Shufang Xue

Equatorially Coordinated Lanthanide Single Ion Magnets

The magnetic relaxation dynamics of low-coordinate Dy(III) and Er(III) complexes, namely three-coordinate ones with an equatorially coordinated triangle geometry and five-coordinate ones with a trigonal bipyramidal geometry, have been exploited for the first time. The three-coordinate Er-based complex is the first equatorially coordinated mononuclear Er-based single-molecule magnet (SMM) corroborating that simple models can effectively direct the design of target SMMs incorporating 4f-elements.

Modulating magnetic dynamics of three Dy2 complexes through keto-enol tautomerism of the o-vanillin picolinoylhydrazone ligand.

Complexation of dysprosium(III) with the heterodonor chelating ligand o-vanillin picolinoylhydrazone (H(2)ovph) in the presence of different bases affords three new dinuclear dysprosium(III) coordination compounds, namely, [Dy(2)(ovph)(2)(NO(3))(2)(H(2)O)(2)]·2H(2)O (1), [Dy(2)(Hovph)(ovph)(NO(3))(2)(H(2)O)(4)]·NO(3)·2CH(3)OH·3H(2)O (2), and Na[Dy(2)(Hovph)(2)(μ(2)-OH)(OH)(H(2)O)(5)]·3Cl·3H(2)O (3), where the aroylhydrazone ligand adopts different coordination modes in respective structures depending on the reaction conditions, as revealed by single-crystal X-ray analyses to be due to their tautomeric maneuver. The magnetic properties of 1-3 are drastically distinct. Compounds 1 and 2 show single-molecule-magnet behavior, while no out-of-phase alternating-current signal is noticed for 3. The structural differences induced by the different coordinate fashions of the ligand may influence the strength of the local crystal field, the magnetic interactions between metal centers, and the local tensor of anisotropy on each Dy site and their relative orientations, therefore generating dissimilar dynamic magnetic behavior.

Magnetic Properties of Dysprosium Cubanes Dictated by the M−O−M Angles of the [Dy4(μ3-OH)4] Core

Two new dysprosium(III) coordination compounds, namely, [Dy(4)(HL)(4)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(4)(mu-OH)(2)(H(2)O)(4)].4CH(3)CN.12H(2)O (1) and Dy(8)(HL)(10)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(8)(OH)(2)(NO(3))(2)(H(2)O)(4)] (2), have been synthesized from the Schiff-base ligand 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid (H(2)L) and dysprosium chloride (1) or dysprosium nitrate (2). Single-crystal X-ray diffraction studies reveal that compound 1 exhibits a tetranuclear cubane-like structure and that 2 is an octanuclear, bis-cubane complex. The [Dy(4)(mu (3)-OH)(4)] cubane cores of 1 and 2 are structurally related; however, the magnetic properties of 1 and 2 are drastically different. Indeed, 2 shows slow relaxation of magnetization while no out-of-phase alternating current (ac) signal is noticed for 1. These significant disparities are most likely due to the different M-O-M angles observed for the respective cubane cores.

A dodecanuclear dysprosium wheel assembled by six vertex-sharing Dy3 triangles exhibiting slow magnetic relaxation.

Reactions of lanthanide(III) (Ln(III)) perchlorate (Ln = Dy and Ho) and a polydentate Schiff base resulted in the unprecedented assembly of novel Ln(12) wheels containing six vertex-sharing Ln(3) triangles. The Dy(12) derivative represents the largest lanthanide wheel based on the peculiar Dy(3) triangles showing slow magnetic relaxation.

Modulating Magnetic Dynamics of Dy2 System through the Coordination Geometry and Magnetic Interaction

Two new dinuclear dysprosium compounds, [Dy2(HL1)2(PhCOO)2(CH3OH)2] (1) and [Dy2(L2)2(NO3)2(CH3OH)2]·2CH3OH·4H2O (2), have been assembled through applying two ligands with different coordination pockets. The different features of ligands H3L1 and H2L2 result in the distinct coordination geometry of the metal ions in their respective structures. The Dy ions of complexes 1 and 2 were linked by the alkoxide- and hydrazone-O, and display the hula hoop-like and the broken hula hoop-like coordination geometry, respectively. Consequently, these two compounds show distinct magnetic properties. Complex 1 behaves as a single molecule magnet (SMM) with rather slow quantum tunneling rate (τ > 274 ms), while no SMM behavior was observed for complex 2. In addition, the comparison of the structural parameters among the similar Dy2 SMMs with hula hoop-like geometry reveals the significant role played by coordination geometry and magnetic interaction in modulating the relaxation dynamics of SMMs.

