2,2′-Oxydiacetato-bridged complexes containing Sm(III) and bivalent cations. Synthesis, structure, magnetic properties and chemical speciation

Heterometallic compounds containing Sm(III), bivalent cations M (M = Cu, Ni, Co, Mn, Ca, Mg), and 2′,2′-oxydiacetate (oda) as connecting ligand have been prepared and characterized. The complexes can be formulated as [Sm2M3(oda)6] · xH2O. The structure of [Sm2Cu3(oda)6(H2O)6] shows the presence of the Sm(III) coordinated by six carboxy and three ether oxygen atoms, and the Cu(II) cation bonded to four carboxy oxygens and two molecules of water. An open 3D framework is observed, containing large hexagonal channels. At room temperature, the polynuclear complexes behave as built by magnetically isolated paramagnetic ions, but at low temperatures, very weak antiferromagnetic interactions M – M are predominant. The chemical systems were also investigated in solution (25.0 °C, I = 0.5 M Me4NCl) by potentiometry. The same kind of polynuclear species have been found.