Coupling Dy<sub>3</sub> Triangles to Maximize the Toroidal Moment

Lin, Shuang‐Yan; Wernsdorfer, Wolfgang; Ungur, Liviu; Powell, Annie K.; Guo, Yun‐Nan; Tang, Jinkui; Zhao, Lang; Chibotaru, Liviu F.; Zhang, Hongjie

doi:10.1002/anie.201206602

Cited by 212 publications

(74 citation statements)

References 46 publications

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“…[7b, 36] This is rather clearly visible in the magnetization data measured at T = 2K,a nd similar to the toroidal moments observed in other Dy structures, such as the Dy 6 wheel,D y 3 triangles, and Dy 4 butterfly complexes. [8,33,[36][37] Analysis of the structural detailsofcomplex 1 indicatesthat it possesses a pseudoC 4 axis of symmetry.…”

Section: Exchange-coupled Moleculementioning

confidence: 99%

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares

Das

Vaidya

Gupta

et al. 2015

Chemistry A European J

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Three cationic [Ln4 ] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy4 (μ4 -OH)(HL)(H2 L)3 (H2 O)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)8 (1), [Tb4 (μ4 -OH)(HL)(H2 L)3 (MeOH)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)4 (2) and [Gd4 (μ4 -OH)(HL)(H2 L)3 (H2 O)2 (MeOH)2 ]Br2 ⋅(CH3 OH)4 ⋅(H2 O)3 (3). The structures are described as hydroxo-centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H2 L(2-) ligand. Alternating current magnetic susceptibility measurements show frequency-dependent out-of-phase signals with two different thermally assisted relaxation processes for 1, whereas no maxima in χM " appears above 2.0 K for complex 2. For 1, the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J1 =+0.01 and J2 =-0.01 cm(-1) for 1 as the two distinct exchange interactions between the Dy(III) ions. Similar parameters are also obtained for complex 1 (and 2) from specific heat measurements. A very weak antiferromagnetic super-exchange interaction (J1 =-0.043 cm(-1) and g=1.99) is observed between the metal centers in 3. The magnetocaloric effect (MCE) was estimated by using field-dependent magnetization and temperature-dependent heat-capacity measurements. An excellent agreement is found for the -ΔSm values extracted from these two measurements for all three complexes. As expected, 3 shows the largest -ΔSm variation (23 J Kg(-1) K(-1) ) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super-exchange interaction facilitates dense population of low-lying excited states, all of which are likely to contribute to the MCE, making complex 3 an attractive candidate for cryogenic refrigeration.

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Section: Exchange-coupled Moleculementioning

confidence: 99%

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares

Das

Vaidya

Gupta

et al. 2015

Chemistry A European J

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“…1–3 The magnetic bistability is essentially controlled by an energy barrier to spin reversal. The value of the energy barrier effectively defines the temperature range over which the magnetization of a SMM is blocked.…”

Section: Introductionmentioning

confidence: 99%

Rational enhancement of the energy barrier of bis(tetrapyrrole) dysprosium SMMs via replacing atom of porphyrin core

et al. 2015

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“…In contrast to the above Dy 6 SMMs, our group constructed a novel Dy 6 molecule coupling two Dy 3 units in an edge-to-edge fashion through a Schiff base ligand with two −OH arms, which provide alkoxide bridges between Dy centers [22]. As shown in Fig.…”

Section: Coupled Dy 3 -Smts Systemsmentioning

confidence: 99%

Single-Molecule Toroics and Multinuclear Lanthanide Single-Molecule Magnets

Tang

Zhang

2015

Lanthanide Single Molecule Magnets

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In this chapter, we first give a clear definition for single-molecule toroic (SMT) on the basis of the toroidal magnetic moments of ground doublets present in triangular Dy 3 SMMs, which is further exemplified via several typical Dy-based single-molecular magnets (SMMs) showing toroidal magnetic moments. Secondly, we examine the typical polynuclear lanthanide complexes showing SMM behavior, and three main synthetic strategies are given as follows: building block approach, organometallic approach, and multidentate ligand approach. The information extracted from such investigation is expected to enhance our understanding to SMM performances of polynuclear lanthanide complexes and facilitate their future applications.Keywords Single-molecule toroic · Toroidal magnetic moments · Building block · Organometallic approach · Multidentate ligand As mentioned in last two chapters, although the mono-and dinuclear lanthanide complexes have exhibited great achievements in obtaining strongly blocked SMMs due to the strong magnetic anisotropy of lanthanide ions, the limited spin centers in the complexes appear still to prevent the further enhancement of their singlemolecular magnet (SMM) properties due to the limited number of unpaired electrons [1]. Theoretically speaking, the more the spin centers in one metal cluster, the larger spin ground state can be achieved when the ferromagnetic coupling interactions are present in the cluster. Nevertheless, it needs an accurate control for the magnetic anisotropy of each metal center and the magnetic exchange interactions between the metal ions, which seems to be a very challenging task. In particular, it turns to be more difficult for multinuclear lanthanide complexes because the core 4f orbital shielded by the external electrons usually leads to extremely strong magnetic anisotropy of lanthanide ions but poor communication with other metal ions. However, considerable effort of researchers has been devoted to this field, and some groundbreaking results were achieved in this respect. Importantly, the

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Coupling Dy₃ Triangles to Maximize the Toroidal Moment

Cited by 212 publications

References 46 publications

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares

Rational enhancement of the energy barrier of bis(tetrapyrrole) dysprosium SMMs via replacing atom of porphyrin core

Single-Molecule Toroics and Multinuclear Lanthanide Single-Molecule Magnets

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Coupling Dy3 Triangles to Maximize the Toroidal Moment

Cited by 212 publications

References 46 publications

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln4 Squares

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln4 Squares

Rational enhancement of the energy barrier of bis(tetrapyrrole) dysprosium SMMs via replacing atom of porphyrin core

Single-Molecule Toroics and Multinuclear Lanthanide Single-Molecule Magnets

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Coupling Dy₃ Triangles to Maximize the Toroidal Moment

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares

Single‐Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln₄ Squares