Two Homometallic Antiferromagnets Based on Oxalato-Bridged Honeycomb Assemblies: (A)2[MII2(C2O4)3] (A = Ammonium Salt Derived from Die

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• 作者：Zhiming Duan^† ; ^‡ ; ; Yan Zhang^§ ; ; Bin Zhang*^† ; ; Francis L. Pratt*
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：March 2, 2009
• 年：2009
• 卷：48
• 期：5
• 页码：2140-2146
• 全文大小：317K
• 年卷期：v.48,no.5(March 2, 2009)
• ISSN：1520-510X

文摘

Oxalato-bridged divalent homometallic compounds A₂[M^II₂(C₂O₄)₃] (M^II = Fe²⁺ (1), Co²⁺ (2)) were obtained by a solvothermal method. They consist of honeycomb anions and cations, that is, the 5-oxo-1,4,7-triazabicyclo[4.3.0]non-6-en-7-yl ammonium ion (hereafter abbreviated as A₁) in 1 and the 2-(2,3-dioxo-1-piperazinyl)eth-1-yl ammonium ion (hereafter abbreviated as A₂) in 2, which were generated from in situ reactions of diethylenetriamine (DETA) with oxalic acid catalyzed by the metal ions and yielded two compounds with different cell parameters: a = 17.2224(4)Å, b = 9.3151(2)Å, c = 15.1518(4)Å, β = 95.767(1)°, V = 2418.5(1)ų, and Z = 4, C2/c for 1 and a = 9.6924(2)Å, b = 15.8325(4)Å, c = 17.2995(4)Å, β = 95.144(1)°, V = 2644.0(1)ų, Z = 4, and P2₁/n for 2. A₁ points its carbonyl group to the pocket of the honeycomb network. A₂ forms a helical chain around the anion layers through hydrogen bonds along the 2₁ axis, and the crystal remains achiral due to the existence of the inversion symmetry. The methanol molecules occupy the holes situated between A₂ and the oxalate network in 2. The distance between two anion layers in 1 was shorter than in 2 due to the template effect of the ammonium salts. In the anion layers, the hexagonal rings are elongated along the a axis in 1 and 2. There are interactions as hydrogen bonds between the cation and anion and between cations. A broad maximum observed in the temperature-dependent susceptibility curve shows antiferromagnetic interactions between paramagnetic ions. The antiferromagnetic ordering at 28 K in 1 and 21 K in 2 was confirmed by ac suspceptibility and specific heat measurements. Hysteresis loops with a coercive field of 17 Oe in 1 and 2300 Oe in 2 were observed at 2 K.