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 t o the former one. The structures consist of three-dimensional networks of m etal ions co-ordinated by malonate ligand acting as bridges. The transition metal and calcium ions exhibit octahedral and eight-co-ordination, respect ively. Thermogravimetric studies confirm the presence of both co-ordinated and hydrated water molecules. Spectroscopic measurements show high spin oct ahedral symmetries for the transition metal ions. Magnetic measurements rev eal the presence of weak antiferromagnetic interactions in all compounds.