Zhang Sheng, Ke Hongshan, Shi Quan, Zhang Jangwei, Yang Qi, Wei Qing, Xie Gang, Wang Wenyuan, Yang Desuo, Chen Sanping
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an, Shaanxi 710069, China.
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
Dalton Trans. 2016 Mar 28;45(12):5310-20. doi: 10.1039/c6dt00219f.
Three mononuclear dysprosium(III) complexes derived from three β-diketonate ligands, 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione (tfmb), 4,4,4-trifluoro-1-(4-fluorophenyl)-1,3-butanedione (tffb) and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (tfnb) as well as auxiliary ligands, 5-nitro-1,10-phenanthroline (5-NO2-Phen), DMF and 2,2'-bipyridine (bpy) have been synthesized and structurally characterized, namely [Dy(5-NO2-Phen)(tfmb)3] (1), [Dy(DMF)2(tffb)3] (2) and [Dy(bpy)2(tfnb)3]·0.5(1,4-dioxane) (3). The metal ions in 1-3 adopt an approximately square-antiprismatic (SAP) coordination environment with D4d axial symmetry. The magnetic properties of 1-3 have been investigated, displaying weak out-of-phase AC signals under a zero-DC field. With an applied DC field of 1200 Oe, the quantum tunnelling of the magnetization was suppressed in 1-3 with the pre-exponential factor τ0 = 5.3 × 10(-7) s and the effective barrier ΔE/kB = 83 K for 1 as well as the pre-exponential factor τ0 = 3.09 × 10(-7) s and the effective barrier ΔE/kB = 39 K for 3. Interestingly, for the frequency dependence of the out-of-phase (χ'') of the AC susceptibility of 2, two slow relaxation of the magnetization processes occurred under the applied magnetic field of 1200 Oe, corresponding to the fast relaxation (FR) phase and slow relaxation (SR) phase, respectively. Arrhenius analysis gave the effective energy barrier (ΔE/kB) of 55 K and the pre-exponential factor (τ0) of 8.23 × 10(-12) for the SR. It is thus very likely that the FR process in complex 2 results from QTM enhanced by dipolar interactions between the Dy ions or the presence of the applied field. The structure-property relationship of some Dy(III) based mononuclear SMMs with the SAP configuration was further discussed.
合成并表征了三种由三种β-二酮配体4,4,4-三氟-1-(4-甲基苯基)-1,3-丁二酮(tfmb)、4,4,4-三氟-1-(4-氟苯基)-1,3-丁二酮(tffb)和4,4,4-三氟-1-(2-萘基)-1,3-丁二酮(tfnb)以及辅助配体5-硝基-1,10-菲咯啉(5-NO₂-Phen)、N,N-二甲基甲酰胺(DMF)和2,2'-联吡啶(bpy)衍生而来的单核镝(III)配合物，即[Dy(5-NO₂-Phen)(tfmb)₃] (1)、[Dy(DMF)₂(tffb)₃] (2)和[Dy(bpy)₂(tfnb)₃]·0.5(1,4-二氧六环) (3)。1 - 3中的金属离子采用具有D₄d轴向对称性的近似四方反棱柱(SAP)配位环境。研究了1 - 3的磁性质，在零直流场下显示出微弱的异相交流信号。在1200 Oe的外加直流场下，1 - 3中磁化强度的量子隧穿被抑制，对于1，预指数因子τ₀ = 5.3×10⁻⁷ s，有效势垒ΔE/kB = 83 K；对于3，预指数因子τ₀ = 3.09×10⁻⁷ s，有效势垒ΔE/kB = 39 K。有趣的是，对于2的交流磁化率异相(χ'')的频率依赖性，在1200 Oe的外加磁场下发生了两个磁化强度的慢弛豫过程，分别对应快速弛豫(FR)相和慢弛豫(SR)相。阿仑尼乌斯分析给出SR的有效能垒(ΔE/kB)为55 K，预指数因子(τ₀)为8.23×10⁻¹²。因此，配合物2中的FR过程很可能是由Dy离子之间的偶极相互作用或外加场的存在增强的量子隧穿引起。进一步讨论了一些具有SAP构型的基于Dy(III)的单核单分子磁体的结构-性质关系。
