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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]

The synthesis, structural characterization and magnetic properties of four heterometallic complexes with formulas Ln2M(OQ)8 [Ln(iii) = Dy, M(ii) = Ca (1), Mg (2); Ln(iii) = Er, M(ii) = Ca (3), Mg (4); HOQ = 8-hydroxyquinoline] are reported. Complexes display a perfectly linear arrangement of three metal ions involving two terminal Ln(iii) ions and one central alkaline earth M(ii) ion, and they are bridged by three phenolato oxygen atoms from three 8-hydroxyquinoline ligands. Direct-current (dc) magnetic susceptibility studies show that there exists a long-range ferromagnetic (FM) interaction between two f-electronic centers in Dy-based complexes 1 and 2 albeit they are separated by diamagnetic alkaline earth ions, and the FM interaction has been successfully reproduced by ab initio calculations. Alternating current (ac) magnetic susceptibility measurements indicate that complexes 1 and 2 exhibit significant single-molecule magnet (SMM) behaviors. This is mostly attributed to the parallel magnetic axes of individual Dy(iii) sites aligning closely to the Dy–M–Dy direction, and the linearly extending magnetic susceptibility tensors of each ion lead to the FM interaction. The dc and ac susceptibility studies of the intramolecularly diluted complexes reveal that the f–f coupling suppresses the QTMs significantly in the absence of the external magnetic field. [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]

Three complexes with formula {Dy(q)2(L)}2(μ3-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 β-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 β-diketonate ligand, which is responsible for their different individual Dy(iii) ions’ magnetic anisotropy and intramolecular coupling, as confirmed by ab initio calculation. [ABSTRACT FROM AUTHOR]