Two 3D metal–organic frameworks with different topologies, thermal stabilities and magnetic properties

Two novel 3D metal-organic frameworks, [ML] sub(n) (M = Co, 1; Mn, 2) were successfully prepared in solvothermal conditions using 3,3'-dimethoxy-4,4'-biphenyldicarboxylic acid (H sub(2)L) as the ligand. X-Ray crystallography analysis reveals that MOF 1 crystallizes in the monoclinic system, space group P2 sub(1)/cin contrast to MOF 2 in the tetragonal system, space group I4&cmb.macr; . MOF 1 contains an elongated [CoO sub(6)] octahedron with two bound methoxy groups in the transposition, whereas MOF 2 has a compressed [MnO sub(6)] octahedron with two coordinated methoxy groups in the cisarrangement. The ligand L shows a novel bis(tridentate) bridging coordination mode. MOF 1 exhibits a 3D framework with CdSO sub(4) (cds) topology consisting of two different nodes and good thermal stability (313 degree C). MOF 2 is a doubly interpenetrated 3D alpha -Po framework with a higher thermal stability (368 degree C). The study of magnetic properties in the temperature range of 1.8-300 K shows the occurrence of weak ferromagnetic interactions (J= 0.15 K) between the high-spin Co(ii) ions in 1, but a weak antiferromagnetic coupling (J= -0.15 cm super(-1)) between Mn(ii) ions in 2 due to the syn-anticarboxylate bridge.