Synthesis, structures and magnetic properties of a family of nitrate-bridged octanuclear [Na2Ln6] (Ln = Dy, Tb, Gd, Sm) complexes

A new family of octanuclear lanthanide compounds [Na2Ln6L8(C6H4NH2COO)2(C2H5OH)2(H2O)4(NO3)]·NO3·C2H5OH·nH2O [H2L = 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid; Ln = Dy (1) (n = 15); Tb (2), Gd (3) (n = 14); Sm (4) (n = 16)] have been prepared under hydrothermal conditions. The X-ray crystal structure analysis reveals that complexes 1–4 are isomorphous. The core of the structure is a [4 + 2] combination of an Ln4 cubane and an Ln2 unit. The two units are bridged by a nitrate ion, which is located in the center of the cluster and displays an unusual μ8-η2:η2:η4 tridentate bridging mode. The magnetic studies for complex 1 show that the [Na2Dy6] unit exhibits slow magnetic relaxation behavior.