Jing Pei, Xi Lu, Lu Jiao, Han Jing, Huang Xiaohui, Jin Chaoyi, Xie Junfang, Li Licun
Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, P. R China.
Chem Asian J. 2021 Apr 1;16(7):793-800. doi: 10.1002/asia.202100062. Epub 2021 Feb 22.
Four biradical-Ln complexes with different transition metal ions, namely [LnM(hfac) (NITPh-PyPzbis)] (M =Mn and Ln =Gd 1, Dy 2; M =Ni and Ln =Tb 3, Dy 4), were prepared by the reaction of Ln(hfac) ⋅ 2H O, Mn(hfac) ⋅ 2H O or Ni(hfac) ⋅ 2H O with NITPh-PyPzbis biradical (hfac=hexafluoroacetylacetonate, NITPh-PyPzbis=5-(3-(2-pyridinyl)-1H-pyrazol-1-yl)-1,3-bis(1'-oxyl-3'-oxido- 4',4',5',5'-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene). In complexes 1-4, the NITPh-PyPzbis biradical chelates one Ln ion by means of its aminoxyl moieties and the transition metal ion is introduced through the two N donors from the pyridyl pyrazolyl moiety. Magnetic investigations indicate that complex 4 displays visible maxima in frequency/temperature-dependent χ'' signals with two-step relaxation processes, but complex 2 exhibits no slow magnetization relaxation. The comparison of structure parameters of both Dy complexes indicates that the symmetries of coordination spheres of two Dy ions are D for 2 and C for 4, which thus probably results in different magnetic relaxation behaviors. This work provides new insight for improving properties of Ln-biradical based SMMs.
通过将Ln(hfac)·2H₂O、Mn(hfac)·2H₂O或Ni(hfac)·2H₂O与NITPh-PyPzbis双自由基（hfac = 六氟乙酰丙酮，NITPh-PyPzbis = 5-(3-(2-吡啶基)-1H-吡唑-1-基)-1,3-双(1'-氧基-3'-氧化-4',4',5',5'-四甲基-4,5-氢-1H-咪唑-2-基)苯）反应，制备了四种含有不同过渡金属离子的双自由基-Ln配合物，即[LnM(hfac)(NITPh-PyPzbis)]（M = Mn且Ln = Gd 1，Dy 2；M = Ni且Ln = Tb 3，Dy 4）。在配合物1 - 4中，NITPh-PyPzbis双自由基通过其氨氧基部分螯合一个Ln离子，过渡金属离子通过吡啶基吡唑基部分的两个N供体引入。磁性研究表明，配合物4在频率/温度相关的χ''信号中显示出明显的最大值，具有两步弛豫过程，但配合物2没有慢磁化弛豫现象。两种Dy配合物结构参数的比较表明，两个Dy离子配位球的对称性对于2为D，对于4为C，这可能导致不同的磁弛豫行为。这项工作为改善基于Ln-双自由基的单分子磁体的性能提供了新的见解。
