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Three new tetranuclear nickel(II) complexes of general formula [Ni4(L)2(N3)2(CH3COO)2(CH3O)2]2·xCH3OH·yH2O (HL = HL1, HL2 and HL3; x = 0, y = 1 for 1; x = 2, y = 0 for 2 and x = 2, y = 4 for 3) were synthesized and characterized by single crystal X-ray diffraction and magnetic measurements. Single crystal X-ray studies reveal that all three complexes exhibit similar tetranuclear face-shared defective double-cubane structure, having azido-, alk/phenoxido- and acetato-bridges. Magnetic susceptibility measurements on the complexes in the range of 300–2 K indicate ferromagnetic coupling between the metal ions. The slightly different magnetic behaviors observed are probably caused by subtle structural differences between the respective [Ni4O4N2] cores induced by ligand variation.

A new dinuclear cobalt(II) complex [Co(2)L(2)Cl(2)(CH(3)OH)(2)] (1), where HL = 3-[(furan-2-ylmethylimino) methyl]-2-hydroxy-5-methylbenzaldehyde, derived from the in situ condensation of 2,6-diformyl- 4-methylphenol with furfurylamine, was prepared and structurally and magnetically characterized. Single crystal X-ray structural determination reveals that the structure consists of centrosymmetric dinuclear units with each Co(II) ion in a slightly distorted octahedral environment. Lines' model, which in principle can theoretically separate in spin-only and orbital contribution, was used to fit the variable temperature susceptibility (2-300 K), suggesting an intramolecular antiferromagnetic interaction between the cobalt(II) ions.

A novel cubane complex with formula of [Ni(μ3-OCH3)L(CH3OH)]4 (1) has been successfully assembled by using o-vanillin as multidentate ligand. Each Ni(II) ion is six coordinate, being bound to four oxygen atoms from four methanol molecules, one phenoxido oxygen atom and one aldehyde oxygen atom from the o-vanillin ligand. The cubane structure is characterized by a Ni4O4 core assembled from four nickel atoms and four deprotonated, bidentate o-vanillin ligands and the cubic array of alternating nickel and oxygen atoms give intracluster metal–metal separations of 3.054(1) and 3.076(1) A respectively. Preliminary magnetic studies suggest the existence of a weak antiferromagnetic coupling between the nickel ions. A novel tetranuclear nickel(II) complex with Ni4O4 cubane core has been assembled by using o-vanillin as multidentate ligand.

Two new manganese complexes with multidentate 3-methoxysalicylaldehyde benzoylhydrazide ligand have been synthesized and structurally characterized. Variations of the reaction conditions (namely, the base, solvent or the counter ion) lead to drastic changes in the nature of the resulting coordination complexes. Depending on the anions involved a di- and a tetranuclear manganese structures are obtained. The magnetic properties of both complexes have been investigated, which show that the different complexes exhibit antiferromagnetic interactions.

A novel polymeric carboxylato-bridged praseodymium(III) complex of fumarate, [Pr2(fum)3(H2O)4]·5H2O (fum, fumarate dianion) has been synthesized and characterized by single-crystal X-ray diffraction studies, magnetic measurements and thermal studies. Single crystal X-ray structural determination reveals that it is a new porous three dimensional pillared layer framework with 1D channel for the accommodation of tetrameric water clusters. A preliminary treatment of the variable-temperature magnetic susceptibility using an expression including the ligand field effects and molecular field approximation leads to zJ′ = −1.60 cm−1, Δ = 0.5 cm−1 and g = 0.84, suggesting the existence of a weak antiferromagnetic coupling between the praseodymium ions.

A novel samarium(III) polymer, [Sm2(C6H5COO)6(CH3OH)3]·CH3OH (1) has been synthesized and characterized by single crystal X-ray diffraction and magnetic measurements. Polymer 1 crystallizes in monoclinic space group P2(1)/c, with a = 15.1247(6), b = 18.3351(7), c = 21.1266(6) A, β = 126.830(2)°, V = 4689.4(3) A3, and Z = 4. Single crystal X-ray analysis reveals a chain-like structure of 1 consisted of alternating eight- and nine-coordinate Sm(III) ions bridged by benzoate ligands in different coordination modes. A treatment of the variable-temperature magnetic susceptibility using an expression deduced from free-ion approximation and molecular field theory suggests the existence of a weak antiferromagnetic coupling between the samarium ions. A novel one-dimensional samarium polymer containing alternating eight- and nine-coordinate Sm(III) ions has been generated by incorporating benzoic acid in three different binding modes in its deprotonated state.

