Home About us Contact
|
Home About us Contact | ||
|
|
||
Nickel
Kinds of Nickel Terms modified by Nickel Selected AbstractsChemInform Abstract: Cobalt(II)/Nickel(II)-Centered Keggin-Type Heteropolymolybdates: Syntheses, Crystal Structures, Magnetic and Electrochemical Properties.CHEMINFORM, Issue 28 2008Guang-Gang Gao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Fabrication of Long Lengths of Epitaxial Buffer Layers on Biaxially Textured Nickel Substrates Using a Continuous Reel-to-Reel Dip-Coating UnitJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001M. Parans Paranthaman A low-cost, nonvacuum, solution precursor route has been developed to produce epitaxial oxide buffer layers of Eu2O3 or La2Zr2O7 on biaxially textured Ni (100) tapes. A reel-to-reel continuous dip-coating unit consisting of a constant-tension tape transport system attached to a controlled atmosphere furnace was fabricated. Nickel tapes were pulled through a 2-methoxyethanol solution of europium methoxyethoxide/acetate or lanthanum zirconium methoxyethoxide. The double-sided dip-coated tapes were then annealed in a preheated furnace at 1000°,1100°C with a high flow rate of Ar/H2 (4%) gas. The dip-coated buffers were dense, continuous, crack-free, and epitaxial with a single cube texture. A critical current (Jc) of >1 MA/cm2 at 77 K and self-field was obtained for YBa2Cu3O7-, (YBCO) films with a layer sequence of YBCO (ex situ BaF2 process)/CeO2 (sputtered)/YSZ (sputtered)/Eu2O3 (dip-coated)/nickel. We have produced 1,2 m lengths of epitaxial buffer layers on textured nickel substrates using a nonvacuum process for the first time. [source] The epidemiology of contact allergy in the general population , prevalence and main findingsCONTACT DERMATITIS, Issue 5 2007Jacob Pontoppidan Thyssen A substantial number of studies have investigated the prevalence of contact allergy in the general population and in unselected subgroups of the general population. The aim of this review was to determine a median prevalence and summarize the main findings from studies on contact allergy in the general population. Published research mainly originates from North America and Western Europe. The median prevalence of contact allergy to at least 1 allergen was 21.2% (range 12.5,40.6%), and the weighted average prevalence was 19.5%, based on data collected on all age groups and all countries between 1966 and 2007. The most prevalent contact allergens were nickel, thimerosal, and fragrance mix. The median nickel allergy prevalence was 8.6% (range 0.7,27.8%) and demonstrates that nickel was an important cause of contact allergy in the general population and that it was widespread in both men and women. Numerous studies demonstrated that pierced ears were a significant risk factor for nickel allergy. Nickel was a risk factor for hand eczema in women. Finally, heavy smoking was associated with contact allergy, mostly in women. Population-based epidemiological studies are considered a prerequisite in the surveillance of national and international contact allergy epidemics. [source] Dose per unit area , a study of elicitation of nickel allergyCONTACT DERMATITIS, Issue 5 2007Louise Arup Fischer Background:, Experimental sensitization depends upon the amount of allergen per unit skin area and is largely independent of the area size. Objectives:, This study aimed at testing if this also applies for elicitation of nickel allergy. Patients/methods:, 20 nickel allergic individuals were tested with a patch test and a repeated open application test (ROAT). Nickel was applied on small and large areas. The varying parameters were area, total dose and dose per unit area. Results:, In the patch test, at a low concentration [15 ,g nickel (,gNi)/cm2], there were significantly higher scores on the large area with the same dose per area as the small area. At higher concentrations of nickel, no significant differences were found. In the ROAT at low concentration (6.64 ,gNi/cm2), it was found that the latency period until a reaction appeared was significantly shorter on the large area compared to the small area. It was also found that the ROAT threshold (per application) was lower than the patch test threshold. Conclusion:, For elicitation of nickel allergy, the size of the exposed area and therefore the total amount of applied nickel, influence the elicitation reaction at some