Structural and magnetic studies of Schiff base complexes of nickel(ii) nitrite: change in crystalline state, ligand rearrangement and a very rare μ-nitrito-1κO:2κN:3κO′ bridging mode

Four new nickel(II) complexes, [Ni2L2(NO2)2]·CH2Cl2·C2H5OH, 2H2O (1), [Ni2L2(DMF)2(m-NO2)]ClO4·DMF (2a), [Ni2L2(DMF)2(m-NO2)]ClO4 (2b) and [Ni3L¢2(m3-NO2)2(CH2Cl2)]n·1.5H2O (3) where HL = 2-[(3-amino-propylimino)-methyl]-phenol, H2L¢ = 2-({3-[(2-hydroxy-benzylidene)-amino]-propylimino}-methyl)-phenol and DMF = N,N-dimethylformamide, have been synthesized starting with the precursor complex [NiL2]·2H2O, nickel(II) perchlorate and sodium nitrite and characterized structurally and magnetically. The structural analyses reveal that in all the complexes, NiII ions possess a distorted octahedral geometry. Complex 1 is a dinuclear di-m2-phenoxo bridged species in which nitrite ion acts as chelating co-ligand. Complexes 2a and 2b also consist of dinuclear entities, but in these two compounds a cis-(m-nitrito-1kO:2kN) bridge is present in addition to the di-m2-phenoxo bridge. The molecular structures of 2a and 2b are equivalent; they differ only in that 2a contains an additional solvated DMF molecule. Complex 3 is formed by ligand rearrangement and is a one-dimensional polymer in which double phenoxo as well as m-nitrito-1kO:2kN bridged trinuclear units are linked through a very rare m3-nitrito-1kO:2kN:3kO¢ bridge. Analysis of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the nickel(II) ions in four complexes, with exchange parameters J of -5.26, -11.45, -10.66 and -5.99 cm-1 for 1, 2a, 2b and 3, respectively

Diagnosing the influence of diabatic processes on the explosive deepening of extratropical cyclones

A novel version of the classical surface pressure tendency equation (PTE) is applied to ERA-Interim reanalysis data to quantitatively assess the contribution of diabatic processes to the deepening of extratropical cyclones relative to effects of temperature advection and vertical motions. The five cyclone cases selected, Lothar and Martin in December 1999, Kyrill in January 2007, Klaus in January 2009, and Xynthia in February 2010, all showed explosive deepening and brought considerable damage to parts of Europe. For Xynthia, Klaus and Lothar diabatic processes contribute more to the observed surface pressure fall than horizontal temperature advection during their respective explosive deepening phases, while Kyrill and Martin appear to be more baroclinically driven storms. The powerful new diagnostic tool presented here can easily be applied to large numbers of cyclones and will help to better understand the role of diabatic processes in future changes in extratropical storminess.

Klaus - an exceptional winter storm over northern Iberia and southern France

The synoptic evolution and impacts of storm ‘Klaus’ that affected Europe on 23–24 January 2009 are assessed. Klaus was the costliest weather hazard event worldwide during 2009. Peak wind gusts reached 55ms-1 (107kn), accompanied by heavy rain, snow and flooding across Northern Iberia and southern France. Klaus underwent explosive development between the Azores and the Iberian Peninsula at an unusually low latitude. This development was supported by an extended and intense polar jet across the North Atlantic Basin, strong upper-air divergence associated with a second jet streak and an extraordinary export of tropical moisture into the genesis region. Copyright © 2011 Royal Meteorological Society

Selective P4 activation by an organometallic nickel(I) radical: formation of a dinuclear nickel(II) tetraphosphide and related di- and trichalcogenides

The reaction of the 17e nickel(I) radical [CpNi(IDipp)] (1, IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with P4 results in a nickel tetraphosphide [{CpNi(IDipp)}2(μ-η1:η1-P4)] with a butterfly-P42− ligand; related chalcogenides [{CpNi(IDipp)}2(μ-E2)] (E = S, Se, Te) and [{CpNi(IDipp)}2(μ-E3)] (E = S, Se) are formed with S8, Se∞ and Te∞.

Self-assembly of a Model Peptide incorporating a Hexa-Histidine sequence attached to an Oligo-Alanine sequence, and binding to Gold NTA/Nickel nanoparticles

Amyloid fibrils are formed by a model surfactant-like peptide (Ala)10-(His)6 containing a hexahistidine tag. This peptide undergoes a remarkable two-step self-assembly process with two distinct critical aggregation concentrations (cac’s), probed by fluorescence techniques. A micromolar range cac is ascribed to the formation of prefibrillar structures, whereas a millimolar range cac is associated with the formation of well-defined but more compact fibrils. We examine the labeling of these model tagged amyloid fibrils using Ni-NTA functionalized gold nanoparticles (Nanogold). Successful labeling is demonstrated via electron microscopy imaging. The specificity of tagging does not disrupt the β-sheet structure of the peptide fibrils. Binding of fibrils and Nanogold is found to influence the circular dichroism associated with the gold nanoparticle plasmon absorption band. These results highlight a new approach to the fabrication of functionalized amyloid fibrils and the creation of peptide/nanoparticle hybrid materials.

