title: Intersystem Crossing Pathways in the Noncanonical Nucleobase 2-Thiouracil: A Time-Dependent Picture.
abstract: The deactivation mechanism after ultraviolet irradiation of 2-thiouracil has been investigated using nonadiabatic dynamics simulations at the MS-CASPT2 level of theory. It is found that after excitation the S2 quickly relaxes to S1, and from there intersystem crossing takes place to both T2 and T1 with a time constant of 400 fs and a triplet yield above 80%, in very good agreement with recent femtosecond experiments in solution. Both indirect S1 → T2 → T1 and direct S1 → T1 pathways contribute to intersystem crossing, with the former being predominant. The results contribute to the understanding of how some noncanonical nucleobases respond to harmful ultraviolet light, which could be relevant for prospective photochemotherapeutic applications.
authors.affiliation: Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, 1090 Vienna, Austria.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Mai
authors.affiliation: Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, 1090 Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Marquetand
authors.affiliation: Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, 1090 Vienna, Austria.
authors.forename: Leticia
authors.initials: L
authors.lastname: González
mesh_terms: D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013889:Thiouracil / Q000737:chemistry*; D013997:Time Factors
chemical_list: D013889:Thiouracil