concentrations, even though the same dose per unit area is applied. [source] P02 Analysis of coupled patch test reactions to nickel, cobalt and chromateCONTACT DERMATITIS, Issue 3 2004Janice Hegewald Concomitant sensitizations to Nickel, Cobalt and Chromate are often observed among patch test patients. However, the reasons for being sensitized to two or more of these substances are not completely understood. Examination of IVDK (http://www.ivdk.org) patch test results with multivariate procedures has been conducted to further elucidate the mechanisms involved with these sensitizations and potential exposure factors that may have led to the concomitant sensitizations. Gender, age, occupational dermatitis, and construction work were considered and examined with multivariate logistic regression models with the dependent response variable being concurrent reactions to a metal pair versus no reactions. In addition to the aforementioned anamnestic data, examination of a poly-sensitizations variable (reactions to 1, 2, or 3 standard series allergens other than Nickel, Cobalt or Chromate) provided information regarding general susceptibility to positive patch test reactions. Combined reactions to Cobalt and Chromate were strongly linked to construction work (OR = 11.23 (7.46, 16.90)) and occupational dermatitis. Female patch test patients had a higher odds of a positive patch test reaction to both Nickel and Cobalt (OR = 4.73 (3.81, 5.87)). Sensitization to other, unrelated standard series substances was associated with concurrent reactions to all of the metal pairs. The association between construction work and Cobalt-Chromate reactions corresponds with the hypothesis that cement exposures lead to cobalt-chromate sensitizations. Individual susceptibility to delayed-type sensitizations, as represented by the poly-sensitization variable, also appears to be associated with coupled sensitizations to metals and warrants further examination. [source] Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping VoltammetryELECTROANALYSIS, Issue 12 2008B. Gholivand Abstract A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N,-bis(salicylaldehydo)4-carboxyphenylenediamine (BSCPDA),complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02,mol L,1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42,,M, pH,9.6 and adsorption potential at ,50,mV versus Ag/AgCl. With an accumulation time of 20,s, the peaks current are proportional to the concentration of nickel and cadmium over the 1,180, and 0.5,200,ng mL,1 with detection limits of 0.06 and 0.03,ng mL,1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98,nA mL ng,1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results. [source] Nickel potentiates the genotoxic effect of benzo[a]pyrene in Chinese hamster lung V79 cellsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2006Cheng Z. Deng Abstract The modulating effect of acute exposure to NiCl2 on the induction of chromosome aberrations by a model carcinogen, benzo[a]pyrene (B[a]P), was examined in Chinese hamster V79 lung cells. At concentrations up to 20 ,g/ml (84.2 ,M), NiCl2 did not significantly increase the frequency of chromosome aberrations in V79 cells when the cells were exposed concomitantly to 0.5 ,g/ml B[a]P. Addition of the S15 liver microsomal fraction together with the B[a]P did not alter the results. Addition of NiCl2 2 hr before treatment of cells with 0.5 ,g/ml B[a]P also did not result in a significant elevation of the frequency of chromosome aberrations, even at NiCl2 concentrations as high as 20 ,g/ml. Contrasting sharply with these findings, when V79 cells were treated with NiCl2 immediately after B[a]P exposure, a significant increase in the frequency of chromosome damage was observed at NiCl2 concentrations as low as 5 ,g/ml (21.1 ,M). NiCl2 -mediated enhancement of chromosome damage was also observed when V79 cells were exposed to the reactive B[a]P intermediate, benzo[a]pyrene,r,7,t,8-dihydrodiol- t,9,10-epoxide (BPDE). In the BPDE-treated cells, the level of NiCl2 -mediated enhancement was similar to that observed with the tumor promoter 12- o -tetradecanoylphorbol-13-acetate (TPA, 100 ng/ml). These results are consistent with the view that the effect of nickel (II) on B[a]P-induced genetic damage is dependent on the relative times of exposure to Ni2+ and B[a]P. NiCl2 did not enhance the frequency of