A Ferromagnetic Mixed‐Valent Mn Supertetrahedron: Towards Low‐Temperature Magnetic Refrigeration with Molecular Clusters

Manoli, Maria; Johnstone, Russell D. L.; Parsons, Simon; Murrie, Mark; Affronte, Marco; Evangelisti, Marco; Brechin, Euan K.

doi:10.1002/ange.200701027

Cited by 54 publications

(19 citation statements)

References 26 publications

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“…The lack of anisotropy is most likely due to the highly symmetric structure which facilitates to cancel out the anisotropy contributions mainly from JT distortions of the Mn III ions. A similar compound with different ligand has been reported in the recent past by Brechin et al [14] [Mn III 11 Mn II (2): The room-temperature value of the magnetic susceptibility and temperature product cT of 61.0 cm 3 K mol À1 (Figure 4 c) is slightly higher than the expected value of 59.25 cm 3 K mol À1 for six Mn II and eleven Mn III ions, indicating dominating ferromagnetic interactions between the manganese ions. The decrease of the cT product below 11 K suggests that additional effects, such as intermolecular antiferromagnetic interactions, are present between the cluster units.…”

Section: Resultssupporting

confidence: 72%

“…However, it was soon realised that there could be an enormous benefit to having high spin molecules with minimal anisotropy, since these could be used for magnetic refrigeration. [11][12][13][14] The concept of magnetic refrigeration is based on the magnetocaloric effect, hereafter MCE. Briefly it can be defined as the magnetic entropy change, and related adiabatic temperature change, due to varying magnetic field.…”

Section: Introductionmentioning

confidence: 99%

“…In all cases the supertetrahedral Mn 10 units display ferromagnetic cooperative coupling, but vanishing anisotropy as a result of the octahedral arrangement of the Mn III centres. [3,4,13,14,16] We therefore decided to study the magnetocaloric properties in detail of the three high-spin manganese clusters 6 ]Cl 2 ·10 MeOH·MeCN (3; with the record ground-spin state of S = 83/2). [17,18]…”

Section: Introductionmentioning

confidence: 99%

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Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Nayak

Evangelisti

Powell

et al. 2010

Chemistry A European J

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Three high-nuclearity mixed valence manganese(II/III) coordination clusters, have been synthesised, that is, [Mn(III) (6)Mn(II) (4)(μ(3)-O)(4)(HL(1))(6)(μ(3)-N(3))(3)(μ(3)-Br)(Br)](N(3))(0.7)/(Br)(0.3)⋅3 MeCN⋅2 MeOH (1) (H(3)L(1)=3-methylpentan-1,3,5-triol), [Mn(III) (11)Mn(II) (6)(μ(4)-O)(8)(μ(3)-Cl)(4)(μ,μ(3)-O(2)CMe)(2)(μ,μ-L(2))(10)Cl(2.34)(O(2)CMe)(0.66)(py)(3)(MeCN)(2)]⋅7 MeCN (2) (H(2)L(2)=2,2-dimethyl-1,3-propanediol and py is pyridine), and [Mn(III) (12)Mn(II) (7)(μ(4)-O)(8)(μ(3)-η(1)N(3))(8)(HL(3))(12)(MeCN)(6)]Cl(2)⋅10 MeOH ⋅MeCN (3) (H(3)L(3)=2,6-bis(hydroxymethyl)-4-methylphenol) with high ground-spin states, S=22, 28±1, and 83/2, respectively; their magnetothermal properties have been studied. The three compounds are based on a common supertetrahedral building block as seen in the Mn(10) cluster. This fundamental magnetic unit is made up of a tetrahedron of Mn(II) ions with six Mn(III) ions placed midway along each edge giving an inscribed octahedron. Thus, the fundamental building unit as represented by compound 1 can be described as a Mn(10) supertetrahedron. Compounds 2 and 3 correspond to two such units joined by a common edge or vertex, respectively, resulting in Mn(17) and Mn(19) coordination clusters. Magnetothermal studies reveal that all three compounds show interesting long-range magnetic ordering at low temperature, originating from negligible magnetic anisotropy of the compounds; compound 2 shows the largest magnetocaloric effect among the three compounds. This is as expected and can be attributed to the presence of a small magnetic anisotropy, and low-lying excited states in compound 2.

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Section: Resultssupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Nayak

Evangelisti

Powell

et al. 2010

Chemistry A European J

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“….0 Hz, 24H, H 9 ), 0.77 (d, 3 J8,10 7.0 Hz, 24H, H 10 ). 13 C{ 1 H} NMR (100.6 MHz, 25 °C, CD2Cl2): δ = 187.1 (C 7 ), 161.0 ( Ar) 147.7 (Ar), 140.5 ( Ar), 123.8 (Ar), 122.2 (Ar), 63.6 (C 1 ), 36.5 ( C 8 ), 19.6, 19.4 (C 8,9 ) ppm. See figure 7 for NMR numbering scheme.…”

