title: Resolving Ultrafast Photoinduced Deactivations in Water-Solvated Pyrimidine Nucleosides.
abstract: For the first time, ultrafast deactivations of photoexcited water-solvated pyrimidine nucleosides are mapped employing hybrid QM(CASPT2)/MM(AMBER) optimizations that account for explicit solvation, sugar effects, and dynamically correlated potential energy surfaces. Low-energy S1/S0ring-puckering and ring-opening conical intersections (CIs) are suggested to drive the ballistic coherent subpicosecond (<200 fs) decays observed in each pyrimidine, the energetics controlling this processes correlating with the lifetimes observed. A second bright1π2π* state, promoting excited-state population branching and leading toward a third CI with the ground state, is proposed to be involved in the slower ultrafast decay component observed in Thd/Cyd. The transient spectroscopic signals of the competitive deactivation channels are computed for the first time. A general unified scheme for ultrafast deactivations, spanning the sub- to few-picosecond time domain, is eventually delivered, with computed data that matches the experiments and elucidates the intrinsic photoprotection mechanism in solvated pyrimidine nucleosides.
authors.affiliation: Dipartimento di Chimica Industriale "Toso Montanari" Viale del Risorgimento, 4, 40136 Bologna, Italy.
authors.forename: Ana Julieta
authors.initials: AJ
authors.lastname: Pepino
authors.affiliation: Laboratoire de Chimie UMR 5182, Université Lyon, ENS de Lyon, CNRS, Université Lyon 1 , F-69342 Lyon, France.
authors.forename: Javier
authors.identifier: http://orcid.org/0000-0002-2076-3406
authors.initials: J
authors.lastname: Segarra-Martí
authors.affiliation: Dipartimento di Chimica Industriale "Toso Montanari" Viale del Risorgimento, 4, 40136 Bologna, Italy.
authors.forename: Artur
authors.initials: A
authors.lastname: Nenov
authors.affiliation: Istituto di Biostrutture e Bioimmagini CNR , Via Mezzocannone 16, I-80134 Napoli, Italy.
authors.forename: Roberto
authors.identifier: http://orcid.org/0000-0003-1004-195X
authors.initials: R
authors.lastname: Improta
authors.affiliation: Dipartimento di Chimica Industriale "Toso Montanari" Viale del Risorgimento, 4, 40136 Bologna, Italy.|Laboratoire de Chimie UMR 5182, Université Lyon, ENS de Lyon, CNRS, Université Lyon 1 , F-69342 Lyon, France.
authors.forename: Marco
authors.identifier: http://orcid.org/0000-0002-0796-289X
authors.initials: M
authors.lastname: Garavelli