Published on Web 12/17/2005
Singlet Excited-State Behavior of Uracil and Thymine in Aqueous Solution: A Combined Experimental and Computational Study of 11 Uracil Derivatives Thomas Gustavsson,*,† AÄ kos Ba´ nya´ sz,†,‡ Elodie Lazzarotto,† Dimitra Markovitsi,† Giovanni Scalmani,§ Michael J. Frisch,§ Vincenzo Barone,| and Roberto Improta*,|,∇ Contribution from the Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM - CNRS URA 2453, CEA Saclay, F-91191 Gif-sur-YVette, France, Gaussian, Inc., 340 Quinnipiac St. Bldg 40,Wallingford, Connecticut 06492, Dipartimento di Chimica, UniVersita Federico II, Complesso UniVersitario Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy, and Istituto Biostrutture e Bioimmagini/CNR, V. Mezzocannone 6-80134 Napoli, Italy Received September 8, 2005; E-mail:
[email protected] Abstract: The excited-state properties of uracil, thymine, and nine other derivatives of uracil have been studied by steady-state and time-resolved spectroscopy. The excited-state lifetimes were measured using femtosecond fluorescence upconversion in the UV. The absorption and emission spectra of five representative compounds have been computed at the TD-DFT level, using the PBE0 exchange-correlation functional for ground- and excited-state geometry optimization and the Polarizable Continuum Model (PCM) to simulate the aqueous solution. The calculated spectra are in good agreement with the experimental ones. Experiments show that the excited-state lifetimes of all the compounds examined are dominated by an ultrafast (
