Cyclooctatetraenide-based single-ion magnets featuring bulky cyclopentadienyl ligand

Abstract

We report a family of organometallic rare-earth complexes with the general formula (COT)M(Cpttt) (where (COT)2− = cyclooctatetraenide, (Cpttt)− = 1,2,4-tri(tert-butyl)cyclopentadienide, M = Y(iii), Nd(iii), Dy(iii) and Er(iii)). Similarly to the prototypical Er(iii) analog featuring pentamethylcyclopentadienyl ligand (Cp*)−, (COT)Er(Cpttt) behaves as a single-ion magnet. However, the introduction of the sterically demanding (Cpttt)− imposes geometric constraints that lead to a simplified magnetic relaxation behavior compared to the (Cp*)− containing complexes. Consequently, (COT)Er(Cpttt) can be viewed as a model representative of this organometallic single-ion magnet architecture. In addition, we demonstrate that the increased steric profile associated with the (Cpttt)− ligand permits preparation, structural characterization and interrogation of magnetic properties of the early-lanthanide complex, (COT)Nd(Cpttt). Such a mononuclear derivative could not be obtained when a (Cp*)− ligand was employed, a testament to larger ionic radius of this early lanthanide ion.