Designing a mononuclear DyIII single-molecule magnet (SMM) by using a N,O,N,O-based multichelating Schiff base ligand and a β-diketonate ligand†,New Journal of Chemistry

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Designing a mononuclear DyIII single-molecule magnet (SMM) by using a N,O,N,O-based multichelating Schiff base ligand and a β-diketonate ligand†
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2018-11-21 00:00:00 , DOI: 10.1039/c8nj04019b
Sheng Zhang _{1,

2,

3,

4,

5} , Wenjiao Mo _{1,

2,

3,

4} , Bing Yin _{4,

6,

7,

8,

9} , Xingqiang Lü _{4,

5,

8,

10,

11} , Jiangwei Zhang _{12,

13,

14,

15}

Affiliation

College of Chemistry and Chemical Engineering
Baoji University of Arts and Sciences
Baoji 721013
China
School of Chemical Engineering
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education
College of Chemistry and Materials Science
Northwest University
Xi’an
Shaanxi Key Laboratory of Degradable Medical Material
Xi'an 710069
Dalian Institute of Chemical Physics
Chinese Academy of Sciences
Dalian 116023
P. R. China

Two mononuclear Ln^III compounds, in which each Ln^III is eight-coordinated, namely [Ln(L)(tmpd)] (Ln = Dy (1) or Er (2)), have been prepared using a multichelating Schiff base ligand N,N′-bis(2-hydroxy-5-methyl-3-formylbenzyl)-N,N′-bis-(pyridin-2-ylmethyl)ethylenediamine (H₂L) and a bidentate chelating β-diketonate ligand (tmpd). The local geometry of the Ln^III ions in 1 and 2 is close to the D_2d symmetry. Notably, magnetic studies reveal that compound 2 displays no slow relaxation of magnetization while compound 1 exhibits single-molecule magnet (SMM) behaviour in the absence of a static magnetic field, with an effective energy barrier (U_eff) of 66.81 cm⁻¹ (96.63 K). To deeply understand their different magnetic behaviours, the magnetic anisotropy of 1 and 2 is systematically studied by ab initio calculations. There was an obvious difference between the first excited state (KD₁) and the experimental U_eff in 1 because the QTM within KD₀ is not completely prohibited and the residual QTM could lead to a large discrepancy between experimentally-fitted U_eff and ab initio calculated crystal field splitting. No temperature/frequency dependence is recorded in the ac susceptibility of 2 because the ab initio magnetic easy axis of 2 does not lie close to any atom of the first sphere since it tries to avoid any strong electrostatic repulsion. Moreover, the g_XY value of KD₀ of 2 is larger than that of 1 by three orders of magnitude leading to the probability of stronger QTM within KD₀ of 2.

中文翻译：

通过使用基于N，O，N，O的多螯合席夫碱配体和β-二酮配体† 设计单核Dy ^III单分子磁体（SMM）

已经使用多螯合席夫碱配体N制备了两个单核Ln ^III化合物，其中每个Ln ^III是八配位的，即[Ln（L）（tmpd）]（Ln = Dy（1）或Er（2））。，N′-双（2-羟基-5-甲基-3-甲酰基苄基）-N，N′-双-（吡啶-2-基甲基）乙二胺（H ₂ L）和双齿螯合β-二酮酸酯配体（tmpd）。Ln ^III离子在1和2中的局部几何形状接近D _2d对称性。值得注意的是，磁性研究表明化合物2化合物1没有显示出缓慢的磁化弛豫，而化合物1在没有静磁场的情况下表现出单分子磁体（SMM）行为，其有效能垒（U _eff）为66.81 cm ^-1（96.63 K）。为了深入了解它们的不同磁行为，通过从头算起系统地研究了1和2的磁各向异性。第一次激发态（KD ₁）与实验U _eff in 1之间存在明显差异，因为QTM在KD _0内并没有完全禁止，残留的QTM可能导致实验拟合的U _eff与从头算出的晶体场分裂之间的巨大差异。没有温度/频率依赖性被记录在的交流磁化率2由于从头易磁化轴的2不位于靠近第一球体的任何原子，因为它会尝试避免任何强烈的静电排斥。此外，KD ₀的2的g _XY值比1的g _XY大三个数量级，从而导致在KD ₀的KD ₀内具有更强QTM的可能性。2。

更新日期：2018-11-21

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