Two Bulky-Decorated Triangular Dysprosium Aggregates Conserving Vortex-Spin Structure

The self-assembly of dysprosium(III) with the tailored chemical modification of the vanillin group affords two decorated Dy(3) compounds, namely, [Dy(3)(μ(3)-OH)(2)(Hpovh(-))(3)(NO(3))(3)(CH(3)OH)(2)H(2)O]·NO(3)·3CH(3)OH·2H(2)O (2) and [Dy(3)(μ(3)-OH)(2)(H(2)vovh(-))(3)Cl(2)(CH(3)OH)(H(2)O)(3)][Dy(3)(μ(3)-OH)(2)(H(2)vovh(-))(3)Cl(2)(H(2)O)(4)]·Cl(4)·2CH(3)OH·2CH(3)CN·7H(2)O (3), where H(2)povh = N-(pyridylmethylene)-o-vanilloylhydrazone and H(3)vovh = N-vanillidene-o-vanilloylhydrazone. Of particular interest is that those two title Dy(3) compounds maintain the peculiar vortex-spin structure of the ground nonmagnetic doublet. Complex 2 displays frequency-dependent slow magnetic relaxation, while 3 still inherits the single-molecule-magnet behavior as the parent Dy(3) prototype. The dissimilar dynamic magnetic behavior originates from the structural differences in light of the coordination environment of Dy(III) ions, which influence the local tensor of anisotropy and crystal-field splitting on each Dy site.

The use of a versatile o-vanilloyl hydrazone ligand to prepare SMM-like Dy3 molecular cluster pair

A novel lanthanide molecular cluster pair (MCP), displaying single molecule magnet behaviour, was assembled using the novel o-vanilloyl hydrazone ligand, versatile in terms of denticity, tautomerism and the rotatable C-C bond.

Molecular Magnetic Investigation of a Family of Octanuclear [Cu(6)Ln(2)] Nanoclusters

Reaction of in situ prepared acylhydrazone ligand with Ln(NO3)3·6H2O and Cu(OAc)2·H2O resulted in the formation of novel isostructural octanuclear Cu6Ln2 compounds (Ln = Dy (1), Tb (2), Gd (3), Y (4)) with an unprecedented octametallic structure, which can be described as an oblate wheel built up from two structurally similar Cu3 fragments linked together by two nodelike mononuclear lanthanide units. A detailed magnetic analysis reveals that the strong antiferromagnetic Cu···Cu interactions via the Cu-N-N-Cu-N-N-Cu linkage and the anticipated ferromagnetic Cu···Gd coupling makes an overall high-spin ground state in favor of the observation of significant magnetic caloric and SMM-like properties in the isotropic and anisotropic derivatives.

A Linear 3d–4f Tetranuclear CoIII2DyIII2 Single-Molecule Magnet: Synthesis, Structure, and Magnetic Properties

A linear tetranuclear 3d-4f Co(2) Dy(2) cluster assembled from a polydentate Schiff base exhibits single-molecule magnet (SMM) behavior with an anisotropic barrier of 33.8 K. Due to the presence of diamagnetic cobalt(III) ions, the tetranuclear cluster of 1 behaves magnetically like a dinuclear Dy(2) system. However, the diamagnetic segment might efficiently minimize undesirable intermolecular magnetic interactions, thereby improving the performance of the SMM behavior of 1. This discrete complex presents us with a unique opportunity to study the magnetic properties and to probe the dynamics of magnetization in a magnetically isolated Dy(2) system.

Field-Induced Multiple Relaxation Mechanism of (Co2DyIII)-Dy-III Compound with the Dysprosium Ion in a Low-Symmetrical Environment

A defective cubane-shaped heterometallic trinuclear Co(III)2Dy(III) compound with only one magnetically interesting ion (Dy(III)) has been assembled by virtue of a multifunctional acylhydrazone ligand. Because of the nonaxial ground state of Dy(III) ion derived from a low-symmetrical crystal field, the title compound displays field-induced multiple relaxation processes which are of molecular and a dipolar-dipolar coupling origin, as revealed by combined experimental and theoretical investigations. The results demonstrate that such a mononuclear dysprosium(III) compound with a low-symmetrical environment of magnetic center appears to be a model system for further investigations to shed light on the complex relaxation mechanism of lanthanide-based single ion magnets.