Synthesis, crystal structures, and magnetic properties of six transition metal phosphonates

Abstract

Six coordination polymers of metal phosphonates, [Co₃(HL)₂(H₂O)₄]·2H₂O (1), [Cu(H₂L)H₂O] (2), [Fe₃(L)₂(H₂O)₃OH]·2H₂O (3), [Cu₂(L)(4,4′-bipy)_1.5]·5H₂O (4), [Co(H₂L)(4,4′-bipy)_0.5] (5), and [Ni(H₂L)(4,4′-bipy)_0.5] (6) (H₄L = 4-F-C₆H₄CH₂N(CH₂PO₃H₂)₂), have been synthesized by hydrothermal methods and structurally characterized by X-ray single-crystal diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Complexes 1–3 exhibit a 2D inorganic layer structure with a regular and alternate arrangement of metal ions and PO₃ groups, where the layers are connected by moderately strong hydrogen bonds to form a supramolecular 3D network. Complexes 4–6 have a one-dimensional chain structure connected through similar coordination modes with 1–3, where each chain is rejoined by 4,4′-bipy bridges, forming layer coordination polymers. In addition, three complexes contain abundant water molecules, which exhibit different aggregation modes, clusters and chains, respectively. The magnetic properties of complexes 1–6 have been quantificationally studied using the Curie–Weiss law and the PHI program package.