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The synthesis and characterization of two new CuII complexes with pyrazole ligands formulated as [Cu3(μ-Pz)3(μ3-OH)(Pz)2Cl2][Cu3(μ-Pz)3(μ3-OH)(Pz)2Cl2(DMF)] ·2DMF ( 1) and [Cu3(μ-DMPz)3(DMF)4(OAc)(μ3-OH)(H2O)]+[Cu3(μ-DMPz)3(DMF)(NCS)3(μ3-OH)]- ( 2) (where Pz = 1 H-pyrazole and DMPz = 3, 5-dimethyl-1 H-pyrazole) are reported. The compounds were prepared by the reaction of zero valent copper metal and Pz or DMPz in the dimethylformamide solution in the presence of the different additional components (chloride or thiocyanate ligands). The crystal structures of both compounds were determined by single-crystal X-ray diffraction analysis. Both compounds 1 and 2 are hexanuclear clusters comprising from neutral ( 1) or charged ( 2) trinuclear triangular fragments Cu3(μ3-OH)(μ-Pz)3 of inverse azametallacrowns aza9-MCCuII-3 topology. Nevertheless, they exhibit relevant differences in their molecular structures. The magnetic measurement shows the isotropic antiferromagnetic interaction in 2 with J1 = -140 cm-1 for the cationic and J2 = -109 cm-1 (-2 JSi · Sj model) for the anionic part of the molecule above 100 K and significant influence of antisymmetric exchange at lower temperatures. [ABSTRACT FROM AUTHOR]

A series of copper(ii) complexes with earlier reported ligands N,N′-bis(2-hydroxyiminopropionyl)-1,2-diaminoethane (H2pen) and 1,3-diaminopropane (H2pap) and novel open chain oxime and amide ligands, N,N′-bis(2-hydroxyiminopropionyl)-1,5-diaminopentane (H2papt), 1,6-diaminohexane (H2pah) and 1,7-diaminoheptane (H2pahp), were prepared and characterized by a variety of spectroscopic methods and X-ray structure analysis. Although a pH-potentiometric study revealed only monomeric species in solution, formation of both binuclear dimeric and 1D-polymeric topologies was found in solid state. In all complexes ligands provide bis-bidentate coordination to Cu2+ions viathe nitrogen atoms of the oxime groups and the oxygen atoms of the amide groups to form CuN2O2planar fragments. Compound [Cu(Hpap)(ClO4)(H2O)]xwas isolated in both dimeric (x= 2) and polymeric (x= n) state, representing an example of supramolecular isomerism. All the complexes are additionally stabilized by short intramolecular hydrogen bonds N–O–HO–N between cis-arranged oximato-groups. Stabilization is more effective in the case of dimeric complexes compared to 1D-polymeric chain, which appears to be the reason of preferable dimerization versuspolymerization in the studied set of compounds. The effect of polymethylene linker length on the conformation of the dimers is described. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of the Zn(II) complex with H 2 L = 2-hydroxyiminopropanoic acid. The final structure incorporated two linear dimeric anions with two Zn 2+ atoms, which are linked by a carbonate anion into a tetranuclear unit. In each dinuclear unit, the two Zn(II) ions are coordinated by three molecules of the doubly deprotonated ligand in two different coordination modes. This result is confirmed both by X-ray crystallography and by ESI-MS investigations of the crystals dissolved in water. Equilibrium studies of the zinc(II) complexes formed by H 2 L in aqueous solution based on independent pH-metric titrations and zinc ion-selective electrode (ISE) titrations indicate that the mononuclear ZnLH complex appears to be the dominating equilibrium species at pH 4–6 at various ligand-to-metal ratios. Under excess of the ligand at pH 6–8, the ZnL 2 H species, further stabilized by a hydrogen bond between the deprotonated and protonated oxime groups, becomes the predominating species besides the ZnL complex. [ABSTRACT FROM AUTHOR]

Abstract: By using a synthetic approach alternative to the ones described up to now two tri- and tetranuclear mixed valence Co(II,III) complexes have been obtained ([Li(H2O)4]2[Co(CoL3)2(Li(H2O)3)2] and K[Co(CoL3)2Co(H2O)5]·H2O, respectively) in which the cobalt ions are linked by (N–O) oxime bridges. For both these compounds, a hydrazide derivative (2-hydroxyiminopropanehydrazide, HPH) has been used as starting ligand and then it underwent hydrolytical decomposition to 2-hydroxyiminopropanoic acid, H2L, ion upon coordination with cobalt. Cobalt(II) complexes formed by 2-hydroxyiminopropanoic acid in aqueous solution have been studied using independent pH-metric titrations as well as a combination of fibre-optics UV–Vis spectroscopy and pH glass-electrode potentiometry. The mononuclear CoL2H complex appeared to be the dominating equilibrium species within pH 6–9, most probably due to a hydrogen bond between the deprotonated and protonated oxime groups stabilizing planar cis-coordination. [Copyright &y& Elsevier]

