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Introduction/Objectives: Since the biological activities and toxicities of 'foreign' and/or excess levels of metal ions are predominantly determined by their precise molecular nature, here we have employed high-resolution 1H NMR analysis to explore the 'speciation' of paramagnetic Ni(II) ions in human saliva, a potentially rich source of biomolecular Ni(II)-complexants/chelators. These studies are of relevance to the in vivo corrosion of nickel-containing metal alloy dental prostheses (NiC-MADPs) in addition to the dietary or adverse toxicological intake of Ni(II) ions by humans. Methods: Unstimulated whole-mouth human saliva samples were obtained from n = 12 pre-fasted (≥8 h) healthy participants, and clear whole-mouth salivary supernatants (WMSSs) were obtained from these via centrifugation. Microlitre aliquots of stock aqueous Ni(II) solutions were sequentially titrated into WMSS samples via micropipette. Any possible added concentration-dependent Ni(II)-mediated pH changes therein were experimentally controlled. 1H NMR spectra were acquired on a JEOL JNM-ECZ600R/S1 spectrometer. Results: Univariate and multivariate (MV) metabolomics and MV clustering analyses were conducted in a sequential stepwise manner in order to follow the differential effects of increasing concentrations of added Ni(II). The results acquired showed that important Ni(II)-responsive biomolecules could be clustered into distinguishable patterns on the basis of added concentration-dependent responses of their resonance intensities and line widths. At low added concentrations (71 µmol/L), low-WMSS-level N-donor amino acids (especially histidine) and amines with relatively high stability constants for this paramagnetic metal ion were the most responsive (severe resonance broadenings were observed). However, at higher Ni(II) concentrations (140–670 µmol/L), weaker carboxylate O-donor ligands such as lactate, formate, succinate, and acetate were featured as major Ni(II) ligands, a consequence of their much higher WMSS concentrations, which were sufficient for them to compete for these higher Ni(II) availabilities. From these experiments, the metabolites most affected were found to be histidine ≈ methylamines > taurine ≈ lactate ≈ succinate > formate > acetate ≈ ethanol ≈ glycine ≈ N-acetylneuraminate, although they predominantly comprised carboxylato oxygen donor ligands/chelators at the higher added Ni(II) levels. Removal of the interfering effects arising from the differential biomolecular compositions of the WMSS samples collected from different participants and those from the effects exerted by a first-order interaction effect substantially enhanced the statistical significance of the differences observed between the added Ni(II) levels. The addition of EDTA to Ni(II)-treated WMSS samples successfully reversed these resonance modifications, an observation confirming the transfer of Ni(II) from the above endogenous complexants to this exogenous chelator to form the highly stable diamagnetic octahedral [Ni(II)-EDTA] complex (Kstab = 1.0 × 1019 M−1). Conclusions: The results acquired demonstrated the value of linking advanced experimental design and multivariate metabolomics/statistical analysis techniques to 1H NMR analysis for such speciation studies. These provided valuable molecular information regarding the identities of Ni(II) complexes in human saliva, which is relevant to trace metal ion speciation and toxicology, the in vivo corrosion of NiC-MADPs, and the molecular fate of ingested Ni(II) ions in this biofluid. The carcinogenic potential of these low-molecular-mass Ni(II) complexes is discussed. [ABSTRACT FROM AUTHOR]

A new cage-like dimeric nickel(II) complex Ni2L2(DMSO)4 based on a ditopic redox-active hydroxy-para-iminobenzoquinone type ligand LH2 (L is 4,4′-(1,3-phenylene-bis(azaneylylidene))-bis(3,6-di-tert-butyl-2-oxycyclohexa-2,5-dien-1-one dianion) was synthesized in DMSO at 120 °C. The molecular structure of the synthesized compound was determined by X-ray diffraction analysis. The complex Ni2L2(DMSO)4 is almost insoluble in all organic solvents, probably due to the presence of a large number of intermolecular contacts in its structure. The electronic spectrum and thermal stability of the crystalline compound have been studied. [ABSTRACT FROM AUTHOR]

The influence of the size of the β-diketonate ligand substituent on the structure and thermal properties of volatile Ni(II) complexes is determined. To this aim, a corresponding heptanedione-3.5 (Hhd) derivative is prepared. The structures of [Ni3(hd)6] and its derivatives [Ni4(OMe)4(hd)4(MeOH)4] and [Ni3(OH) (hd)5(H2O)]2 are studied by XRD. The trinuclear complex is similar to its simplest β-diketonate analogue. Such a tetranuclear structure is typical for mixed-ligand alkoxy-β-diketonate divalent metal complexes, whereas the hexuclear structure is unique. Thermal properties of Ni(II) β-diketonates in the series L = RC(O)CHC(O)R, R = Me, Et, tBu are compared by the thermogravimetry method. [ABSTRACT FROM AUTHOR]

