Lu Jiao, Jing Pei, Jin Chaoyi, Xie Junfang, Li Licun
Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.
Dalton Trans. 2021 Mar 9;50(9):3280-3288. doi: 10.1039/d1dt00090j.
Self-assembling the novel nitronyl nitroxide radical NIT-3Py-5-Ph (2-(5-phenyl-3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) with Ln(hfac)3·2H2O and Cu(hfac)2 (hfac = hexafluoroacetylacetonate) resulted in two heterometallic complexes with formula [LnCu(hfac)5(NIT-3Py-5-Ph)2] (Ln = Gd 1, Dy 2), in which two NIT-3Py-5-Ph radicals are coordinated with the LnIII ion via their nitroxide units in the cis-arrangement manner and the CuII ion is ligated by the pyridyl N donors of the radicals. Interestingly, when the phenyl group of NIT-3Py-5-Ph was replaced with a p-pyridyl group, a new family of 2D networks, namely, {[Ln(hfac)3][Cu(hfac)2]2(NIT-3Py-5-4Py)2}n (Ln = Gd 3, Tb 4, Dy 5; NIT-3Py-5-4Py = 2-(5-(4-pyridyl)-3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was obtained. In the 2D sheet, each NIT-3Py-5-4Py ligand serves as a μ3-bridge to bind one LnIII center by the aminoxyl moiety and two CuII ions through two pyridine groups to form a 2D structure. The LnIII ion is coordinated by two NO units of two radicals in a trans configuration. DC magnetic measurements indicate that ferromagnetic LnIII-NO exchange occurs in 1-5. AC studies reveal that 2 displays slow relaxation of the magnetization while no such magnetic relaxation is found in complex 5. The observed different magnetic relaxation behaviors of two Dy analogues could be attributed to the different coordination modes of NO groups of the radicals, and the coordination geometry of the Dy center is from C2v in 2 to D2d in 5.
将新型硝酰基氮氧化物自由基NIT-3Py-5-Ph（2-(5-苯基-3-吡啶基)-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物）与Ln(hfac)3·2H2O和Cu(hfac)2（hfac = 六氟乙酰丙酮）自组装，得到了两种化学式为[LnCu(hfac)5(NIT-3Py-5-Ph)2]的异金属配合物（Ln = Gd 1，Dy 2），其中两个NIT-3Py-5-Ph自由基通过其硝酰基单元以顺式排列方式与LnIII离子配位，而CuII离子则由自由基的吡啶基N供体配位。有趣的是，当NIT-3Py-5-Ph的苯基被对吡啶基取代时，得到了一个新的二维网络家族，即{[Ln(hfac)3][Cu(hfac)2]2(NIT-3Py-5-4Py)2}n（Ln = Gd 3，Tb 4，Dy 5；NIT-3Py-5-4Py = 2-(5-(4-吡啶基)-3-吡啶基)-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物）。在二维片中，每个NIT-3Py-5-4Py配体作为一个μ3-桥，通过氨氧基部分连接一个LnIII中心，并通过两个吡啶基团连接两个CuII离子，形成二维结构。LnIII离子由两个处于反式构型的自由基的两个NO单元配位。直流磁性测量表明，1-5中发生了铁磁LnIII-NO交换。交流研究表明，2表现出磁化强度缓慢弛豫，而配合物5中未发现这种磁弛豫。观察到的两种Dy类似物不同的磁弛豫行为可归因于自由基NO基团的不同配位模式，并且Dy中心的配位几何构型从2中的C2v变为5中的D2d。
