Synthesis, Crystal Structure, Magnetism, and Magnetic Anisotropy of Cyclic Clusters Comprising six Iron(III) Ions and Entrapping Alkaline Ions

Caneschi, Andréa; Cornia, Andrea; Fabretti, Antonio C.; Foner, S.; Gatteschi, Dante; Grandi, Romano; Schenetti, Luisa

doi:10.1002/chem.19960021109

Cited by 153 publications

(126 citation statements)

References 42 publications

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“…www.chemeurj.org L-band is well documented for a number of molecular spin clusters, such as the AFM wheels, [5,10,15,25,43,47,48] the modified AFM wheels, [39,42,49] the [3 3] grids, [13,50,51] the {Mo 72 Fe 30 } cage [52] and other clusters. Observing the E-band directly is possible only with INS, hence evidence is scarce; it is well documented for the AFM wheels, [15] and the Mn-[3 3] grid; [50] for {Mo 72 Fe 30 } evidence is also strong.…”

Section: Discussionmentioning

confidence: 99%

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Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Ochsenbein¹,

Tuna²,

Rancan³

et al. 2008

Chemistry A European J

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We report the synthesis and structural characterisation of a family of finite molecular chains, specifically [{[R(2)NH(2)](3)[Cr(6)F(11)(O(2)CCMe(3))(10)]}(2)] (in which R=nPr 1, Et 2, nBu 3), [{Et(2)NH}(2){[Et(2)NH(2)](3)[Cr(7)F(12)(O(2)CCMe(3))(12)][HO(2)CCMe(3)](2)}(2)] (4), [{[Me(2)NH(2)](3)[Cr(6)F(11)(O(2)CCMe(3))(10)]2.5 H(2)O}(4)] (5) and [{[iPr(2)NH(2)](3)[Cr(7)F(12)(O(2)CCMe(3))(12)]}(2)] (6). The structures all contain horseshoes of chromium centres, with each Cr...Cr contact within the horseshoe bridged by a fluoride and two pivalates. The horseshoes are linked through hydrogen bonds to the secondary ammonium cations in the structure, leading to di- and tetra-horseshoe structures. Through magnetic measurements and inelastic neutron scattering studies we have determined the exchange coupling constants in 1 and 6. In 1 it is possible to distinguish two exchange interactions, J(A)=-1.1 meV and J(B)=-1.4 meV; J(A) is the exchange interactions at the tips of the horseshoe and J(B) is the exchange within the body of the horseshoe (1 meV=8.066 cm(-1)). For 6 only one interaction was needed to model the data: J=-1.18 meV. The single-ion anisotropy parameters for Cr(III) were also derived for the two compounds as: for 1, D(Cr)=-0.028 meV and |E(Cr)|=0.005 meV; for 6, D(Cr)=-0.031 meV. Magnetic-field-dependent inelastic neutron scattering experiments on 1 allowed the Zeeman splitting of the first two excited states and level crossings to be observed. For the tetramer of horseshoes (5), quantum Monte Carlo calculations were used to fit the magnetic susceptibility behaviour, giving two exchange interactions within the horseshoe (-1.32 and -1.65 meV) and a weak inter-horseshoe coupling of +0.12 meV. Multi-frequency variable-temperature EPR studies on 1, 2 and 6 have also been performed, allowing further characterisation of the spin Hamiltonian parameters of these chains.

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Section: Discussionmentioning

confidence: 99%

“…Obtaining reasonable estimates for D turns out to be fairly easy; several approximates were suggested. [5,[25][26][27][28]43] For e(q), the situation is much more involved; very recently spin-wave theory (SWT) was suggested. [25,30,44] The L&E-band structure is currently believed to emerge for systems with a "classical" spin structure.…”

Section: Discussionmentioning

confidence: 99%

Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Ochsenbein¹,

Tuna²,

Rancan³

et al. 2008

Chemistry A European J

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“…[25][26][27] Through pair-wise coupling the spin function can be expressed as: Table 1. For all three spin states the calculated g values are slightly lower than those observed experimentally, but overall, the vectorcoupling model provides a good explanation for the experimentally observed g values and confidence in the correct assignment of multiple transitions to contributions from different isomers.…”

