Wei Rong-Min, Liu Ting, Li Jing, Zhang Xiuling, Chen Yuting, Zhang Yi-Quan
Key Laboratory of Coordination Chemistry and Functional Materials in Universities of Shandong, School of Chemistry and Chemical Engineering, Dezhou University, Dezhou, 253023, P. R. China.
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, P. R. China.
Chem Asian J. 2019 Jun 3;14(11):2029-2035. doi: 10.1002/asia.201900139. Epub 2019 May 9.
By using paramagnetic [Fe(CN) ] anions in place of diamagnetic [Co(CN) ] anions, two field-induced mononuclear single-molecular magnets, [Nd(18-crown-6)(H O) ][Co(CN) ]⋅2 H O (1) and [Nd(18-crown-6)(H O) ][Fe(CN) ]⋅2 H O (2), have been synthesized and characterized. Single-crystal X-ray diffraction analysis revealed that compounds 1 and 2 were ionic complexes. The Nd ions were located inside the cavities of the 18-crown-6 ligands and were each bound by four water molecules on either side of the crown ether. Magnetic investigations showed that these compounds were both field-induced single-molecular magnets. By comparing the slow relaxation behaviors of compounds 1 and 2, we found significant differences between the direct and Raman processes for these two complexes, with a stronger direct process in compound 2 at low temperatures. Complete active space self-consistent field (CASSCF) calculations were also performed on two [Nd(18-crown-6)(H O) ] fragments of compounds 1 and 2. Ab initio calculations showed that the magnetic anisotropies of the Nd centers in complexes 1 and 2 were similar to each other, which indicated that the difference in relaxation behavior was not owing to the magnetic anisotropy of Nd . Our analysis showed that the magnetic interaction between the Nd ion and the low-spin Fe ion in complex 2 played an important role in enhancing the direct process and suppressing the Raman process of the single-molecular magnet.
通过用顺磁性的[Fe(CN)₆]阴离子取代抗磁性的[Co(CN)₆]阴离子，合成并表征了两种场诱导的单核单分子磁体，[Nd(18-冠-6)(H₂O)₂][Co(CN)₆]·2H₂O (1) 和 [Nd(18-冠-6)(H₂O)₂][Fe(CN)₆]·2H₂O (2)。单晶X射线衍射分析表明化合物1和2是离子配合物。Nd离子位于18-冠-6配体的腔内，并且在冠醚的两侧分别与四个水分子结合。磁性研究表明这些化合物都是场诱导的单分子磁体。通过比较化合物1和2的慢弛豫行为，我们发现这两种配合物的直接过程和拉曼过程之间存在显著差异，在低温下化合物2中的直接过程更强。还对化合物1和2的两个[Nd(18-冠-6)(H₂O)₂]片段进行了完全活性空间自洽场 (CASSCF) 计算。从头算计算表明配合物1和2中Nd中心的磁各向异性彼此相似，这表明弛豫行为的差异不是由于Nd的磁各向异性。我们的分析表明，配合物2中Nd离子与低自旋Fe离子之间的磁相互作用在增强单分子磁体的直接过程和抑制拉曼过程中起重要作用。
