The synthesis,characterization and melting properties of thiophene-containing dithiocarboxylate complexes of nickel(II)

The reactions of a series of 5-alkyl-2-thiophenedithiocarboxylates with nickel(II) chloride afforded two types of complexes, blue nickel(II) complexes with two terminal dithiocarboxylate ligands, [Ni(S₂CTR)₂] and violet nickel(II) complexes with perthio- and dithiocarboxylate ligands, [Ni(S₂CTR)(S₃CTR)] (where T = 2,5-disubstituted thiophene, R = C_nH_2n+1, n = 4, 6, 8, 12, 16). The blue monomers are preferred for the shorter chains (C₄ and C₆) and the violet compounds form exclusively for the longer chains (C₈, C₁₂, and C₁₆) in the alkylthiophene complexes. In addition to the above series, [Ni(S₂CTCH₃)₂], was prepared in a one-pot reaction in THF and both the blue and violet products were isolated. It was possible to convert the blue complexes [Ni(S₂CTR)₂] (R = butyl, hexyl) into the corresponding violet complexes [Ni(S₂CTR)(S₃CTR)] after stirring in THF solutions for prolonged periods of time. Liquid-crystalline properties of these complexes were examined by DSC and POM. The violet complexes with C₈ and C₁₂ alkyl chains showed liquid-crystalline properties.     

Thermoanalytical, spectral and biological study of 4-bromobenzoatozinc(II) complexes containing bioactive organic ligands

New zinc(II) 4-bromobenzoate complex compounds with general formula [Zn(4-BrC₆H₄COO)₂L₂]·xH₂O (where L?=?urea, nicotinamide, phenazone or thiourea, x?=?0?C2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition, the neutral organic ligand, bis(4-bromophenyl)methanone and carbon dioxide were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 800?°C was zinc oxide, which was confirmed by X-ray powder diffractometry. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternata and M. gypseum). It was found that bacterium S. aureus and fungi A. alternata are the most sensitive to the studied compounds.     

Nickel speciation via voltammetric quantification of nickel metal,oxides and salts

A practical speciation method for a solid mixture of nickel species applicable to atmospheric monitoring of Ni⁰, Ni²⁺ and NiO_x is reported. This involves magnetic extraction of Ni⁰ to separate it from the water-soluble nickel salts and the insoluble oxides, followed by adsorptive stripping voltammetry to quantify the nickel in each fraction. The separation scheme was validated by using calibration standards and by simulating air-filter samples prepared with authentic nickel products. The recoveries of nickel were Ni⁰ 94–105% and total nickel 95–102%.     

Phase formation, structural and microstructural characterization of novel oxynitride-perovskites synthesized by thermal ammonolysis of (Ca,Ba)MoO4 and (Ca,Ba)MoO3

Reactions of AMoO₄ and AMoO₃ (A=Ca²⁺, Ba²⁺) with ammonia were investigated at 873 K<T<1123 K with the particular intention to synthesize novel oxynitride-perovskites of the general composition AMo(O,N)₃ and to study their crystal structure. CaMo(O,N)₃ and BaMo(O,N)₃ were prepared by thermal ammonolysis of the corresponding CaMoO₃ and BaMoO₃ precursors at T=898 and 998 K, respectively. The structural parameters of the oxynitrides were obtained from Rietveld refinements of X-ray and neutron powder diffraction data. CaMo(O,N)₃ crystallizes in the GdFeO₃ distorted perovskite structure with orthorhombic space group Pbnm and a=5.5029(1) Å, b=5.5546(1) Å, c=7.8248(1) Å as determined by X-ray powder diffraction. Its O/N content refined from the neutron diffraction data corresponds to the composition CaMoO_1.7(1)N_1.3(1). BaMo(O,N)₃ crystallizes in the cubic perovskite structure with space group Pm3¯m and a=4.0657(1) Å as determined by X-ray powder diffraction. Transmission electron microscopy reveals a complex microstructure for both CaMoO₃ and CaMoO_1.7(1)N_1.3(1) represented by twin domains of different orientation.     

Synthesis, characterization and catalytic behaviors of water-soluble phosphine-sulfonato nickel methyl complexes bearing PEG-amine labile ligand

Two novel water-soluble phosphine-sulfonato nickel (II) methyl complexes [(P^O)NiMeL] (P^O = κ²-P,O-2-(2-MeO-C₆H₄)₂PC₆H₄SO₃, L = H₂N(CH₂CH₂O)_nMe, n = ca. 52, 2a; n = ca. 16, 2b) have been prepared and characterized by ¹H, ³¹P NMR and elemental analysis, and their reactivity towards ethylene was studied.     

