Tuning Transverse Anisotropy in CoIII鈥揅oII鈥揅oIII Mixed-Valence Complex toward Slow Magnetic Relaxation

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• 作者：Dayu Wu ; Xingxing Zhang ; Ping Huang ; Wei Huang ; Mingyue Ruan ; Z. W. Ouyang
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：October 7, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：10976-10982
• 全文大小：459K
• 年卷期：v.52,no.19(October 7, 2013)
• ISSN：1520-510X

文摘

Two cobalt mixed-valence complexes with different substituents have been prepared and structurally characterized by single-crystal X-ray diffraction to alter slow magnetic relaxation by tailoring the transverse anisotropy. The trinuclear complexes [(L¹)₄Co₃(H₂O)₂](NO₃)₄路CH₃OH路5H₂O (1-NO₃) and [(L²)₄Co₃(H₂O)₂](NO₃)₄路6H₂O (2-NO₃) feature a distorted octahedral Co(II) strongly hindered in a trinuclear Co^III鈥揅o^II鈥揅o^III mixed-valence array. Detailed magnetic studies of 1-NO₃ and 2-NO₃ have been conducted using direct- and alternating-current magnetic susceptibility data. In accordance with variable-field magnetic susceptibility data at low temperatures, high-field electron paramagnetic resonance (HF-EPR) spectroscopy reveals the presence of an easy-plane anisotropy (D > 0) with a significant transverse component, E, in complexes 1-NO₃ and 2-NO₃. These findings indicate that the onset of the variation of distortion within complex 2-NO₃ leads to a suppression of quantum tunneling of the magnetization within the easy plane, resulting in magnetic bistability and slow relaxation behavior. Consequently, the anisotropy energy scale associated with the relaxation barrier, 5.46 cm^鈥? (蟿_o = 1.03 脳 10^鈥? s), is determined by the transverse E term. The results demonstrate that slow magnetic relaxation can be switched through optimization of the transverse anisotropy associated with magnetic ions that possess easy-plane anisotropy.