A six-legged piano stool dysprosium single-molecule magnet

Dysprosium single-molecule magnets (SMMs) with two mutually trans- anionic ligands have shown large crystal field (CF) splitting, giving record effective energy barriers to magnetic reversal (Ueff) and hysteresis temperatures (TH). However, these complexes tend to be bent, imposing a transverse field that reduces the purity of the mJ projections of the CF states and promotes magnetic relaxation. A complex with only one anionic ligand could have more pure CF states, and thus high Ueff and TH. Here we report the first example of an SMM with this topology, [Dy(C5Me5)(FPh)6][{Al[OC(CF3)3]3}2(µ-F)]2 (1-Dy), which exhibits Ueff = 564(33) cm–1 and TH = 14 K at sweep rates of 22 Oe s–1; the C5Me5 ligand imposes a strong axial CF and the five equatorially-bound neutral fluorobenzenes present only weak transverse interactions. We show that complexes such as 1-Dy can be useful starting materials for heteroleptic Ln complexes as the fluorobenzenes are easily displaced.