四价钴（II）配合物中的慢磁弛豫。非弹性中子散射和高频高场EPR光谱研究磁各向异性,Inorganic Chemistry

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四价钴（II）配合物中的慢磁弛豫。非弹性中子散射和高频高场EPR光谱研究磁各向异性
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2016-12-07 00:00:00 , DOI: 10.1021/acs.inorgchem.6b01544
Lei Chen ₁ , Hui-Hui Cui ₁ , Shelby E. Stavretis ₂ , Seth C. Hunter ₂ , Yi-Quan Zhang ₃ , Xue-Tai Chen ₁ , Yi-Chen Sun ₄ , Zhenxing Wang ₄ , You Song ₁ , Andrey A. Podlesnyak ₅ , Zhong-Wen Ouyang ₄ , Zi-Ling Xue ₂

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三种具有不同抗衡阳离子Ph ₄ P ⁺（1），MePh ₃ P ⁺（2）和Ph ₄ As ⁺（3）的单核四硝酸钴（II）配合物（A）₂ [Co（NO ₃）₄ ]具有通过X射线单晶衍射，磁测量，非弹性中子散射（INS），高频和高场EPR（HF-EPR）光谱以及理论计算来进行合成和研究。X射线衍射研究表明，四硝酸盐钴阴离子的结构随抗衡阳离子而变化。1和2表现出高度不规则的七坐标几何形状，而中心的Co（II）离子3处于扭曲的十二面体配置。在INS光谱中观察到的唯一磁跃变为1 – 3对应于从22.5（2）cm ^–1 in 1到26.6（3）cm的零场分裂（2（D ² + 3 E ²）^1/2）^–1英寸2和11.1（5）cm ^–1英寸3。对于1证明了D值的正号，因此证明了易平面磁各向异性由INS在磁场和HF-EPR光谱下进行研究。INS和HF-EPR数据的联合分析得到d值10.90（3），12.74（3），和4.50（3）厘米^-1为1 - 3分别。依赖于频率和温度的交流磁化率测量结果显示，在施加的600 Oe直流磁场下，磁化弛豫速度为1和2，这是磁场感应的单分子磁体（SMM）的特征。的电子结构和磁各向异性的原点1 - 3分别通过在CASPT2 / NEVPT2水平计算显示。

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Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy

Three mononuclear cobalt(II) tetranitrate complexes (A)₂[Co(NO₃)₄] with different countercations, Ph₄P⁺ (1), MePh₃P⁺ (2), and Ph₄As⁺ (3), have been synthesized and studied by X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. The X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1–3 corresponds to the zero-field splitting (2(D² + 3E²)^1/2) from 22.5(2) cm^–1 in 1 to 26.6(3) cm^–1 in 2 and 11.1(5) cm^–1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm^–1 for 1–3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). The electronic structures and the origin of magnetic anisotropy of 1–3 were revealed by calculations at the CASPT2/NEVPT2 level.

更新日期：2016-12-07

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