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2D and 3D mixed MII/CuII metal–organic frameworks (M = Ca and Sr) with N,N′-2,6-pyridinebis(oxamate) and oxalate: preparation and magneto-structural study†
Dalton Transactions ( IF 3.5 ) Pub Date : 2018-08-06 00:00:00 , DOI: 10.1039/c8dt01686k
Tamires S. Fernandes 1, 2, 3, 4, 5 , Wanessa D. C. Melo 1, 2, 3, 4, 5 , Lucas H. G. Kalinke 1, 2, 3, 4, 5 , Renato Rabelo 1, 2, 3, 4, 5 , Ana K. Valdo 1, 2, 3, 4, 5 , Cameron C. da Silva 1, 2, 3, 4, 5 , Felipe T. Martins 1, 2, 3, 4, 5 , Pedro Amorós 6, 7, 8, 9 , Francesc Lloret 8, 9, 10, 11 , Miguel Julve 8, 9, 10, 11 , Danielle Cangussu 1, 2, 3, 4, 5
Affiliation  

Three heterobimetallic complexes of formula [Ca2Cu3(mpyba)2(2-apyma)(H2O)7]·8.3H2O (1), [Sr2Cu3(mpyba)2(2-apyma)(H2O)8]·11.6H2O (2) and [Sr4.5Cu4(mpyba)4(ox)(H2O)20]·8.5H2O (3) [H4mpyba = N,N′-2,6-pyridinebis(oxamic acid), 2-apyma = 2-(6-aminopyridinyl)oxamate and ox = oxalate] have been synthesized and structurally characterized. Complexes 1 and 2 are isostructural compounds, with tricopper(II) units having mpyba and its hydrolytic product (2-apyma) as ligands. They are interlinked through strontium(II) (1) and calcium(II) (2) ions to afford neutral two-dimensional networks. Two of the copper(II) ions are five-coordinate in distorted square pyramidal (Cu3) and trigonal bipyramidal (Cu1) surroundings, whereas the other (Cu2) is six-coordinate in an elongated octahedral environment. The main difference between their structures, apart from the number of water molecules, resides in the nature of the alkaline earth cation coordinated to the oxamate fragments, Sr2+ (1)/Ca2+ (2), which exhibit eight and seven coordination, respectively. The π–π interactions and an extensive network of hydrogen bonds in 1 and 2 lead to supramolecular 3D structures. The relatively small size of their cavities, in the micropore domain, hinders the inclusion of N2 but allows CO2 adsorption (0.45 and 0.52 mmol g−1 for 1 and 2, respectively). The structure of 3 is made up of [3,3] metallacyclophane-type motifs, having the formula [Cu2(mpyba)2(H2O)2]4−. These act as tetrakis(bidentate) ligands towards the strontium(II) ions (Sr1, Sr2 and Sr3), leading to a sheet-like polymer growing in the bc plane, which extends further along the crystallographic a axis by a bis(chelating) oxalate between the Sr1 atoms. The investigation of the magnetic properties of 1–3 in the temperature range 1.9–300 K shows the occurrence of an overall antiferromagnetic behaviour for 1 and 2 [J12 = J23 = −9.71(2) (1) and −10.81(5) cm−1 (2), with the Hamiltonian being defined as H = −J12S1·S2J23S2·S3 + gβH[S1 + S2 + S3], and a ferromagnetic coupling within the dicopper(II) metallacylophane unit of 3 [J = +1.86(1) cm−1 through the Hamiltonian H = −JS1·S2 + gβH(S1 + S2)]. Simple orbital symmetry considerations (1–3) and the spin polarization mechanism (3) account for the observed magnetic properties.

中文翻译:

2D和3D混合中号II /铜II金属有机骨架(M = Ca和Sr)与ÑÑ '-2,6- pyridinebis(草氨酸乙酯)和草酸盐:制备和磁结构研究

三种式[Ca 2 Cu 3(mpyba)2(2-apyma)(H 2 O)7 ]·8.3H 2 O(1),[Sr 2 Cu 3(mpyba)2(2-apyma)( H 2 O)8 ]·11.6H 2 O(2)和[Sr 4.5 Cu 4(mpyba)4(ox)(H 2 O)20 ]·8.5H 2 O(3)[H 4 mpyba = NN合成了'-2,6-吡啶双(草酰胺酸),2-ap = 2-(6-氨基吡啶基)草酸酯和=草酸酯]并对其结构进行了表征。配合物12是同结构的化合物,其中三甲基铜(II)单元具有mpyba及其水解产物(2-缩醛)作为配体。它们通过锶(II)(1)和钙(II)(2)离子相互连接,以提供中性的二维网络。铜)离子在扭曲的方形锥体(Cu3)和三角双锥体(Cu1)环境中为五坐标,而另一个(Cu2)在细长的八面体环境中为六坐标。除水分子的数量外,它们结构之间的主要区别在于与草酸盐碎片Sr 2+1)/ Ca 2+2)配位的碱土金属阳离子的性质,其表现出八和七的配位, 分别。π-π相互作用和12中广泛的氢键网络导致超分子3D结构。在微孔区域,它们的空腔相对较小,阻碍了N 2的包埋。但允许CO 2吸附(12分别为0.45和0.52 mmol g -1)。3的结构由具有式[Cu 2(mpyba)2(H 2 O)2 ] 4-的[3,3]金属环烷型基序组成。这些充当四(二齿)配体朝向锶(II)离子(SR1,SR2和Sr3的),导致了片状聚合物中的生长BC平面,其进一步沿着晶体延伸一个由一个双轴线(螯合剂) Sr1原子之间的草酸酯。磁性能的研究在1.9–300 K的温度范围内的1-3表明发生了12的整体反铁磁行为[ J 12 = J 23 = -9.71(2)(1)和−10.81(5)cm -12) ,哈密顿量定义为H = − J 12 S 1 · S 2J 23 S 2 · S 3 + gβH [ S 1 + S 2 + S 3],并且在Dicopper(II)金属内甲oph烷单元内通过哈密顿量H [ -= J S 1 · S 2 + gβHS 1 + S 2)]的铁铜耦合度为3 [ J = +1.86(1)cm -1 ]。简单的轨道对称性考虑因素(1-3)和自旋极化机制(3)解释了所观察到的磁性。
更新日期:2018-08-06
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