Study of the [CaM(C3H2O4)(2)(H2O)(4)]center dot nH(2)O [M = Mn, Fe or Co (n=0) and Ni (n=2)] systems: synthesis, structure, spectroscopic and magnetic properties

The [CaM(mal)(2)(H2O)(4)] (M = Mn, Fe or Co; mal = C3H2O4) and [CaNi(mal)(2)(H2O)(4)]. 2H(2)O compounds have been synthesized and characterized. X-Ray single crystal diffraction analysis was carried out on the [CaMn(C3H2O4)(2)(H2O)(4)] and [CaNi(C3H2O4)(2)(H2O)(4)]. 2H(2)O complexes. The [CaM(C3H2O4)(2)(H2O)(4)] (M = Fe or Co) compounds are considered to be isostructural to the former one. The structures consist of three-dimensional networks of metal ions co-ordinated by malonate ligand acting as bridges. The transition metal and calcium ions exhibit octahedral and eight-co-ordination, respectively. Thermogravimetric studies confirm the presence of both co-ordinated and hydrated water molecules. Spectroscopic measurements show high spin octahedral symmetries for the transition metal ions. Magnetic measurements reveal the presence of weak antiferromagnetic interactions in all compounds.