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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

Global static pictureof the cycloreversion mechanism of CHDEPObased on MEP calculations. Final energies relative to the GS minimum(in eV) were calculated at MS-CASPT2//SA4-CASSCF(14,12)/ANO-RCC levelof theory. Other information on the MEP calculations can be foundin the Supporting Information. The statelabeling was inferred from the final products of the MEP.
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fig3: Global static pictureof the cycloreversion mechanism of CHDEPObased on MEP calculations. Final energies relative to the GS minimum(in eV) were calculated at MS-CASPT2//SA4-CASSCF(14,12)/ANO-RCC levelof theory. Other information on the MEP calculations can be foundin the Supporting Information. The statelabeling was inferred from the final products of the MEP.

Mentions: The cycloreversionmechanism was investigated with a MEP startingfrom the Franck–Condon region following the gradient of thebrighter second excited state (third root). Similarly to the MEP fromthe first excited state in Figure 2, this pathproceeds showing neither minima nor energy barriers toward a CI withthe GS, see Figure 3. On the way to the GS,however, a CI S2/S1 with the second root isalso found that might deviate population to the lower lying state.The S1/S0 conical intersection is expected tobifurcate population between two minima in the ground PES, i.e., theFranck–Condon minimum (MinFC) and MinSW.


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)

Global static pictureof the cycloreversion mechanism of CHDEPObased on MEP calculations. Final energies relative to the GS minimum(in eV) were calculated at MS-CASPT2//SA4-CASSCF(14,12)/ANO-RCC levelof theory. Other information on the MEP calculations can be foundin the Supporting Information. The statelabeling was inferred from the final products of the MEP.
© Copyright Policy
Related In: Results  -  Collection

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

fig3: Global static pictureof the cycloreversion mechanism of CHDEPObased on MEP calculations. Final energies relative to the GS minimum(in eV) were calculated at MS-CASPT2//SA4-CASSCF(14,12)/ANO-RCC levelof theory. Other information on the MEP calculations can be foundin the Supporting Information. The statelabeling was inferred from the final products of the MEP.
Mentions: The cycloreversionmechanism was investigated with a MEP startingfrom the Franck–Condon region following the gradient of thebrighter second excited state (third root). Similarly to the MEP fromthe first excited state in Figure 2, this pathproceeds showing neither minima nor energy barriers toward a CI withthe GS, see Figure 3. On the way to the GS,however, a CI S2/S1 with the second root isalso found that might deviate population to the lower lying state.The S1/S0 conical intersection is expected tobifurcate population between two minima in the ground PES, i.e., theFranck–Condon minimum (MinFC) and MinSW.

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