多齿席夫碱配体构筑的Ln^(Ⅲ)_(2)配合物的晶体结构及磁性

Crystal Structures and Magnetic Properties of Ln^(Ⅲ)_(2) Complexes Based on a Polydentate Schiff Base Ligand

使用多齿席夫碱配体,通过溶剂热法,设计与合成了3例新的稀土配合物[Ln_(2)(L)_(2)(acac)_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(Ln=Sm(1)、Gd(2)、Ho(3),H_(2)L=吡啶⁃2⁃羧酸⁃(1⁃甲基⁃3⁃氧代丁烯基)⁃酰肼),并对配合物1~3的结构与磁性质进行了系统的研究。单晶结构测试结果表明配合物1~3为同构,每个中心稀土Ln(Ⅲ)离子为八配位,其配位几何构型为扭曲的四方反棱柱;相邻的中心稀土Ln􀃮离子通过2个μ_(2)⁃O连接形成了平行四边形的[Ln_(2)O_(2)]核心。磁性测试揭示配合物2具有磁制冷性质,其最大磁熵变(-ΔS_(max))为31.9 J·K^(-1)·kg^(-1)(T=2.0 K,ΔH=70 kOe);配合物3表现出了慢磁驰豫行为。

Three new Ln^(Ⅲ)_(2) complexes based on a polydentate Schiff base ligand,namely[Ln_(2)(L)_(2)(acac)_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(Ln=Sm(1),Gd(2),Ho(3),H2L=pyridine⁃2⁃carboxylic acid(1⁃methyl⁃3⁃oxo⁃butylidene)⁃hydrazide,Hacac=acetylacetone),have been synthesized by using solvothermal method.The crystal structures and magnetic proper⁃ties of these complexes have been systematically studied.The crystal structures measurement results reveal that complexes 1⁃3 are isostructural and each eight⁃coordinated Ln(Ⅲ)ion possesses a square antiprism geometry;the adjacent central rare earth Ln(Ⅲ)ions are connected by twoμ_(2)⁃O to form a parallelogram[Ln_(2)O_(2)]core.The magnetic study showed that complex 2 displayed significant magnetic refrigeration property with a larger magnetic entropy(-ΔS_(max))of 31.9 J·K^(-1)·kg^(-1) atΔH=70 kOe and T=2.0 K;while complex 3 shows slow magnetic relaxation behavior.CCDC:2052182,1;2052183,2;2052184,3.