Switching a 2D Co(II) Layer to a 3D Co₇‑Cluster-Based Metal–Organic Framework: Syntheses, Crystal Structures, and Magnetic Properties

Two 2D layered coordination networks with formulas of {[Co­(TPA)­Cl]­(H2O)2.5}n (1) and {[Co­(TPA)­(μ2-OH)]­(H2O)2}n (2) (HTPA = 4-(1,2,4-triazol-4-yl)­phenylacetic acid) were solvothermally synthesized and fully characterized. Interesting 1D Co2+-Cl or Co2+-μ2-OH chain structures were observed. By carefully adjusting the reaction conditions, a new 3D metal–organic framework (MOF) with a formula of {[Co7(TPA)6(μ3-OH)4(μ2-OH)2(H2O)4]­(TPA)2(DMF)3(H2O)3}n (3) was obtained. MOF 3 is built from Co7 clusters and fully deprotonated TPA ligands, which display a cubic pcu topology. Factors that influence the structures of the three TPA-based complexes, as well as their magnetic properties, were investigated in detail. The heptanuclear-Co­(II)-cluster-based MOF 3 shows interesting magnetization dynamics at low temperature.我们通过溶剂热法合成了两种二维层状配位网络，其分子式分别为{[Co(TPA)Cl]·(H₂O)₂.₅}ₙ（标记为1）与{[Co(TPA)(μ₂-OH)]·(H₂O)₂}ₙ（标记为2），其中HTPA代表4-(1,2,4-三唑-4-基)苯乙酸（HTPA），并对二者进行了全面表征。研究中观察到了有趣的一维Co²⁺-Cl或Co²⁺-μ₂-羟基链结构。通过精准调控反应条件，我们获得了一种新型三维金属有机框架（Metal-Organic Framework, MOF），其分子式为{[Co₇(TPA)₆(μ₃-OH)₄(μ₂-OH)₂(H₂O)₄]·(TPA)₂(DMF)₃(H₂O)₃}ₙ（标记为3）。该MOF 3由Co₇团簇与完全去质子化的TPA配体构筑，呈现立方pcu拓扑结构。本研究详细探究了影响三种基于TPA的配合物结构的各类因素，并对它们的磁学性质进行了系统研究。基于七核Co(II)团簇的MOF 3在低温条件下展现出了有趣的磁化动力学行为。