Solvent-tuned magnetic exchange interactions in Dy systems ligated by a μ-phenolato heptadentate Schiff base.

A series of binuclear dysprosium compounds, namely, [Dy(api)] (1), [Dy(api)]·2CHCl (2), [Dy(Clapi)]·2CHO (3), and [Dy(Clapi)]·2CHO (4) (Hapi = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline; HClapi = 2-(2'-hydroxy-5'-chlorophenyl)-1,3-bis[3'-aza-4'-(2''-hydroxy-5''-chlorophenyl)prop-4'-en-1'-yl]-1,3-imidazolidine), have been isolated by the reactions of salen-type ligands Hapi/HClapi with DyCl·6HO in different solvent systems. Structural analysis reveals that each salen-type ligand provides a heptadentate coordination pocket (NO) to encapsulate a Dy ion and all of the Dy centers in 1-4 adopt a distorted square antiprism geometry with symmetry. Magnetic studies showed that compound 1 did not exhibit single-molecule magnetic (SMMs) behavior. With the introduction of different lattice solvents, compounds 2-4 showed filed-induced slow magnetic relaxation with barriers of 18.2 K (2), 28.0 K (3) and 16.4 K (4), respectively. calculations were employed to interpret the magnetization behavior of 1-4. The combination of experimental and theoretical data reveal the importance of the weak exchange interaction between the Dy ions in the observation of slow magnetic relaxation, and a relaxation mechanism has been developed to rationalize the observed difference in the values. The different lattice solvents influence Dy-O-Dy bond angles and thus alter the torsion of the square antiprism geometry, consequently resulting in distinct magnetic interactions and the magnetic behavior.