chromosome aberrations induced by Chromium (VI), regardless of the order of addition of the chemicals to the V79 cells. These results suggest that nickel may act as a promoter of chemically-induced genetic damage through induction of error-prone repair. Environ. Mol. Mutagen., 2006. © 2005 Wiley-Liss, Inc. [source] Phage display as a novel screening tool for primary toxicological targetsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2010Bieke Van Dorst Abstract In the present study the use of phage display as a screening tool to determine primary toxicological targets was investigated. These primary toxicological targets are the targets in the cell with which a chemical compound initially interacts and that are responsible for consecutive (toxic) effects. Nickel was used as model compound for the present study. By selection of Ni-binding peptides out of a 12-mer peptide phage library, it was possible to identify primary toxicological targets of Ni (and other metals). The selected Ni-binding peptides showed similarities to important primary toxicological targets of Ni, such as the hydrogenase nickel incorporation protein (hypB) and the Mg/Ni/Co transporter (corA). This shows that phage display, which is already widely used in other research fields, also has potential in ecotoxicology, as a novel screening tool with which to determine primary toxicological targets of chemical compounds. Environ. Toxicol. Chem. 2010;29:250,255. © 2009 SETAC [source] Influence of water quality and age on nickel toxicity to fathead minnows (Pimephales promelas)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Tham Chung Hoang Abstract This research characterized the effects of water quality and organism age on the toxicity of nickel (Ni)to fathead minnows (Pimephales promelas) to facilitate the accurate development of site-specific water-quality criteria. Nickel sulfate hexa-hydrate (NiSO4·6H2O) was used as the Ni source for performing acute toxicity tests (median lethal concentration after 96-h exposure [96-h LC50]) with <1-d-old and 28-d-old P. promelas under varying regimes of hardness, pH, alkalinity, and natural organic matter (NOM). The toxicity of Ni was inversely related to water hardness between hardness values of 20 and 150 mg/L (as CaCO3). Below 30 mg/L alkalinity, Ni toxicity was related to alkalinity. The effect of pH was confounded by hardness and the presence of NOM. In the absence of NOM, the toxicity of Ni increased as pH increased at high hardness and alkalinity. In general, 28-d-old fish were less sensitive than <1-d-old fish to Ni. This lower sensitivity ranged from 12-fold at low hardness and alkalinity (20 and 4 mg/L, respectively) to 5-fold at high hardness and alkalinity (100 and 400 mg/L, respectively). The presence of NOM (10 mg/L as dissolved organic carbon [DOC]) reduced Ni toxicity by up to 50%, but this effect appeared to be saturated above DOC at 5 mg/L. Incubating Ni with the NOM solution from 1 to 17 days had no effect on Ni toxicity. When using multivariate analysis, the 96-h LC50 for Ni was a function offish age, alkalinity, hardness, and NOM (96-h LC50 = ,0.642 + 0.270(fish age) + 0.005(alkalinity) + 0.018(hardness) + 0.138(DOC)). When using this model, we found a strong relationship between measured and predicted 96-h LC50 values (r2 = 0.94) throughout the treatment water qualities. The biotic ligand model (BLM) did not accurately predict Ni toxicity at high or low levels of alkalinity. Results of our research suggest that the BLM could be improved by considering NiCO3 to be bioavailable. [source] 1,3,5-Triazapentadiene Nickel(II) Complexes Derived from a Ketoxime-Mediated Single-Pot Transformation of NitrilesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2010Maximilian N. Kopylovich Abstract A series of cationic (2+) [Ni{HN=C(R)NHC(R)=NH}2](X)2 {R = 4-(Cl)C6H4 (1), 3-(NC)C6H4 (3), 4-(NC)C6H4 (4) and Me (7); X = Cl, (1, 3, 4) or MeCOO,·H2O (7)} and neutral [Ni{HN=C(R)NC(R)=NH}2](solvate) {R = 3-(Cl)-4-py (2), 3-py (5) and 4-py (6); solvate = MeOH and/or H2O; py = pyridyl} N,N -chelating bis(1,3,5-triazapentadiene/ato)nickel(II) [Ni(tap)2]2+/0 complexes has been easily generated by a ketoxime-mediated single-pot reaction of a nickel(II) salt [NiCl2·2H2O or Ni(MeCOO)2·4H2O] with 4-chlorobenzonitrile, isophthalonitrile, terephthalonitrile, acetonitrile, 2-chloro-4-cyanopyridine, 3-cyanopyridine or 4-cyanopyridine, respectively. The obtained compounds have been characterized by IR, 1H and 13C{1H} NMR spectroscopy, FAB-MS(+) or ESI-MS(+), elemental analyses and single-crystal X-ray diffraction [for 7 and solvated mono- {1a·(Me2CO)0.33·(MeOH)0.67} and bis-deprotonated (2b·2Me2CO, 4b·CHCl3, 5b·Me2CO and 6b·MeOH) products, formed upon recrystallization of 1, 2, 4, 5 and 6, respectively]. The crystal structures of all compounds bear similar monomeric Ni(tap)2 units with a nearly square-planar geometry. In addition, the structure of 7 features the formation of infinite 1D zig-zag water,acetate chains {[(H2O)2(MeCOO)2]2,}n, which multiply interact with the [Ni(tap)2]2+ cations to generate a 2D hydrogen-bonded supramolecular assembly. [source] Pseudo-Octahedral Schiff Base Nickel(II) Complexes: Does Single Oxidation Always Lead to the Nickel(III) Valence Tautomer?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2008Olaf Rotthaus Abstract With the aim of establishing correlations between the ligand structure and the oxidation site in nickel complexes from Schiff base ligands, five ligands and their nickel complexes have been synthesized. The prototypical asymmetric Schiff base ligand HL1 contains both phenol and pyridine pendant arms with a pivotal imine nitrogen atom. Ligands HL2,5 differ from HL1 by either their phenolate para substituent, the hybridization of the pivotal nitrogen atom, and/or the N-donor properties of the pyridine moiety. The five complexes [Ni(L1,5)2] are obtained by treating the corresponding ligands with 0.5 equiv. of Ni(OAc)2·4H2O in the presence of NEt3. X-ray crystal-structure diffraction studies as well as DFT calculations reveal that [Ni(L1,5)2] involves a high-spin nickel(II) ion within a pseudo-octahedral geometry. The two ligands are arranged in a meridional fashion when the pivotal nitrogen atom is an imine {as in [Ni(L1,2)2] and [Ni(L4,5)2]}, while the fac isomer is preferred in [Ni(L3)2] (amino pivotal nitrogen atom). [Ni(L1)2] is characterized by an oxidation potential at ,0.17 V vs. Fc+/Fc. The one-electron-oxidized species [Ni(L1)2]+ exhibits an EPR signal at g = 2.21 attributed to a phenoxyl radical that is antiferromagnetically coupled to a high-spin NiII ion. [Ni(L2)2] differs from [Ni(L1)2] by the phenolate para substituent (a tert -butyl instead of the methoxyl group) and exhibits an oxidation potential that is ca. 0.16 V higher. Compared to [Ni(L1)2]+ the cation [Ni(L2)2]+ exhibits a SOMO that is more localized on the metal atom. The EPR and electrochemical signatures of [Ni(L3)2]+ are similar to those of [Ni(L1)2]+, thus showing that an imino to amino substitution compensates for a methoxy to tert -butyl one. Replacement of the pyridine by a quinoline group in [Ni(L4,5)2] makes the complexes slightly harder to oxidize. The EPR signatures of the cations [Ni(L4,5)2]+ are roughly similar to those of the pyridine analogs [Ni(L1,2)2]+. The oxidation site is thus not significantly affected by changes in the N-donor properties of the terminal imino nitrogen atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Studies on Nickel(II) Complexes with Amide-Based Ligands: Syntheses, Structures, Electrochemistry and Oxidation ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Jyoti Singh Abstract The present work discusses the nickel chemistry in a set of amide-based open-chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square-planar geometry. Absorption spectra and NMR studies reveal that the solid-state square-planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Amphiphilic Iron(II) and Nickel(II) Complexes Based on Alkylated Diazaoxa- and TriazacyclononaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2008David Domínguez-Gutiérrez Abstract It is known that including a metal into a micellar solution enhances both the colour and catalytic potential of such systems. This fact is well exemplified by the broad use of surfactant species as phase-transfer catalysts. In the present work, we report our studies concerning the aggregation properties of a series of iron and nickel-based triazacyclononane metalloamphiphiles. Upon multiple alkylation of the triazamacrocycle, we were able to obtain amphiphilic complexes that aggregate in toluene. We characterised the sizes and shapes of the aggregates by dynamic light scattering while their nature was assessed by atomic force microscopy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Coordination Chemistry of 3-Mercapto-2-(mercaptomethyl)propanoic Acid (Dihydroasparagusic Acid) with Iron and NickelEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006Phillip I. Volkers Abstract The first transition-metal complexes bearing the natural product dihydroasparagusic acid, (HSCH2)2CHCO2H, as a ligand are reported. Various coordination modes and nuclearities are demonstrated for the chelating ligand by a series of iron and nickel complexes. Fe2[(SCH2)2CHCO2H](CO)6 retains carbonyl substitution reactivity typical of Fe2(SR)2(CO)6 complexes, yet carboxy coordination to FeI was unobserved. Coupling of the carboxylic acid with amines yields the corresponding amides Fe2[(SCH2)2CHC(O)NHR](CO)6 (R = Et, gly,O,tBu). Fe2[(SCH2)2CHCO2H](CO)4(PMe3)2 catalyzes H2 production, but no better than unfunctionalized alkyl dithiolate analogs. Reactions of the ligand with NiCl2(dppe) afforded mono-, di-, and trinuclear complexes. Noteworthy is Ni3[(SCH2)2CHCO2]2(dppe)2, which features an octahedrally coordinated NiII center linked to a pair of square-planar NiII centers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis and Characterization of Heterotrinuclear Complexes of Nickel and Palladium with Pyridinecarboxylate as Bridging LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2005José Ruiz Abstract Heterotrinuclear pyridinecarboxylate complexes of nickel(II) and palladium(II) of the types [Ni(mcN3)(pyridinecarboxylate)]2{,-[Pd(C6F5)2]}(PF6)2 [mcN3 = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (Me3 -mcN3) or 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene (Me4 -mcN3)] have been prepared by two different routes. The corresponding monomeric pyridinecarboxylate complexes of nickel and the monomeric pyridinecarboxylic acid/ester complexes of palladium have also been prepared. The crystal structures of two precursors [Ni(Me4 -mcN3)(NC5H4 -3-COO)]PF6 and cis -[Pd(C6F5)2(NC5H4 -4-CH2COOCH3)2] have been established by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Configuration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Aminou Mohamadou Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Second-Order Nonlinear Optical Properties of Tetraaza-Coordinated Nickel(II) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Santo Di Bella Abstract In this contribution, we report the design and theoretical analysis, using the INDO/SCI-SOS quantum chemical formalism, of novel molecular architectures based on planar [N4]-, (2-aminobenzylideneiminato)- and tetraazamacrocycle-coordinated nickel(II) complexes, having second-order nonlinear optical (NLO) properties. Calculations indicate that these molecules possess comparable, or even larger, second-order nonlinearity to the bis(salicylaldiminato)NiII Schiff-base analogues. The nonlinearity of substituted complexes is dominated by the nature and position of substituents on the tribenzo[b,f,l] and/or cyclotetradecine rings, and is determined by the relative directions of the ground- and excited-state dipole moments. Moreover, substitution with acceptor groups in the dibenzo[b,l] rings involves a significant octupolar contribution to optical nonlinearity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Ennio Zangrando Abstract We report new series of NiII and CoIII complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar,N,N,OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). NiII derivatives were obtained either as trimers of formula [Ni3(Ar,N,N,OH)3Br4(OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. CoIII complexes were obtained only as bis(chelated) derivatives, with the two ligands coplanar. The "iso -oriented" arrangement of ligands in bis(chelated) CoIII complexes is favored by weak interactions between the two ligands, namely O,H···O hydrogen bond and stacking interactions between the aryl groups. CoIII complexes might find application as catalysts for living or controlled radical polymerization of polar olefins, and preliminary results are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] A Rigid Molecular Scaffold Affixing a (Polypyridine)ruthenium(II)- and a Nickel(II)-Containing Complex: Spectroscopic Evidence for a Weakly Coupled Bichromophoric SystemEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2003Yann Pellegrin Abstract The synthesis of DppztBuSalH2 (7), a rigid conjugated ditopic ligand containing a Dppz (dipyrido[3,2- a:2,,3,- c]phenazine) skeleton and a salophen-type chelate, is reported. The complexes DppztBuSalNi (10), [Ru(bpy)2(DppztBuSalH2)]2+ (11), and [Ru(bpy)2(DppztBuSalNi)]2+ (12) have been prepared and characterised using common spectroscopic methods. Electrochemical, UV/Vis spectroelectrochemical and EPR studies were conducted on compounds 7, 10, 11, and 12. The singly reduced radical forms of 7 and 10 can be generated electrochemically, with the lone electron located on the low-lying phenazine ,*-molecular orbital. Complexes 11 and 12 show several reduction waves and electronic and EPR data obtained for the electrogenerated singly reduced species show them to be closely related to the radical species 7·, and 10·,, respectively. The presence of nickel(II) in compound 12 renders the addition of the second electron on the phenazine group reversible. Both 11 and 12 show common features on the cathodic side of their cyclic voltammograms, with reversible one-electron ruthenium-centred oxidation. An additional low-potential reversible-oxidation wave is observed for 12, and this is ascribed to oxidation of the nickel(II) ion. The combined spectroscopic data best describe the ruthenium-containing complexes as weakly coupled bichromophoric systems. Photophysical studies attest to the formation of a charge-separated state for 11, whereas a strong quenching is detected for 12. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Size Independent Shape Memory Behavior of Nickel,Titanium,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Blythe G. Clark While shape memory alloys such as NiTi have strong potential as active materials in many small-scale applications, much is still unknown about their shape memory and deformation behavior as size scale is reduced. This paper reports on two sets of experiments which shed light onto an inconsistent body of research regarding the behavior of NiTi at the nano- to microscale. In situ SEM pillar bending experiments directly show that the shape memory behavior of NiTi is still present for pillar diameters as small as 200,nm. Uniaxial pillar compression experiments demonstrate that plasticity of the phase transformation in NiTi is size independent and, in contrast to bulk single crystal observations, is not influenced by heat treatment (i.e., precipitate structure). [source] Kinetics and Mechanism of the Demetallation of Macrocyclic Nickel(II) Complexes by CyanideHELVETICA CHIMICA ACTA, Issue 3 2005Liselotte Siegfried The kinetics and the mechanism of the cyanide-induced demetallation of a series of Ni2+ complexes with macrocyclic ligands of different ring size (12- to 14-membered; see 1,4) and steric constraints was studied. Although the rates differ by almost five orders of magnitude when compared to each other under fixed experimental conditions (pH,10.5, [CN,]=10,2,M), all reactions proceed through the relatively rapid formation of cyano adducts [Ni(CN)nL] (n=1, 2), which then react with additional CN, or HCN to give the final products. Of paramount importance for the reaction rate is the geometry and configuration of the cyano adducts [Ni(CN)nL] (n=1,2). cis -Dicyano derivatives with a folded macrocycle react faster than trans -compounds. In the case of (1,4,8,11-tetraazacyclotetradecane)nickel(2+) ([Ni (4)]2+), which gives a trans- dicyano adduct, the base-catalyzed N-inversion necessary to obtain the cis- dicyano derivative becomes rate determining at high CN, concentrations. [source] Molecular Recognition of a Peptide by the Nickel(II) Complex of 1,4,7,10-Tetraazacyclododecane-2,9-dioneHELVETICA CHIMICA ACTA, Issue 3 2003Jian Gao The nickel(II) complex of the macrocycle 1,4,7,10-tetraazacyclododecane-2,9-dione (dota) was found to be efficient in the recognition of the dipeptide, glycyl-glycine (Gly-Gly) in aqueous solution. This (dota)NiII complex serves as a targeting molecule to form a stable ternary complex with the dipeptide at pH,8.3 in aqueous solution. The recognition constant (log K=19.20) and the recognition mechanism were investigated based on the potentiometric method. The single-crystal of a six-coordinated (dota)2NiII complex is also reported. [source] Competitive Abnormal Grain Growth between Allotropic Phases in Nanocrystalline NickelADVANCED MATERIALS, Issue 10 2010L. N. Brewer Electron backscatter diffraction-generated phase map showing the distribution of the abnormally grown grains for both the face centered cubic (red) and hexagonal close packed (blue) phases. Annealing condition was 17,h at 548,K. [source] Nickel(0)/Imidazolium Carbene Catalyst System for Efficient Cross-Coupling of Aryl Bromides and Chlorides with Organomanganese ReagentsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2006Anne Leleu Abstract N,N, -Bis(2,6-diisopropylphenyl)imidazolium chloride associated with nickel(II) acetylacetonate (3,5 mol,%) was used as catalyst to efficiently cross-couple functionalized aryl bromides with organomanganese reagents. The reactions were performed between 0,°C and room temperature, giving unsymmetrical biaryls in 0.25 to 24,h with 52 to 100,% yields for isolated materials. Aryl chlorides showed slightly diminished reactivity in Ni/2 IPr-catalyzed cross-couplings and good yields could only be attained with activated or neutral substrates. [source] Metallurgical characterization, galvanic corrosion, and ionic release of orthodontic brackets coupled with Ni-Ti archwiresJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Myrsini S. Darabara Abstract In orthodontics, a combination of metallic alloys is placed into the oral cavity during medical treatment and thus the corrosion resistance and ionic release of these appliances is of vital importance. The aim of this study is to investigate the elemental composition, microstructure, hardness, corrosion properties, and ionic release of commercially available orthodontic brackets and Copper Ni-Ti archwires. Following the assessment of the elemental composition of the orthodontic wire (Copper Ni-TiÔ) and the six different brackets (Micro Loc, Equilibrium, OptiMESHXRT, Gemini, Orthos2, and Rematitan), cyclic polarization curves were obtained for each material to estimate the susceptibility of each alloy to pitting corrosion in 1M lactic acid. Galvanic corrosion between the orthodontic wire and each bracket took place in 1M lactic acid for 28 days at 37°C and then the ionic concentration of Nickel and Chromium was studied. The orthodontic wire is made up from a Ni-Ti alloy with copper additions, while the orthodontic brackets are manufactured by different stainless steel grades or titanium alloys. All tested wires and brackets with the exception of Gemini are not susceptible to pitting corrosion. In galvanic corrosion, following exposure for 28 days, the lowest potential difference (,250 mV) appears for the orthodontic wire Copper Ni-Ti and the bracket made up from pure titanium (Rematitan) or from the stainless steel AISI 316 grade (Micro Loc). Following completion of the galvanic corrosion experiments, measurable quantities of chromium and nickel ions were found in the residual lactic acid solution. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2006David W O'Connell Abstract A series of adsorption studies was carried out on a glycidyl methacrylate- modified cellulose material functionalised with imidazole (Cellulose- g -GMA-Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose- g -GMA-Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose- g -GMA-Imidazole sorbent of approximately 48 mg g,1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo-second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re-adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3,6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re-adsorption capability. Copyright © 2006 Society of Chemical Industry [source] Recycling of nickel,metal hydride batteries.JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2004I: Dissolution, solvent extraction of metals Abstract Nickel,metal hydride batteries contain valuable metallic components and although they are not considered a hazardous waste, recovery of these materials is necessary from an economic point of view. In this work a hydrometallurgical method for the dissolution and separation of the metals from cylindrical nickel,metal hydride rechargeable batteries was investigated. Hydrochloric acid was employed as the leaching agent to dissolve the metals from the batteries. Dissolution of metals was investigated as a function of acid concentration, leaching time and temperature. Suitable conditions for maximum metal dissolution were 3 h leaching with 4.0 mol dm,3 hydrochloric acid solutions at 95 °C. Extraction of 98% of nickel, 100% of cobalt and 99% of rare earth elements was achieved under these conditions. Separation of the rare earths from nickel and cobalt was preliminarily investigated by single batch solvent extraction with 25% bis(2-ethylhexyl)phosphoric acid. Efficient separation via complete extraction of the rare earths was obtained at a pH of approximately 2.5 while leaving nickel and cobalt in the raffinate. A shrinking particle model which can enable, under certain conditions, evaluation of the extent of metal dissolution present in nickel,metal hydride batteries was developed. A proposed electrochemical recovery of nickel and cobalt is also briefly discussed. Copyright © 2004 Society of Chemical Industry [source] Analysis of the signal transduction pathway of nickel-induced matrix metalloproteinase-2 expression in the human keratinocytes in vitro: preliminary findingsJOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2007Brunella Perfetto Background:, Nickel can induce cellular and nuclear damages responsible for chronic diseases, like allergic contact dermatitis (ACD). We previously showed that matrix metalloproteinase-2 (MMP-2) gene expression was induced by nickel in nontumorigenic human keratinocytes cell line (HaCat). Objective:, To investigate the signal transduction pathways involved in gelatinolytic activity induced in HaCat under nickel stimulation. Methods:, We analyzed the involvement of protein kinase A (PKA), protein kinase C (PKC), tyrosine kinase (PTK), nuclear factor-kB (NF-kB) and activator protein-1 (AP-1) using specific inhibitors (H89, calphostin C, genistein, carpain and curcumin) by electrophoretic mobility shift assay, reverse transcription-polymerase chain reaction and gelatin zymography. Results:, Our results indicate that nickel-induced MMP-2 production was inhibited with PTK, PKC and AP-1 specific inhibitors. Moreover, both PKA and NF-kB were not involved in nickel pathway. Conclusions:, Using HaCat, we showed that curcumin and genistein can revert nickel-induced MMP-2 upregulation. Whether the use of PTK and AP-1 inhibitors has therapeutic ramifications in the management of ACD remains to be investigated. [source] Controlled vinyl-type polymerization of norbornene with a Nickel(II) diphosphinoamine/methylaluminoxane catalytic systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Georgios C. Vougioukalakis Abstract A novel nickel-based complex coordinated with an asymmetric diphosphinoamine ligand was synthesized and fully characterized. Single crystals of good quality were also obtained, and the solid-state structure of the complex was studied via X-rays diffraction. The catalytic activity of this Ni(II) complex in the vinyl-type polymerization of norbornene was studied with methylaluminoxane (MAO) as the cocatalyst/activator. The influence of the reaction time, the equivalents of MAO used, and the concentration of the monomer on: (i) the activity of the catalytic system; (ii) the isolated yield of the polymer; and (iii) the molecular weight and molecular weight distribution of the polymer were investigated. The isolated polynorbornene (PNB) yields are significantly higher compared with those reported for other similar nickel-based systems. The as-obtained PNBs are characterized by high molecular weights and relatively narrow and monomodal molecular weight distributions (amongst the narrowest reported in the literature). The linear dependence of the molecular weight of the obtained PNB on the concentration of norbornene points toward a controlled polymerization reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5241,5250, 2009 [source] Nickel(II) and palladium(II) complexes with ,-dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Bernd Berchtold Abstract Nickel(II) and palladium(II) complexes with ,-dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2-cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo-Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two-step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3,n and B(C6F5)3,nEtn; and (2) Al(C6F5)nEt3,n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1-dodecene as chain-transfer agents; the molar mass can be varied in the number-average molecular weight range from 2 · 103 to 9 · 105 g · mol,1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604,3614, 2002 [source] | |||||||||||||||||||||||||||||||||||||||||||||||||