A Rare Octahedral Yb(III) Complex Exhibiting Field-Induced Single-Molecule Magnet Behavior

Ytterbium-(III) complexes have attracted growing interest due to their unique magnetic properties and potential applications in molecular magnetism. From this perspective, the synthesis, structural characterization, and magnetic and theoretical studies of a new mononuclear Yb-(III) complex, [YbI₂(OPPh₃)₄]-(I₃) (<b>1</b>), are reported. Compound <b>1</b> features a six-coordinate Yb-(III) ion that adopts a distorted octahedral geometry with two axial iodide ions (I^-) and four equatorial triphenylphosphine oxide (Ph₃PO) ligands. Magnetic studies reveal that complex <b>1</b> exhibits entirely visible out-of-phase signals below 7 K under an 800 Oe applied <i>dc</i> field and slow magnetic relaxation, consistent with field-induced single-molecule magnetism behavior. <i>Ab initio</i> calculations rationalize the experimental magnetic dynamics, suggesting the dominance of the Raman mechanism in <b>1</b> over the Orbach relaxation pathway. The LoProp charges study elucidates the contribution of the equatorial ligand's oxygen atoms and the polarizability of the negatively charged axial iodide ligands, which enhances the magnetic anisotropy of the prolate Yb-(III) ion, resulting in significant crystal-field splitting.