Tetranuclear lanthanide (III) complexes containing dimeric subunits: single-molecule magnet behavior for the Dy4 analogue.
Tetranuclear lanthanide (III) complexes containing dimeric subunits: single-molecule magnet behavior for the Dy4 analogue.
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DOI：
10.1021/ic401652f
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发表时间：
2013-10
影响因子：
4.6
通讯作者：
V. Chandrasekhar;Sourav Das;Atanu Dey;Sakiat Hossain;J. Sutter
中科院分区：
文献类型：
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作者：
V. Chandrasekhar;Sourav Das;Atanu Dey;Sakiat Hossain;J. Sutter
镧系（III）盐[Dy(III), Tb(III), Gd(III)]与异给体螯合配体N'-（2-羟基-3-甲氧基苄基苄基）-6-（羟甲基）吡啶酰肼（LH3）和戊酸（PivH）在四正丁基氢氧化铵（TBAH）存在下反应得到四核Ln（III）配位化合物[Ln4(LH)2(LH2)2(μ2-η(1)η(1)Piv)2(η(1)Piv)4]·2CHCl3 [Ln = Dy(1), Tb(2), Gd(3)]。这些配合物的分子结构表明，这些四核衍生物是由两个双核亚基组成的，它们通过吡啶酰肼配体的配位作用相互连接。在每个亚基中存在两种不同类型的Ln（III）离子。其中一个是扭曲的三角形十二面体几何中的八坐标，而另一个是扭曲的球面覆盖方形反棱镜几何中的九坐标。复合物1的交流磁化率测量结果显示，在1kOe直流磁场下，复合物1存在频率和温度相关的两阶失相信号，这是单分子磁体（SMM）行为的特征。磁数据分析得到各向异性势垒和弛豫时间：Δ/kB = 62.6 K, τ0 = 8.7 × 10(-7) s；慢弛豫和快弛豫分别为Δ/kB = 26.3 K, τ0 = 1.26 × 10(-6) s。
The reaction of the lanthanide(III) salts [Dy(III), Tb(III), and Gd (III)] with a hetero donor chelating ligand N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide (LH3) and pivalic acid (PivH) in the presence of tetra-n-butylammonium hydroxide (TBAH) afforded the tetranuclear Ln(III) coordination compounds, [Ln4(LH)2(LH2)2(μ2-η(1)η(1)Piv)2(η(1)Piv)4]·2CHCl3 [Ln = Dy(1), Tb(2), and Gd(3)]. The molecular structure of these complexes reveals that the tetranuclear derivatives are composed of two dinuclear subunits which are interconnected through the coordination action of the picolinoyl hydrazine ligand. Within each subunit two different types of Ln(III) ions are present. One of these is eight-coordinate in a distorted triangular dodecahedral geometry while the other is nine-coordinate in a distorted spherical capped square antiprism geometry. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent two step out-of-phase signals under 1kOe DC field which is characteristic of a single-molecule magnet (SMM) behavior. Analysis of the magnetic data afforded the anisotropic barriers and relaxation times: Δ/kB = 62.6 K, τ0 = 8.7 × 10(-7) s; Δ/kB = 26.3 K, τ0 = 1.26 × 10(-6) s for the slow and fast relaxations respectively.