A High-Performance Single-Molecule Magnet Utilizing Dianionic Aminoborolide Ligands

The first example of a homoleptic f-block borolide sandwich complex is presented and shown to be a high-performance single-molecule magnet (SMM). The bis­(borolide) complex [K(2.2.2)]­[[1-(piperidino)-2,3,4,5-tetraphenylborolyl]₂Dy] (1) features an unusual example of an anionic Ln³⁺ metallocene that supports short metal–ligand bonds and a high degree of linearity around the central Dy³⁺ ion, resulting in comparatively large barriers to magnetization reversal (U_eff = 1600 cm^–1 for the most linear orientation) and, importantly, a high blocking temperature (T_B, defined as T(τ_100s)) of 66 K. These metrics put complex 1 among the very best performing SMMs reported to date and highlight the potential of dianionic borolide ligands to increase ligand field axiality, compared to monoanionic cyclic ligands, to ultimately maximize magnetic anisotropy in f-block-based SMMs.