Aqueous Chemistry of High-Valent Manganese. Structure, Magnetic, and Redox Properties of a New Type of Mn-Oxo Cluster, [Mn4IVO4(bpy)6]4+: Relevance to the Oxygen Evolving Center in Plants

Philouze, Christian; Blondin, Geneviève; Girerd, Jean‐Jacques; Guilhem, Jean; Pascard, Claudine; Lexa, Doris

doi:10.1021/ja00098a016

Cited by 95 publications

(86 citation statements)

References 14 publications

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“…Besides these physical effects, investigations on chemical aspects resulting from oxo-bridge protonation have hardly been studied, expect in a few reports where it was observed that catalase activity of [Mn(salpn)(m-O)] 2 (salpn = 1,3-bis(salicylideneamineto)propane) is inhibited by a single protonation on the oxo-bridge [18], whereas disproportionation of a (Mn III ) 2 complex requires oxo-bridge protonation [19]. It is also of note that oxo-bridge protonation in multinuclear higher-valent Mn complexes sometimes leads to cluster breakup [16] [20], rendering their redox chemistry H …”

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confidence: 99%

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Das

Bhattacharyya

Mukhopadhyay

2006

HCA

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In aqueous media (pH 2.5 -6.0), the Mn IV tetramer [Mn 4 (m-O) 6 A C H T U N G T R E N N U N G (bipy) 6 ] 4+ (1 4+ ; bipy = 2,2'-bipyridine) oxidizes both glyoxylic and pyruvic acid to formic and acetic acid, respectively, under formation of CO 2 . Kinetics studies suggest that the species 1 4+ , its oxo-bridge protonated form [1H], the reducing acids (RH) and their conjugate bases (R À ) all take part in the reaction. The oxo-bridge protonated oxidant [1H] 5+ was found to react much faster than 1 4+. Thereby, the gemdiol forms of the a-oxo acids (especially in the case of glyoxylic acid) are the possible reductants. A one-electron/one-proton electroprotic mechanism operates in the rate-determining step.Introduction. , resulting from protonation of the oxo bridges, has important implications in interpreting the changes in magnetic behavior of the OEC upon S-state advancement and changes in configuration. Oxo-bridge protonations also cause a substantial increase in the MnÀMn distance in multinuclear Mn complexes, and an increase in reduction potential [14 -18]. Besides these physical effects, investigations on chemical aspects resulting from oxo-bridge protonation have hardly been studied, expect in a few reports where it was observed that catalase activity of [Mn(salpn)(m-O)] 2 (salpn = 1,3-bis(salicylideneamineto)propane) is inhibited by a single protonation on the oxo-bridge [18], whereas disproportionation of a (Mn III ) 2 complex requires oxo-bridge protonation [19]. It is also of note that oxo-bridge protonation in multinuclear higher-valent Mn complexes sometimes leads to cluster breakup [16] [20], rendering their redox chemistry H

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confidence: 99%

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Das

Bhattacharyya

Mukhopadhyay

2006

HCA

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“…The first states thus obey, qualitatively, the idea proposed, but the agreement is not quantitative since the individual J values do not obey the condition for the validity of the perturbation theory. Qualitatively, we can retain the idea that the two external spins are AF-coupled through an almost diamagnetic system, as explained by Philouze et al [29] …”

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confidence: 88%

“…[29] When the two central ions (b,c) are strongly antiferromagnetically coupled, the two terminal spins (a,d) appear to be coupled by an antiferromagnetic (AF) effective interaction. In this present case we found that if IJ ab / J bc I ϽϽ 1 there is an effective J eff ϭ 2.5J ab 2 /J bc .…”

Section: Magnetic Propertiesmentioning

confidence: 99%

Synthesis, Structure and Characterizations in Solid State and Solution of Dinuclear Pentacoordinated Fe^II and Mn^II Complexes and of a Linear Tetranuclear Fe^III Complex Obtained with the Ligand N,N,N′,N′‐Tetrakis[(6‐methyl‐2‐pyridyl)methyl]propane‐1,3‐diamine

et al. 2004

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Two neutral complexes [(L634M)Fe2Cl4]·2H2O·2CHCl3 (1) and [(L634M)Mn2Cl4]·CH3CN (2) have been synthesized {L634M = N,N,N′,N′‐tetrakis[(6‐methyl‐2‐pyridyl)methyl]propane‐1,3‐diamine} and their molecular structures established by X‐ray crystallography. Both structures are similar, with each metal center in a trigonal‐bipyramidal environment. No magnetic coupling is observed between the metal centers. UV/Vis spectra and cyclic voltammograms were recorded in CH2Cl2 and CH3CN solutions. Both complexes are stable in CH2Cl2, whereas only 2 is stable in CH3CN. On the contrary, 1 is in equilibrium with another FeII species in CH3CN. When this last solution is aerated, monocrystals of the neutral linear tetranuclear complex [(L634M)Fe4(μ‐O)3Cl6]·2CH3CN (3) can be isolated. Its structure is unusual with two FeIII ions pentacoordinate and the two others tetracoordinate with only chloro ligands and oxo bridges. The magnetic properties reveal that two consecutive metal centers are strongly antiferromagnetically coupled. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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“…This is presumably because the ionic radius of Mn II is too large to Tetranuclear manganese clusters are interesting from the magnetic point of view, [26] or as synthetic models of the dioxygen-evolving complex of photosystem II. [27] Of 4+ cation, [28,29] the [Mn 2 IIIMn 2 II (Me-hmp) 6 Cl 4 ] cluster [Me-hmpH = 2-(hydroxymethyl)-6-methylpyridine], [30] [HL = a (2-hydroxyphenyl)bipyridine or -phenanthroline ligand]. [31,32] All of these display a cis conformation with respect to the central [Mn 2 O 2 ] unit (Scheme 2), while complex www.eurjic.org1 is the first example of the trans form as forced presumably by the structure of the (H 2 L3) 3-ligand.…”

