Insights into the deactivation of 5-bromouracil after ultraviolet excitation.
5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the brightππ* state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C-Br photodissociation. Based on accurate MS-CASPT2 optimizations, we propose that ground-state relaxation should be the predominant deactivation pathway in the gas phase. We then employ different electronic structure methods to assess their suitability to carry out excited-state dynamics simulations. MRCIS (multi-reference configuration interaction including single excitations) was used in surface hopping simulations to compute the ultrafast ISC dynamics, which mostly involves the1nOπ* and3ππ* states.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.
Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Francesca
http://orcid.org/0000-0002-7813-8216
F
Peccati
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
Sebastian
http://orcid.org/0000-0001-5327-8880
S
Mai
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria leticia.gonzalez@univie.ac.at.
Leticia
http://orcid.org/0000-0001-5112-794X
L
González
D065966:Absorption, Physicochemical; D001976:Bromouracil / Q000737:chemistry* / Q000378:metabolism; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D014466:Ultraviolet Rays
D001976:Bromouracil
excited states; non-adiabatic dynamics; nucleobase analogues