Three sandwich-type zinc(ii)–lanthanide(iii) clusters: structures, luminescence and magnetic properties

Abstract

Three new sandwich-type hexanuclear Zn^II–Ln^III 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 Zn^II–Ln^III clusters display a hydroxyl bridged tetranuclear Ln^III₄ 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.