Structural stability of the synthetic thermoelectric ternary and nickel-substituted tetrahedrite phases

The purity and structural stability of the high thermoelectric performance Cu12Sb4S13 and Cu10.4Ni1.6Sb4S13 tetrahedrite phases, synthesized by solid–liquid–vapor reaction and Spark Plasma Sintering, were studied at high temperature by Rietveld refinement using high resolution X-ray powder diffraction data, DSC/TG measurements and high resolution transmission electron microscopy. In a complementary study, the crystal structure of Cu10.5Ni1.5Sb4S13 as a function of temperature was investigated by powder neutron diffraction. The temperature dependence of the structural stability of ternary Cu12Sb4S13 is markedly different to that of the nickel-substituted phases, providing clear evidence for the significant and beneficial role of nickel substitution on both sample purity and stability of the tetrahedrite phase. Moreover, kinetic effects on the phase stability/decomposition have been identified and discussed in order to determine the maximum operating temperature for thermoelectric applications. The thermoelectric properties of these compounds have been determined for high density samples (>98%) prepared by Spark Plasma Sintering and therefore can be used as reference values for tetrahedrite samples. The maximum ZT of 0.8 was found for Cu10.4Ni1.6Sb4S13 at 700 K.

Comparative analysis of the fit of 3-unit implant-supported frameworks cast in nickel-chromium and cobalt-chromium alloys and commercially pure titanium after casting, laser welding, and simulated porcelain firings

This study compared the vertical misfit of 3-unit implant-supported nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloy and commercially pure titanium (cpTi) frameworks after casting as 1 piece, after sectioning and laser welding, and after simulated porcelain firings. The results on the tightened side showed no statistically significant differences. On the opposite side, statistically significant differences were found for Co-Cr alloy (118.64 mu m [SD: 91.48] to 39.90 mu m [SD: 27.13]) and cpTi (118.56 mu m [51.35] to 27.87 mu m [12.71]) when comparing 1-piece to laser-welded frameworks. With both sides tightened, only Co-Cr alloy showed statistically significant differences after laser welding. Ni-Cr alloy showed the lowest misfit values, though the differences were not statistically significantly different. Simulated porcelain firings revealed no significant differences.

Surface spin disorder in nickel ferrite nanomagnets studied by in-field Mossbauer spectroscopy

The magnetic structure of NiFe(2)O(4) nanoparticles has been investigated by means of Mossbauer spectra at T=4.2 K in applied fields up to 12 T. Four samples were studied, with mean particle diameters ranging from 4.3 to 8.9 nm. All spectra could be decomposed into three sextets, two corresponding to the ferrimagnetic sublattices of Fe ions in the spinel structure (core) and the third one to randomly frozen spins near the particle surface (shell). The shell thickness, calculated from the fraction of disordered spins, was found to be about one-third of the particle radius at H (app)=e0 and to decrease with the applied field toward a common limit of similar to 0.4 nm. The mean canting angle relative to the field was also found to decrease for increasing fields, at a rate inversely correlated to the particle size.

Formation of beta-nickel hydroxide plate-like structures under mild conditions and their optical properties

Nanostructural beta-nickel hydroxide (beta-Ni(OH)(2)) plates were prepared using the microwave hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H(2)O)(6)](2+) to control the growth of beta-Ni(OH)(2) nuclei. A trigonal beta-Ni(OH)(2) single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni(2+) in oxygen octahedral sites were revealed by UV-vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the beta-Ni(OH)(2) nanoplates. (C) 2011 Elsevier Inc. All rights reserved.

Adsorption kinetics and charge inversion in layer-by-layer films from nickel tetrasulfonated phthalocyanine and poly(allylamine hydrochloride)

Layer-by-layer (LBL) films of nickel tetrasulfonated phthalocyanine (NiTsPc) alternated with poly(allylamine hydrochloride) (PAH) have been prepared, whose surface charge has been evaluated using surface potential measurements. From adsorption kinetics results, we obtained the immersion time of similar to 40 s, which was used to assemble layers of NiTsPc. The effect of gold (Au) and aluminum (Al) electrodes on the charge behavior was examined. We found that the surface potential (i.e. surface charge) was inverted each time a layer of PAH was alternated with another of NiTsPc molecules for the two types of electrodes, which was attributed to charge overcompensation between positive charges of PAH molecules, and negative charges from NiTsPc molecules. (C) 2009 Elsevier B.V. All rights reserved.