Three Radical-Ln(III)-Radical complexes based on nitronyl nitroxide radicals have been synthesized, structurally and magnetically characterized: [Gd(hfac)(3)(NITPhOEt)(2)] (1) (hfac=hexafluoroacetylacetonate, and NITPhOEt=4'-ethoxy-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), [Gd(hfac)(3) (NITPhOCH2Ph)(2)] (2) (NITPhOCH2Ph = 4'-benzyloxy-pheny1-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and [Lu(hfac)(3)(NITPhOCH2Ph)(2)] (3). The X-ray crystal structure analyses show that the structures of the three compounds are similar and all consist of the isolated molecules, in which central ions Gd-III or Lu-III are coordinated by six oxygen atoms from three hfac and two oxygen atoms from nitronyl radicals. The magnetic studies show that in both of the two Gel complexes, there are ferromagnetic Gd-III-Rad interactions and antiferro-magnetic Rad-Rad interactions in the molecules (with J(Rad-Gd)=0.27 cm(-1), 2.97 cm(-1) for 1: and J(Rad-Gd)=0.62 cm(-1), j(Rad-Rad)=7.01 cm(-1) for 2). An analogous complex of [Lu(hfac)(3) (NITPhOCH2Ph)(2)] (3) containing diamagnetic Lu-III ions has also been introduced for further demonstrating the nature of magnetic coupling between radicals. (C) 2010 Elsevier Inc. All rights reserved.

Five new complexes based on rare-earth-radical [Ln(hfac)(3)(NIT-5-Br-3py)](2) (Ln = Pr (1), Sm (2), Eu (3), Tb (4), Tm (5); hfac = hexafluoroacetylacetonate; NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) have been synthesized and characterized by X-ray crystal diffraction. The single-crystal structures show that these complexes have similar structures, in which a NIT-5-Br-3py molecule acts as a bridging ligand linking two Ln(III) ions through the oxygen atom of the N-O group and nitrogen atom from the pyridine ring to form a four-spin system. Both static and dynamic magnetic properties were measured for complex 4, which exhibits single-molecule magnetism behavior.

The bimetallic complex of Ni2Co(TTHA)·12H2O (TTHA = triethylene tetraminehexaacetic acid) was synthesized and characterized structurally and magnetically. The title complex crystallizes in the triclinic space group P ī with a = 0.7316(2), b = 0.8624(2), c = 1.5041(4) nm; α = 73.38(2), β = 83.97(2), γ = 70.50(2)°. The crystal structure is built up of [Ni2(TTHA)(H2O)2]2−, Co(H2O)62+ and water molecules. The variable magnetic measurement shows that there is strong antiferromagnetic interaction between two Ni(II) ions in [Ni2(TTHA) (H2O)2]2− with JNi−Ni = −141.64 cm−1, gNi = 2.21 and that the constant of spin-orbit coupling of Co(II) ion is −134.8 cm−1.

Two novel 3d-4f polymers [La(H2O)(4)][M(2)TTHA(SCN)(2)]center dot H3O+ (M = Ni(1), Cu(2), H-6 TTHA = triethylenetetraaminehexaacetic acid) were synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, IR and magnetic properties. Two complexes show 3D framework, comprising an unusual infinite 1D chain based on heterometallic La2M2 rings (M = Ni(1), Cu(2)). (c) 2007 Elsevier B.V. All rights reserved.

A new kind of copper(II) complex, CuL(MeOH) (H2L = (E)-N 1-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N 2-(2-benzyl-4-chlorophenyl)oxalamide) has been synthesized and its structure determined by single-crystal X-ray methods. Copper(II) ion is five-coordinate, bonding to four nitrogen atoms from H2L and one oxygen atom from MeOH. Hydrogen bonds in the crystal result in the formation of a one-dimensional structure. EPR spectra are discussed. Computer simulation gave g|| = 2.200, g⊥ = 2.002. On the basis of the synthesis and the crystal structure, the mechanism of the metal template reaction involved in the formation of the complex was verified.

A novel complex, [Gd(hfac)3(NIT-5-Br-3py)]2 (hfac = hexafluoroacetylacetonat, NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) has been synthesized and characterized structurally and magnetically, in which a NIT-5-Br-3py molecular acts as a bridge ligand linking two Gd(III) ions through the oxygen atom of the N–O group and nitrogen atom from the pyridine ring to form a four-spin system. The fitting result of the magnetic susceptibility shows two different magnetic interactions between Gd(III) ion and NIT-5-Br-3py in one complex: a weak ferromagnetic interaction (J1 = +2.60 cm−1) through the N–O group, and a much weaker antiferromagnetic (J2 = −0.24 cm−1) interaction through pyridine ring.

