Trinuclear Zn^II-Ln^III Complexes:Single-Ion Magnet Behavior in the Zn₂Dy Analogue

Placing diamagnetic transition metal ions in the vicinity of lanthanide ions separated by a single coordinated oxygen atom has emerged as an effective strategy to suppress quantum tunneling of magnetization (QTM), thereby enhancing the performance of single-molecule magnets. In this context, we have synthesized trinuclear Zn^II-Ln^III [LnZn₂L₂(CH₃COO)₂(H₂O)(CH₃OH)]·NO₃ (Ln= Dy(<b>1</b>) and Gd(<b>2</b>)) complexes employing a multisite coordinating Schiff base ligand, <i>(E)-2-(hydroxymethyl)-4-methyl-6-[{(pyridine-2-ylmethyl)imino}methyl]phenol,</i> in the presence of Ln(NO₃)₃.xH₂O and Zn(OAc)₂·2H₂O. The complexes crystallize in the monoclinic crystal system with the <i>P</i>2₁/<i>c</i> space group. The trimetallic system mainly consists of two Zn ions, one Ln ion, two deprotonated ligands, a solvent molecule (CH₃OH), aqua ligands, and NO₃^– present outside the coordination sphere. Magnetic studies demonstrate complex <b>1</b> as a single ion magnet with <i>U</i>_eff = 56.88 K and pre-exponential parameter τ = 1.94 × 10^–6 s. State-average CASSCF/RASSI-SO calculations performed on the Zn₂Dy complex reveal a large magnetization reversal barrier of 375 cm^–1 which is in accordance with the field-induced SMM behavior of this complex.