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

Abstract

Three new sandwich-type hexanuclear ZnII-LnIII clusters based on a methoxy substituted salicylamide Salen-like ligand and o-vanilline, [Zn2Ln4(HL)4(o-vanilline)2(OH)4(CH3OH)2]·2NO3·5CH3OH (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 ZnII-LnIII clusters display a hydroxyl bridged tetranuclear LnIII4 core sandwiched in an environment of two ZnII ions, four doubly deprotonated HL2- and two singly deprotonated o-vanilline. Photophysical determinations indicate that the ZnII-EuIII cluster shows mixed emissions both originating from ligands and EuIII ions, and the other two only display ligand-centered emission in visible region. The magnetic studies reveal that the ZnII-DyIII cluster displays rare ferromagnetic behavior with slow magnetic relaxation behavior at zero field.