Slow magnetic relaxation in a neodymium metallocene tetraphenylborate complex

Abstract

Lanthanide-based single-molecule magnet research has historically focused on molecules of the highly anisotropic Dy3+ and Tb3+ ions, while studies on the lighter, more abundant lanthanides are still relatively scarce. Recent advances with Dy3+ metallocene complexes in particular have led to some truly exceptional systems and the highest relaxation barrier to date, in excess of 1200 cm−1. Even still, the design and understanding of systems incorporating the earlier lanthanides is arguably of great importance if the field is to shift in the direction of identifying systems for practical application. Herein, we present magnetic characterization of the mononuclear metallocene complex Cp*2Nd(BPh4) ([Cp*]− = pentamethylcyclopentadienyl anion), which exhibits slow magnetic relaxation with a relaxation barrier of Ueff = 29(1) cm−1 in the presence of a small dc magnetic field, illustrating that the metallocene ligand framework can also be utilized in the design of single-molecule magnets of the earlier lanthanides. We also discuss dynamic magnetic susceptibility data for the Cp*2Ho(BPh4) and Cp*2Er(BPh4) congeners, which reveal that this particular ligand field is best suited to lanthanides ions exhibiting an oblate 4f electron density.