A coordination polymer of nickel(II), namely, {[Ni1.5(dppa)(bpa)1.5(H2O)]·5H2O}n [H3dppa = 5-(3,4-dicarboxyphenyl)picolinic acid, bpa = 1,2-bis(4-pyridyl)ethane] was designed and synthesized under hydrothermal condition. Its structure was characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction data. The structural analysis shows that the H3dppa is completely deprotonated to connect adjacent Ni(II) ions into a 1D chain, and again bridged by bpa ligands to a 2D coordination polymer. The 3D supramolecular network is formed through O–H···O hydrogen bonds. Thermal analysis (TGA) feature and solid-state variable temperature magnetic susceptibility data of the title compound are reported as well. The magnetic susceptibility data indicate that dominant ferromagnetic interactions are mediated between Ni(II) centers. [ABSTRACT FROM AUTHOR]

Two monomeric octahedral complexes {[Ni(N(CN)2)2(bpy)2]2·H2O (1) and [Mn(N(CN)2)2(bpy)2] (2) where bpy = 2,2′‐bipyridine} were synthesized and characterized by single crystal X‐ray diffraction, elemental analysis, UV–visible, and IR spectra. The geometry optimization through DFT measurements predicts that both the complexes have similar monomeric structures with hexa‐coordinated metal centers having a couple of bpy and mononegative dca anions and thus satisfying the octahedral geometry. Moreover, it is found that the HOMO–LUMO energy gaps are ΔE = 4.981 and 5.563 eV for complexes 1 and 2, respectively, which are responsible for the stabilization of the complex formation. The calculated absorption bands are located at 304 and 235 nm, which are in excellent agreement with the experimental result. Moreover, the DFT study of the electronic spectra of both complexes shows that the calculated absorption bands are in well agreement with the experimental results. In the electrical studies, direct current (dc) measurements on the copper/complex (1 or 2)/copper structure confirm a definite development in the device current with applied bias. Complex 1 has shown better electrical conductance compared to complex 2 based on the reduction of device resistance. [ABSTRACT FROM AUTHOR]

This work dealt with the extractive performance and behaviors of new three Schiff base amphiphiles ligands derived from 3-mercapto-1,2,4-triazole and different alkyl chains for recovery of nickel(II) from concentrated saline chloride medium (1 M ± 0.01) at 30 ± 1 °C. The chloroform has been used as solvent for research purposes only. The effects of the main experimental parameters such as extraction time, pH, extractant concentration and ionic strength of the aqueous medium on the extraction process of nickel(II) with amphiphilic Schiff bases (ASBn) were studied and compared. The analysis of extraction data revealed that the synthesized Schiff bases exhibit a better and faster extractability than many extractants reported in the literature. The extraction constants, log Kex, of these chelating extractants increased with an increase in the alkyl chain. A good recovery (E = 75–100%± 0.05) of nickel was obtained with amphiphilic Schiff bases. The hydrophobic Schiff base amphiphile (ASB18) was the most effective extractant for nickel ions from chloride solutions in the acidic pH range (2.41 − 2.90 ± 0.02). Ni(II) was readily extracted by ASB18 in 5 min. Extracted complexes NiL2 into chloroform phase were ascertained by slope analysis method for all extractants. The extraction mechanism of nickel(II) have been finally suggested. The results obtained are promising and can find practical applications such as for recovering of Ni(II) from Ni-MH battery wastes and electroplating industries effluents. However, in view of the acute toxicity of the solvent chloroform, implementation of this process in large-scale nickel processing strategies needs to be thoroughly evaluated from an environmental perspective. [ABSTRACT FROM AUTHOR]

Constants of stability of nickel(II)–cryptand[2.2.2] complexes in aqueous dimethyl sulfoxide solutions with variable contents of the organic cosolvent are determined via potentiometric titration at T = 298 K. It is found that the stability of mononuclear nickel(II) cryptate falls as that of the binuclear complex rises along with the concentration of dimethyl sulfoxide in a solution. An increase in the stability of protonated nickel(II) cryptate is also observed in the region of high dimethyl sulfoxide concentrations. The Gibbs energies of transferring nickel(II) ions from water to a water–dimethyl sulfoxide solvent are calculated using literature data. The contributions from the resolvation of the reactants in water–dimethyl sulfoxide mixtures to the change in the stability of nickel(II)–cryptand[2.2.2] complexes are determined. [ABSTRACT FROM AUTHOR]

