Three sandwich-type zinc(II)-lanthanide(III) clusters: structures, luminescence and magnetic properties

Three new sandwich-type hexanuclear Zn-II-Ln(III) clusters based on a methoxy substituted salicylamide Salen-like ligand and o-vanilline, [Zn(2)Ln(4)(HL)(4)(o-vanilline) (2)(OH)(4)(CH3OH)(2)]center dot 2NO(3)center dot 5CH(3)OH (Ln = Eu, Tb and Dy, H3L = 1-(2-hydroxy-4-methoxy-benzamido)-2-(2-hydroxy-3-methoxy-benzylideneamino)ethane) were synthesised. Single-crystal structure analyses reveal that these Zn-II-Ln(III) clusters display a hydroxyl bridged tetranuclear Ln(4)(III) core sandwiched in an environment of two Zn-II ions, four doubly deprotonated HL2- and two singly deprotonated o-vanilline. Photophysical determinations indicate that the Zn-II-Eu-III cluster shows mixed emissions both originating from ligands and Eu-III ions, and the other two only display ligand-centered emission in visible region. The magnetic studies reveal that the Zn-II-Dy-III cluster displays rare ferromagnetic behavior with slow magnetic relaxation behavior at zero field.