Chiral Zn₃Ln₃ Hexanuclear Clusters of an Achiral Flexible Ligand

Abstract

Multifunctional single-molecule magnets (SMMs) have sparked great interest, but chiral SMMs obtained via spontaneous resolution are rarely reported. We synthesized a series of chiral trinuclear hepta-coordinate lanthanide complexes [Zn^II₃Ln^III₃] (<b>1</b> for Dy, <b>2</b> for Tb, <b>3</b> for Gd, and <b>4</b> for Dy_0.07Y_0.93) using the achiral flexible ligand H₂L (2,2'-[1,2-ethanediylbis[(ethylimino)methylene]]bis[3,5-dimethylphenol]). The complexes crystallize in the chiral <i>P</i>6₃ group space, and two enantiomers of different chirality are spontaneously resolved. Three [Zn(L)Cl]^- anions utilize the two phenoxy oxygen atoms of each L^2- to coordinate with three lanthanide ions, respectively, and the three hepta-coordinate <i>D</i>_5h lanthanide ions are arranged in a triangle. The chirality comes from the propeller arrangement of the peripheral three bidentate chelate L^2- ligands like octahedral [M(AA)₃]^<i>n</i>+/- (M = transition metal ions; AA = bidentate chelate ligands, e.g., 2,2'-bipyridine, 1,10-phenathroline, ethylenediamine, acac^- or oxalate). Complex <b>1</b> exhibits an AC susceptibility signal and is frequency-dependent, which is typical of SMMs. Complex <b>4</b>, doped with a large amount of diamagnetic Y(III) in Dy(III), exhibits <i>U</i>_eff = 48.3 K and τ₀ = 4.4 × 10^-8 s in experiments. Complex <b>2</b> shows circularly polarized luminescence and apparent photoluminescence, typical of the f-f transitions of Tb(III).