into account both bulk effects and the cybotactic region it is possible to reproduce solvent effects on the energy and the intensities of the electronic spectra, especially for n->π* transitions.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006