A family of tetranuclear quinolinolate Dy(III)-based single-molecule magnets: effects of periphery ligand replacement on their magnetic relaxation

摘要

Three complexes with formula {Dy(q)(2)(L)}(2)(mu(3)-OH)(2){Dy(q)(L)}(2)(solvents) (where q = 8-quinolinolate; L = acetylacetone (acac) with (CH2Cl2)(2) = solvent (1), 1,3-diphenyl-1,3-propanedione (DBM) and (CH2Cl2)(2) = solvent (2), and hexafluoroacetylacetone (hfac) and CHCl3 = solvent (3)) were structurally and magnetically characterized. They have similar Dy4 structural cores bridged by N and O atoms from 8-quinolinolate, and only differ in the peripheral beta-diketonate ligands. The variable-frequency and temperature alternating-current (ac) magnetic susceptibility measurements reveal that complexes 1 and 2 display significant zero-field single-molecule-magnet (SMM) behavior, while complex 3 exhibits the field-induced SMM behavior, albeit they possess the nearly same primary coordination sphere. The ac susceptibility measurement on the diluted samples verified that their relaxation was of purely molecular origin, and their distinct slow magnetic behaviors were related to the replacement of the peripheral beta-diketonate ligand, which is responsible for their different individual Dy(III) ions' magnetic anisotropy and intramolecular coupling, as confirmed by ab initio calculation.