The Synthesis of Some New Sulfur-Bearing Various Heterocyclic Systems Derived from Asymmetrical N,N′-Disubstituted Thiourea Derivatives

The heterocyclization of an asymmetrical N,N′-disubstituted thiourea (1a–d) in ring closure reactions with Br₂/AcOH, ethyl chloroacetate, diethyl oxalate, diethyl malonate, and hydrazine hydrate led to the direct formation of sulfur-bearing various heterocyclic systems (2–8) in which the thiaenolization is toward the aryl group. The synthetic work and reactivity investigations have been well supported by standard modern spectroscopic techniques (IR, ¹ H NMR, ¹³ C NMR, mass spectrum, and microanalysis).     

Electrochemical corrosion behaviors and corrosion protection properties of Ni–Co alloy coating prepared on sintered NdFeB permanent magnet

In this study, a protective Ni–Co alloy coating was prepared on sintered NdFeB magnet applying electrodeposition technique. A pure nickel coating was also studied for a comparison. The microstructure, surface morphologies, and chemical composition of coatings were investigated using X-ray diffraction, scanning electron microscope, and energy dispersive spectroscopy, respectively. The corrosion protection properties of coatings for NdFeB magnet in neutral 3.5 wt.% NaCl solutions were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The microstructure and surface morphologies analysis showed that the addition of cobalt element into matrix metal Ni altered the preferential orientation of pure nickel coating from (2 0 0) crystal face for pure nickel coating to (1 1 1) crystal face for Ni–Co alloy coating, and made the surface morphologies more compact and uniform due to the grain-refining. The results of potentiodynamic polarization test showed that compared with pure nickel coating, Ni–Co alloy coating exhibited much nobler corrosion potential (E _corr) and lower corrosion current density (j _corr), indicating better anticorrosive properties. The long-term immersion test by dint of EIS indicated that the Ni–Co alloy coating still presented high impedance value of 1.9 × 10⁵ Ω cm² with the immersion time of 576 h indicating the excellent anticorrosive properties, and corrosion protection properties of nickel coating for NdFeB magnet practically disappeared with the immersion time of 144 h, which also indicated that the Ni–Co alloy coating provided better corrosion protection properties for the NdFeB magnet compared with nickel coating.     

Synthesis and X-ray diffraction studies of chiral nickel(II), zinc(II), manganese(II), and cobalt(II) complexes with C 2-symmetric 2,6-bis[4′-(R)-ethoxyoxazolin-2′-yl]pyridine

Chiral nickel(II), zinc(II), manganese(II), and cobalt(II) complexes with C ₂-symmetric 2,6-bis[4′-(R)-ethoxyoxazolin-2′-yl]pyridine were prepared, the single crystal of nickel(II) complex, [Ni((R,R)-Et-Py-box)(H₂O)₂Cl]Cl ((R,R)-Et-Pybox is 2,6-bis[4′-(R)-ethoxyoxazolin-2′-yl]pyridine), was obtained and indicated by X-ray diffraction analysis. The nickel(II) complex crystallizes in the orthorhombic system, space group P2₁2₁2₁ with a = 7.7346(4) Å, b = 19.7133(13) Å, c = 25.8014(14) Å, V = 3934.1(4) ų, Z = 8, and R = 0.0526 against 7010 reflections with I > 2σ (I). A feature of interest was noted in the unit cell of the compound, where two types of molecules exist, which similarly have a distorted octahedral geometry but only slightly differ in the orientation of the coordinated atoms to the central Ni atom. These two types of molecules interact with each other by O-H…Cl hydrogen bonds, giving rise to one dimensional ribbon structure.     

Nucleation and particle growth in the preparation of silica-supported nickel catalysts by a two-step procedure

The mechanism of nucleation and growth of particles in the preparation of supported catalysts has been investigated in the case of the Ni/SiO₂ system. The separation of this two-step mechanism is achieved as follows:i) the “nickel nuclei” are prepared by ion-exchange or by impregnation followed by washing. They are in strong interaction with the support and act as anchoring sites for the metal particles.ii) The “nickel reservoir” constituted of nickel ion precursors and necessary for the nickel particle growth on the nuclei, is deposited by impregnation on the support. It is in weak interaction with the support and easily reducible. After temperature programmed reduction of the samples prepared by the above two-step procedure, the nickel particles are smaller and more homogeneous in size than those of catalysts prepared in one step by single impregnation of a pure silica support.     

Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite

Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise a synthetic nickel substituted aurichalcite a zinc/nickel hydroxy carbonate, (Zn²⁺, Cu²⁺, Ni²⁺)₅(CO₃)₂(OH)₆. XRD patterns show high orientation and indicate the presence of some minor impurities. The diffraction patterns for the Ni-aurichalcite are well correlated with the standard reference patterns. EDAX analyses indicate variations in chemical composition of Zn/Ni ratios of ∼20:1. The symmetry of the carbonate anion in aurichalcite is C_s and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band for the Ni-aurichalcite at 1070 cm⁻¹ is assigned to the ν₁(CO₃)²⁻ symmetric stretching mode. Three Raman bands assigned to the ν₃(CO₃)²⁻ antisymmetric stretching modes are observed for Ni-aurichalcite at 1372, 1480 and 1543 cm⁻¹. Multiple Raman bands are observed in the regions from 800 to 850 cm⁻¹ and 720 to 750 cm⁻¹, and are attributed to ν₂ and ν₄ bending modes confirming the reduction of the carbonate anion symmetry in the aurichalcite structure. This research proves that nickel containing aurichalcites can be synthesised in the laboratory thus mimicing the natural nickel containing aurichalcites.     

Influence of Submicron Fibrillated Cellulose Fibers from Cotton on Hydration and Microstructure of Portland Cement Paste

This paper reports the influence of submicron hydrophilic fibers on the hydration and microstructure of Portland cement paste. Submicron fibrillated cellulose (SMC) fibers was prepared by the acid hydrolysis of cotton fibers in H₂SO₄ solution (55% v/v) for 1.5 h at a temperature of 50 °C. The SMC fibers were added into cement with a dosage of 0.03 wt.%, and the effect of SMC on the hydration and microstructure of cement paste was investigated by calorimeter analysis, XRD, FT-IR, DSC-TG, and SEM. Microcrystalline cellulose (MCC) fibers were used as the contrast admixture with the same dosage in this study. The results show that the addition of SMC fibers can accelerate the cement hydration rate during the first 20 h of the hydration process and improve the hydration process of cement paste in later stages. These results are because the scale of SMC fibers more closely matches the size of the C-S-H gel compared to MCC fibers, given that the primary role of the SMC is to provide potential heterogeneous nucleation sites for the hydration products, which is conducive to an accelerated and continuous hydration reaction. Furthermore, the induction and bridging effects of the SMC fibers make the cement paste microstructure more homogeneous and compact.     

Synthesis,characterization and antimicrobial studies of mixed ligand silver(I) complexes of thioureas and triphenylphosphine; crystal structure of {[Ag(PPh3)(thiourea)(NO3)]2·[Ag(PPh3)(thiourea)]2(NO3)2}

Mixed ligand silver(I) complexes of triphenylphosphine and thioureas (thiourea (Tu), N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu) and N,N′-diethylthiourea (Detu)) with the general formulae, [(Ph₃P)₂Ag(thione)]NO₃ and [(Ph₃P)Ag(thione)₂]NO₃, have been prepared and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The crystal structure of one of them has been determined by X-ray crystallography. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). The single crystal X-ray structure of complex 1, {[Ag(PPh₃)(thiourea)(NO₃)]₂·[Ag(PPh₃)(thiourea)]₂(NO₃)₂}, shows that the complex consists of two independent centrosymmetric binuclear units, each having the silver atoms coordinated to one PPh₃ and two bridging thiourea molecules. In one of the independent units the silver atom is additionally bound to a nitrate ion, leading to a tetrahedral geometry, while in the other unit the silver atom adopts a trigonal planar environment. Antimicrobial activities of the complexes were evaluated by their minimum inhibitory concentration and the results showed that the complexes show a wide range of activity against two gram-negative bacteria (Escherichiacoli, Pseudomonasaeruginosa) and molds (Aspergillusniger, Penicilliumcitrinum), while the activities were poor against yeasts (Candidaalbicans, Saccharomycescerevisiae). However, the title complex did not show activity against any tested microorganism.     

