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 ZnII-LnIII [LnZn2L2(CH3COO)2(H2O)(CH3OH)]·NO3 (Ln= Dy(1) and Gd(2)) complexes employing a multisite coordinating Schiff base ligand, (E)-2-(hydroxymethyl)-4-methyl-6-[{(pyridine-2-ylmethyl)imino}methyl]phenol, in the presence of Ln(NO3)3.xH2O and Zn(OAc)2·2H2O. The complexes crystallize in the monoclinic crystal system with the P21/c 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 1 as a single ion magnet with Ueff = 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.