A new series of layered transition metal oxalates: hydrothermal synthesis, structural and magnetic studies

The hydrothermal synthesis and crystallographic study of a new family of isostructural transition metal oxalate compounds, Ba2M2(ox) 3Cl2(H2O)4(M = Mn(II)(1), Fe(II)(2) or Co(II)(3)) is reported. The crystal structure has C2/c symmetry and contains two types of oxalate. These dianionic ligands bridge the transition metal ions in two different modes, which together form a 2-D net comprised of linked chains of transition metal ions. The iron derivative shows strong evidence of antiferromagnetic coupling interactions and significant short-range magnetic order at low temperatures but there is no evidence of long-range ordering above 2 K. Attempts to fit the observed magnetic susceptibility to several approximate models is reviewed. The Co derivative also shows antiferromagnetic coupling and additionally appears to have a magnetic phase transition at about 11(1) K.