Synthesis, Characterization, and Magnetic Studies of Coordination Polymers with Co(II) and Mn(II) Ions

An ether bridged tricarboxylic acid ligand, 5-(4-carboxybenzyloxy)­isophthalic acid (p-cbiaH3) has been used to construct three coordination polymers with Co­(II) salts in presence of different nitrogen donor ligands such as 1,4-bis­(4-pyridinylmethyl)­piperazine (bpmp), dipyridine-4-yl-diazene (dpd), and 4,4′-bipyridine (bpy). The products formed under hydrothermal conditions are formulated as {[Co3(p-cbia)2(bpmp)2(H2O)6]·10H2O}n (1), {[Co2(p-cbiaH)2(dpd)­(H2O)2]}n (2) and {[Co3(p-cbia)2(bpy)­(H2O)8]·6H2O}n (3). Reacting with MnCl2·4H2O under solvothermal condition, it affords {[Mn3(p-cbia)2(DMF)2]·DMF}n (4). All the complexes have been characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction (PXRD) measurements. Topological analysis reveals that 1 is a (3,4)-connected jeb net, 2 is a (3,8)-connected tfz-d net, while 3 forms a 3-connected hcb type net. However, with the Mn­(II) salt, it forms a 3D coordination polymer with a novel (5,6,6)-connected, three nodal net with novel pkb-4 topology. Magnetic susceptibility measurements of complexes 1, 2, and 4 were carried out in the temperature range 2–300 K. Complex 1 exhibits weak ferromagnetic ordering at low temperature owing to the frustration of one of the Co­(II) ions in the unit cell. Complex 2 shows a peak at ∼6.1 K in ZFC susceptibility, which might result from weak ferromagnetic interactions between carboxylate-bridged Co­(II) ions. Complex 4 shows a signature of antiferromagnetic behavior followed by weak ferromagnetic interactions at low temperature.

以醚桥联三羧酸配体5-(4-羧基苄氧基)间苯二甲酸（p-cbiaH3）为配体，分别与Co(II)盐在不同氮供体配体（1,4-双(4-吡啶甲基)哌嗪（bpmp）、偶氮二(4-吡啶)（dpd）以及4,4'-联吡啶（bpy））存在下构筑了三种配位聚合物。水热条件下得到的产物分别为{[Co3(p-cbia)2(bpmp)2(H2O)6]·10H2O}n（1）、{[Co2(p-cbiaH)2(dpd)(H2O)2]}n（2）以及{[Co3(p-cbia)2(bpy)(H2O)8]·6H2O}n（3）。将该配体与氯化锰(II)四水合物（MnCl2·4H2O）在溶剂热条件下反应，得到配位聚合物{[Mn3(p-cbia)2(DMF)2]·DMF}n（4），其中DMF为N,N-二甲基甲酰胺。所有配合物均通过单晶X射线衍射、红外光谱、热重分析、元素分析以及粉末X射线衍射（PXRD）进行了表征。拓扑分析表明，配合物1为(3,4)-连接的jeb拓扑网络，配合物2为(3,8)-连接的tfz-d拓扑网络，配合物3为3-连接的hcb型拓扑网络。而以Mn(II)盐得到的配合物4为三维配位聚合物，其具有新颖的(5,6,6)-连接三节点网络，且呈现独特的pkb-4拓扑结构。对配合物1、2和4开展了2~300 K温度区间内的磁化率测试。由于晶胞内一个Co(II)离子的磁阻挫效应，配合物1在低温下表现出弱铁磁有序行为。配合物2的零场冷却（Zero Field Cooling, ZFC）磁化率曲线在约6.1 K处出现峰值，这可能源于羧酸桥联Co(II)离子间的弱铁磁相互作用。配合物4则先表现出反铁磁行为，随后在低温下呈现弱铁磁相互作用的特征。