J. Phys. Chem. B 2009, 113, 14491–14503
14491
Quantum Dynamics of the Ultrafast ππ*/nπ* Population Transfer in Uracil and 5-Fluoro-Uracil in Water and Acetonitrile Roberto Improta,† Vincenzo Barone,‡ Alessandro Lami,§ and Fabrizio Santoro*,§ Dipartimento di Chimica and INSTM-Village, UniVersita´ Federico II, Complesso Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy, Scuola Normale Superiore di Pisa, P.zza dei CaValieri 7, I-56126 Pisa, Italy, and Istituto per i Processi Chimico-Fisici - CNR, Area della Ricerca del CNR Via Moruzzi, 1 I-56124 Pisa, Italy ReceiVed: July 10, 2009
We present the first fully quantum-mechanical dynamical study of the ππ* f nπ* decay in photoexcited uracil derivatives in solution. The dynamics of this process for uracil (U) and 5-fluoro-uracil (5FU) in acetonitrile and aqueous solution is investigated, by treating both electrons and nuclei at the quantum-mechanical level, and solving the time-dependent Schro¨dinger equation for the evolution of the photoexcited system. The potential energy surfaces along the most relevant nuclear degrees of freedom have been obtained at the time-dependent density functional theory level, accounting for the solvent effect by mixed atomistic/continuum models. The obtained results nicely agree with experimental evidence. For U, we predict an ultrafast (
