Modulation of Slow Magnetic Relaxation for Tb(III)-Metallacrown Complexes by Controlling Axial Halide Coordination
Modulation of Slow Magnetic Relaxation for Tb(III)-Metallacrown Complexes by Controlling Axial Halide Coordination
复制标题
通过控制轴向卤化物配位调节 Tb(III)-金属冠配合物的慢磁弛豫
DOI：
10.6023/a20030077
复制
发表时间：
2020
影响因子：
2.5
通讯作者：
Tong Ming-Liang
中科院分区：
文献类型：
--
作者：
Wan Rui-Chen;Wu Si-Guo;Liu Jun-Liang;Jia Jian-Hua;Huang Guo-Zhang;Li Quan-Wen;Tong Ming-Liang
单分子磁体具有磁双稳性和缓慢的磁化弛豫特性，在数据存储和信息处理等领域有着广阔的应用前景。由于镧系离子的轨道动量不猝灭和强各向异性，镧系金属自组装材料得到了很大的发展。根据晶场理论，镧系离子的磁各向异性是由晶场分裂引起的。合理安排镧系离子的配位环境（包括局域对称性和电荷分布）是设计高性能自组装金属材料的关键。然而，合成具有一定配位环境的镧系化合物仍然是一个巨大的挑战。利用金属冠醚（MC）方法，通过溶剂热反应成功地合成了一系列3d-4f配合物{TbNi 5X 2 }（X = F，Cl，Br）.为了得到这些配合物，化学计量的金属盐和喹哪啉羟肟酸与过量的吡啶衍生物的混合物溶解在甲醇中，然后在75 ℃下加热2d。X射线单晶衍射分析表明，Tb（III）位与[15-MC Ni（II）-5]呈赤道配位，而轴向被卤离子封端。结果表明，镧系离子具有较高的轴性，具有五角双锥结构（D5 h）.交流磁化率数据表明，f-电子和配体电子之间的静电相互作用在调制磁弛豫动力学中起着重要的作用。在{TbNi 5 F2}中首次报道了[F-Ln-F] +结构，将其轴向电荷密度最大化，并将扁球形Tb（III）置于合理的晶场中.在1 kOe直流电场下，{TbNi 5 F2}的异相信号具有明显的温度和频率依赖性。此外，{TbNi 5 F2}的慢磁化弛豫可用幂律或Arrhenius曲线拟合，其反转势垒为19.0K.通过降低轴向连接的静电相互作用，异相信号在{TbNi 5Cl 2 }中显著减弱，甚至在{TbNi 5 Br 2 }中消失。{TbNi 5Cl 2 }和{TbNi 5 Br 2 }的磁各向异性下降加速了磁化强度的快速量子隧穿。研究结果首次表明，通过提高轴向配体的电负性，可以对Off/Part/On慢磁化弛豫进行调制。
Single-molecule magnets (SMMs), exhibiting magnetic bistability and slow magnetization relaxation, have fasci-nated scientific community for their promising applications in data storage and information processing. Great development has been achieved in lanthanide-based SMMs due to the unquenched orbital momentum and strong anisotropy of lanthanide ions. According to the crystal-field theory, the magnetic anisotropy of lanthanide ions arises from crystal-field splitting. Ap-propriate arrangement of coordination environment of lanthanide ion (including the local symmetry as well as the charge distribution) is key to design high-performance SMMs. However, it still remains a huge challenge to generate lantha-nide-containing compounds with certain coordination environment. Taking advantage of metallacrown (MC) approach, herein a series of 3d-4f complexes {TbNi 5 X 2 } (X ＝ F, Cl, Br) were successfully isolated via solvothermal reactions. To obtain these complexes, a mixture of stoichiometric metal salt and quinaldichdroxamic acid with excess of pyridine derivative was dis-solved in methanol and then heated at 75 ℃ for 2 d. X-ray single-crystal diffraction analysis indicated that the Tb(III) site equatorially coordinates with [15-MC Ni(II) -5], whilst is axially capped by halide ions. As a result, the lanthanide ion possesses high axiality with a pentagonal bipyramid geometry ( D 5 h ). Alternative current magnetic susceptibility data revealed that the electrostatic interactions between f-electrons and ligand electrons play an important role in modulating the magnetic relaxation dynamics. Maximizing the axial charge density in {TbNi 5 F 2 } where the [F-Ln-F] ＋ moiety is firstly reported in lanthanide chemistry, the oblate Tb(III) is placed in a judicious crystal field. The out-of-phase signal of {TbNi 5 F 2 } shows obvious temperature and frequency dependence under 1 kOe applied dc field. Additionally, the slow magnetization relaxation of {TbNi 5 F 2 } can be fitted by the power law or Arrhenius plot with reversal barrier of 19.0 K. By lowering the electrostatic interactions of axial ligation, the out-of-phase signal significantly weakens in {TbNi 5 Cl 2 } and even vanishes in {TbNi 5 Br 2 }. The decline of magnetic anisotropy in {TbNi 5 Cl 2 } and {TbNi 5 Br 2 } accelerates the fast quantum tunneling of magnetization. The results demonstrate for the first time that the Off/Part/On slow magnetization relaxation can be modulated via the im-provement of electronegativity of axial ligands.
DOI：
10.1016/s1369-7021(06)71579-6
发表时间：
2020-03
期刊：
SpringerBriefs in Applied Sciences and Technology
影响因子：
--
作者：
通讯作者：
--
影响因子：
0.7
作者：
Hendrickson, DN;Christou, G;Aromi, G
通讯作者：
Aromi, G