Tuning Interchain Interactions in Two-Dimensional Networks of MnIII Schiff-Base Complexes and Dicarboxylic Acids by Varying the Linker

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• 作者：Yoshitaka Aono ; Hiroki Yoshida ; Keiichi Katoh ; Brian K. Breedlove ; Koichi Kagesawa ; Masahiro Yamashita
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：July 20, 2015
• 年：2015
• 卷：54
• 期：14
• 页码：7096-7102
• 全文大小：445K
• ISSN：1520-510X

文摘

Two-dimensional (2D) coordination polymers consisting of Mn^III Schiff-base complexes and dicarboxylic acids, [{Mn(salen)}₄(L1)](PF₆)₂路(CH₃OH)₂ (C4; H₂L1 = adipid acid) and [{Mn(salen)}₄(L2)](PF₆)₂路(CH₃OH)₄ (C4鈥? H₂L2 = E,E-1,3-butadiene-1,4-dicarboxylic acid) (salen^{2鈥?/sup> = N,N鈥?(ethylene)bis(salicylideneiminato), were synthesized by using a one-pot reaction and characterized by using single-crystal X-ray crystallographic analysis. One-dimensional (1D) chains composed of Mn(salen) dimers, [Mn₂], bridged by carboxylato ligands (鈭抂Mn₂]鈥揙CO鈥?[Mn₂]鈭?, were linked by dicarboxylato ligands with n-butyl (鈭扖₄H₈鈭? (C4) and butadienyl aliphatic groups (鈭扖₄H₄鈭? (C4鈥?. From static magnetic measurements on both C4 and C4鈥? there were ferromagnetic interactions between the MnIII ions through the phenoxo oxygen atoms of the salen2鈥?/sup>, and antiferromagnetic interactions between the MnIII ions through carboxylato ligands (鈭扥CO鈭?. As a result, weak ferromagnetism occurred because of the zigzag-shaped chain structure of C4 and C4鈥? and magnetic anisotropy for Mn(salen). In the magnetization curves for C4鈥? weak interchain interactions (J_linker) occurred through the 蟺-conjugated butadienyl linkers in C4鈥? which C4 did not have. In other words, changing from saturated to unsaturated aliphatic groups in the dicarboxylic acid linkers resulted in weak interactions between 1D-magnetic chain moieties. Therefore, in the case of only C4鈥? antiferromagnetic phase transition appeared at 2.3 K. Both coordination polymers exhibited slow relaxation of the magnetizations, which originated from SCM moieties, because C4 and C4鈥?showed magnetic correlations. It is noteworthy that alternating current (ac) susceptibilities for C4鈥?are frequency-dependent around the N茅el temperature. From analysis of the ac susceptibilities for C4, 伪 (dispersion coefficient of the relaxation of magnetization) varied linearly with 1/T. This signifies that C4 behaved as an SCM with a single relaxation process. On the other hand, in 伪 versus 1/T plots for C4鈥? an inflection point was observed at the N茅el temperature, indicating that J_linkers had an effect on the distribution of the relaxation times. Moreover, the inflection point for C4鈥?disappeared when a dc magnetic field was applied. This is the first report showing a direct correlation between an antiferromagnetic phase transition and slow magnetic relaxation.}