Novel antiferromagnetic oxo-bridged manganese complex

Plaksin, P. M.; Stoufer, R. Carl; Mathew, M.; Palenik, Gus J.

doi:10.1021/ja00761a059

Cited by 158 publications

(90 citation statements)

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“…4,[13][14][15][16] The ST = ½ state manifests itself in CW-EPR as a characteristic multiline signal centered at g~2. This is in contrast to the Ni-Fe and Fe-Fe cofactor systems discussed above, 11,12 both of which display a large g-anisotropy which [18][19][20] ; C) mono-μ-hydroxo, bis-μ-carboxylato Mn II -(μOH)-Mn III PivOH complex; 21 D, E) the Mn/Mn cofactor of Thermus thermophilus catalase (MnCat) poised in the Mn II Mn III (bis-μ-hydroxo, mono-μ-carboxylato) and Mn III Mn IV (bis-μ-oxo, mono-μ-carboxylato) oxidation level; 3,4 F) the Mn III Fe III cofactor of the R2lox protein (mono-μ-hydroxo, bis-μ-carboxylato). 9,22 The bridging μ-oxo oxygen atoms of the BIPY complex are identical whereas the bridging μ-oxo oxygen atoms of the DTNE and MnCat complexes are not strictly identical.…”

Section: Introductionmentioning

confidence: 57%

Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory

et al. 2015

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Multifrequency pulsed EPR data are reported for a series of oxygen bridged (μ-oxo/μ-hydroxo) bimetallic manganese complexes where the oxygen is labeled with the magnetically active isotope (17)O (I = 5/2). Two synthetic complexes and two biological metallocofactors are examined: a planar bis-μ-oxo bridged complex and a bent, bis-μ-oxo-μ-carboxylato bridge complex; the dimanganese catalase, which catalyzes the dismutation of H2O2 to H2O and O2, and the recently identified manganese/iron cofactor of the R2lox protein, a homologue of the small subunit of the ribonuclotide reductase enzyme (class 1c). High field (W-band) hyperfine EPR spectroscopies are demonstrated to be ideal methods to characterize the (17)O magnetic interactions, allowing a magnetic fingerprint for the bridging oxygen ligand to be developed. It is shown that the μ-oxo bridge motif displays a small positive isotropic hyperfine coupling constant of about +5 to +7 MHz and an anisotropic/dipolar coupling of -9 MHz. In addition, protonation of the bridge is correlated with an increase of the hyperfine coupling constant. Broken symmetry density functional theory is evaluated as a predictive tool for estimating hyperfine coupling of bridging species. Experimental and theoretical results provide a framework for the characterization of the oxygen bridge in Mn metallocofactor systems, including the water oxidizing cofactor of photosystem II, allowing the substrate/solvent interface to be examined throughout its catalytic cycle.

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Section: Introductionmentioning

confidence: 57%

Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory

et al. 2015

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“…In the late 1970s and early 1980s mixed valent (Mn III Mn IV ) complexes using bipyridyl ligands were synthesized, structurally characterized [105] and spectroscopically interrogated [21,[106][107][108]. Dismukes recognized the similarity between the multiline signal observed in the EPR spectrum for these dimers (g = 2, 16 lines) and that of the OEC in the S 2 (g = 2, 19-22 lines) [109][110][111].…”

Section: Mn-μ-o 2 -Mnmentioning

confidence: 99%

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Mullins

Pecoraro

2008

Coordination Chemistry Reviews

328

252

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Recent advances in the study of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) include structural information attained from several X-ray crystallographic (XRD) and spectroscopic (XANES and EXAFS) investigations. The possible structural features gleaned from these studies have enabled synthetic chemists to design more accurate model complexes, which in turn, offer better insight into the possible pathways used by PSII to drive photosynthetic water oxidation catalysis. Mononuclear model compounds have been used to advance the knowledge base regarding the physical properties and reactivity of high-valent (Mn(IV) or Mn(V)) complexes. Such investigations have been especially important in regard to the manganyl (Mn(IV)=O or Mn(V)≡O) species, as there are no reports, to date, of any structural characterized multinuclear model compounds that incorporate such a functionality. Dinuclear and trinuclear model compounds have also been thoroughly studied in attempts to draw further comparison to the physical properties observed in the natural system and to design systems of catalytic relevance. As the reactive center of the OEC has been shown to contain an oxo-Mn(4)Ca cluster, exact structural models necessitate a tetranuclear Mn core. The number of models that make use of Mn(4) clusters has risen substantially in recent years, and these models have provided evidence to support and refute certain mechanistic proposals. Further work is needed to adequately address the rationale for Ca (and Cl) in the OEC and to determine the sequence of events that lead to O(2) evolution.

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“…The synthesis and structure determination of the di-#-oxo Mr~(III,IV) bipyridine by Plaksin et al (1972) provided a molecule with significant consequences. The observation and assignment of its EPR spectrum by Cooper et al (1978) provided an immediate guide to Dismukes and Siderer (1981) when they subsequently observed the now famous multiline EPR signal that is the hallmark of the S 2 state.…”

Section: The Di-p-oxo Bridged Mn Dimer and The Multiline Epr Signal Fmentioning

confidence: 99%

Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

1993

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This review describes the progress in our understanding of the structure of the Mn complex in Photosystem II over the last two decades. Emphasis is on the research from our laboratory, especially the results from X-ray absorption spectroscopy, low temperature electron paramagnetic resonance and electron spin echo envelope modulation studies. The importance of the interplay between electron paramagnetic resonance studies and X-ray absorption studies, which has led to a description of the oxidation states of manganese as the enzyme cycles through the Kok cycle, is described. Finally, the path, by which our group has utilized these two important methods to arrive at a working structural model for the manganese complex that catalyzes the oxidation of water to dioxygen in higher plants and cyanobacteria, is explained.

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Novel antiferromagnetic oxo-bridged manganese complex

Cited by 158 publications

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Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory

Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

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Novel antiferromagnetic oxo-bridged manganese complex

Cited by 158 publications

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Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency17O-Hyperfine EPR Spectroscopies and Density Functional Theory

Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency17O-Hyperfine EPR Spectroscopies and Density Functional Theory

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

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Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory

Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency¹⁷O-Hyperfine EPR Spectroscopies and Density Functional Theory