Slow magnetic relaxation in mononuclear complexes of Tb, Dy, Ho and Er with the pentadentate (N3O2) Schiff-base dapsc ligand

Abstract

Isostructural mononuclear complexes of heavy lanthanides with the pentadentate Schiff-base dapsc ligand were synthesized, [Ln(H₂dapsc)(H₂O)₄](NO₃)₃ (Ln = Tb, Dy, Ho, Er), and characterized structurally and magnetically. AC magnetic susceptibility measurements revealed that complexes of Dy³⁺ and Er³⁺ Kramers ions are field-induced single-ion magnets whereas the Tb and Ho complexes show no slow magnetic relation in DC fields up to 6000 Oe. DC and AC magnetic properties of these complexes were rationalized in terms of superposition crystal-field model calculations for Ln³⁺ ions, which have resulted in good agreement between the experiment and the theory. It is shown that low single-molecule magnet characteristics of the Dy and Er complexes and the absence of slow-magnetic relaxation in the Tb and Ho complexes are primarily due to the low-symmetry coordination of Ln³⁺ ions.