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Octanuclear heterobimetallic {Ni4Ln4} assemblies possessing Ln4 square grid [2×2] motifs : synthesis, structure and magnetism

机译:具有Ln4方格[2×2]图案的八核异双金属{Ni4Ln4}组件:合成,结构和磁性

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摘要

Octanuclear heterobimetallic complexes, [Ln4Ni4(H3L)4(µ3-OH)4(µ2-OH)4]4Cl·xH2O·yCHCl3 (Dy3+ , x = 30.6, y = 2 (1); Tb3+ , x = 28, y = 0 (2) ; Gd3+ , x = 25.3, y = 0 (3); Ho3+ , x = 30.6, y = 3 (4)) (H5L = N1, N3-bis(6-formyl-2-(hydroxymethyl)\ud-4-methylphenol) diethylenetriamine) are reported. These are assembled by the cumulative coordination action of four doubly deprotonated compartmental ligands, [H3L] 2- , along with eight exogenous –OH ligands. Within the core of these complexes, four Ln3+ are distributed to the four corners of a perfect square grid while four Ni2+ are projected away from the plane of the Ln4 unit. Each of the four Ni2+ possesses distorted octahedral geometry while all the Ln3+ are crystallographically equivalent and are present in an elongated square antiprism geometry. The magnetic properties of compound 3 are dominated by an easy-plane single-ion anisotropy of the Ni2+ ions [DNi = 6.7(7) K] and dipolar interactions between Gd3+ centers. Detailed ac magnetometry reveals the presence of distinct temperature-dependent out-of-phase signals for compounds 1 and 2, indicative of slow magnetic relaxation. Magnetochemical analysis of complex 1 implies the 3d and the 4f metal ions are engaged in ferromagnetic interactions with SMM behavior, while dc magnetometry of compound 2 is suggestive of an antiferromagnetic Ni-Tb spin-exchange with slow magnetic relaxation due to a field-induced level crossing. Compound 4 exhibits an easy-plane single-ion anisotropy for the Ho3+ ions and weak interactions between spin centers. \ud
机译:八核杂双金属配合物[Ln4Ni4(H3L)4(µ3-OH)4(µ2-OH)4] 4Cl·xH2O·yCHCl3(Dy3 +,x = 30.6,y = 2(1); Tb3 +,x = 28,y = 0(2); Gd3 +,x = 25.3,y = 0(3); Ho3 +,x = 30.6,y = 3(4))(H5L = N1,N3-双(6-甲酰基-2-(羟甲基))\报道了ud-4-甲基苯酚二亚乙基三胺)。这些是通过四个双去质子化的区室配体[H3L] 2-和八个外源性-OH配体的累积配位作用组装而成的。在这些配合物的核心内,四个Ln3 +分布到一个完美正方形网格的四个角,而四个Ni2 +则远离Ln4单元的平面投影。四个Ni2 +的每一个都具有扭曲的八面体几何形状,而所有Ln3 +的晶体学均等价且以细长的方形反棱镜几何形状存在。化合物3的磁性主要由Ni2 +离子的易平面单离子各向异性[DNi = 6.7(7)K]和Gd3 +中心之间的偶极相互作用决定。详细的交流磁强法揭示了化合物1和2存在明显的随温度变化的异相信号,表明磁弛豫缓慢。配合物1的磁化学分析表明3d和4f金属离子参与了具有SMM行为的铁磁相互作用,而化合物2的dc磁力分析表明,由于场致能级,反铁磁Ni-Tb自旋交换具有缓慢的磁弛豫穿越。化合物4对Ho3 +离子表现出易平面的单离子各向异性,并且自旋中心之间的相互作用较弱。 \ ud

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