Based on crystal-field theory, design strategies in consideration of local symmetry are highlighted for lanthanide-based single-molecule magnets, accompanied by practical concerns about magnetic studies and representative cases.

A reversible single-crystal-to-single-crystal transformation is used to dramatically change the relaxation behavior of a single-ion magnet. The coordination geometry of the Dy^III site of a [Zn–Dy–Zn] complex changes from pentagonal–bipyramid (quasi-D_5h) to octahedron (quasi-O_h), inducing an energy barrier change from 305 cm⁻¹ (439 K) to a negligible value, respectively. Ab initio calculations reveal that the ideal D_5h–Dy^III is of perfect axiality with a substantial energy barrier in accordance with the experimental result.