MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, 510275, PR China.
Dalton Trans. 2012 Feb 28;41(8):2320-9. doi: 10.1039/c1dt10869g. Epub 2011 Dec 21.
The syntheses, structural determinations and magnetic studies of tetranuclear M(II)Ln(III) complexes (M = Ni, Zn; Ln = Y, Gd, Dy) involving an in situ compartmentalized schiff base ligand HL derived from the condensation of o-vanillin and 2-hydrazinopyridine as main ligand are described. Single-crystal X-ray diffraction reveals that all complexes are closely isostructural, with the central core composed of distorted {M(2)Ln(2)O(4)} cubes of the formulas Ni(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(4)(H(2)O)(3.5)(2)·3H(2)O (Ln = Y 1 and Gd 2), Ni(2)Dy(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)(1.5)·EtOH·H(2)O (3) and Zn(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)·2EtOH·1.5H(2)O (Gd 4 and Dy 5). The Ln(III) ions are linked by two hydroxo bridges and each M(II) ion is also involved in a double phenoxo-hydroxo bridge with the two Ln(III) ions, so that each hydroxo group is triply linked to the two Ln(III) and one M(II) ions. The magnetic properties of all complexes have been investigated. Ni(2)Y(2) (1) has a ferromagnetic Ni(II)Ni(II) interaction. A weak ferromagnetic Ni(II)Ln(III) interaction is observed in the Ni(2)Ln(2) complexes (Ln = Gd 2, Dy 3), along with a weak antiferromagnetic Ln(III)Ln(III) interaction, a D zero-field splitting term for the nickel ion and a ferromagnetic Ni(II)Ni(II) interaction. The isomorphous Zn(2)Ln(2) (Ln = Gd 4, Dy 5) does confirm the presence of a weak antiferromagnetic Ln(III)Ln(III) interaction. The Ni(2)Dy(2) complex (3) does not behave as a SMM, which could result from a subtractive combination of the Dy and Ni anisotropies and an increased transverse anisotropy, leading to large tunnel splittings and quantum tunneling of magnetization. On the other hand, Zn(2)Dy(2) (5) exhibits a possible SMM behavior, where its slow relaxation of magnetization is probably attributed to the presence of the anisotropic Dy(III) ions.
四核 M(II)Ln(III)配合物（M = Ni，Zn；Ln = Y，Gd，Dy）的合成、结构测定和磁性研究，涉及原位分隔的希夫碱配体 HL，其由邻香草醛和 2-肼吡啶缩合而成，作为主要配体。单晶 X 射线衍射表明，所有配合物均具有紧密的同构结构，中心核由扭曲的{ M(2)Ln(2)O(4)}立方组成，化学式为Ni(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(4)(H(2)O)(3.5)(2)·3H(2)O（Ln = Y 1 和 Gd 2），Ni(2)Dy(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)(1.5)·EtOH·H(2)O（3）和Zn(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)·2EtOH·1.5H(2)O（Gd 4 和 Dy 5）。Ln(III)离子由两个羟桥连接，每个 M(II)离子也参与双酚氧-羟桥与两个 Ln(III)离子，使得每个羟桥基团三重连接到两个 Ln(III)和一个 M(II)离子。所有配合物的磁性性质都已得到研究。Ni(2)Y(2)（1）具有铁磁 Ni(II)Ni(II)相互作用。在 Ni(2)Ln(2)配合物（Ln = Gd 2，Dy 3）中观察到弱铁磁 Ni(II)Ln(III)相互作用，以及弱反铁磁 Ln(III)Ln(III)相互作用、镍离子的 D 零场分裂项和铁磁 Ni(II)Ni(II)相互作用。同构的 Zn(2)Ln(2)（Ln = Gd 4，Dy 5）确实证实了弱反铁磁 Ln(III)Ln(III)相互作用的存在。Ni(2)Dy(2)配合物（3）不表现为 SMM，这可能是由于 Dy 和 Ni 各向异性的相减组合以及横向各向异性的增加，导致较大的隧道分裂和磁化的量子隧道。另一方面，Zn(2)Dy(2)（5）表现出可能的 SMM 行为，其磁化的缓慢弛豫可能归因于各向异性 Dy(III)离子的存在。
