Study of the [CaM(C_3H_2O_4)_2(H_2O)_4] (centre dot) nH_2O [M = Mn, Fe or Co (n = 0) and Ni (n = 2)] systems: synthesis, structure, spectroscopic and magnetic properties

摘要

The [CaM(mal)(H_2O)_4] (M = Mn, Fe or Co; mal = C_3H_2O_4) and [CaNi(mal)_2(H_2O) (centre dot) 2H_2O compounds have been synthesized and characterized. X-Ray single crystal diffraction analysis was carried out on the [CaMn(C_3H_2O_4)_2(H_2O)_4] and [CaNi(C_3H_2O_4)_2(H_2O)_4] (centre dot) 2H_2O complexes. The [CaM(C_3H_2O_4)_2(H_2O)_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.