Synthesis,structure and magnetic properties of mono- and di-nuclear nickel(II) thiocyanate complexes with tridentate N3 donor Schiff bases

The 1:1 condensation of N-methyl-1,3-diaminopropane and N,N-diethyl-1,2-diminoethane with 2-acetylpyridine, respectively at high dilution gives the tridentate mono-condensed Schiff bases N-methyl-N′-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L¹) and N,N-diethyl-N′-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine (L²). The tridentate ligands were allowed to react with methanol solutions of nickel(II) thiocyanate to prepare the complexes [Ni(L¹)(SCN)₂(OH₂) (1) and [{Ni(L²)(SCN)}₂] (2). Single crystal X-ray diffraction was used to confirm the structures of the complexes. The nickel(II) in complex 1 is bonded to three nitrogen donor atoms of the ligand L¹ in a mer orientation, together with two thiocyanates bonded through nitrogen and a water molecule, and it is the first Schiff base complex of nickel(II) containing both thiocyanate and coordinated water. The coordinated water initiates a hydrogen bonded 2D network. In complex 2, the nickel ion occupies a slightly distorted octahedral coordination sphere, being bonded to three nitrogen atoms from the ligand L², also in a mer orientation, and two thiocyanate anions through nitrogen. In contrast to 1, the sixth coordination site is occupied by a sulfur atom from a thiocyanate anion in an adjacent molecule, thus creating a centrosymmetric dimer. A variable temperature magnetic study of complex 2 indicates the simultaneous presence of zero-field splitting, weak intramolecular ferromagnetic coupling and intermolecular antiferromagnetic interactions between the nickel(II) centers.     

Studies on novel thermally stable segmented polyurethanes based on thiourea-derivative diols

Novel thermoplastic segmented poly(urethane-thiourea)s (PURs) were synthesized via one-step polymerization from aromatic diols containing sulfur (thiourea linkage) in the main-chain, including terephthaloyl bis (3-(2-hydroxopyridyl) thiourea) (TBHPT) and terephthaloyl bis (3-(5-naphtholyl) thiourea) (TBNT), along with 1,4-phenylene diisocyanate (PDI) as hard segment and 20, 50 and 80 mol% polyethylene glycol (PEG) as a soft segment. The prepared chain extenders and polymers were characterized by conventional methods, and physical properties such as η_inh, solubility, thermal stability and thermal behavior were studied. Easily processable PURs with excellent thermal stability were obtained by incorporating 20 mol% PEG in the soft segment. Thermogravimetric analysis indicated that poly(urethane-thiourea)s were fairly stable above 500 °C and own high glass transition temperatures about 263-266 °C. These polymers also showed partially crystalline structures. Ultimately, weight average molecular weights (M_w) of PURs were up to 109 × 10³. Compared to typical polyurethanes, PURs exhibited better thermal stability and T_g’s owing to rigid hard segment structure.     

A novel online visualization system for observing polymer extrusion foaming

Cell nucleation and premature cell growth in extrusion foaming are critical to elaborate the morphology of final foams. These courses happen in the extrusion die which has been unknown for real extrusion foaming process. In this study, a novel visualization system was developed to online observe the cell nucleation and evolution behavior in the extrusion die. The cell evolution and real time pressure along the flow direction could also be obtained with the system. It was found that the solution pressure P_solution was influential to the critical nucleation radius R_cr and the nucleation rate N₀. The higher screw rotating speed corresponded to higher P_solution, lower in die N₀ and less premature cells, while higher cell density for extrude foams. In addition, premature cells with radius over critical break radius R_crb would break into several small cells under sufficient stress gradient in the extrusion flow field.     

Porous cobalt hydroxide film electrodeposited on nickel foam with excellent electrochemical capacitive behavior

A new porous cobalt hydroxide film has been successfully electrodeposited on nickel foam from 0.1?M cobalt nitrate electrolyte at ?1.0?V vs. SCE without adding any surfactant. The microstructure and surface morphology of prepared cobalt hydroxide films were physically characterized by X-ray diffraction analysis and scanning electron microscopy. The results indicate that an interlaced network structure was obtained. The effects of electrodeposition time, deposition potential, and different substrates on the specific capacitance and microstructure of prepared porous ??-Co(OH)₂ thin film were systematically studied. The results indicate that the film deposited on nickel foam at ?1.0?V has excellent electrochemical properties. A maximum specific capacitance of 1473?F?g^?1 could be achieved at a current density of 2?A?g^?1.     

