Spin Frustration in High-Spin Triiron(III) Complexes: An Inelastic Neutron Scattering Study

Cannon, Roderick D.; Jayasooriya, Upali A.; Wu, Ruowen; arapKoske, Samuel K.; Stride, John A.; Nielsen, Olav F.; White, Ross P.; Kearley, Gordon J.; Summerfield, Dean

doi:10.1021/ja00105a029

Cited by 58 publications

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“…Trinuclear iron compounds are of interest because oxo-bridged polynuclear Fe(III) centres perform important biological functions, such as oxygen storage and transport in a variety of proteins. It has been established that the iron atoms in the Fe 3 O core are coupled antiferromagnetically both for Fe(III) and mixed valence (Fe(II)/Fe(III)), and spin frustation occurs due to the triangular geometry [2]. The magnetic Jahn-Teller effect has been observed in a few such compounds causing deviation of the clusters from an equilateral configuration [3].…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…It has been established that the iron atoms in the Fe 3 O core are coupled antiferromagnetically both for Fe(III) and mixed valence (Fe(II)/Fe(III)), and spin frustation occurs due to the triangular geometry [2]. The magnetic Jahn-Teller effect has been observed in a few such compounds causing deviation of the clusters from an equilateral configuration [3].In the title compound, the (Fe 3O(dmgly)7(H2O)2) 7+ cation has no crystallographic imposed symmetry. Two of the Fe(III) ions are coordinated by four dimethylglycine molecules, one water molecule and the bridging oxide ion, while the third metal ion has the water molecule trans to the central oxide ion replaced by another dimethylglycine molecule.…”

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Crystal structure of diaqua-monodimethylglycine-hexakis(μ2-dimethylglycine- O:O)-μ3-oxo-triiron(III) heptanitrate—water—dimethylgycine solvate (1:4:0.63), Fe3O(C4H9NO2)7(H2O)2(NO3)7 · 4H2O · 0.63C4H9NO2

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et al. 2003

Zeitschrift Für Kristallographie - New Crystal Structures

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Source of materialThe title compound was obtained from an aqueous solution of dimethylglycine and iron nitrate in a 3:1 proportion. After many months of room temperature evaporation of the solvent small single crystals were grown. They showed hygroscopic behaviour. Experimental detailsThe crystals were inserted in capillary and then tested by Laue photographic methods. The H atoms of the organic moieties were placed at calculated positions and refined as riding using SHELXL-97 [1] defaults. H atoms of the water molecules were not located. DiscussionThe title compound contains a triiron core linked by a m 3-bridging oxide ion. Trinuclear iron compounds are of interest because oxo-bridged polynuclear Fe(III) centres perform important biological functions, such as oxygen storage and transport in a variety of proteins. It has been established that the iron atoms in the Fe 3 O core are coupled antiferromagnetically both for Fe(III) and mixed valence (Fe(II)/Fe(III)), and spin frustation occurs due to the triangular geometry [2]. The magnetic Jahn-Teller effect has been observed in a few such compounds causing deviation of the clusters from an equilateral configuration [3].In the title compound, the (Fe 3O(dmgly)7(H2O)2) 7+ cation has no crystallographic imposed symmetry. Two of the Fe(III) ions are coordinated by four dimethylglycine molecules, one water molecule and the bridging oxide ion, while the third metal ion has the water molecule trans to the central oxide ion replaced by another dimethylglycine molecule. Each of the Fe(III) ions has a distorted octahedral geometry with distances to the basal planes of 0.192(2) Å, 0.101(2) Å and 0.202(2) Å for Fe1, Fe2, Fe3 respectively. The shortest Fe···Fe distance is 3.277(2) Å, too large to allow direct metal-metal interactions. A magnetic superexchange mechanism mainly through the central oxide ion has been used to explain the observed magnetic properties in similar compounds [2], the Fe-O1 distances range from 1.902(3) Å to 1.951(3) Å. The dimethylglycine molecules are present in neutral zwitterionic form, with the carboxylic group deprotonated and the amino group positively charged. The nitrate cations are disordered in the structure which accounts for their high displacement factors. One of the ions was refined in two different orientations. There is an extra dimethyl-glycine molecule that does not coordinate the metal core and its occupation refines to less than the unity. The oxygen atoms of four solvent water molecules were also located. These high solvent content and disorder is usual in these type of compounds [2]

