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Time-Resolved Insight into the Photosensitized Generation of Singlet Oxygen in Endoperoxides.

Martínez-Fernández L, González-Vázquez J, González L, Corral I - J Chem Theory Comput (2014)

Bottom Line: Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O-O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products.The triplet states do not intervene in this mechanism, as opposed to the O-O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable.In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O-O homolysis with a quantum yield of 65%.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química, Universidad Autónoma de Madrid , 28049 Cantoblanco, Madrid, Spain.

ABSTRACT

A synergistic approach combining high-level multiconfigurational static calculations and full-dimensional ab initio surface hopping dynamics has been employed to gain insight into the photochemistry of endoperoxides. Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O-O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products. Our results reveal that cycloreversion or the rupture of the two C-O bonds occurs via an asynchronous mechanism that can lead to the population of a ground-state intermediate showing a single C-O bond. Furthermore, singlet oxygen is directly generated in its most stable excited electronic state (1)Δg. The triplet states do not intervene in this mechanism, as opposed to the O-O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable. In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O-O homolysis with a quantum yield of 65%.

No MeSH data available.


Related in: MedlinePlus

Time evolution of two representative trajectoriesof deuteratedCHDEPO leading to B + 1O2 products. Singletstates are represented by solid lines, (S0 in red, S1 in green, S2 in blue, and S3 in pink),while triplet states are denoted with dotted lines in light blue T1, yellow T2, black T3, and gray T4. Black points indicate the current potential energy of thesystem at each time.
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fig6: Time evolution of two representative trajectoriesof deuteratedCHDEPO leading to B + 1O2 products. Singletstates are represented by solid lines, (S0 in red, S1 in green, S2 in blue, and S3 in pink),while triplet states are denoted with dotted lines in light blue T1, yellow T2, black T3, and gray T4. Black points indicate the current potential energy of thesystem at each time.

Mentions: In this section,several trajectories representative for the O–O homolysis andcycloreversion photoreactions will be discussed in detail. Figures 6 and 7A, respectively, exemplifythe generation of 1O2 and H2 fromexcited CHDEPO.


Time-Resolved Insight into the Photosensitized Generation of Singlet Oxygen in Endoperoxides.

Martínez-Fernández L, González-Vázquez J, González L, Corral I - J Chem Theory Comput (2014)

Time evolution of two representative trajectoriesof deuteratedCHDEPO leading to B + 1O2 products. Singletstates are represented by solid lines, (S0 in red, S1 in green, S2 in blue, and S3 in pink),while triplet states are denoted with dotted lines in light blue T1, yellow T2, black T3, and gray T4. Black points indicate the current potential energy of thesystem at each time.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4325559&req=5

fig6: Time evolution of two representative trajectoriesof deuteratedCHDEPO leading to B + 1O2 products. Singletstates are represented by solid lines, (S0 in red, S1 in green, S2 in blue, and S3 in pink),while triplet states are denoted with dotted lines in light blue T1, yellow T2, black T3, and gray T4. Black points indicate the current potential energy of thesystem at each time.
Mentions: In this section,several trajectories representative for the O–O homolysis andcycloreversion photoreactions will be discussed in detail. Figures 6 and 7A, respectively, exemplifythe generation of 1O2 and H2 fromexcited CHDEPO.

Bottom Line: Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O-O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products.The triplet states do not intervene in this mechanism, as opposed to the O-O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable.In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O-O homolysis with a quantum yield of 65%.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química, Universidad Autónoma de Madrid , 28049 Cantoblanco, Madrid, Spain.

ABSTRACT

A synergistic approach combining high-level multiconfigurational static calculations and full-dimensional ab initio surface hopping dynamics has been employed to gain insight into the photochemistry of endoperoxides. Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O-O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products. Our results reveal that cycloreversion or the rupture of the two C-O bonds occurs via an asynchronous mechanism that can lead to the population of a ground-state intermediate showing a single C-O bond. Furthermore, singlet oxygen is directly generated in its most stable excited electronic state (1)Δg. The triplet states do not intervene in this mechanism, as opposed to the O-O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable. In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O-O homolysis with a quantum yield of 65%.

No MeSH data available.


Related in: MedlinePlus