Immobilization of Poly(propylene imine) Dendrimer/Nickel Phtalocyanine as Nanostructured Multilayer Films To Be Used as Gate Membranes for SEGFET pH Sensors

We describe the assembly of layer-by-layer films based on the poly(propylene imine) dendrimer (PPID) generation 3 and nickel tetrasulfonated phthalocyanine (NiTsPc) for application as chemically sensitive membranes in sepal alive extended-gate field effect transistor (SEGFET) pH sensors PPID/NiTsPc films wet e adsorbed on quartz, glass. indium tin oxide. or gold (Au)-covered glass substrates Multilayer formation was monitored via UV-vis absorption upon following the increment in the Q-band intensity (615 nm) of NiTsPc The nanostructured membranes were very stable in a pH range of 4-10 and displayed a good sensitivity toward H(+), ca 30 mV/pH for PPID/N(1)TsPc films deposited on Au-covered substrates For films deposited on ITO, the sensitivity was ca 52 4 mV/pH. close to the expected theoretical value for ton-sensitive membranes. The use of chemically stable PPID/NiTsPc films as gate membranes in SEGFETs, as introduced here, may represent an alternative for the fabrication of nanostructured, porous platforms for enzyme immobilization to be used in enzymatic biosensors.

Syntheses, crystal structure and theoretical investigation of novel heteroleptic complexes of nickel(II) with N-R-sulfonyldithiocarbimate and phosphine ligands

Five new complexes of general formula: [Ni(RSO(2)N=CS(2))(dppe)], where R = C(6)H(5) (1), 4-ClC(6)H(4) (2), 4-BrC(6)H(4) (3), 4-IC(6)H(4) (4) and dppe = 1,2-bis(diphenylphosphino) ethane and [Ni(4-IC(6)H(4)SO(2)N=CS(2))(PPh(3))(2)] (5), where PPh3 = triphenylphosphine, were obtained in crystalline form by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate K(2)(RSO(2)N=CS(2)) and dppe or PPh(3) with nickel(II) chloride in ethanol/water. The elemental analyses and the IR, (1)H NMR, (13)C NMR and (31)P NMR spectra are consistent with the formation of the square planar nickel(II) complexes with mixed ligands. All complexes were also characterized by X-ray diffraction techniques and present a distorted cis-NiS(2)P(2) square-planar configuration around the Ni atom. Quantum chemical calculations reproduced the crystallographic structures and are in accord with the spectroscopic data. Rare C-H center dot center dot center dot Ni intramolecular short contact interactions were observed in the complexes 1-5. (C) 2011 Elsevier B. V. All rights reserved.

Synthesis and Characterization of Homoleptic and Heteroleptic Cobalt, Nickel, Copper, Zinc and Cadmium Compounds with the 2-(Tosylamino)-N-[2-(tosylamino)benzylidene]aniline Ligand

The electrochemical oxidation of anodic metal (cobalt, nickel, copper, zinc and cadmium) in an acetonitrile solution of the Schiff-base ligand 2-(tosylamino)-N-[2-(tosylamino)-benzylidene] aniline (H(2)L) afforded the homoleptic compounds [ML]. The addition of 1,1-diphenylphosphanylmethane (dppm), 2,2`-bipyridine (bipy) or 1,10-phenanthroline (phen) to the electrolytic phase gave the heteroleptic complexes [NiL(dppm)], [ML(bipy)] and [ML(phen)]. The crystal structures of H(2)L (1), [NiL] (2), [CuL] (3), [NiL(dppm)] (4), [CoL(phen)] (5), [CuL(bipy)] (6) and [Zn(Lphen)] (7) were determined by X-ray diffraction. The homoleptic compounds [NiL] and [CuL] are mononuclear with a distorted square planar [MN(3)O] geometry with the Schiff base acting as a dianionic (N(amide)N(amide)N(imine)O(tosyl)) tetradentate ligand. Both compounds exhibit an unusual pi-pi stacking interaction be-tween a six-membered chelate ring containing the metal and a phenylic ring of the ligand. In the heteroleptic complex [NiL(dppm)], the nickel atom is in a distorted tetrahedral [NiN(3)P] environment defined by the imine, two amide nitrogen atoms of the L(2-) dianionic tridentate ligand and one of the phosphorus atoms of the dppm molecule. In the other heteroleptic complexes, [CoL(phen)], [CuL(bipy)] and [ZnL(phen)], the metal atom is in a five-coordinate environment defined by the imine, two amide nitrogen atoms of the dianionic tridentate ligand and the two bipyridine or phenanthroline nitrogen atoms. The compounds were characterized by microanalysis, IR and UV/Vis (Co, Ni and Cu complexes) spectroscopy, FAB mass spectrometry and (1)H NMR ([NiL] and Zn and Cd complexes) and EPR spectroscopy (Cu complexes).

New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium. MEM, at 37 degrees C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and ""in vitro"" cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM It remains passivated until the transpassivation potential, above which generalized corrosion occurs F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558. ISO 5832-9 and F138 do not present cytotoxic character Therefore, these results suggest that P558 SS can be applied in orthopedic implants (C) 2010 Elsevier BV All rights reserved