Switching of Slow Magnetic Relaxation Dynamics in Mononuclear Dysprosium(III) Compounds with Charge Density

The symmetry around a Dy ion is recognized to be a crucial parameter dictating magnetization relaxation dynamics. We prepared two similar square-antiprismatic complexes, [Dy­(L_OMe)₂(H₂O)₂]­(PF₆) (<b>1</b>) and Dy­(L_OMe)₂(NO₃) (<b>2</b>), where L_OMe = [CpCo­{P­(O)­(O­(CH₃))₂}₃], including either two neutral water molecules (<b>1</b>) or an anionic nitrate ligand (<b>2</b>). We demonstrated that in this case relaxation dynamics is dramatically affected by the introduction of a charged ligand, stabilizing the easy axis of magnetization along the nitrate direction. We also showed that the application of either a direct-current field or chemical dilution effectively stops quantum tunneling in the ground state of <b>2</b>, thereby increasing the relaxation time by over 3 orders of magnitude at 3.5 K