Lanthanide Coordination Polymers with 4,4鈥?Azobenzoic Acid: Enhanced Stability and Magnetocaloric Effect by Removing Guest Solvents

详细信息    查看全文

• 作者：Shaowei Zhang ; Eryue Duan ; Zongsu Han ; Leilei Li ; Peng Cheng
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：July 6, 2015
• 年：2015
• 卷：54
• 期：13
• 页码：6498-6503
• 全文大小：533K
• ISSN：1520-510X

文摘

Three lanthanide coordination polymers (Ln-CPs) formulated as [Ln(azdc)(HCOO)]_n [Ln = Gd^III (1), Tb^III (2), Dy^III (3); H₂azdc = 4,4鈥?azobenzoic acid] have been successfully obtained by the solvothermal reaction of Ln^III ions with H₂azdc ligands in the mixed solvent N,N-dimethylformamide (DMF)/H₂O. Compared with our previous work on Ln-CPs with H₂azdc ligands, [Gd₂(azdc)₃(DMA)₂]_n路2nDMA (1鈥?/b>; DMA = dimethylacetamide), in which the DMA molecules coordinate to Gd^III ions that are replaced by HCOO^{鈥?/sup> groups in 1, resulting in the distinct structures and properties of the final products. Adjacent LnIII ions in 1鈥?b>3} are connected by HCOO^{鈥?/sup> groups through bridging and chelating modes to give 2D layers, which are further linked by azdc2鈥?/sup> ligands to produce 3D frameworks. Magnetic results declare that antiferromagnetic couplings exist in 1, although two different magnetic interactions among adjacent GdIII ions derived from antiferromagnetic interactions of the smaller Gd鈥揙鈥揋d angles (Gd路路路Gd distances) and weak ferromagnetic interactions of the larger Gd鈥揙鈥揋d angles (Gd路路路Gd distances) coexist in 1. Furthermore, the magnetocaloric effect (MCE) value of 1 is 1.5 times as large as that of 1鈥?/b>. More importantly, 1 exhibits excellent stabilities toward air, thermal, solvent, and acid/alkaline conditions. The results manifest that the crystalline structure of 1 can be stable at at least 425 掳C supported by the in situ variable-temperature powder X-ray diffraction patterns and thermogravimetric analyses, in air for at least 3 months, and in common solvents for more than 1 week, as well as in aqueous solutions ranging from pH = 2 to 12 for more than 1 week.}