Xi Lu, Jin Chaoyi, Song Hongwei, Wang Xiaotong, Xie Junfang, Ma Yue, Tang Jinkui, Li Licun
Key Laboratory of Advanced Energy Materials Chemistry, Department of Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China.
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
Chemistry. 2022 Nov 21;28(65):e202202239. doi: 10.1002/chem.202202239. Epub 2022 Sep 19.
In spite of achievement of a lot of Ln-radical SMMs, how to improve magnetic behavior of Ln-radical system remains challenging. Here, two series of Ln-radical complexes have successfully been built using an imino nitroxide biradical, namely, [Ln (hfac) (ImPhPyobis) ] (Ln =Gd 1, Tb 2, Dy 3) and [Ln Cu (hfac) (ImPhPyobis) ] (Ln =Gd 4, Dy 5; hfac=hexafluoroacetylacetonate and ImPhPyobis=5-(4-oxypyridinium-1-yl)-1,3-bis(1'-oxyl-4',4',5',5'-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene). For these biradical-metal complexes, two imino nitroxide biradicals bind two Ln(III) ions via their oxygen atoms coming from 4-oxypyridinium units to produce a binuclear {Ln O } unit. Those imino nitroxide groups are free for complexes 1-3, however one of imino nitroxide groups of the biradical is ligated to the copper(II) ion for complexes 4 and 5. The distinct magnetic relaxation behaviors are observed for two Dy derivatives, as revealed by ac magnetic studies: complex 3 presents one magnetic process with the effective energy barrier(U ) of 74.0 K while complex 5 exhibits dual relaxation processes with U values for the fast- and slow-relaxation being 20.2 K and 30.9 K, respectively, which implies that the second coordination sphere of Dy ion plays a critical role for magnetic relaxation.
尽管已经合成了许多镧系自由基单分子磁体，但如何改善镧系自由基体系的磁行为仍然具有挑战性。在此，使用亚氨基氮氧双自由基成功构建了两个系列的镧系自由基配合物，即[Ln (hfac) (ImPhPyobis) ]（Ln = Gd 1、Tb 2、Dy 3）和[Ln Cu (hfac) (ImPhPyobis) ]（Ln = Gd 4、Dy 5；hfac = 六氟乙酰丙酮，ImPhPyobis = 5-(4-氧代吡啶鎓-1-基)-1,3-双(1'-氧基-4',4',5',5'-四甲基-4,5-氢-1H-咪唑-2-基)苯）。对于这些双自由基-金属配合物，两个亚氨基氮氧双自由基通过来自4-氧代吡啶鎓单元的氧原子与两个Ln(III)离子结合，形成双核{Ln O }单元。对于配合物1-3，那些亚氨基氮氧基团是自由的，然而对于配合物4和5，双自由基的一个亚氨基氮氧基团与铜(II)离子配位。交流磁性研究表明，两种Dy衍生物表现出不同的磁弛豫行为：配合物3呈现一个磁过程，有效能垒（U ）为74.0 K，而配合物5表现出双弛豫过程，快速和慢速弛豫的U值分别为20.2 K和30.9 K，这意味着Dy离子的第二配位层对磁弛豫起着关键作用。
