Search

New heteronuclear Zn2Ln2 clusters [Zn2L2Ln2(hfac)6] (Ln = Eu (1), Tb (2) and Dy (3)) have been synthesized based on a flexible Schiff base (H2L = N,N′-bis(salicylidene)-3,6-dioxa-1,8-diaminooctane) and β-diketonate ligand (hfac = hexafluoroacetylacetonate). The structures of the isomorphous complexes 1–3 were determined by single-crystal X-ray crystallography. Photophysical studies indicate that the short intramolecular distance of Zn…Ln allows energy transfer from the Zn2L2-based sensitizers to the Eu(iii) and Tb(iii) centres; the lanthanide luminescence is indeed “lighted up” by the excitation of the zinc complex. More interestingly, white light emission was realized by codoping Eu(iii) ion into the Dy(iii) complex for the first time. [ABSTRACT FROM AUTHOR]

A series of dinuclear dysprosium complexes bridged by pyridine-NO ligands with formula [Ln2(BTA)6(pyNO)2] (1Dy, Ln = Dy, 1Y, Ln = Y and 1Gd, Ln = Gd) (BTA = benzoyltrifluoroacetone, pyNO = pyridine-N-oxide) were structurally and magnetically characterized. The X-ray crystallographic analyses of the structures revealed that the NO group serves as the effective bridge to link two Dy(iii) centers and the periphery β-diketonate (BTA) ligands complete the rest of the coordination sphere. The dynamic magnetic measurements revealed that complex 1Dy displayed significant zero-field single-molecule magnetic (SMM) behaviour with 72 K energy barrier and 2.5 K hysteresis temperature. In order to extend this dinuclear system, double N-oxide bridged ligand 4,4′-bpdo(4,4′-bipyridine-N,N′-dioxide) was used, and consequently, a series of one-dimensional chain complexes possessing repeated [Ln2(BTA)6(pyNO)2] units were synthesized with formula [Ln2(BTA)6(4,4′-bpdo)]n·2EtOH (2Dy, Ln = Dy, 2Y, Ln = Y and 2Gd, Ln = Gd). The AC magnetic susceptibility measurements revealed that complex 2Dy exhibited significant zero-field slow magnetic relaxation behavior with a higher effective energy barrier of 87 K and a hysteresis temperature of 3 K than 1Dy albeit the separation between the repeated units is large. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A novel family of lanthanide compounds with a 1-D chain structure [Ln2L(TTA)4(OAc)2]n [Ln = Sm (1), Eu (2) Gd (3) and Yb (4)] was constructed from β-diketonate (TTA = 2-thenoyltrifluoroacetone) and an auxiliary ligand Schiff base (H2L = N,N′-bis(salicylidene)butane-1,6-diamine). The structures of the isostructural complexes 1–4 were determined via single-crystal and powder X-ray crystallography. The optical properties of these compounds could be simply enhanced using a doping method, enabling the doped materials with tunable visible and near-infrared emission. The quantum yields of the doped samarium and europium compounds reached 6.8% and 76.2%, respectively, which were higher compared with other previously reported studies. Subsequently, a multifunctional sensor was employed to detect CH3COOH and poisonous HS− anions. The notable quenching effect proved that this doped material is a promising fluorescence probe for the sensing of anions and organic small molecules with high identification ability and sensitivity. Moreover, the possible mechanism for luminescence sensing has been studied in detail. [ABSTRACT FROM AUTHOR]