Two Locally Chiral Dysprosium Compounds with Salen-Type Ligands That Show Slow Magnetic Relaxation Behavior

Two Dy compounds, [Dy-4(mu(4)-O)L-2(C6H5COO)(6)]center dot 3CH(3)OH (1) and [Dy2L(H2L)(teaH(2))(o-vanillin)(H2O)](ClO4)(2)center dot 2CH(3)OH center dot H2O (2, teaH(3) = triethanolamine), were assembled by the reactions of the salen-type ligand N, N'-bis(3-methoxysalicylidene)-1,2-cyclohexanediamine (H2L) and different dysprosium salts and bases. These compounds show both local chirality and slow magnetic relaxation. The former is induced by an unprecedented coordination mode of the ligand H2L, in which the N2O2 pocket encapsulates one Dy ion. Compound 1, which has four Dy ions in distinct coordination environments, demonstrates the rare Dy-4 tetrahedron motif supported by a central mu(4)-O atom, which is akin to a chiral carbon atom in organic molecules, as revealed by single-crystal X-ray analyses. In contrast, the formation of 2, which shows an unusual structural motif with a tail, is driven by the presence of triethanolamine. In spite of the low-symmetry coordination geometry around each Dy ion, both compounds display slow magnetic relaxation behavior, but with fast quantum tunneling relaxation, as indicated by alternating current (ac) susceptibility measurements.