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Crystal structure of diaqua-monodimethylglycine-hexakis(μ2-dimethylglycine- O:O)-μ3-oxo-triiron(III) heptanitrate—water—dimethylgycine solvate (1:4:0.63), Fe3O(C4H9NO2)7(H2O)2(NO3)7 · 4H2O · 0.63C4H9NO2

Silva

Beja

Paixão

et al. 2003

Zeitschrift Für Kristallographie - New Crystal Structures

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“…23 Spin level splitting measure ments in related iron complexes by inelastic neutron scat tering at helium temperatures were also reported. 10, 24 The results obtained suggest that to describe splittings between the spin levels for S = 1/2 and S = 3/2, one should use the spin Hamiltonian given by expressions (4) …”

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“…, (24) and substituting expressions (22) into these relationships. Therefore, information on the dynamics or possible lo calization of the atom O can only be extracted by probing upper lying levels.…”

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Jahn-Teller effect in trigonal μ-oxoclusters

2004

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A theory of the Jahn-Teller effect in trinuclear Cr III and Fe III µ oxocomplexes based on the generalized angular overlap model is developed. The central bridging O atom is not local ized at the center of the triangle formed by the metal atoms. Rather, it executes a free or hindered motion along a circular groove of radius 0.05-0.1 Å. The theory provides a qualita tive explanation for apparent discrepancy between the X ray structural data and the results of the heat capacity, magnetic susceptibility, and inelastic neutron scattering measurements. Namely, X ray structural data correspond to a regular triangle symmetry while other data correspond to an equilateral or even irregular triangle symmetry.

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Analyse der Symmetrie von Kristallpackungskräften unter Nutzung des Tunnelns von Methylprotonen: eine Methode zum eindeutigen Nachweis des magnetischen Jahn-Teller-Effekts in Molekülen

et al. 1998

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Intrinsische und äußere Gründe für das Auftreten von Verzerrung in Metallatomclustern lassen sich gut unterscheiden, wenn diese in eine geeignete Ligandenumgebung eingebettet werden und dann das Tunneln von Protonen in peripheren Liganden anhand der inelastischen Neutronenbeugung analysiert wird. Beim hier untersuchten Modellsystem [Cr3O(OOCCH3)6(H2O)3]Cl⋅6H2O zeigte sich, daß die Tunnelprozesse sehr empfindlich auf Umgebungseinflüsse reagieren. Damit hat man ein Werkzeug zur Hand, um bei Strukturverzerrungen die Ursache sicherer zu ermitteln.

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Spin Frustration in High-Spin Triiron(III) Complexes: An Inelastic Neutron Scattering Study

Cited by 58 publications

References 2 publications

Crystal structure of diaqua-monodimethylglycine-hexakis(μ2-dimethylglycine- O:O)-μ3-oxo-triiron(III) heptanitrate—water—dimethylgycine solvate (1:4:0.63), Fe3O(C4H9NO2)7(H2O)2(NO3)7 · 4H2O · 0.63C4H9NO2

Crystal structure of diaqua-monodimethylglycine-hexakis(μ2-dimethylglycine- O:O)-μ3-oxo-triiron(III) heptanitrate—water—dimethylgycine solvate (1:4:0.63), Fe3O(C4H9NO2)7(H2O)2(NO3)7 · 4H2O · 0.63C4H9NO2

Jahn-Teller effect in trigonal μ-oxoclusters

Analyse der Symmetrie von Kristallpackungskräften unter Nutzung des Tunnelns von Methylprotonen: eine Methode zum eindeutigen Nachweis des magnetischen Jahn-Teller-Effekts in Molekülen

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