Successive syntheses and magnetic properties of homodinuclear lanthanide macrocyclic complexes.

A series of homodinuclear ß-diketone lanthanide(III) complexes, formulated as [(acac)4Ln2(L1)] (Ln3+ = Dy3+ (1), Tb3+ (2), and Gd3+ (3), respectively) were first synthesized based on a closed-macrocyclic ligand (H2L1) derived from the [2 + 2] cyclocondensation of 4-tert-butyl-2,6-diformylphenol and o-phenylenediamine in the presence of lanthanide acetylacetonates. Subsequently, by using the above compounds as building blocks to assemble directly with another Schiff base ligand, N,N'-bis(5-chlorosalicylidene)-o-phenylenediamine (H2L2), three new homodinuclear sandwich-type lanthanide complexes with the general formula [Ln2(L1)(L2)2] (Ln3+ = Dy3+ (4), Tb3+ (5), and Gd3+ (6), respectively) were further designed and prepared. Single-crystal X-ray analyses show that the central Ln3+ ion adopts a distorted square antiprism conformation with D4d local symmetry. Magnetic studies reveal ferromagnetic interaction between Dy3+ and Tb3+ centres and zero-field slow relaxation of magnetization for Dy complexes 1 and 4. The corresponding magneto-structural correlations of SMMs 1 and 4 were further discussed by theoretical calculations and with experimental outcomes.

Controllable syntheses and magnetic properties of novel homoleptic triple-decker lanthanide complexes.

Four novel homoleptic triple-decker lanthanide complexes, [Ln2(L)(Cl-salphen)2]·0.5ClCH2CH2Cl (Ln3+ = Gd3+ (1), Ho3+ (2), Tb3+ (3), and Dy3+ (4)), have been designed and synthesized based on a Schiff base ligand N,N'-bis(5-chlorosalicylidene)-o-phenylenediamine (Cl-salphenH2) and the building blocks [(acac)4Ln2(L)]; these complexes were derived from a closed-macrocyclic ligand (H2L) obtained by the [2 + 2] template condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane in the presence of lanthanide acetylacetonates. Single-crystal X-ray analyses show that central Ln3+ ions adopt distorted square antiprism conformations with D4d symmetry. Theoretical analysis and magnetic measurements reveal that Dy complex 4 behaves as a typical SMM with the characteristics of slow magnetic relaxation behavior and intermetallic ferromagnetic interaction.

Syntheses, structures, and magnetic properties of homodinuclear lanthanide complexes based on dinucleating Schiff base ligands.

The first two families of homodinuclear lanthanide(III) complexes, formulated as [(L(OEt))2Ln2(L1)] and [(LOEt)2Ln2(L2)] (Ln(3+) = Dy(3+), Tb(3+), Ho(3+), Gd(3+), and Y(3+); L1(4-) = 2,2',2'',2'''-[1,2,4,5-benzenetetrayltetrakis(nitrilomethylidyne)]tetrakisphenolate; L2(4-) = 2,2',2'',2'''-[[1,1'-biphenyl]-3,3',4,4'-tetrayltetrakis(nitrilomethylidyne)]tetrakis(4-chlorophenolate); L(OEt)(-) = (η(5)-cyclopentadienyl)tris(diethylphosphito-p)cobaltate(III)), were successfully synthesized based on Kläui's tripodal building block NaL(OEt) and two dinucleating Schiff base ligands, H(4)L1 and H(4)L2, respectively. Single-crystal X-ray analyses show that these lanthanide complexes have two seven-coordinated metal binding sites, linked to each other with a phenyl or biphenyl bridge. Variable temperature dc magnetic measurements reveal the weakly antiferromagnetic coupling between paramagnetic lanthanide ions, while ac magnetic data exhibit the field-induced relaxation of magnetization for the corresponding Dy2 complexes 1 and 6. A further magnetic dilution study for 1 suggests that the slow magnetic relaxation originates from the single-ion magnetic behaviour of Dy(3+) ions.

3,5-Dibromo-4-oxo-2,2,6,6-tetra-methyl-piperidin-1-yl oxide.

In the title compound, C(9)H(14)Br(2)NO(2), the substituted ring exhibits a chair conformation. A crystallographic mirror plane, passing through the N atom, the O atoms and the C atom in the 4-position, bis-ects the mol-ecule.