Section: Discussionmentioning

confidence: 99%

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr₇Ni, Cr₆Ni₂, and Cr₇Ni₂ Rings Templated About Imidazolium Cations

Boeer

Collison

Muryn

et al. 2009

Chemistry A European J

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The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4-DiMe-ImidH][Cr(7)Ni(II)F(8)(O(2)CtBu)(16)] 1 (2,4-DiMe-ImidH=the cation of 2,4-dimethylimidazole), [ImidH](2)[Cr(6)Ni(II) (2)F(8)(O(2)CCtBu)(16)] 2 (ImidH=the cation of imidazole), and [1-Bz-ImidH](2) [Cr(7)Ni(II) (2)F(9)(O(2)CtBu)(18)] 3 (1-Bz-ImidH=the cation of 1-benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3. In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X-ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J approximately -5.8 cm(-1), and it is not possible to differentiate the exchange between two Cr(III) centers (J(CrCr)) from the exchange between a Cr(III) and a Ni(II) center (J(CrNi)). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present.

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“…However, the experimental and theoretical work has suggested a very different picture of the excitations, which is denoted here as L&E-band concept. This concept has its roots in Anderson's 1952 paper on antiferromagnetic spin waves (Anderson, 1952), and emerged in the course of several works (Anderson, 1984;Bernu et al, 1992;Caneschi et al, 1996;Chiolero and Loss, 1998;Lhuillier, 2002;Schnack and Luban, 2000;Waldmann, 2002b). The L&E-band concept is classical in nature, though some subtleties are present, and the meaning of "classical" in this context is in fact not yet completely understood.…”

Section: Condensed Matter Techniquesmentioning

confidence: 99%

Magnetic Cluster Excitations

Fürrer

2010

Int. J. Mod. Phys. B

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Magnetic clusters, i.e., assemblies of a finite number (between two or three and several hundred) of interacting spin centers which are magnetically decoupled from their environment, can be found in many materials ranging from inorganic compounds, magnetic molecules, artificial metal structures formed on surfaces to metalloproteins. The magnetic excitation spectra in them are determined by the nature of the spin centers, the nature of the magnetic interactions, and the particular arrangement of the mutual interaction paths between the spin centers. Small clusters of up to four magnetic ions are ideal model systems to examine the fundamental magnetic interactions which are usually dominated by Heisenberg exchange, but often complemented by anisotropic and/or higher-order interactions. In large magnetic clusters which may potentially deal with a dozen or more spin centers, the possibility of novel many-body quantum states and quantum phenomena are in focus. In this review the necessary theoretical concepts and experimental techniques to study the magnetic cluster excitations and the resulting characteristic magnetic properties are introduced, followed by examples of small clusters demonstrating the enormous amount of detailed physical information which can be retrieved. The current understanding of the excitations and their physical interpretation in the molecular nanomagnets which represent large magnetic clusters is then presented, with an own section devoted to the subclass of the singlemolecule magnets which are distinguished by displaying quantum tunneling of the magnetization. Finally, some quantum many-body states are summarized which evolve in magnetic insulators characterized by built-in or field-induced magnetic clusters. The review concludes addressing future perspectives in the field of magnetic cluster excitations.

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Synthesis, Crystal Structure, Magnetism, and Magnetic Anisotropy of Cyclic Clusters Comprising six Iron(III) Ions and Entrapping Alkaline Ions

Cited by 153 publications

References 42 publications

Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr₇Ni, Cr₆Ni₂, and Cr₇Ni₂ Rings Templated About Imidazolium Cations

Magnetic Cluster Excitations

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Synthesis, Crystal Structure, Magnetism, and Magnetic Anisotropy of Cyclic Clusters Comprising six Iron(III) Ions and Entrapping Alkaline Ions

Cited by 153 publications

References 42 publications

Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Studies of Finite Molecular Chains: Synthesis, Structural, Magnetic and Inelastic Neutron Scattering Studies of Hexa‐ and Heptanuclear Chromium Horseshoes

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr7Ni, Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium Cations

Magnetic Cluster Excitations

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Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr₇Ni, Cr₆Ni₂, and Cr₇Ni₂ Rings Templated About Imidazolium Cations