19F NMR Spectra and Structures of Halogenated Porphyrins

Birnbaum, Eva R.; Hodge, Julia A.; Grinstaff, Mark W.; Schaefer, William P.; Henling, Lawrence M.; Labinger, Jay A.; Bercaw, John E.; Gray, Harry B.

doi:10.1021/ic00118a010

Cited by 121 publications

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“…2). These spectroscopic features are characteristic of a nonplanar porphyrin (16)(17)(18)(19)(20)(21)(22). Steric repulsion between the β-cyano groups and the meso-phenyl substituents leads to deformation of the tetrapyrrolic ring from its original planar geometry.…”

Section: Resultsmentioning

confidence: 99%

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Megiatto

Antoniuk-Pablant

Sherman

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

112

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In the photosynthetic photosystem II, electrons are transferred from the manganese-containing oxygen evolving complex (OEC) to the oxidized primary electron-donor chlorophyll P680 •+ by a proton-coupled electron transfer process involving a tyrosine-histidine pair. Proton transfer from the tyrosine phenolic group to a histidine nitrogen positions the redox potential of the tyrosine between those of P680 •+ and the OEC. We report the synthesis and time-resolved spectroscopic study of a molecular triad that models this electron transfer. The triad consists of a high-potential porphyrin bearing two pentafluorophenyl groups (PF 10 ), a tetracyanoporphyrin electron acceptor (TCNP), and a benzimidazole-phenol secondary electron-donor (Bi-PhOH). Excitation of PF 10 in benzonitrile is followed by singlet energy transfer to TCNP ( τ = 41 ps), whose excited state decays by photoinduced electron transfer ( τ = 830 ps) to yield . A second electron transfer reaction follows ( τ < 12 ps), giving a final state postulated as BiH + -PhO • -PF 10 -TCNP •- , in which the phenolic proton now resides on benzimidazole. This final state decays with a time constant of 3.8 μs. The triad thus functionally mimics the electron transfers involving the tyrosine-histidine pair in PSII. The final charge-separated state is thermodynamically capable of water oxidation, and its long lifetime suggests the possibility of coupling systems such as this system to water oxidation catalysts for use in artificial photosynthetic fuel production.

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Section: Resultsmentioning

confidence: 99%

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Megiatto

Antoniuk-Pablant

Sherman

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

112

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“…A fluorinated detergent, CF3(CF2)5C2H4-O-maltose, was reconstituted into a lipid bilayer model membrane system to demonstrate the feasibility of determining solvent accessibility and membrane immersion depth of each fluorinated group by 19 F NMR. Apolar oxygen, which is known to partition with an increasing concentration gradient toward the hydrophobic membrane interior, exhibits a range of paramagnetic relaxation effects on 19 F nuclei, depending on its depth in the membrane.…”

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confidence: 99%

“…Apolar oxygen, which is known to partition with an increasing concentration gradient toward the hydrophobic membrane interior, exhibits a range of paramagnetic relaxation effects on 19 F nuclei, depending on its depth in the membrane. This effect, which is predominately associated with spin-lattice relaxation rates (R1) and chemical shifts, can be amplified greatly with minimal line broadening by increasing the partial pressure of O 2 at least 100-fold (i.e., PO 2 greater than 20 bar).…”

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confidence: 99%

“…This result contrasts with the reverse trend, which is observed on addition of a membrane surface-associated paramagnetic species, 4-(N,N-dimethyl-N-hexadecyl) ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (CAT-16) at ambient pressures. Thus, differential relaxation rates may be observed in 19 F-labeled membraneassociated molecules resulting from the addition of apolar oxygen under high pressure. The results demonstrate that the degree of solvent accessibility and membrane immersion depth of specific fluorinated species in membrane-associated macromolecules can be probed by 19 F NMR.…”

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confidence: 99%

“…Thus, differential relaxation rates may be observed in 19 F-labeled membraneassociated molecules resulting from the addition of apolar oxygen under high pressure. The results demonstrate that the degree of solvent accessibility and membrane immersion depth of specific fluorinated species in membrane-associated macromolecules can be probed by 19 F NMR.…”

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confidence: 99%

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Using O ₂ to probe membrane immersion depth by ¹⁹ F NMR

Prosser

Luchette

Westerman

2000

Proc. Natl. Acad. Sci. U.S.A.

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(β-Octafluoro-meso-tetraarylporphyrin)manganese Complexes: Synthesis, Characterization and Catalytic Behaviour in Monooxygenation Reactions

Porhiel

Bondon

Leroy

2000

Eur. J. Inorg. Chem.

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The synthesis and characterization of manganese complexes of β‐octafluoro‐meso‐tetraarylporphyrins are reported. The presence of the electron‐withdrawing β‐fluorine atoms induces a very large shift of the redox potential for the oxidation of the manganese(II) derivatives. With the meso‐aryl group bearing two ortho‐chlorine atoms (2,6‐dichlorophenyl) or five fluorine atoms (pentafluorophenyl), metal complexation leads to the isolation of pure manganese(II) compounds. The stability and catalytic activity of these new derivatives have been studied using hydrogen peroxide and iodosylbenzene as oxidants, and standard substrates for epoxidation and hydroxylation reactions. The results are compared to those obtained with the β‐hydrogenated analogs under the same conditions. In the case of hydrogen peroxide, the high level of porphyrin degradation prevents efficient catalytic activity. With iodosylbenzene as oxidant, both stability and epoxidation are similar to those of the β‐hydrogenated porphyrins, however, a substantial improvement in the efficiency of the hydroxylation of cyclohexane is observed with up to 33 turnovers with (perfluorotetraphenylporphyrin)manganese(II).

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19F NMR Spectra and Structures of Halogenated Porphyrins

Cited by 121 publications

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Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Using O ₂ to probe membrane immersion depth by ¹⁹ F NMR

(β-Octafluoro-meso-tetraarylporphyrin)manganese Complexes: Synthesis, Characterization and Catalytic Behaviour in Monooxygenation Reactions

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19F NMR Spectra and Structures of Halogenated Porphyrins

Cited by 121 publications

References 0 publications

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Using O 2 to probe membrane immersion depth by 19 F NMR

(β-Octafluoro-meso-tetraarylporphyrin)manganese Complexes: Synthesis, Characterization and Catalytic Behaviour in Monooxygenation Reactions

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Using O ₂ to probe membrane immersion depth by ¹⁹ F NMR