Two unique antiferromagnetic 3D frameworks with unusual CuII4 cluster and alternate CuII4 + CuII1 structural motif tuned by aromatic polycarboxylate coligand

Two new 3-amino-1,2,4-triazole (amtrz)-based 3D MOFs, [Cu4(amtrz)2(μ3-OH)2(btc)2]n (1), and [Cu5(amtrz)2(H2O)2(μ3-OH)2(btec)2]n (2) (btc3− = 1,3,5-benzenetricarboxylate and btec4− = 1,2,4,5-benzenetetracarboxylate), were hydrothermally synthesized and structurally and magnetically characterized. Each cationic [Cu4(amtrz)2(μ3-OH)2]6+ cluster in 1 is periodically extended into an infinite 3,6-connected rtl-type topological network via six btc3− ligands. In contrast, analogous CuII4 clusters to 1 and square-planar CuII1 cores in 2 are alternately interlinked through btec4− linkers to generate a 3D (44·62)2(46·64)4(48·66·8)3 framework, which is a scarcely observed higher-dimensional coordination polymer with a CuII4 + CuII1 motif. More interestingly, both the coordination polymers display strong antiferromagnetic couplings up to −154.6 cm−1 due to the favorable multiple heterobridges in the analogous CuII4 component.