A series of dinuclear Dy(iii) complexes bridged by 2-methyl-8-hydroxylquinoline: replacement on the periphery coordinated β-diketonate terminal leads to different single-molecule magnetic properties. Issue 9 (1st February 2016) - Zhang, Wan-Ying
Abstract : A series of dinuclear Dy(iii ) complexes bridged by 2-methyl-8-hydroxylquinoline were reported, in which the replacement on the β-diketonate terminal leads to different structures and further affect their SMM properties. Abstract : A series of HMq-bridged dinuclear dysprosium complexes, namely, [Dy(acac)2 (CH3 OH)]2 (μ-HMq)2 (1 ), [Dy(DBM)2 ]2 (μ-HMq)2 ( n -C6 H14 ) (2 ), [Dy(hmac)2 ]2 (μ-HMq)2 (3 ) and [Dy(hfac)3 ]2 (μ-HMq)2 (4 ) (HMq = 2-methyl-8-hydroxyquinoline, acac = acetylacetone, DBM = dibenzoylmethane, hmac = hexamethylacetylacetonate and hfac = hexafluoroacetylacetonate), were structurally and magnetically characterized. X-ray crystallographic analyses of the structures reveal that HMq serves as the effective bridge to link two Dy(iii ) centers by means of the phenoxyl oxygen and nitrogen atoms and the periphery β-diketonate ligands complete the coordination sphere by bidentate oxygen atoms. The different substituents on the β-diketonate terminal lead to different coordination models mostly due to the steric hindrance of these substituents, and the electron-withdrawing or donating effects likely influence the strength of the ligand fields and the Dy(iii ) ion anisotropy. Measurements of alternating-current (ac) susceptibility on complexes1–4 reveal that complexes3 and4 display significant zero-field single-molecule magnetic (SMM) behavior with barrier energy U eff / k B = 14.8 K, τ 0 = 1.8 × 10 −5 s and U eff / k B = 9.2 K, τ 0 = 1.7 × 10 −5 s, respectively, whereas1 and2 exhibit field-induced SMM behavior, and these differences are attributed to the alteration on the periphery β-diketonate ligands. Their distinct slow magnetic relaxation behaviors were related to their different individual Dy(iii ) ion magnetic anisotropy and intramolecular coupling, which were confirmed by ab initio calculations.