Department of Chemistry, Memorial University, St. John's, NL A1B 3X7, Canada.
Dalton Trans. 2013 Jun 7;42(21):7781-94. doi: 10.1039/c3dt32732a.
The lanthanide coordination chemistry of a tri-functional vanillin-hydrazone-oxime ligand reveals a variety of different products, depending on reaction conditions, with mono-nuclear (Dy), dinuclear (Yb, Tm), tetranuclear (Gd) and hexanuclear (Gd, Tb, Dy) examples. The Ln6 (Ln = Gd, Dy, Tb) complexes form in the presence of both triethylamine and acetic acid, and have unique, flat hexanuclear structures built on a μ3-O bridged triangular core, with the six lanthanide ions bridged further through μ-acetate and μ-Ohydrazone connections in an expanded fused triangular array. Similar reaction conditions with Yb(III) and Tm(III) lead preferentially to dinuclear systems, while in the presence of a competitive benzoate ligand a rectangular Gd4 complex results. Variable temperature DC magnetic data for the Gd(III) complexes reveal weak antiferromagnetic exchange. AC magnetic data on the other polynuclear complexes down to 2 K, both in the absence and presence of external bias fields, revealed no significant out of phase signals normally indicative of SMM behavior. However, the mononuclear Dy(III) complex shows frequency dependent AC signals and maxima in the temperature range 2-20 K in the presence of an external bias field, indicative of SMM behaviour, with Ueff = 36(1) K, and τ0 = 4.4(2) × 10(-6) s.
一种三功能香草醛-腙-肟配体的镧系配位化学揭示了多种不同的产物，具体取决于反应条件，包括单核（Dy）、双核（Yb、Tm）、四核（Gd）和六核（Gd、Tb、Dy）实例。在三乙胺和乙酸的存在下形成了 Ln6（Ln = Gd、Dy、Tb）配合物，具有独特的、扁平的六核结构，构建在一个μ3-O 桥接的三角形核心上，六个镧系离子通过μ-乙酸和μ-腙连接进一步桥接，形成扩展的融合三角形排列。类似的反应条件与 Yb（III）和 Tm（III）优先导致双核体系，而在竞争的苯甲酸盐配体存在下，则得到矩形 Gd4 配合物。Gd（III）配合物的变温直流磁数据显示出弱反铁磁交换。其他多核配合物在 2 K 以下的交流磁数据，无论是在没有还是存在外部偏置场的情况下，都没有显示出通常表明 SMM 行为的明显异相信号。然而，单核 Dy（III）配合物在存在外部偏置场的情况下，在 2-20 K 的温度范围内显示出频率相关的交流信号和最大值，表明存在 SMM 行为，有效场 Ueff = 36(1) K，τ0 = 4.4(2) × 10(-6) s。