Adsorptive stripping voltammetry of nickel with 1-nitroso-2-napthol using a bismuth film electrode

A sensitive procedure is presented for the voltammetric determination of nickel. The procedure involves an adsorptive accumulation of nickel 1-nitroso-2-napthol (NN) complex on a bismuth film electrode prepared ex situ by electrodeposition. The most suitable operating conditions and parameters such as pH, ligand concentration (C_NN), adsorptive potential (E_ads), adsorptive time (t_ads), scan rate and others were selected and the determination of nickel in aqueous solutions using the standard addition method was possible. The adsorbed Ni-NN complex gives a well defined cathodic stripping peak current at −0.70 V, which was used for the determination of nickel in the concentration range of 10.0-70.0 μg L⁻¹ (pH 7.5; C_NN 6.5 μmol L⁻¹; E_ads −0.30 V; t_ads 60 s) with a detection limit of 0.1 μg L⁻¹. The relative standard deviation for a solution containing 10.0 μg L⁻¹ of Ni(II) was 3.5% (n = 4). The proposed method was validated determining Ni(II) in certified reference waste water (SPS-WW1) and Certified Reference Water for Trace Elements (TMDA 51.3) with satisfactory results. Then lake water samples were analyzed.     

Thermodynamics of metal cyanide coordination : Part IX. Log K, ΔH, and ΔS values for the Ni-, Zn-, Cd-, and Hg- CN systems at 10, 25, and 40 °C

Log K, ΔH⁰, and ΔS⁰ values valid at zero ionic strength are reported or summarized from previous studies for cyanide ion interaction with bivalent nickel, zinc, cadmium, and mercury at 10, 25, and 40 °C. From the values of ΔH⁰ as a function of temperature, average ΔC_p⁰ values are calculated.     

Nickel nitrosyl complexes in a sulfur-rich environment: The first poly(mercaptoimidazolyl)borate derivatives

The diamagnetic nickel mononitrosyl complexes (Tm^R)Ni(NO) (R = Bu^t, p-Tol) and (Bm^R)Ni(PPh₃)(NO) (R = Me, Bu^t) have been readily prepared from Ni(PPh₃)₂(NO)Br and the appropriate Na(Tm^R) or Na(Bm^R) reagents, respectively. These species constitute the first nickel nitrosyl complexes supported by these ligand systems. An X-ray diffraction study of (Tm^p-Tol)Ni(NO) confirmed its pseudo-tetrahedral geometry and the presence of a nearly linear nitrosyl ligand. In contrast, (Bm^Me)Ni(PPh₃)(NO) can be best described as having a trigonal pyramidal geometry, a spatial arrangement unprecedented in nickel nitrosyl chemistry, which is facilitated by the disposition of the Bm^Me ligand and the presence of a weak intramolecular Ni?H–B interaction opposite to the apical triphenylphosphine ligand.     

Quantitation of protein orientation in flow-oriented unilamellar liposomes by linear dichroism

The linear dichroism of the visible wavelength transitions of retinal have been used to analyse linear dichroism spectra to determine the orientation of aromatic and peptide structural motifs of Bacteriorhodopsin incorporated into unilamellar soy bean liposomes. The results are consistent with the available X-ray data. This proves that visible light absorbing chromophores can be used to analyse linear dichroism data to give the orientation of membrane proteins in membrane mimicking environments. The work has been extended by screening a wide range of hydrophobic molecules with high extinction coefficients in transitions above 300 nm to find molecules that could be used as independent probes of liposome orientation for experiments involving proteins incorporated into liposomes. Three probes were found to have potential for future work: bis-(1,3-dibutylbarbituric acid)pentamethine oxonol (DiBAC₄), retinol and rhodamine B. All three can be used to determine the orientation of the porphyrin of cytochrome c, the aromatic residues of gramicidin and the helices of both proteins. The orientation parameter, S, for the liposomes varied from batch to batch of unilamellar liposomes prepared by extruding through a 100 nm membrane. The value and variation in S was 0.030 ± 0.010. Repeat experiments with the same batch of liposomes showed less variation. Film LD data were measured for DiBAC₄ and rhodamine B to determine the polarisations of their long wavelength transitions.