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

Funding

D.C.T.F. and A.M.d.P. acknowledge financial support from the funding agencies Fapemig, CNPq, and CAPES and INCT in Carbon Nanomaterials. We thank Dr. S. Santabarbara for preparing the PBS and T. A. S. Brand?o (UFMG, Department of Chemistry) for helping with PL measurements. I.H.M.V.S. and G.C. acknowledge support from Horizon 2020 (Grant No. 654148, Laserlab-Europe). G.C. and M.G. acknowledge support from the H2020 Grant Agreement number 765266 (LightDyNAmics) and the European Research Council Advanced Grant STRATUS (ERC-2011-AdG No. 291198).

FundersFunder number
Horizon 2020 Framework Programme765266, 291198, 284464
European Research CouncilERC-2011-AdG
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção
Horizon 2020654148

    Keywords

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

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