Enhancing the Magnetic Anisotropy of Linear Cr(II) Chain Compounds Using Heavy Metal Substitutions

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• 作者：Jonathan H. Christian ; David W. Brogden ; Jasleen K. Bindra ; Jared S. Kinyon ; Johan van Tol ; Jingfang Wang ; John F. Berry ; Naresh S. Dalal
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 5, 2016
• 年：2016
• 卷：55
• 期：13
• 页码：6376-6383
• 全文大小：603K
• 年卷期：0
• ISSN：1520-510X

文摘

Magnetic properties of the series of three linear, trimetallic chain compounds Cr₂Cr(dpa)₄Cl₂, 1, Mo₂Cr(dpa)₄Cl₂, 2, and W₂Cr(dpa)₄Cl₂, 3 (dpa = 2,2′-dipyridylamido), have been studied using variable-temperature dc and ac magnetometry and high-frequency EPR spectroscopy. All three compounds possess an S = 2 electronic ground state arising from the terminal Cr²⁺ ion, which exhibits slow magnetic relaxation under an applied magnetic field, as evidenced by ac magnetic susceptibility and magnetization measurements. The slow relaxation stems from the existence of an easy-axis magnetic anisotropy, which is bolstered by the axial symmetry of the compounds and has been quantified through rigorous high-frequency EPR measurements. The magnitude of D in these compounds increases when heavier ions are substituted into the trimetallic chain; thus D = −1.640, −2.187, and −3.617 cm^–1 for Cr₂Cr(dpa)₄Cl₂, Mo₂Cr(dpa)₄Cl₂, and W₂Cr(dpa)₄Cl₂, respectively. Additionally, the D value measured for W₂Cr(dpa)₄Cl₂ is the largest yet reported for a high-spin Cr²⁺ system. While earlier studies have demonstrated that ligands containing heavy atoms can enhance magnetic anisotropy, this is the first report of this phenomenon using heavy metal atoms as “ligands”.