[L2Mn2(.mu.-O)2(.mu.-O2)](ClO4)2. The first binuclear (.mu.-peroxo)dimanganese(IV) complex (L = 1,4,7-trimethyl-1,4,7-triazacyclononane). A model for the S4 .fwdarw. S0 transformation in the oxygen-evolving complex in photosynthesis

Bossek, Ursula; Weyhermueller, Thomas; Wieghardt, Karl; Nuber, Bernhard; Weiß, Johannes

doi:10.1021/ja00173a031

Cited by 164 publications

(110 citation statements)

References 5 publications

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“…[17,18] At this stage, however, we should mention two important exceptions, namely the formation of two dinuclear Mn-peroxo species directly from molecular oxygen. [19,20] These compounds may be the plausible precursors that precede the formation of di-moxo-Mn IV species.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Dioxygen by a Dimanganese Unit Bonded Inside a Cavity Provided by a Pyrrole-Based Dinucleating Ligand

et al. 2001

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A novel class of dinucleating ligands has been introduced into manganese chemistry to study the reactivity of this metal towards dioxygen under strictly controlled conditions. Such N4 ligands combine some of the major peculiarities of tetradentate Schiff bases and the porphyrin skeleton. They are derived from the condensation between 2-pyrrolaldehyde and ethylenediamine or o-phenylenediamine, leading to pyrenH2 (LH2, 1), pyrophenH2 (L'H2, 2) and Me2pyrophenH2, (L"H2, 3), respectively. Their metallation with [Mn3-(Mes)6] (Mes = 2,4,6-trimethylphenyl) led to [Mn2L2] (4), [MnL'(thf)2] (5) and [MnL"(thf)2] (6). Complex 4 displays a double-stranded helical structure, while 5 and 6 are mononuclear complexes containing hexacoordinated metals. Regardless of their structure, complexes 5 and 6 behave in a similar manner to 4 in their reaction with dioxygen, namely, as a dimetallic unit inside a cavity defined by two dinucleating ligands. These reactions led to dinuclear MnIII/MnIV oxo-hydroxo derivatives, [Mn2L2(mu-O)(mu-OH)] (7), [Mn2L'2(mu-O)(mu-OH)] (8) and [Mn2L"2(mu-O)(mu-OH)] (9), in which the two Mn ions are strongly antiferromagnetically coupled [J = -53 (7), J = -64 (8), J = -60 cm(-1) (9)]. The crystal structure of 7 could only be solved with synchrotron radiation as the crystals diffracted very poorly and suffered from twisting and disorder. The formation of 7-9 has been proposed to occur through the formation of an intermediate dinuclear hydroperoxo species.

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Section: Resultsmentioning

confidence: 99%

Reduction of Dioxygen by a Dimanganese Unit Bonded Inside a Cavity Provided by a Pyrrole-Based Dinucleating Ligand

et al. 2001

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“…There are, however, surprisingly few examples of structurally characterized manganese-dioxygen adducts. Wieghardt has reported the only system isolated directly from dioxygen: a dinuclear Mn(IV) complex with a l-1,2-peroxo bridge [83]. The molecular structure of the complex revealed a triple bridge core ( Fig.…”

Section: Manganese-dioxygen Complexesmentioning

confidence: 99%

Dioxygen Binding and Activation: Reactive Intermediates

Borovik

Zinn

Zart

2006

Activation of Small Molecules

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“…Chemical modeling (Pecoraro 1988, Bossek et al 1990, Philouze et al 1992) as well as EXAFS results on the Mn-Mn distances in the photosynthetic Mn-cluster (Yachandra et al 1986, George et al 1989, Sauer et al 1992, Penner-Hahn et al 1990) suggest the involvement of#-oxo bridges for ligating the Mn atoms. Information on the protonation state and shifts of the bridging oxygens in synthetic systems is now available.…”

Section: Possible Mechanisms For Proton Releasementioning

confidence: 99%

Proton release during the redox cycle of the water oxidase

1993

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Old and very recent experiments on the extent and the rate of proton release during the four reaction steps of photosynthetic water oxidation are reviewed. Proton release is discussed in terms of three main sources, namely the chemical production upon electron abstraction from water, protolytic reactions of Mn-ligands (e.g. oxo-bridges), and electrostatic response of neighboring amino acids. The extent of proton release differs between the four oxidation steps and greatly varies as a function of pH both, but differently, in thylakoids and PS II-membranes. Contrastingly, it is about constant in PS II-core particles. In any preparation, and on most if not all reaction steps, a large portion of proton transfer can occur very rapidly (<20 μs) and before the oxidation of the Mn-cluster by Yz (+) is completed. By these electrostatically driven reactions the catalytic center accumulates bases. An additional slow phase is observed during the oxygen evolving step, S3⇒S4→S0. Depending on pH, this phase consists of a release or an uptake of protons which accounts for the balance between the number of preformed bases and the four chemically produced protons. These data are compatible with the hypothesis of concerted electron/proton-transfer to overcome the kinetic and energetic constraints of water oxidation.

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[L2Mn2(.mu.-O)2(.mu.-O2)](ClO4)2. The first binuclear (.mu.-peroxo)dimanganese(IV) complex (L = 1,4,7-trimethyl-1,4,7-triazacyclononane). A model for the S4 .fwdarw. S0 transformation in the oxygen-evolving complex in photosynthesis

Cited by 164 publications

References 5 publications

Reduction of Dioxygen by a Dimanganese Unit Bonded Inside a Cavity Provided by a Pyrrole-Based Dinucleating Ligand

Reduction of Dioxygen by a Dimanganese Unit Bonded Inside a Cavity Provided by a Pyrrole-Based Dinucleating Ligand

Dioxygen Binding and Activation: Reactive Intermediates

Proton release during the redox cycle of the water oxidase

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