Synthesis and magnetic properties of 3D-metal oxalate networks as molecular-based magnets

The reaction of oxalic acid, metal(II) salt and tetra(n-butyl) ammonium bro mide or dimethyl dioctadecyl ammonium bromide in a molar ratio of 1.5:1:1 i n water or ethanol-water at room temperature afforded polymetallic assembli es with the formulae {(NBu4)(2)[M-2(OX)(3)]}(x) [M = Mn2+(1), Fe2+(2), Co2(3)] and {(DMDOA)(2)[M-2(OX)(3)]}(x) [M = Mn2+(4), Fe2+(5), Co2+(6)]. The m agnetic susceptilbility data of 5 and 6 in the range 20 K < T < 300 K obey the Curie-Weiss law and on lowering the temperature the effective magnetic moment decreases gradually and reveals antiferromagnetic phase transition. They have also been characterized by FAB mass, IR, electronic and ESR spect ra.