Department of Chemistry , Indian Institute of Technology , Kharagpur 721302 , India.
Department of Inorganic Chemistry, Faculty of Science , Palacký University , 17 Listopadu 12 , 77146 Olomouc , Czech Republic.
Inorg Chem. 2019 Sep 16;58(18):12184-12198. doi: 10.1021/acs.inorgchem.9b01517. Epub 2019 Sep 4.
New Schiff base ligand HL containing NOS donor atoms has been explored for its ability to provide complexes of selected 3d and 4f metal ions. Room temperature reaction of HL with NiCl·6HO and Ln(NO)·5HO in the presence of EtN in MeCN-MeOH (2:1) medium resulted in [NiLn(L)(μ-Cl)(μ-OH)(HO)]Cl·2HO (where Ln = Dy (), Tb (), and Ho () and HL = 2-((2-(2-(2-hydroxy-3-methoxybenzylideneamino)ethylthio)ethylimino)methyl)-6-methoxyphenol). Use of Ni(SCN)·4HO during synthesis provided SCN ions for bridging and terminal coordination in [NiLn(L)(μ-NCS)(μ-OH)(NCS)(HO)]·MeOH·HO (where Ln = Dy (), = 2, = 4; Tb () and Ho (), = 0, = 14.1). All six complexes possess a hexanuclear defective tetracubane topology having exchangeable bridging groups. The study of direct current magnetic susceptibility measurements revealed that the Ni(II) ions are engaged in ferromagnetic interaction with the Dy, Tb, and Ho ions and have significant magnetic anisotropy in all six complexes. Alternating current susceptibility measurements confirmed that both of the two types of compounds qualify as zero-field single-molecule magnets (SMMs), and the effective barrier for the reversal of the magnetic moment was found to be in the range = 23-31 K for - and -, respectively. Detailed insight into the electronic structure and magnetic properties was calculated using DFT- and CASSCF-based analyses. The found isotropic exchange parameter () values are = -4.7 cm for and = +29.2 cm for and clearly indicate that the μ-NCS-bridge is a better candidate than μ-Cl for ferromagnetic exchange interactions. Out of the six complexes, only complex displays Tb centered emission peaks at 451 and 480 nm.
新型希夫碱配体 HL 含有 NOS 供体原子，用于与选定的 3d 和 4f 金属离子形成配合物。在 MeCN-MeOH（2:1）介质中，HL 与 NiCl·6HO 和 Ln(NO)·5HO（Ln = Dy (), Tb (), 和 Ho ()）和 EtN 室温反应，得到 [NiLn(L)(μ-Cl)(μ-OH)(HO)]Cl·2HO。使用 Ni(SCN)·4HO 进行合成提供了 SCN 离子用于桥接和末端配位，得到 [NiLn(L)(μ-NCS)(μ-OH)(NCS)(HO)]·MeOH·HO（Ln = Dy (), = 2, = 4； = Tb ()和 Ho (), = 0, = 14.1）。所有六个配合物都具有具有可交换桥接基团的六核缺陷四棱体拓扑结构。直流磁化率测量研究表明，Ni(II)离子与 Dy、Tb 和 Ho 离子之间存在铁磁相互作用，并且在所有六个配合物中都具有显著的磁各向异性。交流磁化率测量证实，这两种化合物都符合零场单分子磁体（SMM）的要求，并且发现磁矩反转的有效势垒在 = 23-31 K 范围内，分别为 - 和 -。使用 DFT- 和 CASSCF 基分析计算了对电子结构和磁性质的深入了解。发现的各向同性交换参数 () 值为 = -4.7 cm 对于 和 = +29.2 cm 对于 ，清楚地表明 μ-NCS 桥是铁磁交换相互作用的更好候选者而不是 μ-Cl。在这六个配合物中，只有配合物 显示出以 Tb 为中心的发射峰，位于 451 和 480 nm 处。
