Hongshan Ke

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 Dy10 Cluster Incorporates Two Sets of Vertex‐Sharing Dy3 Triangles

The study of paramagnetic metal-ion aggregates has been of increasing interest in the last three decades or so, mainly stimulated by rapid development of molecular magnetism. An area of particular interest is the investigation of single molecule magnets (SMMs) for which slow relaxation and quantum tunnelling of the magnetization is purely of molecular origin. This has led to intense activity to be able to consistently manufacture molecular structures with a finite number of interacting magnetic centres suitable for detailed magnetic study. Indeed, since the discovery in the early 1990s of the first single molecule magnet, Mn12 acetate, [2,3] a large number of compounds displaying these magnetic properties have been reported. Most of them, especially in the early years, contain only 3d ions. However, despite the large number of new molecules, no significant increase has been achieved in the blocking temperature. Recently, particular emphasis has been placed on the design of new single molecule magnets either incorporating, or made exclusively from 4f metal ions given that lanthanide ions can produce fascinating magnetic behaviour, not only through their potential to contribute high spins, but also to introduce anisotropy to a molecule as a result of the nature of the felectron shell. This magnetic anisotropy is the major component to observe the slow relaxation of the magnetization and gives the complexes by essentially different mechanism from that of the well-established 3d-based SMMs. Compared to the 3d metal SMMs, far fewer pure 4f metal SMMs have been reported. A peculiar triangular Dy cluster has attracted much interest, owing to the unusual slow relaxation behaviour in spite of the almost non-magnetic ground state. This intriguing behaviour originates from the non-collinearity of the single ion easy axes of magnetization of the Dy ions, as demonstrated by single crystal magnetic studies, as well as ab initio calculations. This peculiar chiral nature of the ground non-magnetic doublet and the resonant quantum tunnelling of the magnetization at the crossings of the discrete energy levels opens new perspectives in quantum computation and data storage in molecular nanomagnets, and thus can stimulate further investigation towards utilizing this highly anisotropic Dy3 triangle for creating novel SMMs with large blocking temperatures. We present here the constructing of Dy10 cluster of formula [Dy10ACHTUNGTRENNUNG(m3-OH)4 ACHTUNGTRENNUNG(OAc)20 ACHTUNGTRENNUNG(H2L)2ACHTUNGTRENNUNG(H3L)2ACHTUNGTRENNUNG{NH2C ACHTUNGTRENNUNG(CH2OH)3}2] with four fused Dy3 triangles by using polydentate Schiff base 2-[{(2-hydroxy-3-methoxyphenyl)methylene}amino]-2(hydroxymethyl)-1,3-propanediol (H4L). This potentially hexadentate ligand combines a tripodal group and a Schiff base group, and has previously been successfully employed to prepare 3d and 3d-4f polynuclear clusters. The reaction of dysprosium acetate with H4L in the mixture of methanol and acetonitrile in 1:4 ratio produces the Dy10 cluster of formula [Dy10ACHTUNGTRENNUNG(m3-OH)4ACHTUNGTRENNUNG(OAc)20ACHTUNGTRENNUNG(H2L)2ACHTUNGTRENNUNG(H3L)2ACHTUNGTRENNUNG{NH2C ACHTUNGTRENNUNG(CH2OH)3}2] (1), whose molecular structure determined by single-crystal X-ray diffraction is depicted in Figure 1. This neutral molecule contains four m3-OH capped triangles held together by acetate groups. Two Dy triangles are fused in a vertex-sharing fashion forming a {Dy5ACHTUNGTRENNUNG(m3OH)2} 13+ subcore. The single m3-OH capped triangle in 1 is less equilateral than that of the previously reported double m3-OH capped triangles, [12] with Dy···Dy distances 3.753, 3.788 and 3.882 for triangle A (Dy1Dy2Dy3) and 3.623, 3.870 and 3.935 for triangle B (Dy3Dy4Dy5) respectively. The dihedral angle between the two triangles A and B is 81.418. Two {Dy5 ACHTUNGTRENNUNG(m3-OH)2}13+ subcores are further linked through double acetate bridges into the Dy10 core, which is further encapsulated by four Schiff bases and two tris(hy[a] H. Ke, Dr. G.-F. Xu, Dr. L. Zhao, Prof. Dr. J. Tang, Prof. Dr. H.-J. Zhang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences Renmin Street 5625, Changchun 130022 (P.R. China) Fax: (+86)431-85262878 E-mail : tang@ciac.jl.cn hongjie@ciac.jl.cn [b] H. Ke, X.-Y. Zhang School of Material Science and Engineering Changchun University of Science and Technology Changchun 130022 (P.R. China)

