Synthesis, Crystal Structures, and Magnetic Properties of New Hexanuclear MnIII2LnIII4 Complexes: SMM Behavior of the Terbium(III) Analogue

Abstract

This investigation reports the syntheses, crystal structures, and magnetic properties of a series of isomorphous hexanuclear MnIII2LnIII4 compounds of composition [MnIII2LnIII4L12L22(µ3‐OH)4(µ1,3‐Pivalate)6(NO3)2]·2CH3CN {Ln = Tb (1), Dy (2), Ho (3), Er (4)}, where H2L1 is the Schiff base ligand that is obtained by [1+1] condensation of 3‐methoxysalicylaldehyde (HL2) with 2‐amino‐2‐methyl‐1‐propanol. While the O(phenoxo)N(imine)O(alkoxo) pocket of the ligand [L1]2– binds a MnIII ion, the other pocket, O(methoxy)O(phenoxo), remains noncoordinated. In contrast, each of the O(methoxy)O(phenoxo) and O(phenoxo)O(aldehyde) sites of [L2]– is occupied by a LnIII ion. Additionally, there are four µ3‐hydroxo, six µ1,3‐pivalate, and two chelating nitrate ligands, stabilizing the hexanuclear cores. Magnetic susceptibility (2–300 K) and magnetization (M) data reveal significant anisotropy in 1–4. Detailed ac susceptibility measurements have revealed single molecule magnet (SMM) behavior in the TbIII analogue with Ueff = 11.12 cm–1 and τ0 = 1.04 × 10–7 s under a 1000 Oe dc field and Ueff = 10.42 cm–1 and τ0 = 1.62 × 10–7 s under a 3500 Oe dc field, while the other three analogues do not show slow relaxation of magnetization.