title: 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.
abstract: A series of HMq-bridged dinuclear dysprosium complexes, namely, [Dy(acac)2(CH3OH)]2(μ-HMq)2 (1), [Dy(DBM)2]2(μ-HMq)2(n-C6H14) (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 complexes 1-4 reveal that complexes 3 and 4 display significant zero-field single-molecule magnetic (SMM) behavior with barrier energy Ueff/kB = 14.8 K, τ0 = 1.8 × 10(-5) s and Ueff/kB = 9.2 K, τ0 = 1.7 × 10(-5) s, respectively, whereas 1 and 2 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.
authors.affiliation: Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Heilongjiang University, Harbin 150080, P. R. China. wenbinsun@126.com yanpf@vip.sina.com.
authors.forename: Wan-Ying
authors.initials: WY
authors.lastname: Zhang
authors.forename: Yong-Mei
authors.initials: YM
authors.lastname: Tian
authors.forename: Hong-Feng
authors.initials: HF
authors.lastname: Li
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Sun
authors.forename: Yi-Quan
authors.initials: YQ
authors.lastname: Zhang
authors.forename: Peng-Fei
authors.initials: PF
authors.lastname: Yan