Syntheses, structures, and magnetic analyses of a family of heterometallic hexanuclear [Ni4M2] (M = Gd, Dy, Y) compounds: observation of slow magnetic relaxation in the Dy(III) derivative.

We described the syntheses, crystal structures, and magnetic behavior of a novel series of heterometallic [Ni(4)M(2)] [M = Gd (1), Dy (2) and Y (3)] hexanuclear compounds afforded by the reaction of rare-earth(III) nitrate, nickel(II) acetate, and Schiff-base ligand 2-(2-hydroxy-3-methoxybenzylideneamino)phenol (H(2)L) in a mixture of ethanol and dichloromethane in the presence of triethylamine. Single-crystal X-ray diffraction measurements reveal that all three compounds have a metal core made up of two Ni(2)MO(4) defective cubanes. The magnetic properties of all compounds have been studied. Solid-state direct-current magnetic susceptibility analyses demonstrate competing antiferromagnetic and ferromagnetic interactions within both compounds 1 and 3. Solid-state alternating-current magnetic susceptibility investigations show a frequency-dependent out-of-phase signal for compound 2 below 4 K, suggestive of slow magnetic relaxation.

Macrocyclic ligand encapsulating dysprosium triangles: axial ligands perturbed magnetic dynamics

Two Dy(3) triangles encapsulated inside the cavity of a macrocycle ligand have been successfully synthesized, providing a unique opportunity to probe the relaxation dynamics of the complexes by altering the axial ligands.

Polydentate-ligand-supported self-assembly of heterometallic T-shaped Co4RE (RE=Gd, Tb, Y) clusters: synthesis, structure and magnetism

A series of mixed-valent heterometallic pentanuclear Co(III)(3)Co(II)RE(III) (RE = Gd (1), Tb (2), Y (3)) clusters have been rationally assembled by taking advantage of a bifunctional ligand with o-vanillin and tripodal tris(hydroxymethyl)aminomethane units. Structural determinations reveal that all compounds are isomorphous and possess a T-shaped Co(4)RE core, which comprises two nearly linear Co(2)RE subunits sharing a common RE ion. Their magnetic properties were thoroughly studied. The static magnetic susceptibility studies of 1 demonstrate the presence of weak ferromagnetic interactions between the magnetic centres and magnetic anisotropy reflected by the single ion zero-field splitting (ZFS) D term. Both 1 and 2 behave magnetically as heterodinuclear metal systems, while the magnetic behaviour of 3 is identical to an isolated Co(II) ion. Moreover, alternating-current susceptibility measurements did not exhibit any out-of-phase signal, suggesting that slow magnetic relaxation is absent above 2 K within them. These isomorphous Co(4)RE clusters offer an opportunity to systematically probe the contribution of different metal ions to the overall magnetic behaviour in Co(II)-RE(III) systems.

Synthesis, crystal structure, and magnetic properties of a phenoxo-bridged dinuclear nickel(II) complex

A new dinuclear nickel complex, [ (H1.5L)2](ClO4) · 2CH3OH · H2O (1) (H3L = 1,3-bis(salicylamino)-2-propanol), was synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, and magnetic measurements. In contrast to commonly observed alcoholic oxygen bridges in previously reported dinuclear complexes, single-crystal X-ray studies reveal that the H3L is highly distorted and links two NiII through the phenoxo oxygens of the ligands forming a [Ni2O2] core. The remarkable distortion of the ligand brings the two non-bridging phenol groups from different ligands close to share one hydrogen, keeping charge neutrality of the complex. Magnetic studies indicate that an overall antiferromagnetic interaction is operative between the metal centers.