Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016 (India) http://www.iitk.ac.in.
Department of Emerging Materials Science, DGIST, Daegu 711-873 (Korea) http://www.dgist.ac.kr.
Chemistry. 2015 Nov 16;21(47):16955-67. doi: 10.1002/chem.201501992. Epub 2015 Sep 30.
The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln = Dy (1), Tb (2), and Gd (3)) and pentanuclear Ln5 complexes (Ln = Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1-6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff) = 16.12(8) K and relaxation time (τo) = 3.3×10(-5) s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: -ΔSm = 26.6 J kg(-1) K(-1) at T = 2.2 K for 3 and -ΔSm = 27.1 J kg(-1) K(-1) at T = 2.4 K for 4, both for an applied field change of 7 T.
希夫碱配体（LH3）与镧系盐、特戊酸和三乙胺以 1:1:1:3 和 4:5:8:20 的化学计量比反应，分别生成十核镧系元素 Ln10（Ln=Dy（1）、Tb（2）和 Gd（3））和五核镧系元素 Ln5 配合物（Ln=Gd（4）、Tb（5）和 Dy（6））。Ln10 和 Ln5 配合物的形成完全受所用试剂化学计量的控制。对这些配合物（1-6）进行了详细的磁性研究。配合物 1 表现出单分子磁体行为，其磁矩反转的有效能垒（Ueff）=16.12(8) K，在 4000 Oe 直流（dc）场下弛豫时间（τo）=3.3×10(-5) s。配合物 6 在零直流场下的反相信号中表现出频率相关的最大值，但在 2 K 以上未达到最大值。配合物 3 和 4 表现出较大的磁热效应，其特征值如下：对于 3，在 T = 2.2 K 时，磁场变化为 7 T，-ΔSm = 26.6 J kg(-1) K(-1)；对于 4，在 T = 2.4 K 时，-ΔSm = 27.1 J kg(-1) K(-1)。