Section: Mass Spectrometrymentioning

confidence: 99%

Structurally Flexible and Solution Stable [Ln₄TM₈(OH)₈(L)₈(O₂CR)₈(MeOH)_y](ClO₄)₄: A Playground for Magnetic Refrigeration

et al. 2016

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The family of compounds of general formula [LnTM(OH)(L)(OCR)(MeOH)](ClO) {[GdZn(OH)(hmp)(OCPr)](ClO) (1a); [YZn(OH)(hmp)(OCPr)](ClO) (1b); [GdCu(OH)(hmp)(OCPr)](ClO) (2a); [YCu(OH)(hmp)(OCPr)](ClO) (2b); [GdCu(OH)(hep)(OCPr)](ClO) (3a); [GdCu(OH)(Hpdm)(OCBu)](ClO) (4a); [GdCu(OH)(ea)(OCMe)](ClO) (5a); [GdNi(OH)(hmp)(OCEt)(MeOH)](ClO) (6a); [YNi(OH)(hmp)(OCEt)(MeOH)](ClO) (6b); [GdCo(OH)(hmp)(OCEt)(MeOH)](ClO) (7a); [YCo(OH)(hmp)(OCEt)(MeOH)](ClO) (7b)} can be formed very simply and in high yields from the reaction of Ln(NO)·6HO and TM(ClO)·6HO and the appropriate ligand blend in a mixture of CHCl and MeOH in the presence of a suitable base. Remarkably, almost all the constituent parts, namely the lanthanide (or rare earth) ions Ln (here Ln = Gd or Y), the transition metal ions TM (here TM = Zn, Cu, Ni, Co), the bridging ligand L (Hhmp = 2-(hydroxymethyl)pyridine; Hhep = 2-(hydroxyethyl)pyridine; Hpdm = pyridine-2,6-dimethanol; Hea = 2-ethanolamine), and the carboxylates can be exchanged while maintaining the structural integrity of the molecule. NMR spectroscopy of diamagnetic complex 1b reveals the complex to be fully intact in solution with all signals from the hydroxide, ligand L, and the carboxylates equivalent on the NMR time scale, suggesting the complex possesses greater symmetry in solution than in the solid state. High resolution nano-ESI mass spectrometry on dichloromethane solutions of 2a and 2b shows both complexes are present in two charge states with little fragmentation; with the most intense peak in each spectrum corresponding to [LnCu(OH)(hmp)(OCPr)](ClO). This family of compounds offers an excellent playground for probing how the magnetocaloric effect evolves by introducing either antiferromagnetic or ferromagnetic interactions, or magnetic anisotropy, by substituting the nonmagnetic Zn (1a) with Cu (2a), Ni (6a) or Co (7a), respectively. The largest magnetocaloric effect is found for the ferromagnetically coupled complex 6a, while the predominant antiferromagnetic interactions in 2a yield an inverse magnetocaloric effect; that is, the temperature increases on lowering the applied field, under the proper experimental conditions. In spite of increasing the magnetic density by adding ions that bring in antiferromagnetic interactions (2a) or magnetic anisotropy (7a), the magnetocaloric effect is overall smaller in 2a and 7a than in 1a, where only four Gd spins per molecule contribute to the magnetocaloric properties.

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“…In spite of their simplicity, they have drawn considerable interest [4][5][6], mainly due to their potential applications in data storage, quantum computing, molecule-based spintronics devices, as well as magnetic cooling technology. The last one is related to their ability to display a very large magnetocaloric effect (MCE) at low temperatures [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters

Mohylna

Žukovič

2020

Magnetochemistry

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Effects of a single-ion anisotropy on magnetocaloric properties of selected spin-s≥1 antiferromagnetic Ising clusters with frustration-inducing triangular geometry are studied by exact enumeration. It is found that inclusion of the single-ion anisotropy parameter D can result in a much more complex ground-state behavior, which is also reflected in a magnetocaloric effect (MCE) at finite temperatures. For negative D (easy-plane anisotropy) with increasing s, the ground-state magnetization as a function of the external field gradually shows increasing number of plateaus of various heights. Except for the cases of integer s with D<D0≤0, the first magnetization plateau is of non-zero height. This property facilitates an enhanced MCE in the adiabatic demagnetization process in the form of an abrupt decrease in temperature as the magnetic field vanishes to zero. The cooling rate can be considerably enhanced in the systems with larger s and D>0 (easy-axis anisotropy), albeit its dependence on these parameters is strongly dependent on the cluster geometry. From the studied systems more favorable conditions for observing a giant MCE were found in the 2CS cluster, consisting of two corner-sharing tetrahedra, the experimental realization of which could be technologically used for efficient refrigeration to ultra-low temperatures.

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A Ferromagnetic Mixed‐Valent Mn Supertetrahedron: Towards Low‐Temperature Magnetic Refrigeration with Molecular Clusters

Cited by 54 publications

References 26 publications

Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Structurally Flexible and Solution Stable [Ln₄TM₈(OH)₈(L)₈(O₂CR)₈(MeOH)_y](ClO₄)₄: A Playground for Magnetic Refrigeration

Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters

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A Ferromagnetic Mixed‐Valent Mn Supertetrahedron: Towards Low‐Temperature Magnetic Refrigeration with Molecular Clusters

Cited by 54 publications

References 26 publications

Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {MnII4MnIII6} Supertetrahedral Units

Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {MnII4MnIII6} Supertetrahedral Units

Structurally Flexible and Solution Stable [Ln4TM8(OH)8(L)8(O2CR)8(MeOH)y](ClO4)4: A Playground for Magnetic Refrigeration

Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters

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Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn^II₄Mn^III₆} Supertetrahedral Units

Structurally Flexible and Solution Stable [Ln₄TM₈(OH)₈(L)₈(O₂CR)₈(MeOH)_y](ClO₄)₄: A Playground for Magnetic Refrigeration