Anion鈭捪€ and Halide鈥揌alide Nonbonding Interactions in a New Ionic Liquid Based on Imidazolium Cation with Three-Dimensional Magnetic Ordering in the Solid State

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• 作者：Abel Garc铆a-Saiz ; Imanol de Pedro ; Pedro Migowski ; Oriol Vallcorba ; Javier Junquera ; Jes煤s Angel Blanco ; Oscar Fabelo ; Denis Sheptyakov ; Joao Carlos Waerenborgh ; Mar铆a Teresa Fern谩ndez-D铆az ; Jordi Rius ; Jairton Dupont ; Jes煤s Antonio Gonzalez ; Jes煤s Rodr铆guez Fern谩ndez
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：August 18, 2014
• 年：2014
• 卷：53
• 期：16
• 页码：8384-8396
• 全文大小：629K
• ISSN：1520-510X

文摘

We present the first magnetic phase of an ionic liquid with anion鈭捪€ interactions, which displays a three-dimensional (3D) magnetic ordering below the N茅el temperature, T_N = 7.7 K. In this material, called Dimim[FeBr₄], an exhaustive and systematic study involving structural and physical characterization (synchrotron X-ray, neutron powder diffraction, direct current and alternating current magnetic susceptibility, magnetization, heat capacity, Raman and M枚ssbauer measurements) as well as first-principles analysis (density functional theory (DFT) simulation) was performed. The crystal structure, solved by Patterson-function direct methods, reveals a monoclinic phase (P2₁ symmetry) at room temperature with a = 6.745(3) 脜, b = 14.364(3) 脜, c = 6.759(3) 脜, and 尾 = 90.80(2)掳. Its framework, projected along the b direction, is characterized by layers of cations [Dimim]⁺ and anions [FeBr₄]^{鈭?/sup> that change the orientation from layer to layer, with Fe路路路Fe distances larger than 6.7 脜. Magnetization measurements show the presence of 3D antiferromagnetic ordering below T_N with the existence of a noticeable magneto鈥揷rystalline anisotropy. From low-temperature neutron diffraction data, it can be observed that the existence of antiferromagnetic order is originated by the antiparallel ordering of ferromagnetic layers of [FeBr₄]鈭?/sup> metal complex along the b direction. The magnetic unit cell is the same as the chemical one, and the magnetic moments are aligned along the c direction. The DFT calculations reflect the fact that the spin density of the iron ions spreads over the bromine atoms. In addition, the projected density of states (PDOS) of the imidazolium with the bromines of a [FeBr₄]鈭?/sup> metal complex confirms the existence of the anion鈭捪€ interaction. Magneto鈥搒tructural correlations give no evidence for direct iron鈥搃ron interactions, corroborating that the 3D magnetic ordering takes place via superexchange coupling, the Fe鈥揃r路路路Br鈥揊e interplane interaction being defined as the main exchange pathway.}