Syntheses, structures and magnetic properties of Mn(II), Co(II) and Ni(II) metal–organic frameworks constructed from 1,3,5-benzenetricarboxylate and formate ligands

Three compounds, [(CH3)2NH2][M3(BTC)(HCOO)4(H2O)]·H2O (M = Mn (1), Co (2), Ni (3), H3BTC = 1,3,5-benzenetricarboxylic acid), were synthesized under hydrothermal conditions and were characterized by single crystal and powder X-ray diffraction, IR spectra, elemental analysis, coupled TG-MS and magnetic measurements. Compounds 1–3 are isostructural analogues and crystallize in monoclinic space group P21/c. Each metal ion in these compounds connects to six oxygen atoms to form a MO6 octahedron. Six MO6 octahedra link to each other to form a corner-shared hexameric M6 cluster, which is linked by BTC ligands to form two-dimensional layers. The two-dimensional layers are further connected by formic ions to form a three-dimensional network with channels, where (CH3)2NH2+ ions and water molecular are located. Magnetic measurements indicate that anti-ferromagnetic ordering occurs at low temperature for these compounds.