Ultrafast Intersystem Crossing of 4-Thiothymidine in Aqueous Solution

Harada, Yosuke; Okabe, Chie; Kobayashi, Takashi; Suzuki, Tadashi; Ichimura, Teijiro; Nishi, Nobuyuki; Xu, Yao−Zhong

doi:10.1021/jz900276x

Cited by 72 publications

(111 citation statements)

References 23 publications

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“…S 1 (nπ*) electronic transitions, respectively [10,18,19,34,200,201]. These assignments are supported by quantum chemical calculations [11,17,18,196,[202][203][204]. Additional absorption bands are observed closer to 200 nm (see, for example, Fig.…”

Section: Steady-state and Time-resolved Photochemistry Of The 4-thiousupporting

confidence: 64%

“…The absorption spectra shift from the UVC region in the nucleic acid monomers out to the UVA region in the thiobases. Furthermore, sulfur substitution inhibits ultrafast internal conversion to the ground state and dramatically increases the rate of intersystem crossing to the triplet manifold by enhanced spin-orbit coupling [11,17,18,27,33], which leads to near-unity triplet yields in these nucleic acid base analogues [11,16,18,22,31,144,195,196].…”

Section: Thiobasesmentioning

confidence: 99%

See 1 more Smart Citation

Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution

Pollum

Martínez‐Fernández

Crespo‐Hernández

2014

Topics in Current Chemistry

111

200

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The steady-state and time-resolved photochemistry of the natural nucleic acid bases and their sulfur- and nitrogen-substituted analogues in solution is reviewed. Emphasis is given to the experimental studies performed over the last 3-5 years that showcase topical areas of scientific inquiry and those that require further scrutiny. Significant progress has been made toward mapping the radiative and nonradiative decay pathways of nucleic acid bases. There is a consensus that ultrafast internal conversion to the ground state is the primary relaxation pathway in the nucleic acid bases, whereas the mechanism of this relaxation and the level of participation of the (1)πσ*, (1) nπ*, and (3)ππ* states are still matters of debate. Although impressive research has been performed in recent years, the microscopic mechanism(s) by which the nucleic acid bases dissipate excess vibrational energy to their environment, and the role of the N-glycosidic group in this and in other nonradiative decay pathways, are still poorly understood. The simple replacement of a single atom in a nucleobase with a sulfur or nitrogen atom severely restricts access to the conical intersections responsible for the intrinsic internal conversion pathways to the ground state in the nucleic acid bases. It also enhances access to ultrafast and efficient inter-system crossing pathways that populate the triplet manifold in yields close to unity. Determining the coupled nuclear and electronic pathways responsible for the significantly different photochemistry in these nucleic acid base analogues serves as a convenient platform to examine the current state of knowledge regarding the photodynamic properties of the DNA and RNA bases from both experimental and computational perspectives. Further investigations should also aid in forecasting the prospective use of sulfur- and nitrogen-substituted base analogues in photochemotherapeutic applications.

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Section: Steady-state and Time-resolved Photochemistry Of The 4-thiousupporting

confidence: 64%

Section: Thiobasesmentioning

confidence: 99%

Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution

Pollum

Martínez‐Fernández

Crespo‐Hernández

2014

Topics in Current Chemistry

111

200

View full text Add to dashboard Cite

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“…14,15 Ultrafast thione T1 state formation dynamics have been investigated by TEAS, as well as by ab initio electronic structure calculations and surface hopping simulations that include spin-orbit coupling. [16][17][18][19][20][21][22][23][24][25][26][27] The emerging picture is of a complicated competition between IC and efficient ISC.…”

Section: Introductionmentioning

confidence: 99%

Triplet state formation and quenching dynamics of 2-mercaptobenzothiazole in solution

Koyama

Orr-Ewing

2016

Phys. Chem. Chem. Phys.

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“…[4][5][6] The introduction of a thiocarbonyl group in thymine or uracil increases their reactivity and results in modified photophysical 30 features such as a red shifted UV absorption and a dramatic increase of the intersystem crossing quantum yield ( ISC ~ 1). [7][8] This leads to highly reactive triplet excited states able to interact with the canonical nucleobases. Thus, it is possible to achieve selective long-wavelength photoactivation of TNB, making them 35 attractive for mechanistic studies and also as potential prodrugs in photodynamic therapy.…”

mentioning

confidence: 99%

“…The experimental results have been correlated with quantum chemical calculations at the B3LYP/6-31+G(d,p)/PCM 55 level. [7][8] The aim of the present work is to determine the influence of C5 substitution on the photophysical properties of 2-thiopyrimidines (2-TPyr). With this purpose, 2-thiouracil, 5-tbutyl-2-thiouracil and 2-thiothymine (TU, BTU and TT, 60 respectively, Fig.…”

mentioning

confidence: 99%

Photophysical properties of 5-substituted 2-thiopyrimidines

Vendrell-Criado

Sáez

Lhiaubet‐Vallet

et al. 2013

Photochem Photobiol Sci

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The aim of the present work is to determine the influence of C5 substitution on the photophysical properties of 2-thiopyrimidines (2-TPyr). With this purpose, 2-thiouracil, 5-t-butyl-2-thiouracil and 2-thiothymine (TU, BTU and TT, respectively) have been selected as target thionucleobases for the experimental studies and, in parallel, for DFT theoretical calculations. The UV spectra displayed by TU, BTU and TT in EtOH were very similar to each other. They showed a maximum around 275 nm and a 10 shoulder at ca. 290 nm. The three 2-TPyr exhibited a strong phosphorescence emission; from the recorded spectra, triplet excited state energies of ca. 307, 304 and 294 kJ/mol were determined for TU, BTU and TT, respectively. Laser excitation at 308 nm gave rise to a broad transient absorption band from 500 nm to 700 nm, which was in principle assigned to the triplet-triplet absorption. The triplet lifetimes were 70 ns, 1.1 s and 2.3 s, for TU, BTU and TT, respectively. This assignment was confirmed by energy 15 transfer experiments, using biphenyl (E T = 274 kJ/mol) as acceptor. The obtained photophysical data, both in phosphorescence and transient absorption measurements, point to significantly different properties of the TT triplet excited state in spite of the structural similarities. This behaviour can be satisfactorily explained by theoretical calculations at the B3LYP/aug-cc-pVDZ/PCM level.

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Ultrafast Intersystem Crossing of 4-Thiothymidine in Aqueous Solution

Cited by 72 publications

References 23 publications

Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution

Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution

Triplet state formation and quenching dynamics of 2-mercaptobenzothiazole in solution

Photophysical properties of 5-substituted 2-thiopyrimidines

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