Synthesis, structures, and magnetic properties of a family of 3d-4f [Na(2)Fe(6)Ln(2)] complexes (Ln = Y, Gd and Dy): effect of ligands on the connection of inorganic subunits

A family of 3d-4f heterometallic compounds [(Na2Fe6Dy2III)-Dy-III(N-3)(4)(HL)(4)(CH3O)(4)(PhCO2)(6)] (1, H4L = 2-{[(2-hydroxy-3-methoxyphenyl)methylene]amino}-2-(hydroxymethyl)-1,3-propanediol), [(Na2Fe6Dy2III)-Dy-III(N-3)(4)(L')(4)(CH3O)(4)(PhCO2)(6)(H2O)] (2, H3L' = (E)-2-ethyl-2-(2-hydroxy-3-methoxybenzylideneamino) propane-1,3-diol), [(Na2Fe6Dy2III)-Dy-III(N-3)(4)(L')(4)(CH3O)(4)((BuCO2)-C-t)(6)] (3) [(Na2Fe6Y2III)-Y-III(N-3)(4)(L')(4)(CH3O)(4)(PhCO2)(6)(H2O)] (4), and [(Na2Fe6Gd2III)-Gd-III(N-3)(4)(L')(4)(CH3O)(4)(PhCO2)(6)(CH3OH)(2)] (5) have been prepared using Schiff-base ligands, trinuclear iron precursor complexes, azides and lanthanide nitrates as reactants. In compounds 1 and 2, the structure of the [(Na2Fe6Dy2III)-Dy-III] cluster forms a couple of cis, trans-isomers with substitution of methyl for a free hydroxyl group which belongs to the Schiff-base ligand. When the pivalates are employed instead of bulkier benzoates, the trans-[(Na2Fe6Dy2III)-Dy-III] clusters act as network nodes in the formation of rhombic gridlike layered structures in compound 3. Compounds 2, 4 and 5 have similar metallic cores, only with different crystal solvent molecules. The magnetic measurements on all the compounds indicate dominant antiferromagnetic interactions between the metal centers