Two new 3D lanthanide metal-organic frameworks constructed from nitrilotriacetate and oxalate ligands

Two isomorphous three-dimensional lanthanide metal-organic frameworks, K[Ln2(NTA)(ox)2(H2O)2]·3H2O (Ln = Pr (1) and Gd (2), NTA = nitrilotriacetate, ox = oxalate) have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, thermogravimetric analysis (TGA) and magnetic analyses. The 3D frameworks of compounds 1 and 2 possess three topologically nonequivalent 4-connected nodes synchronously and exhibit unprecedented (65∙ 8)(43∙ 63)(4∙65) topologies. Variable-temperature magnetic susceptibility measurements for complexes 1 and 2 indicate there exist antiferromagnetic interactions between magnetic centers.