Structure-Property Relationships in Tricyanoferrate(III) Building Blocks and Trinuclear Cyanide-Bridged Complexes

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• 作者：Yuanzhu Zhang ; Uma P. Malik ; Benjamin Quiggins ; Hung Nguyen ; Christopher C. Beedle ; Alexey E. Kovalev ; Rodolphe Cl&eacute ; rac ; Stephen Hill ; Benjamin J. Bythell and Stephen M. Holmes
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：2016
• 期：15-16
• 页码：2432-2442
• 全文大小：1910K
• ISSN：1099-0682c

文摘

The preparation, structures, and magnetic properties of two tricyanoferrates, [NEt₄]₂[(Tp*^Me)Fe^II(CN)₃]·MeCN (1) and [NEt₄][(Tp*^Me)Fe^III(CN)₃]·H₂O (2), and three trinuclear derivatives, {[(Tp*^Me)Fe^III(CN)₃]₂[Ni^II(L)₂]}·n(solvent) (L = bpy, 3; tren, 4; DETA, 5) are described. Magnetic measurements show that 2 is an S = ¹/₂ complex [g = 2.65(1)], while 3–5 display S_T = 2 spin ground states, owing to cyanide-mediated ferromagnetic exchange between Fe^III_LS (S = ¹/₂) and Ni^II (S = 1) ions. The χT vs. T data for 3–5 were modelled using an isotropic Heisenberg model and give J/k_B and g_avg values of +11.1(1) K and 2.48(1) for 3, 9.1(1) K and 2.6(1) for 4, and +11.2(1) K and 2.41(5) for 5 (with zJ′ = –0.28 K). High-field/frequency EPR data indicates significant g-anisotropy in 2 (g_z = 3.6, g_y = 2.2, g_x = 2.0) and [NEt₄][(Tp*)Fe^III(CN)₃]·H₂O (6) (g_z = 3.5, g_y = 2.0, g_x = 1.3), while 5 shows D = –2.09 cm^–1, E = 0.08 cm^–1, and B₄⁰ = –2.3 × 10^–3 cm^–1 with g_z = 2.4 and g_x = g_y = 1.95. Despite significant magnetic anisotropy in 3–5, frequency-dependent behavior is only seen for 5 above 1.8 K, suggesting that rapid quantum tunnelling of the magnetization is operative.