Manganese Cluster in Photosynthesis:  Where Plants Oxidize Water to Dioxygen

Yachandra, Vittal K.; Sauer, Kenneth; Klein, Melvin P.

doi:10.1021/cr950052k

Cited by 1,027 publications

(1,138 citation statements)

References 120 publications

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“…Manganese-oxo complexes have also been designed for PCET and HAT reactions, and have been studied extensively in the context of the special role of manganese oxo clusters in the oxygen evolving complex of photosystem II [60][61][62][63]. Borovik has disclosed a compound with the backbone structure 4, which features an unusual non-bridging terminal hydroxo ligand, and has measured its pK a and redox properties ( Figure 7) [64][65][66].…”

Section: Metal-oxo Complexes For C-h Bond Oxidationmentioning

confidence: 99%

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Miller

Tarantino

Knowles

2016

Topics in Current Chemistry Collections

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Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter we aim to highlight the origins, development and evolution of PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.

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Section: Metal-oxo Complexes For C-h Bond Oxidationmentioning

confidence: 99%

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Miller

Tarantino

Knowles

2016

Topics in Current Chemistry Collections

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“…We previously proposed that in the S 4 state a dioxyl radical is produced which spontaneously converts to a peroxo species with the formation of an O-O bond ( Figure 7). 5 This proposal results from the study of a synthetic inorganic di-μ-oxobridged di-Cu compound that has been shown to convert into an isomer with the formation of an O-O bond between the two bridged oxygens. 90 Alternatively, the formation of the oxyl radical on one dimer in the S 3 state and its reaction with OH − or H 2 O either on the other Mn dimer or in the outer sphere during the subsequent S state conversion can lead to the formation of the O-O bond ( Figure 7).…”

Section: Implication To the Mechanism Of Water Oxidationmentioning

confidence: 99%

“…10 This model represents one of the simplest explanations of the EXAFS data but is not unique. 5,11,15 The Mn cluster is proposed to consist of two di-μ-oxo-bridged Mn-Mn binuclear units which are linked to each other by a mono-μ-oxo-bridging ligand.…”

Section: Introductionmentioning

confidence: 99%

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

et al. 2000

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The oxygen-evolving complex of Photosystem II in plants and cyanobacteria catalyzes the oxidation of two water molecules to one molecule of dioxygen. A tetranuclear Mn complex is believed to cycle through five intermediate states (S 0 -S 4 ) to couple the four-electron oxidation of water with the one-electron photochemistry occurring at the Photosystem II reaction center. We have used X-ray absorption spectroscopy to study the local structure of the Mn complex and have proposed a model for it, based on studies of the Mn K-edges and the extended X-ray absorption fine structure of the S 1 and S 2 states. The proposed model consists of two di-μ-oxo-bridged binuclear Mn units with Mn-Mn distances of ~2.7 Å that are linked to each other by a mono-μ-oxo bridge with a Mn-Mn separation of ~3.3 Å. The Mn-Mn distances are invariant in the native S 1 and S 2 states. This report describes the application of X-ray absorption spectroscopy to S 3 samples created under physiological conditions with saturating flash illumination. Significant changes are observed in the Mn-Mn distances in the S 3 state compared to the S 1 and the S 2 states. The two 2.7 Å Mn-Mn distances that characterize the di-μ-oxo centers in the S 1 and S 2 states are lengthened to ~2.8 and 3.0 Å in the S 3 state, respectively. The 3.3 Å Mn-Mn and Mn-Ca distances also increase by 0.04-0.2 Å. These changes in Mn-Mn distances are interpreted as consequences of the onset of substrate/water oxidation in the S 3 state. Mn-centered oxidation is evident during the S 0 →S 1 and S 1 →S 2 transitions. We propose that the changes in Mn-Mn distances during the S 2 →S 3 transition are the result of ligand or water oxidation, leading to the Supporting Information Available: E-space S 3 state EXAFS spectrum; the data in k-space and the background that was removed to reduce the low-frequency contributions that show up as peaks at <1 Å in the Fourier transform; and the Fourier isolate of the k-space S 3 spectrum, shown overplotted on the S 3 EXAFS spectrum (PDF). This material is available free of charge via the Internet at http:// pubs.acs.org. NIH Public Access

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“…Decades of biophysical study have provided a solid groundwork for this project. Crystal structures of photosystem II [1,2] (PSII) have revealed the location of many important components such as chlorophylls and the oxygen-evolving center (OEC) while spectroscopy such as EXAFS [3][4][5][6][7], EPR [8][9][10][11][12], and IR [13,14] have allowed the study of reactive intermediates, the composition of the OEC and the protein ligation of the metal centers. Unfortunately, while we now have a much better structural and mechanistic basis for PSII, we still are some way from the goal of a molecular mechanistic understanding of water oxidation.…”

Section: Introductionmentioning

confidence: 99%

Functional models for the oxygen-evolving complex of photosystem II

Cady

Crabtree

Brudvig

2008

Coordination Chemistry Reviews

387

255

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In the last ten years, a number of advances have been made in the study of the oxygen-evolving complex (OEC) of photosystem II (PSII). Along with this new understanding of the natural system has come rapid advance in chemical models of this system. The advance of PSII model chemistry is seen most strikingly in the area of functional models where the few known systems available when this topic was last reviewed has grown into two families of model systems. In concert with this work, numerous mechanistic proposals for photosynthetic water oxidation have been proposed. Here, we review the recent efforts in functional model chemistry of the oxygen-evolving complex of photosystem II.

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Manganese Cluster in Photosynthesis: Where Plants Oxidize Water to Dioxygen

Cited by 1,027 publications

References 120 publications

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Functional models for the oxygen-evolving complex of photosystem II

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Manganese Cluster in Photosynthesis: Where Plants Oxidize Water to Dioxygen

Cited by 1,027 publications

References 120 publications

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Structural Change of the Mn Cluster during the S2→S3 State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Functional models for the oxygen-evolving complex of photosystem II

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Product

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Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy