Ambidentate coordination of isonitrosoacetylacetone imines in their nickel(II) and palladium(II) complexes

Nickel(I1) and palladium(I1) complexes of the types Ni(R-IAI)(IAI'), Pd(IAI)(IAI'), and Pd(R-IAI), , where IAI and IAI' represent isonitrosoacetylacetone imine and R-IAI represents its Aralkyl derivative, have been prepared. The molar conductance, molecular weight, magnetic moment, and ir, pmr, and electronic spectra of these com- plexes have been studied. It is suggested that the isonitroso group of R-IAI coordinates through the nitrogen and that of IAI' thiough the oxygen in Ni(R-IAI)(IAI'). In Pd(R-IAI), the isonitroso groups of both ligands coordinate through nitrogen while Pd(IAI)(IAI') has a structure similar to that of Ni(R-IAI)(IAI'). The amine- exchange reactions of nickel(I1) and palladium(I1) complexes are discussed and compared on the basis of their structures.

Wrought aluminum-nickel alloys for high strength-high conductivity applications

Aluminum-Nickel alloys ranging from 0.06 pct to 6.1 pct (by wt) Ni have been developed for high strength-high conductivity applications. These alloys were produced by solidification in a permanent mold followed by homogenization, hot extrusion or hot rolling and cold drawing to wire form. This sequence of fabrication a) led to the production of fine fibrous dispersoids of NiAl3 as part of the Al-NiAl3 eutectic during the initial casting operation, b) permitted the retention of fine fibrous dispersiods of NiAl3 produced during casting without any significant coarsening during processing and c) led to uniform dispersion and general alignment of these fibrous dispersoids along a given direction in the product without any measurable fiber-matrix separation, extensive fiber-fragmentation or crack production in the matrix. These alloys can be processed to wire form as easily as aluminum and when processed by the above sequence, possess very attractive combination of high strength-high electrical conductivity. Tensile strengths range from 173 N/mm2 (at 0.6 pct Ni) to 241 N/mm2 (at 6.1 pct Ni) in combination with corresponding conductivity values between 62 pct IACS and 55.5 pct IACS. The wires also possess attractive yield strength; for instance, the 0.2 pct off-set strength of Al-6.1 pct Ni wire is 213 N/mm2. Using simple composite rules, the estimated strength and the conductivity of NiAl3 fibers were found to be 1380 N/mm2 and 18 pct IACS respectively, in these wires.

Bromination of Intermolecular Chelate Linkage Isomers of 3-Oximino-4,9-Dimethyl (or 4,7,9-Trimethyl)-5,8-Diazadodeca-4,8-Diene-2,11-Dionato Nickel(II)

The reaction of the title complexes (FIG. 1) with N-bromosuccinimide or bromine in chloroform yields isomeric bromo complexes on substitution of the γ-CH carbon proton by bromine. The brominated products have been characterised by ir, pmr, electronic absorption spectra, conductivity and magnetic susceptibility measurements. The linkage isomerisation of the brominated products in chloroform has been shown to depend on the diamine residue.

Linkage isomerism in nickel(II) I-isonitroso-imine ligand complexes

I-isonitroso-imine ligand complexes of nickel(II), namely, bis(isonitrosomethylacetoacetate-imino)Ni(II), Ni(IMI)(IMI); bis(isonitrosobenzoylacetoneimino)Ni(II), Ni(IBI)(IBI) and bis(isonitrosoacetoacetanilideimino)Ni(II), Ni(IANI)(IANI), have been prepared and characterized. On the basis of their spectroscopic and magnetic properties, these complexes are suggested to have a square-planar stereochemistry around the metal ion with both nitrogen (ligand denoted without prime) and oxygen (ligand denoted with prime) coordinated isonitroso groups. The i.r. and NMR spectra of these and other similar complexes are discussed.

Responses of Scots pine to nickel and copper exposure and herbivory

The goal of this thesis was to examine the ecophysiological responses of Scots pine (Pinus sylvestris L.), with an emphasis on the oxidative enzyme peroxidase and plant phenolics to environmental stresses like elevated levels of nickel (Ni) and copper (Cu), and herbivory. The effects of Ni and Cu were studied in a gradient survey at a sulphur dioxide contaminated site in the Kola Peninsula, and with experiments in which seedlings were exposed to Ni mist or to Ni and Cu amended into the soil. In addition, experimental Ni exposure was combined with disturbance of the natural lichen cover of the forest ground layer. Pine sawfly attack was simulated in the early season defoliation experiment, in which mature Scots pine were defoliated (100 %) during two successive years in a dry, nutrient-poor Scots pine stand. In addition, the effect of previous defoliation on the growth of sawfly (Diprion pini L.) larvae was studied. Apoplastic peroxidase activity was elevated in the needles of pine in a Ni- , Cu- and SO2- polluted environment, which indicated an increased oxidative stress. Increased foliar peroxidase activity due to Ni contamination was shown in the experiment, in which Ni was added as mist. No such response was found in peroxidase acitivity of the roots exposed to elevated Ni and/or Cu in the soil. Elevated Ni in the soil increased the concentration of foliar condensed tannins, which are able to bind heavy metals in the cells. Addition of low levels of Ni in the soil appeared to benefit pine seedlings, which was seen as promoted shoot growth and better condition of the roots. Wet Ni deposition of 2000 mg m-2 reduced growth and survival of pine seedlings, whereas deposition levels 200 mg m-2 or 20 mg m-2 caused no effects in a 2-y lasting experiment. The lichen mat on the forest floor did not act as an effective buffer against the adverse impacts of heavy metals on pine seedlings. However, some evidence was found indicating that soil microbes profited from the lichen mat. Artificial defoliation increased peroxidase activity in the Scots pine needles. In addition, defoliation decreased nitrogen, diamine putrescine and glucose concentrations in the needles and increased the concentrations of several phenolic compounds, starch and sucrose. Previous artificial defoliation led to poor growth of sawfly larvae reared on the pines, suggesting delayed induced resistance in Scots pine. However, there was no consistent relationship between inducibility (proportional increase in a compound following defoliation) and adverse effects on the growth of pine sawfly larvae. The observed inducible responses in needle phenolics due to previous defoliation thus appear to represent non-specific responses against sawflies.

Structure of bis(thiocyanato-N)bis(thiosemicarbazide-N1,S)nickel(II): a redetermination

[Ni(NCS)2(CHsN3S)2], Mr = 356.7, monoclinic, P21/c , a = 5-297 (1), b = 7.869 (1), c - 16-078 (2) A,/3 = 91.53 (1) °, V-= 669.9 A 3, Z= 2, Om = 1"76, Dx = 1"771 g cm -3, A(Mo Ka) = 0-71069 ]k, /.~ = 19"9 cm-l, F(000) = 364, T = 295 K, final R = 0.026 for 1576 significant [F > 10g(F)] reflections. The complex lies on a crystallographic centre of symmetry. The Ni atom is octahedrally coordinated by two thiocyanates (through N atoms) and by two thiosemicarbazide molecules (through hydrazinic N and S atoms). The crystal structure is stabilized by N--H...S hydrogen bonds. Early work on this structure [Garaj & Dunaj-Jurco (1968). Chem. Commun. p. 518] used photographic data and was refined to R = 0-13 for 512 reflections.

Growth factor-loaded microparticles for tissue engineering: The discrepancies of in vitro characterization assays

Efficient and effective growth factor (GF) delivery is an ongoing challenge for tissue regeneration therapies. The accurate quantification of complex molecules such as GFs, encapsulated in polymeric delivery devices, is equally critical and just as complex as achieving efficient delivery of active GFs. In this study, GFs relevant to bone tissue formation, vascular endothelial growth factor (VEGF) and bone morphogenetic protein 7 (BMP-7), were encapsulated, using the technique of electrospraying, into poly(lactic-co-glycolic acid) microparticles that contained poly(ethylene glycol) and trehalose to assist GF bioactivity. Typical quantification procedures, such as extraction and release assays using saline buffer, generated a significant degree of GF interactions, which impaired accurate assessment by enzyme-linked immunosorbent assay (ELISA). When both dry BMP-7 and VEGF were processed with chloroform, as is the case during the electrospraying process, reduced concentrations of the GFs were detected by ELISA; however, the biological effect on myoblast cells (C2C12) or endothelial cells (HUVECs) was unaffected. When electrosprayed particles containing BMP-7 were cultured with preosteoblasts (MC3T3-E1), significant cell differentiation into osteoblasts was observed up to 3 weeks in culture, as assessed by measuring alkaline phosphatase. In conclusion, this study showed how electrosprayed microparticles ensured efficient delivery of fully active GFs relevant to bone tissue engineering. Critically, it also highlights major discrepancies in quantifying GFs in polymeric microparticle systems when comparing ELISA with cell-based assays.

Study of fracture behaviour of bond coats on nickel superalloy by three-point bending of microbeams

A microbeam testing geometry is designed to study the variation in fracture toughness across a compositionally graded NiAl coating on a superalloy substrate. A bi-material analytical model of fracture is used to evaluate toughness by deconvoluting load-displacement data generated in a three-point bending test. It is shown that the surface layers of a diffusion bond coat can be much more brittle than the interior despite the fact that elastic modulus and hardness do not display significant variations. Such a gradient in toughness allows stable crack propagation in a test that would normally lead to unstable fracture in a homogeneous, brittle material. As the crack approaches the interface, plasticity due to the presence of Ni3Al leads to gross bending and crack bifurcation.

Amino Acid Based MOFs: Synthesis, Structure, Single Crystal to Single Crystal Transformation, Magnetic and Related Studies in a Family of Cobalt and Nickel Aminoisophthales

Four new 5-aminoisophthalates of cobalt and nickel have been prepared employing hydro/solvothermal methods: [Co2(C8H5NO4)2(C4H4N2)(H2O)2]·3H2O (I), [Ni2(C8H5NO4)2(C4H4N2)(H2O)2]·3H2O (II), [Co2(H2O)(μ3-OH)2(C8H5NO4)] (III), and [Ni2(H2O)(μ3-OH)2(C8H5NO4)] (IV). Compounds I and II are isostructural, having anion-deficient CdCl2 related layers bridged by a pyrazine ligand, giving rise to a bilayer arrangement. Compounds III and IV have one-dimensional M−O(H)−M chains connected by the 5-aminoisophthalate units forming a three-dimensional structure. The coordinated as well as the lattice water molecules of I and II could be removed and inserted by simple heating−cooling cycles under the atmospheric conditions. The removal of the coordinated water molecule is accompanied by changes in the coordination environment around the M2+ (M = Co, Ni) and color of the samples (purple to blue, Co; green to dark yellow, Ni). This change has been examined by a variety of techniques that include in situ single crystal to single crystal transformation studies and in situ IR and UV−vis spectroscopic studies. Magnetic studies indicate antiferromagnetic behavior in I and II, a field-induced magnetism in III, and a canted antiferromagnetic behavior in IV.

Crystallite size effects in stacking faulted nickel hydroxide and its electrochemical behaviour

P-Nickel hydroxide comprises a long range periodic arrangement of atoms with a stacking sequence of AC AC AC-having an ideal composition Ni(OH)(2). Variation in the preparative conditions can lead to the changes in the stacking sequence (AC AC BA CB AC AC or AC AC AB AC AC) This type of variation in stacking sequence can result in the formation of stacking fault in nickel hydroxide. The stability of the stacking fault depends on the free energy content of the sample. Stacking faults in nickel hydroxide is essential for better electrochemical activity. Also there are reports correlating particle size to the better electrochemical activity. Here we present the effect of crystallite size on the stacking faulted nickel hydroxide samples. The electrochemical performance of stacking faulted nickel hydroxide with small crystallite size exchanges 0.8e/Ni, while the samples with larger crystallite size exchange 0.4e/Ni. Hence a right combination of crystallite size and stacking fault content has to be controlled for good electrochemical activity of nickel hydroxide. (C) 2008 Elsevier B.V. All rights reserved.

The effect of ageing on microstructure and nanoindentation behaviour of dc magnetron sputter deposited nickel rich NiTi films

Nickel rich NiTi films were sputter deposited on p-doped Si left angle bracket1 0 0right-pointing angle bracket substrates maintained at 300 °C. The films were subsequently solution treated at 700 °C for 30 min followed by ageing at 400 and 500 °C for 5 h. The microstructure of the films was examined by TEM and these studies revealed that the NiTi films were mostly amorphous in the as-deposited condition. The subsequent solution treatment and ageing resulted in crystallization of the films with the film aged at 400 °C exhibiting nanocrystalline grains and three phases viz. B2 (austenite), R and Ni3Ti2 whereas the film aged at 500 °C shows micron sized grains and two phases viz. R and Ni3Ti2. Nanoindentation studies revealed that the nature of the load versus indentation depth response for the films aged at 400 and 500 °C was different. For the same load, the indenter penetrated to a much greater depth for the film aged at 400 °C as compared to the film aged at 500 °C. Also the ratio of the residual indentation depth (hf) to maximum indentation depth (hmax) is lower for the film aged at 400 °C as compared to the film aged at 500 °C. This was attributed to the occurrence of stress induced martensitic transformation of the B2 phase present in the film aged at 400 °C during indentation loading which results in a transformation strain in addition to the normal elastic and plastic strains and its subsequent recovery on unloading. The hardness and elastic modulus measured using the Oliver and Pharr analysis was also found to be lower for the film aged at 400 °C as compared to the film aged at 500 °C which was also primarily attributed to the same effect.

The Use of Liquid-Liquid Interface (Biphasic) for the Preparation of Benzenetricarboxylate Complexes of Cobalt and Nickel

New metal-organic frameworks (MOFs) [Ni(C12N2H10)(H2O)][C6H3(COO)2(COOH)] (I), [Co2(H2O)6][C6H3(COO)3]2·(C4N2H12)(H2O)2 (II), [Ni2(H2O)6][C6H3(COO)3]2·(C4N2H12)(H2O)2 (III), [Ni(C13N2H14)(H2O)][C6H3(COO)2(COOH)] (IV), [Ni3(H2O)8][C6H3(COO)3] (V) and [Co(C4N2H4)(H2O)][C6H3(COO)3] (VI) {C6H3(COOH)3 = trimesic acid, C12N2H10 = 1,10-phenanthroline, C4N2H12 = piperazine dication, C13N2H14 = 1,3-bis(4-pyridyl)propane and C4N2H4 = pyrazine} have been synthesized by using an interface between two immiscible solvents, water and cyclohexanol. The compounds are constructed from the connectivity between the octahedral M2+ (M = Ni, Co) ions coordinated by oxygen atoms of carboxylate groups and water molecules and/or by nitrogen atoms of the ligand amines and the carboxylate units to form a variety of structures of different dimensionality. Strong hydrogen bonds of the type O-H···O are present in all the compounds, which give rise to supramolecularly organized higher-dimensional structures. In some cases ··· interactions are also observed. Magnetic studies indicate weak ferromagnetic interactions in I, IV and V and weak antiferromagnetic interactions in the other compounds (II, III and VI). All the compounds have been characterized by a variety of techniques.

Exfoliation of alpha-hydroxides of nickel and cobalt in water

p-Aminobenzoate ion intercalated alpha-hydroxides of nickel/cobalt were synthesized by precipitation using ammonia (pH = similar to 12). Aqueous colloidal suspension of alpha-hydroxide of nickel/cobalt was obtained on washing the precipitate as the pH was reduced to similar to 7. The development of partial positive charge on the amine end of the intercalated anion causes repulsion between the layers leading to exfoliation and colloidal suspension of monolayers in water. While theb layers could be restacked from the colloidal suspension in the presenceof other anions in the case of alpha-cobalt hydroxide, the exfoliation could not be reversed easily in the case of the nickel analog. (C) 2010 Elsevier Inc. All rights reserved.