A manganese(V)-oxo complex

Collins, Terrence J.; Gordon‐Wylie, Scott W.

doi:10.1021/ja00194a063

Cited by 180 publications

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“…The occupation numbers for r, p, and p ? bonding orbitals are usually 2.0 for the stable Mn-oxo triple bonds such as those in Collins complexes [73][74][75]. However, pseudo double excitations to the antibonding orbitals are significant in the case of Ia, Ib, and Ic.…”

Section: Computational Results For Model I and Iimentioning

confidence: 99%

“…The situation is the same for carbon monoxide (C¼ ¼O) with one pr-pr bond and two pp-pp bonds. The stable Mn(V)¼ ¼O species by Collins and collaborators [73][74][75] is regarded as such an example: however note that too much stability prevents oxygen activation, suggesting the necessity of an elongation of Mn-O bond or another ligands such as acetate anion for the purpose [33]. However, such structural modification entails a breakdown of the closed-shell picture.…”

Section: Computational Methods and Homo-lumo Mixingmentioning

confidence: 99%

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Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Saitô

Yamanaka

Kanda

et al. 2011

Int J of Quantum Chemistry

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Recently, Umena et al. have revealed the X-ray diffraction structure of the CaMn 4 O 5 cluster in the oxygen evolving complex (OEC) of photosystem II (PSII) refined to 1.9 Å resolution. Their X-ray structure has first elucidated hydrogen-bonding networks and proton release pathways at OEC of PSII. Here, several working hypotheses Additional Supporting Information may be found in the online version of this article Correspondence to: S. Yamanaka; e-mail: syama@chem.sci.osaka-u.ac.jp Contract grant sponsor: Grants-in-Aid for Scientific Research; Contract grant numbers: 19750046, 19350070, 18350008, 23550016 (heuristic principles) for water splitting reaction are derived from their X-ray structure for theoretical modeling. These hypotheses suggest how water can be oxidized at OEC of PSII: namely possible reaction mechanisms for the reaction. To confirm them, we have also performed broken-symmetry (BS) UB3LYP calculations for active site models based on their XRD structure. The bond lengths of formal Mn(V)AO with labile dp-pp bonds are optimized to clarify possible roles of the species that are often introduced as a key intermediate in the catalytic (Kok) cycle for water splitting reaction at OEC of PSII. Location of the transition structure for the oxygen-oxygen (OAO) bond formation is also performed by the energy optimization technique. The natural orbital (NO) analysis of the UB3LYP solutions has been performed to obtain the natural molecular orbitals and their occupation numbers that have been useful for classification of localized d-electrons, labile chemical bonds and closed-shell (valence) orbitals. The localized d-electrons characterized by the NO analysis are the origins for the magnetism revealed by ENDOR and other magnetic experiments. On the other hand, the nature of labile (soft) dp-pp bonds responsible for the OAO bond formation has been investigated on the basis of chemical indices such as effective bond order (b), diradical character (y), and spin density (Q) indices that are calculated using the orbital overlap between broken-symmetry orbitals. These chemical indices have been calculated for the transition structure of the OAO bond formation at OEC of PSII. Implications of present computational results are discussed in relation to the derived hypotheses and available accumulated experimental results.

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Section: Computational Results For Model I and Iimentioning

confidence: 99%

Section: Computational Methods and Homo-lumo Mixingmentioning

confidence: 99%

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Saitô

Yamanaka

Kanda

et al. 2011

Int J of Quantum Chemistry

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“…[25,28,[34][35][36][37][38] Indeed, these complexes possess the ability to form high-valent Mn-oxo species, [39,40] the sixth position being occupied by various ligands. [41,42] In particular, the use of pyridine as the sixth ligand has been proposed to assist the formation of Mn Voxo species from the [(salen)Mn III ] + complex, using tertbutyl hydroperoxide as the oxidant.…”

Section: Mnmentioning

confidence: 99%

Synthesis, Structure and Characterisation of a New Trinuclear Di‐μ‐phenolato‐μ‐carboxylato Mn^IIIMn^IIMn^III Complex with a Bulky Pentadentate Ligand: Chemical Access to Mononuclear Mn^IV–OH Entities

et al. 2005

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“…In the former cases, a high reorganization barrier is expected for electron transfer between the water-oxidizing Mn IV site and the JahnTeller distorted Mn III site. In the latter case, an octahedral Mn V water-oxidizing site would lead to a lower reorganization barrier due to a lower degree of Jahn-Teller distortion in Mn V as compared with Mn III , but electron exchange between a square pyramidal Mn V (a probable geometry for an Mn V ]O moiety; Collins & Gordon-Wylie 1989;Collins et al 1990;MacDonnell et al 1994) and an adjacent octahedral Mn IV would again lead to high reorganization barriers. In all cases, the manganese with the oxo or oxyl radical bound to it would be expected to have a preference for the higher-oxidation state, leading to slow electron exchange.…”

Section: Electron Transfer Between Manganese Ions In the Oxygen-evolvmentioning

confidence: 99%

Water oxidation chemistry of photosystem II

Vrettos

Brudvig

2002

Phil. Trans. R. Soc. Lond. B

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Photosystem II (PSII ) uses light energy to split water into protons, electrons and O 2 . In this reaction, nature has solved the difficult chemical problem of efficient four-electron oxidation of water to yield O 2 without significant amounts of reactive intermediate species such as superoxide, hydrogen peroxide and hydroxyl radicals. In order to use nature's solution for the design of artificial catalysts that split water, it is important to understand the mechanism of the reaction. The recently published X-ray crystal structures of cyanobacterial PSII complexes provide information on the structure of the Mn and Ca ions, the redox-active tyrosine called Y Z and the surrounding amino acids that comprise the O 2 -evolving complex (OEC). The emerging structure of the OEC provides constraints on the different hypothesized mechanisms for O 2 evolution. The water oxidation mechanism of PSII is discussed in the light of biophysical and computational studies, inorganic chemistry and X-ray crystallographic information.

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A manganese(V)-oxo complex

Cited by 180 publications

References 0 publications

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Synthesis, Structure and Characterisation of a New Trinuclear Di‐μ‐phenolato‐μ‐carboxylato Mn^IIIMn^IIMn^III Complex with a Bulky Pentadentate Ligand: Chemical Access to Mononuclear Mn^IV–OH Entities

Water oxidation chemistry of photosystem II

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A manganese(V)-oxo complex

Cited by 180 publications

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Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn4O5 cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn4O5 cluster of PSII refined to 1.9 Å X‐ray resolution

Synthesis, Structure and Characterisation of a New Trinuclear Di‐μ‐phenolato‐μ‐carboxylato MnIIIMnIIMnIII Complex with a Bulky Pentadentate Ligand: Chemical Access to Mononuclear MnIV–OH Entities

Water oxidation chemistry of photosystem II

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Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Synthesis, Structure and Characterisation of a New Trinuclear Di‐μ‐phenolato‐μ‐carboxylato Mn^IIIMn^IIMn^III Complex with a Bulky Pentadentate Ligand: Chemical Access to Mononuclear Mn^IV–OH Entities