Abstract: The synthesis, crystal structure and magnetic properties of manganese(III) binuclear complexes [MnIII 2(L–3Н)2(CH3ОH)4]·2CH3ОH (1) and [MnIII 2(L–3Н)2(Py)4]·2Py (2) (L =3-[(1E)-N-hydroxyethanimidoyl]-4-methyl-1H-pyrazole-5-carboxylic acid) are reported. The ligand contains two distinct donor compartments formed by the pyrazolate-N and the oxime or the carboxylic groups. The complexes were characterized by X-ray single crystal diffraction, revealing that both 1 and 2 consist of dinuclear units in which the two metal ions are linked by double pyrazolate bridges with a planar {Mn2N4} core. Cryomagnetic measurements show antiferromagnetic interaction with g =1.99, J =−3.6cm−1, Θ =−2.02K for 1 and g =2.00, J =−3.7cm−1, Θ =1.43K for 2. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt(III) complexes with new open chain oxime ligands: N,N′-bis(2-hydroxyiminopropionyl)-1,2-aminoethane (H2pen) and N,N′-bis(2-hydroxyiminopropionyl)-1,3-diaminopropane (H2pap) have been investigated. Single crystals of Co(papH−1)(Im2)·CH3OH (1) and Co(papH−1)(MEA)2·1.5H2O (2) (where Im=imidazole, MEA=monoethanolamine) suitable for X-ray crystallography were grown by slow evaporation of methanol/water solutions at room temperature. The molecular structures have been determined using single-crystal X-ray diffraction methods. The potentiometric and spectrophotometric results in aqueous solution reveal that both of the open chain ligands show a very high efficacy in the coordination of Co(II) ions. As it has been indicated, differences between the two oxime ligands in complexing ability may be attributed to the longer –CH2– chain in H2pap and by that a better fit of the relatively large Co(II) ion to the accessible binding site. One of the complex species confirmed under inert atmosphere, namely of type Co(LH−1)− (where L = pap or pen), has been shown as the “active” form, capable of dioxygen uptake followed by irreversible oxidation to Co(III). [ABSTRACT FROM AUTHOR]

Complex formation properties of a novel water soluble thiazolyloxime 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (H3L1) with Cu2+ and Ni2+ were investigated in solution by potentiometrical and spectral (UV–Vis, EPR, NMR) methods. All Cu2+ and most of Ni2+ complex species detected in solution were found to have square-planar MN4 core with oxime and heterocyclic nitrogen atoms which was rationalized in terms of destabilizing effect of repulsive interaction between oxygen atom of carboxylic group and nitrogen atom of thiazole ring in N,O-coordinated ligand conformation. It has been found that stability of metal complexes in a series of oxime ligands is dependent upon basicity of nitrogen atom of oxime group. The thiazolyloxime forms less stable complexes with Cu2+ but stronger ones with Ni2+ ions when compared to parent 2-(hydroxyimino)propanoic acid. The lower stability obtained for Cu2+ complexes was elucidated in terms of negative inductive effect of the thiazole and nitrile substituents as well as an effect of intramolecular attractive interaction between thiazolyl sulfur and oxime oxygen atoms in thiazolyloxime. In the case of Ni2+ the complexes formed are square-planar and it is why thiazolyl ligand is more effective in metal ion binding than simple 2-(hydroxyimino)propanoic acid forming only octahedral species. The solid state structure of the Co3+ complex K3[Co(HL1)3]·5.5H2O (1) was studied by X-ray analysis. The thiazolyloxime ligand is coordinated to Co3+ via oxime nitrogen and carboxylate oxygen atoms forming five-membered chelate rings. [Copyright &y& Elsevier]

A dodecanuclear 3 × [2 × 2] nickel(II) complex has been obtained via the self-association of three tetranuclear [2 × 2] molecular grids. X-ray diffraction shows a "propeller-like" structure of the [Ni4]3 scaffold with a central μ3-hydroxide. The dodecanuclear species remains stable in solution and can be deposited without decomposition on highly ordered pyrolytic graphite surfaces. [ABSTRACT FROM AUTHOR]

The title compound, [Cu2(C2O4)Cl2(C7H9N3)2], contains neutral mol­ecules of a centrosymmetric dinuclear oxalate-bridged copper(II) complex, in which the oxalate ligand is coordinated in a bis-bidentate bridging mode to the Cu atoms. Each Cu atom has a distorted square-pyramidal environment, being coordinated by two N atoms of the [1-(pyridin-2-yl)­ethyl­idene]hydrazine ligand, two O atoms of the doubly deprotonated oxalate anion and one Cl− anion. [ABSTRACT FROM AUTHOR]