A Unified Experimental/Theoretical Description of the Ultrafast Photophysics of Single and Double Thionated Uracils

Danielle Cristina Teles-Ferreira, Irene Conti, Rocío Borrego-Varillas, Artur Nenov, Ivo H.M. Van Stokkum, Lucia Ganzer, Cristian Manzoni, Ana Maria de Paula*, Giulio Cerullo, Marco Garavelli

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

Photoinduced processes in thiouracil derivatives have lately attracted considerable attention due to their suitability for innovative biological and pharmacological applications. Here, sub-20 fs broadband transient absorption spectroscopy in the near-UV are combined with CASPT2/MM decay path calculations to unravel the excited-state decay channels of water solvated 2-thio and 2,4-dithiouracil. These molecules feature linear absorption spectra with overlapping ππ* bands, leading to parallel decay routes which we systematically track for the first time. The results reveal that different processes lead to the triplet states population, both directly from the ππ* absorbing state and via the intermediate nπ* dark state. Moreover, the 2,4-dithiouracil decay pathways is shown to be strongly correlated either to those of 2- or 4-thiouracil, depending on the sulfur atom on which the electronic transition localizes.

Original languageEnglish
Pages (from-to)336-343
Number of pages8
JournalChemistry - A European Journal
Volume26
Issue number1
Early online date21 Nov 2019
DOIs
Publication statusPublished - 2 Jan 2020

Keywords

  • CASPT2
  • conical intersections
  • QM/MM
  • thiobases
  • transient absorption
  • ultrafast spectroscopy

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