Tetranuclear Lanthanide Complexes Containing a Hydrazone-type Ligand. Dysprosium [2 × 2] Gridlike Single-Molecule Magnet and Toroic

Abstract

A multidentate hydrazone-type ligand (Z,Z)-bis(1-(pyridin-2-yl)-1-amino-methylidene)oxalohydrazide (H₂L) was utilized in the synthesis of three new isomorphous tetranuclear complexes of the general formula [Ln₄(HL)₄(H₂L)₂(NO₃)₄](NO₃)₄·4CH₃OH (Ln = Gd^III, 1, Tb^III, 2, Dy^III, 3) with the gridlike [2 × 2] topology. The analysis of the static magnetic data revealed weak anti-ferromagnetic interaction among lanthanide(III) atoms, whereas dynamic magnetic data led to the observation of the single-molecule magnet behavior in zero static magnetic field for the Dy₄ compound 3 with U_eff = 42.6 K and τ₀ = 1.50 × 10^-5 s. The theoretical CASSCF calculations supported also the presence of the net toroidal magnetic moment, which classifies compound 3 also as a single-molecule toroic.