Communication: the dark singlet state as a doorway state in the ultrafast and efficient intersystem crossing dynamics in 2-thiothymine and 2-thiouracil.
Enviado por Carlos E Crespo-Hernández el
Título | Communication: the dark singlet state as a doorway state in the ultrafast and efficient intersystem crossing dynamics in 2-thiothymine and 2-thiouracil. |
Publication Type | Journal Article |
Year of Publication | 2014 |
Autores | Pollum, M, Crespo-Hernández, CE |
Journal | J Chem Phys |
Volume | 140 |
Issue | 7 |
Pagination | 071101 |
Date Published | 2014 Feb 21 |
ISSN | 1089-7690 |
Abstract | Femtosecond broadband transient absorption experiments are reported for 2-thiothymine and 2-thiouracil in aqueous buffer solution and in acetonitrile. It is shown that the S1(nπ*) state acts as a doorway state in the ultrafast and efficient population of the T1(ππ*) state upon 316 nm excitation. A sequential kinetic model is presented to explain the excited-state dynamics in 2-thiothymine and 2-thiouracil upon UVA excitation: S2(ππ*) → S1(nπ*) → T1(ππ*). The experimental results are also used to scrutinize the excited-state relaxation pathways recently predicted for 2-thiouracil at the CASPT2//CASSCF level of theory [G. Cui and W. Fang, J. Chem. Phys. 138, 044315 (2013)]. The efficient population of the T1(ππ*) state for both 2-thiothymine and 2-thiouracil in a few hundreds of femtoseconds lends further support to the emerging idea that thiobase derivatives exhibit photo-toxic properties that can be effectively harnessed in photo-chemotherapeutic applications. |
DOI | 10.1063/1.4866447 |
Alternate Journal | J Chem Phys |
PubMed ID | 24559331 |