The first complex [Mn(H2O)6][NiCo(TTHA)(H2O)2] · 4H2O 1 (TTHA6− = triethylenetetraminehexaacetate) containing MnII–CoII–NiII three different 3d metal ions is synthesized and magnetic measurement suggests that ferromagnetic interactions occur between Ni2+ ions and rarely found low-spin Co2+ ions.

Two novel three-dimensional (3D) 3d-4f mixed complexes [Ln(H(2)O)(4)][Ni(2)TTHA(SCN)(2)].H(3)O+ [Ln = Pr (1), Ce (2); H(6)TTHA = triethylenetetraaminehexaacetic acid], based on the building blocks of [Ni(2)TTHA(SCN)(2)](4-), were synthesized and characterized by X-ray crystal diffraction and magnetic properties. The single-crystal structures show that these complexes form a 3D framework, comprised of an unusual infinite one-dimensional chain based on heterometallic Ln2Ni2 rings. The temperature-dependent magnetic susceptibilities were analyzed by an approximate model, leading to g = 2.06. Delta = 2.83, zJ' = -0.6 cm-1 for complex 1 and g = 2.07, Delta = 1.00, zJ' = -0.5 cm(-1) for complex 2.

A new cyano-bridged Tb(III)-Cr(III) heterometallic complex [Tb(H(2)O)(2)(DMF)(4){Cr(CN)(6)}]·H(2)O (DMF = dimethylformamide) (1), assembled from paramagnetic hexacyanochromium(III) [Cr(CN)(6)](3-) building block and highly anisotropic terbium(III) ion has been prepared and structurally and magnetically characterized. Complex 1 shows one-dimensional (1D) zig-zag chain-like structural motif which is further extended into three-dimensional network through hydrogen-bonding interactions. The long-range magnetic ordering observed in complex 1, which is possibly due to interchain magnetic dipolar interactions, illuminates that this complex is a molecule-based magnet with critical temperature of about 5 K. This higher critical temperature among those of Ln(III)-Cr(III) heterometallic complexes exhibiting long-range magnetic ordering is probably due to the introduction of highly anisotropic terbium(III) ion.

The reaction of Dy(NO(3))(3)·6H(2)O with the ligand 2-((1-hydroxybutan-2-ylimino)methyl)phenol (H(2)L, ) generates the nonanuclear compound [Dy(9)L(8)(μ(3)-OH)(8)(μ(4)-OH)(2)(CH(3)OH)(8)](OH)(CH(3)OH)(3) (Dy(9)), whose single-crystal X-ray structure reveals the presence of two square pyramidal pentanuclear units assembled via the apical metal center. The square pyramidal core of a previously reported [Dy(5)(μ(4)-OH)(μ(3)-OH)(4)(μ-η(2)-Ph(2)acac)(4)(η(2)-Ph(2)acac)(6)] (Dy(5); Ph(2)acac = dibenzoylmethanide), is structurally related to those herein described; however, the magnetic properties of Dy(9) and Dy(5) are drastically different. Indeed, Dy(5) shows slow relaxation of magnetization while no out-of-phase ac signal is noticed for Dy(9). The underlying mechanism is not clear due to the complexity of such systems; however, the different anisotropy of the respective structures, which is dictated by the combination of the metal topology, the ligands involved and the structural parameters of the molecule, is mostly responsible for the distinctive relaxation dynamics observed.

Two new dysprosium(III) coordination compounds, namely, [Dy(4)(HL)(4)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(4)(mu-OH)(2)(H(2)O)(4)].4CH(3)CN.12H(2)O (1) and Dy(8)(HL)(10)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(8)(OH)(2)(NO(3))(2)(H(2)O)(4)] (2), have been synthesized from the Schiff-base ligand 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid (H(2)L) and dysprosium chloride (1) or dysprosium nitrate (2). Single-crystal X-ray diffraction studies reveal that compound 1 exhibits a tetranuclear cubane-like structure and that 2 is an octanuclear, bis-cubane complex. The [Dy(4)(mu (3)-OH)(4)] cubane cores of 1 and 2 are structurally related; however, the magnetic properties of 1 and 2 are drastically different. Indeed, 2 shows slow relaxation of magnetization while no out-of-phase alternating current (ac) signal is noticed for 1. These significant disparities are most likely due to the different M-O-M angles observed for the respective cubane cores.

Two new supramolecular polymeric coordination complexes, {Zn(phen)2[Au2(CN)4](H2O)}·1.5H2O 1 and {Mn(phen)[Au2(CN)4](H2O)}·PriOH 2, have been obtained through a self-assembly process. The three-dimensional supramolecular architectures of compounds 1 and 2 are sustained by aurophilic, hydrogen-bonding, and/or π–π interactions. Gold atoms linked with aurophilic bonds arrange in a pattern not frequently observed.