Structure and properties of a tetranuclear iron(III) cage complex. A model for hemerythrin

Sessler, Jonathan L.; Sibert, John W.; Lynch, Vincent M.; Markert, J. T.; Wooten, Chris L.

doi:10.1021/ic00057a022

Cited by 51 publications

(18 citation statements)

References 2 publications

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“…For comparison, the tetranuclear complex [LFe 2 OA] 2 (PF 6 ) 4 , (A = the dianion of glutaric acid), shows two analogous consecutive peaks at −0.500 and 0.635 V (vs. Ag/AgNO 3 ). 22 The electrochemical behavior of 2 and 5 suggests the possibility of preparing mixed valence analogues of these complexes. The difference between the first and second reduction potentials for complexes 2 (1.36 V) and 5 (1.20 V) specifies the thermodynamic stability of their mixed valence states.…”

Section: Electrochemical Propertiesmentioning

confidence: 99%

Tetranuclear iron(iii) complexes of an octadentate pyridine-carboxylate ligand and their catalytic activity in alkane oxidation by hydrogen peroxide

et al. 2006

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Reaction of the octadentate ligand 2,6-bis{3-[N,N-di(2-pyridylmethyl)amino]propoxy}benzoic acid (LH) with Fe(ClO4)3 leads to the formation of the tetranuclear complexes [Fe4(mu-O)2(LH)2(ClCH2-CO2)4](ClO4)4 (1), [{Fe2(mu-O)L(R-CO2)}2](ClO4)4 (2 R = C6H5-, 3 R = CH3-, 4, R = ClCH2-). The crystal structures of complexes 1 and 2 reveal that they consist of two Fe(III)2(mu-O)(mu-RCO2)2 cores that are linked via the two LH/L ligands to give a "dimer of dimers" structure. Complex assumes a helical shape, with protonated carboxylic acid moieties of the two ligands forming a hydrogen-bonded pair at the center of the cation. In complexes 2, 3 and 4, central carboxylates of the two ligands bridge the iron ions in each of the two Fe2O units, with an interdimer iron-iron separation of approximately 10 A and an intradimer separation of approximately 3.1 A. The second carboxylate bridge within the Fe2O units is defined by exogenous benzoate (2), acetate (3) or chloroacetate (4) ligands. The aqua complex [{Fe2(mu-O)L(H2O)2}2](ClO4)6 (5) is proposed to have a similar structure, but with the exogenous bridging carboxylates replaced by two terminal water ligands. These complexes exhibit electronic and Mössbauer spectral features that are similar to those of (mu-oxo)diiron(III) proteins as well as other related (mu-oxo)bis(mu-carboxylato)diiron(III) complexes. This similarity shows that these properties are not significantly affected by the nature of the bridging exogenous carboxylate, and that the octadentate framework ligand is essential in stabilizing the "dimer of dimers" structure. This structural feature remains in highly diluted solution (10(-5) M) as evidenced by electrospray ionization mass-spectroscopy (ES MS). Cyclic voltammetric studies of complexes 2 and 5 showed two irreversible two-electron reductions, indicating that the two Fe2O units of the tetranuclear complexes behave as distinct redox entities. Complexes 2, 3 and, especially, the aqua complex 5 are active alkane oxidation catalysts. Catalytic reactions carried out with alkane substrate molecules and hydrogen peroxide predominantly gave alcohols. High stereospecificity in the oxidation of cis-1,2-dimethylcyclohexane supports the metal-based molecular mechanism of O-insertion into C-H bonds postulated for non-heme iron enzymes such as methane monooxygenase.

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Section: Electrochemical Propertiesmentioning

confidence: 99%

Tetranuclear iron(iii) complexes of an octadentate pyridine-carboxylate ligand and their catalytic activity in alkane oxidation by hydrogen peroxide

et al. 2006

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“…The Schiff base complexes are also involved in the study of the artificial metallo proteins and metallo enzymes. 27 Cobalt(III) and nickel(II) complexes of multidentate Schiff base ligands have been extensively used 28 because of these ligands can bind with one or more metals involving various coordination modes and allow the synthesis of homo-and/or hetero nuclear metal complexes with interesting stereochemistry. 29 Cobalt chelate complexes are useful in highly selective catalytic oxidation reactions using molecular oxygen, as models for oxygenases, peroxidases or mono-and dioxygenases.…”

Section: Introductionmentioning

confidence: 99%

Molecular oxygen reduction catalyzed by a highly oxidative resistant complex of cobalt–hydrazone at the liquid/liquid interface

Kamyabi

Soleymani‐Bonoti

Bikas

et al. 2015

Phys. Chem. Chem. Phys.

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A new complex of Co(III) using an oxidative stable hydrazone ligand, CoL, was synthesized and characterized by elemental analysis, spectroscopic methods and single crystal X-ray analysis where HL is bis-[(E)-N'-(phenyl(pyridin-2-yl)methylene)]carbohydrazide. X-ray analysis revealed that the complex is mononuclear and the coordination environment around the Co(III) core is trans-[CoN4Cl2]. The catalytic activity of the complex in the oxygen reduction reaction was investigated. The complex is a highly oxidative resistant cobalt-hydrazone which can efficiently catalyze the reduction of oxygen (O2) by a weak electron donor ferrocene, (Fc), at the polarized water/1,2-dichloroethane (DCE) interface. Oxygen reduction is coupled with proton transfer from water to the organic phase to form hydrogen peroxide, which is extracted into the aqueous phase.

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“…[1,2] The wide variety of available linkers between the two [9]aneN 3 groups, such as alkanes, [3][4][5][6][7][8] xylenes, [9,10] napthalenes [10][11][12] alcohols, [13] and phenols, [14] offers an array of tuneable coordination modes for metal complexation that are dependent on the functionality and structure of the linker. We have recently reported the synthesis and structures of copper(II) complexes of some xylene-bridged bis(tacn) ligands bearing phenyl, carboxylic acid, or nitro substituents on the aromatic ring.…”

Section: Introductionmentioning

confidence: 99%

Bi-Nuclear Metal Complexes of 2,6-Bis(1,4,7-triazacyclonon-1-yl-methylene)pyridine with Zinc(II), Copper(II), and Nickel(II)

et al. 2015

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The coordination chemistry of 2,6-bis(1,4,7-triazacyclonon-1-ylmethyl)pyridine (L pyx , 1) has been investigated and shown to yield bi-nuclear metal complexes in the presence of zinc(II), copper(II), or nickel(II) ions. . In all cases, the L pyx ligand binding is unsymmetrical between the two metal centres being tridentate to one and tetradentate to the other through an additional coordination of the pyridyl linker.

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Structure and properties of a tetranuclear iron(III) cage complex. A model for hemerythrin

Cited by 51 publications

References 2 publications

Tetranuclear iron(iii) complexes of an octadentate pyridine-carboxylate ligand and their catalytic activity in alkane oxidation by hydrogen peroxide

Tetranuclear iron(iii) complexes of an octadentate pyridine-carboxylate ligand and their catalytic activity in alkane oxidation by hydrogen peroxide

Molecular oxygen reduction catalyzed by a highly oxidative resistant complex of cobalt–hydrazone at the liquid/liquid interface

Bi-Nuclear Metal Complexes of 2,6-Bis(1,4,7-triazacyclonon-1-yl-methylene)pyridine with Zinc(II), Copper(II), and Nickel(II)

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