Section: (Py) 5 ] (1) Which Displays An Un-mentioning

confidence: 99%

A Zig‐Zag [Mn^II₄] Cluster from a Novel Bis(β‐diketonate) Ligand

et al. 2006

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Keywords: Ligand design / O ligands / NMR spectroscopy / Magnetism / MnA new ligand, H 5 L3, has been synthesized featuring seven linearly arranged oxygen donors in form of two 1,3-diketone and three phenol groups. The X-ray structure of H 5 L3 unveils a rare case where one of the diketones is in the enolic form and the other one in the bis(carbonyl) form. This structure is shown by 1 H NMR to persist in solution. Reaction of H 5 L3 with Mn(AcO) 2 in pyridine leads to the novel tetranuclear cluster [Mn 4 (H 2 L3) 2 (OAc) 2 (py) 5 ] (1), which displays an un-The preparation of molecular cluster complexes of interacting transition-metal ions is useful to areas as important and diverse as molecular magnetism, [1,2] homogeneous catalysis [3] or bioinorganic chemistry. [4,5] A very successful approach for accessing such species has been the assembly of metal ions by means of small bridging ligands, such as carboxylates, where growth into infinite arrays is often prevented by additional terminal ligands. [6,7] Such a method has been sometimes termed "serendipitous approach" since it does not allow prediction of the structure of the final species.[8] An alternative strategy has been the design and preparation of complicated multidentate ligands favoring the assembly of metal ions into aggregates with topologies that may be anticipated from the structure of these ligands. This second course of action has led to the production of a large amount of polynuclear edifices displaying sophisticated shapes and architectures, such as helicates, [9] grids, [10] cylinders, [11] catenates, [12] and many more. Of these molecular species, only a minority have the metal ions disposed in close proximity so as to show cooperative effects resulting from strong magnetic-exchange interactions [13] or metalmetal bonding.[ Scheme 1), [15,16] aimed at forming molecular strings of metal ions in close proximity. Maximum occupancy of their coordination pockets would result in tetranuclear clusters in form of [M 4 ] chains [17] for H 3 L1 and aligned [M 2 ] 2 dimers of dimers for H 4 L2. Reactions of the latter with M(OAc) 2 salts have resulted invariably in the formation of complexes of the type [M 2 (H 2 L2) 2 (S) n ] (n = 2 or 4; S = solvent; M = Mn, Ni, Co, Cu).[16] Similar dinuclear compounds have been obtained with H 3 L1.[18] However, in the absence of a coordinating solvent, molecules exhibiting higher occupancy, [Co 3 (HL1) 3 ] and [Mn 3 (HL1) 3 ], were characterized, which represented a new asymmetric topology within the context of coordination helicates. [19] Inspired by these early results, we have now designed and synthesized a new ligand displaying as many as six adjacent coordination pockets (H 5 L3, Scheme 1). Reaction of H 5 L3 with Mn II produces a very rare magnetically exchanged tetranuclear complex featuring an [Mn 4 O 6 ] core in form of a zig-zag chain.The new ligand H 5 L3 {2-hydroxy-1,3-bis[3-(2-hydroxyphenyl)-3-oxopropionyl]benzene} was prepared from the methoxide derivative H 4 L4 (Scheme 1).[20] The latter is also a n...

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Aqueous Chemistry of High-Valent Manganese. Structure, Magnetic, and Redox Properties of a New Type of Mn-Oxo Cluster, [Mn4IVO4(bpy)6]4+: Relevance to the Oxygen Evolving Center in Plants

Cited by 95 publications

References 14 publications

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Synthesis, Structure and Characterizations in Solid State and Solution of Dinuclear Pentacoordinated Fe^II and Mn^II Complexes and of a Linear Tetranuclear Fe^III Complex Obtained with the Ligand N,N,N′,N′‐Tetrakis[(6‐methyl‐2‐pyridyl)methyl]propane‐1,3‐diamine

A Zig‐Zag [Mn^II₄] Cluster from a Novel Bis(β‐diketonate) Ligand

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Aqueous Chemistry of High-Valent Manganese. Structure, Magnetic, and Redox Properties of a New Type of Mn-Oxo Cluster, [Mn4IVO4(bpy)6]4+: Relevance to the Oxygen Evolving Center in Plants

Cited by 95 publications

References 14 publications

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Mechanistic Studies on the Oxidation of Glyoxylic and Pyruvic Acid by a [Mn4O6]4+ Core in Aqueous Media: Kinetics of Oxo-Bridge Protonation

Synthesis, Structure and Characterizations in Solid State and Solution of Dinuclear Pentacoordinated FeII and MnII Complexes and of a Linear Tetranuclear FeIII Complex Obtained with the Ligand N,N,N′,N′‐Tetrakis[(6‐methyl‐2‐pyridyl)methyl]propane‐1,3‐diamine

A Zig‐Zag [MnII4] Cluster from a Novel Bis(β‐diketonate) Ligand

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Synthesis, Structure and Characterizations in Solid State and Solution of Dinuclear Pentacoordinated Fe^II and Mn^II Complexes and of a Linear Tetranuclear Fe^III Complex Obtained with the Ligand N,N,N′,N′‐Tetrakis[(6‐methyl‐2‐pyridyl)methyl]propane‐1,3‐diamine

A Zig‐Zag [Mn^II₄] Cluster from a Novel Bis(β‐diketonate) Ligand