A slowly magnetic relaxing SmIII monomer with a D5h equatorial compressed ligand field†
By using a bi-dentate phosphine oxide ligand L (L = bis(diphenylphosphino)methane dioxide), two mono-nuclear lanthanide complexes [LnL2(DMF)Cl2]Cl (Ln = Sm, 1; Dy, 2) with a D5h equatorial ligand field (LF) are obtained. Ab initio CASSCF calculations suggest that the equatorial LF promotes the magnetic anisotropy of the central SmIII and impair that of DyIII. Alternating current (ac) susceptibility measurements reveal that the samarium complex is the first SmIII mono-nuclear complex with slow magnetic relaxation. The isostructural DyIII compound, in contrast, relaxes much faster. Further magnetic property studies were then performed to probe the origin of magnetic anisotropy and magnetic relaxations.