Low-temperature structural and magnetic characterization of the chromium(III) dimers bis(.mu.-hydroxo)bis[tetraamminechromium(III)] dithionate tetrahydrate and bis(.mu.-hydroxo)bis[tetraamminechromium(III)] chloride tetrahydrate, [Cr(NH3)4OH]2(S2O6)2.4H2O and [Cr(NH3)4OH]2Cl4.4H2O

Cline, Susan J.; Hodgson, Derek J.; Kallesoe, Solveig; Larsen, Sine; Pedersen, Erik

doi:10.1021/ic00146a013

Cited by 30 publications

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“…Again, changing the NH3 salt to the dithionate compound changes [75] -2J to 6.2 em-I (8.9 K). The difficulties involved in finding a magnetostructural correlation are illustrated by the fact that the exchange constant for is J = -0.63 em -1 when obtained from spectral analysis [74] and -2.48 cm -1 (a factor of 4 larger) when obtained from susceptibility data [75].…”

Section: Some Other Dimersmentioning

confidence: 99%

Introduction to Magnetic Exchange: Dimers and Clusters

Carlin

1986

Magnetochemistry

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Energy Levels and Specific Heats 71configurational mixing of states such as M+ F M2+. The electron on Fin (c) and (d) can now couple with the lone electron in a d z 2 orbital on an adjoining Ni2+ . The preferred coupling is to give a singlet state [(c), called antiferromagnetic] rather than a triplet, (d). This in turn stabilizes the singlet state (a) with respect to the triplet (b). The strength of the interaction will depend on the amount of overlap, and we present here only a model of 180° superexchange. Metal ion orbitals can also overlap with p" ligand orbitals at a 90° angle, and much recent research effort has gone into finding the factors which influence this superexchange interaction.This model, which has been applied to a variety of systems [1,2] is somewhat similar to that which is used for explaining spin-spin coupling in NMR spectroscopy [3]. The Hamiltonian in use for metal-metal exchange interaction in magnetic insulators is of the form (5.2) where the sum is taken over all pair-wise interactions of spins i and j in a lattice. For the moment, we shall restrict our attention to dimers, and thereby limit the summation to the two atoms 1 and 2 in the dimeric molecule, so thatThis is called an isotropic (note the dot product between the two spins, S) or Heisenberg Hamiltonian, and we adopt the convention that negative J refers to antiferromagnetic (spin-paired or singlet ground state in a dimer) interactions, and positive J refers to ferromagnetic (spin-triplet ground state) interactions. The exchange constant J is given in energy units (Kelvins) and measures the strength ofthe interaction. The reader must be careful in comparing different authors, for a variety of conventions (involving the negative sign and even the factor of 2) are in use. (The symbol J now takes a different meaning from its earlier use as the quantum operator for total angular momentum.) Energy Levels and Specific HeatsAn antiferromagnetic interaction ofthe type given in Eq. (5.3), when applied to two ions each of!/ = t gives a spin-singlet ground state and a spin-triplet 2J in energy above the singlet ( Fig. 5.2). Naturally, ifthe interaction were ferromagnetic, the diagram is simply inverted. For an external field applied along the z-axis of the pair, the complete Hamiltonian will be taken as

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Section: Some Other Dimersmentioning

confidence: 99%

Introduction to Magnetic Exchange: Dimers and Clusters

Carlin

1986

Magnetochemistry

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“…(3) A in the other Cr(III) alkoxo-bridged dimers,12•23'24 and the Cr-O-Cr bridging angle ( ) is 101. 7 (2)°. As is also shown in Table IV, these R and values are again comparable to those in the analogues studied earlier.…”

Section: Description Of the Structurementioning

confidence: 99%

Synthesis and characterization of the alkoxo-bridged chromium(III) dimer bis(.mu.-methoxo)bis[bis(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III)]

Fischer¹,

Hodgson²,

Pedersen³

1984

Inorg. Chem.

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“…[2][3][4][5][6][7][8][9][10] The first example of a quantitative magneto-structural relationship was developed many years ago by Hatfield and Hodgson for a large family of di-µ-OH bridged {Cu II 2} complexes, in which the magnetic exchange (J) was found to be governed by the magnitude of the Cu-OH-Cu angle. [11][12][13][14] Thereafter, magneto-structural correlations were also attempted and established for (dimeric) complexes containing other first row transition metal ions such as Fe III , [15][16][17] Cr III , [18][19][20][21] Mn II22 and Mn III . 23 In addition to experimental studies, theoretical methods based on density functional theory (DFT) have become important tools to compute the magnetic exchange interactions and develop magneto-structural correlations.…”

Section: Introductionmentioning

confidence: 99%

Rationalizing the sign and magnitude of the magnetic coupling and anisotropy in dinuclear manganese(iii) complexes

et al. 2018

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We have synthesised twelve manganese(iii) dinuclear complexes, 1-12, in order to understand the origin of magnetic exchange (J) between the metal centres and the magnetic anisotropy (D) of each metal ion using a combined experimental and theoretical approach. All twelve complexes contain the same bridging ligand environment of one μ-oxo and two μ-carboxylato, that helped us to probe how the structural parameters, such as bond distance, bond angle and especially Jahn-Teller dihedral angle affect the magnetic behaviour. Among the twelve complexes, we found ferromagnetic coupling for five and antiferromagnetic coupling for seven. DFT computed the J and ab initio methods computed the D parameter, and are in general agreement with the experimentally determined values. The dihedral angle between the two Jahn-Teller axes of the constituent MnIII ions are found to play a key role in determining the sign of the magnetic coupling. Magneto-structural correlations are developed by varying the Mn-O distance and the Mn-O-Mn angle to understand how the magnetic coupling changes upon these structural changes. Among the developed correlations, the Mn-O distance is found to be the most sensitive parameter that switches the sign of the magnetic coupling from negative to positive. The single-ion zero-field splitting of the MnIII centres is found to be negative for complexes 1-11 and positive for complex 12. However, the zero-field splitting of the S = 4 state for the ferromagnetic coupled dimers is found to be positive, revealing a significant contribution from the exchange anisotropy - a parameter which has long been ignored as being too small to be effective.

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Low-temperature structural and magnetic characterization of the chromium(III) dimers bis(.mu.-hydroxo)bis[tetraamminechromium(III)] dithionate tetrahydrate and bis(.mu.-hydroxo)bis[tetraamminechromium(III)] chloride tetrahydrate, [Cr(NH3)4OH]2(S2O6)2.4H2O and [Cr(NH3)4OH]2Cl4.4H2O

Abstract: An roten Kristallen der beiden Komplexe wurden u.a. durch Weissenberg‐Aufnahmen bei 90 K für das Dithionat die Raumgruppe Pbcades orthorhombischen Systems mit Z=4 und für das Chlorid P21/n, monoklin, Z=2 ermittelt.

Cited by 30 publications

References 0 publications

Introduction to Magnetic Exchange: Dimers and Clusters

Introduction to Magnetic Exchange: Dimers and Clusters

Synthesis and characterization of the alkoxo-bridged chromium(III) dimer bis(.mu.-methoxo)bis[bis(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III)]

Rationalizing the sign and magnitude of the magnetic coupling and anisotropy in dinuclear manganese(iii) complexes

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