Effect of Coordinated Solvent Molecules on Metal Coordination Sphere and Solvent-Induced Transformations

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• 作者：Wen-Qian Zhang ; Wen-Yan Zhang ; Rui-Dong Wang ; Chun-Yan Ren ; Quan-Quan Li ; Yan-Ping Fan ; Bin Liu ; Ping LiuYao-Yu Wang
• 刊名：Crystal Growth & Design
• 出版年：2017
• 出版时间：February 1, 2017
• 年：2017
• 卷：17
• 期：2
• 页码：517-526
• 全文大小：673K
• ISSN：1528-7505

文摘

Four similar Mn(II) metal–organic frameworks (MOFs), {[Mn₂(nbtc)(H₂O)₂(S)]·S·0.5H₂O}_n [S = DMF (1), DMA (2), NMP (3), DEF (4)] (DMF = N,N′-dimethylformamide, DMA = N,N′-dimethylacetamide, NMP = N-methyl-2-pyrrolidinone, DEF = N,N′-diethylformamide), have been assembled solvothermally from the nitro and carboxyl doubly functionalized ligand 6,6′-dinitro-2,2′,4,4′-biphenyl tetracarboxylic acid (H₄nbtc) and characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectroscopy, thermogravimetric analyses, and powder X-ray diffraction. All MOFs exhibit unique three-dimensional double-walled open-frameworks with one-dimensional parallelogram channels and have guest/coordinated water and carbonyl solvent molecules, reasonably providing a good example of the competitive behavior of water and carbonyl solvent molecules and an excellent candidate for studying the single crystal coordinated solvent exchange transformations. Interestingly, because of the different steric hindrance of the series of coordinated carbonyl solvent molecules, the MOFs’ structural differences primarily display on the coordination mode of O1W and coordination sphere of Mn1/Mn2 between MOFs 1(4) and 2(3). And it is also found that a small variation of the lattice parameters, unit cell volume, and density occurs. Furthermore, MOFs 1–3 show solvent-induced single-crystal-to-single-crystal (SCSC) transformations, which only exchange coordinated and guest carbonyl solvent molecules (DMF, DMA, NMP). And fortunately, the available single crystal data of 2′ and 2″ have been collected, which were obtained by soaking 1 and 3 in DMA solution for 5 days and 7 days respectively, and they have the same molecular formula as 2 but slightly different structures from 2. In such transformations, the complete solvent exchanging time discrimination of 2 to 3 (10 days), 3 to 2 (7 days), 3 to 1 (5 days), 1 to 2 (5 days), and 2 to 1 (3 days) is susceptible to the size of carbonyl solvent molecules (NMP > DMA > DMF), and the metal coordination sphere of SCSC regenerated samples is influenced not only by the character of coordinated carbonyl solvents but also the nature of mother crystals. In addition, MOFs 1–4 exhibit antiferromagnetic coupling, confirmed through magnetic susceptibility measurements.