Influence of bridging and chelating co-ligands on the distinct single-molecule magnetic behaviours in ZnDy complexes

Abstract

Four new heterometallic ZnDy complexes, [ZnDy(L)(NO₃)₃(py)]·CH₂Cl₂ (1) (py stands for pyridine), [ZnDy(L)(μ-OAc)(OAc)₂]·3H₂O (2), [ZnDy(L)(μ-OAc)(OAc)(NO₃)] (3), and [ZnDy(L)(μ-piv)(piv)₂][ZnDy(L)(μ-piv)(piv)(OAc)]·1.5H₂O (4), have been synthesized from a methyl substituted o-vanillin based compartmental Schiff base ligand, N,N′-bis(3-methoxy-5-methylsalicylidene)-1,2-phenylenediamine (H₂L), in association with various secondary co-ligands like acetate (OAc), nitrate and pivalate (piv), and magneto-structurally characterised. They possess a nearly identical [Zn(II)–Dy(III)] core, bridged by the phenoxo-O atoms of the compartmental Schiff base ligand. Magnetic studies revealed the distinct single-molecule magnetic (SMM) behaviours through single to multiple relaxation channels, in which 1, 2 and 4 can display slow relaxation of magnetisation at a zero dc field, the performance of which can be further improved by applying a magnetic field at the expense of the reduction of under barrier relaxation processes, while 3 shows only field-induced weaker slow magnetic relaxation behaviours. Ab initio calculations were performed for the in-depth understanding of the magnetic dynamics in these complexes. The difference in the magnetic behaviours of the four complexes can be ascribed to the effect of bridging/chelating co-ligands in these complexes. Therefore, the present report highlights that the magnetic anisotropy is sensitive to the bridging/chelating co-ligands used, leading to the distinct magnetic dynamics in these systems.