On the Relaxation Mechanisms of 6-Azauracil
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
20/10/2012
20/10/2012
2011
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Resumo |
The nonadiabatic photochemistry of 6-azauracil has been studied by means of the CASPT2//CASSCF protocol and double-zeta plus polarization ANO basis sets. Minimum energy states, transition states, minimum energy paths, and surface intersections have been computed in order to obtain an accurate description of several potential energy hypersurfaces. It is concluded that, after absorption of ultraviolet radiation (248 nm), two main relaxation mechanisms may occur, via which the lowest (3)(pi pi*) state can be populated. The first one takes place via a conical intersection involving the bright (1)(pi pi*) and the lowest (1)(n pi*) states, ((1)pi pi*/(1)n pi*)(CI), from which a low energy singlet-triplet crossing, ((1)n pi*/(3)pi pi*)(STC), connecting the (1)(n pi*) state to the lowest (3)(pi pi*) triplet state is accessible. The second mechanism arises via a singlet-triplet crossing, ((1)pi pi*/(3)n pi*)(STC), leading to a conical intersection in the triplet manifold, ((3)n pi*/(3)pi pi*)(CI), evolving to the lowest (3)(pi pi*) state. Further radiationless decay to the ground state is possible through a (gs/(3)pi pi*)(STC). CAPES (Coordenacao de Amparo ao Pessoal de Ensino Superior)[2272/09-1] Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Spanish MEC/FEDER Spanish MEC/FEDER[CTQ2010-14892] Spanish MEC/FEDER[CSD2007-010] Spanish MEC/FEDER |
Identificador |
JOURNAL OF PHYSICAL CHEMISTRY B, v.115, n.19, p.6243-6251, 2011 1520-6106 http://producao.usp.br/handle/BDPI/31321 10.1021/jp200297z |
Idioma(s) |
eng |
Publicador |
AMER CHEMICAL SOC |
Relação |
Journal of Physical Chemistry B |
Direitos |
restrictedAccess Copyright AMER CHEMICAL SOC |
Palavras-Chave | #NEUTRAL AQUEOUS-SOLUTION #LOWEST TRIPLET-STATE #NUCLEIC-ACID BASES #PERTURBATION-THEORY #PYRIMIDINE-BASES #ULTRAFAST DECAY #EXCITED-STATES #3-STATE MODEL #GAS-PHASE #AB-INITIO #Chemistry, Physical |
Tipo |
article original article publishedVersion |