Syntheses, structures and magnetic properties of two isostructural metal-phosphonate frameworks

A phosphonic acid, 4-(1,2,4-triazol-4-yl)phenylphosphonic acid (H2ptz) was used as a new ligand to construct magnetic materials, by which two 2-dimensional (2D) layered metal phosphonates, [M5(Hptz)2(ptz)4]n (where M = Co(II) (1) and Mn(II) (2)) have been hydrothermally synthesized. Both compounds were characterized by elemental analyses, infrared spectroscopy, powder X-ray diffraction and X-ray single-crystal diffraction. Structure analyses reveal that 1 and 2 are isostructures, where the metal and ptz ligands form M5(Hptz)2(ptz)4 subunits, which are further linked together into a 2-D layered structure. The magnetism studies over the temperature range 2–300 K showed pronounced antiferromagnetic interactions between the combined oxo- and diazo-bridged metal centers in both 1 and 2.