Self-Assembled Lanthanide Phosphinate Square Grids (Ln = Er, Dy, and Tb): Dy₄ Shows SMM/SMT and Tb₄ SMT Behavior

Tetranuclear [2 × 2] square-grid-like Ln^III clusters have been synthesized by reacting LnCl₃·6H₂O salts with bis[α-hydroxy(p-bromophenyl)methyl]phosphinic acid [R₂PO₂H, where R = CH(OH)PhBr] and pivalic acid. Single-crystal X-ray diffraction studies show the formation of [Me₄N]₂[Ln₄(μ₂-η¹:η¹-PO₂R₂)₈(η²-CO₂Bu^t)₄(μ₄-CO₃)] [Ln = Er (1), Dy (2), and Tb (3)]. Direct-current studies reveal significant ferromagnetic interactions between Dy^III in 2 and Tb^III in 3 and an antiferromagnetic interaction between Er^III in 1. Dynamic magnetic susceptibility measurements confirm a single-molecule magnet (SMM) behavior in both 0 and 1200 Oe applied magnetic fields for 2. Complexes 2 and 3 show single molecular toroic (SMT) behavior with a mixed magnetic moment.