Self-Assembled Lanthanide Phosphinate Square Grids\n(Ln = Er, Dy, and Tb): Dy<sub>4</sub> Shows SMM/SMT and Tb<sub>4</sub> SMT Behavior

Tetranuclear [2 × 2] square-grid-like\nLn<sup>III</sup> clusters\nhave been synthesized by reacting LnCl<sub>3</sub>·6H<sub>2</sub>O salts with bis[α-hydroxy(<i>p</i>-bromophenyl)methyl]phosphinic\nacid [R<sub>2</sub>PO<sub>2</sub>H, where R = CH(OH)PhBr] and pivalic\nacid. Single-crystal X-ray diffraction studies show the formation\nof [Me<sub>4</sub>N]<sub>2</sub>[Ln<sub>4</sub>(μ<sub>2</sub>-η<sup>1</sup>:η<sup>1</sup>-PO<sub>2</sub>R<sub>2</sub>)<sub>8</sub>(η<sup>2</sup>-CO<sub>2</sub>Bu<sup>t</sup>)<sub>4</sub>(μ<sub>4</sub>-CO<sub>3</sub>)] [Ln = Er (<b>1</b>), Dy (<b>2</b>), and Tb (<b>3</b>)]. Direct-current\nstudies reveal significant ferromagnetic interactions between Dy<sup>III</sup> in <b>2</b> and Tb<sup>III</sup> in <b>3</b> and an antiferromagnetic interaction between Er<sup>III</sup> in <b>1</b>. Dynamic magnetic susceptibility measurements confirm a\nsingle-molecule magnet (SMM) behavior in both 0 and 1200 Oe applied\nmagnetic fields for <b>2</b>. Complexes <b>2</b> and <b>3</b> show single molecular toroic (SMT) behavior with a mixed\nmagnetic moment.