Selective oxidation of alcohols towards carbonyl‐based products, such as aldehydes, is a subject of significant interest in the field of catalysis. Herein, a Zn‐based MOF with 2‐methylimidazolate linker (ZIF‐8) is modified and introduced as catalysts in a selective oxidation of alcohol with benzyl alcohol as the model of the reaction. Modification of ZIF‐8 includes the inclusion of Co(II), Cu(II) or Ni(II) ions as partial replacements for the original Zn(II) metal ions during the synthesis process. The resulting modified ZIF‐8 displays similar PXRD patterns to that of ZIF‐8, indicating no alteration of structures after the introduction of Co(II), Cu(II) or Ni(II) ions. However, the addition of Co(II) was found to modify the resulting ZIF‐8 composition to a higher extent compared to that of Cu(II) and Ni(II) ions. The catalytic test of benzyl alcohol oxidation was performed in a solvent‐free condition with TBHP as the oxidant. Reaction optimization includes reaction temperature, mass of catalysts, TBHP concentration, and reaction time. Among all the catalysts employed in the oxidation of benzyl alcohol, Co(II)‐ and Cu(II)‐modified ZIF‐8 show the highest catalytic activity with 64 % and 62 % conversion, respectively. Furthermore, the catalyst leaching and recyclability tests show that the reactions proceed in heterogeneous systems. [ABSTRACT FROM AUTHOR]

The study covers the results of investigations on performance of packed bed column as a continuous contactor for nickel [Ni(II)] and cadmium [Cd(II)] biosorption on pellets of brewery sludge. Experiments were conducted to assess influence of design variables such as bed height (2.5 to 10 cm) and flow rate (2.5 to 10 mL/min). By fitting the column data into the model equations, the parameters of the Thomas and bed depth service time (BDST) models, which are utilized in the design of packed column adsorbers, were determined. For Ni(II) biosorption, the computed values of N0 and KA obtained using the BDST model were 1833 mg/L and 0.022 L/mg.h, respectively, whereas for Cd(II) biosorption, the values were 5424 mg/L and 0.005 L/mg.h, respectively. Predicted Ni(II) and Cd(II) uptake using the Thomas model were 7.33 mg/g and 14.79 mg/g at 2.5 mL/min flow rate. Optimal biosorption conditions for Ni(II) and Cd(II) were observed at 2.5 mL/min flow rate and 10 cm bed height. Critical design factors such as length of the unused bed (LUB), stoichiometric time (t*), and mass transfer zone (Δt) needed for scaling up the biosorption process were also determined. The present study has demonstrated that the biosorption of Ni(II) and Cd(II) onto pellets of brewery sludge in packed bed column is intraparticle mass transfer controlled process. [ABSTRACT FROM AUTHOR]

The coordination compound [NiCl2L(2-PrOH)]n (where L is 2-(4-bromophenoxy)acetohydrazide; 2-PrOH is isopropanol) was obtained for the first time. The complex was characterized by means of elemental analyses, molar conductance, thermogravimetric analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. It was determined that the coordination compound exhibits a polymeric structure. The complexing agent is six-coordinated, and its distorted octahedron forms due to the bidentate coordination of 2-(4-bromophenoxy)acetohydrazide through the carbonyl oxygen atom and the amine nitrogen. The oxygen of the molecule of isopropanol, the chlorine atom, and two chlorine atoms serve as bridges between two metal atoms. [ABSTRACT FROM AUTHOR]

New manganese(II) and nickel(II) 1-D zigzag coordination polymers [M2+(pQ2−)·2(solv)]n (M2+ = Mn2+, solv = N,N'-dimethylacetamide (1) and M = Ni2+, solv = N,N'-dimethylformamide (2); pQ2− - dianionic form of 2,5-di-hydroxy-3,6-di-tert-butyl-para-quinone) have been synthesized and characterized. Both compounds 1 and 2 are isomorphic. Their physicochemical properties such as thermal stability, gas sorption, redox and magnetic properties are described. [ABSTRACT FROM AUTHOR]

Introduction/Objectives: Since the biological activities and toxicities of ‘foreign’ and/or excess levels of metal ions are predominantly determined by their precise molecular nature, here we have employed high-resolution 1H NMR analysis to explore the ‘speciation’ of paramagnetic Ni(II) ions in human saliva, a potentially rich source of biomolecular Ni(II)-complexants/chelators. These studies are of relevance to the in vivo corrosion of nickel-containing metal alloy dental prostheses (NiC-MADPs) in addition to the dietary or adverse toxicological intake of Ni(II) ions by humans. Methods: Unstimulated whole-mouth human saliva samples were obtained from n = 12 pre-fasted (≥8 h) healthy participants, and clear whole-mouth salivary supernatants (WMSSs) were obtained from these via centrifugation. Microlitre aliquots of stock aqueous Ni(II) solutions were sequentially titrated into WMSS samples via micropipette. Any possible added concentration-dependent Ni(II)-mediated pH changes therein were experimentally controlled. 1H NMR spectra were acquired on a JEOL JNM-ECZ600R/S1 spectrometer. Results: Univariate and multivariate (MV) metabolomics and MV clustering analyses were conducted in a sequential stepwise manner in order to follow the differential effects of increasing concentrations of added Ni(II). The results acquired showed that important Ni(II)-responsive biomolecules could be clustered into distinguishable patterns on the basis of added concentration-dependent responses of their resonance intensities and line widths. At low added concentrations (71 µmol/L), low-WMSS-level N-donor amino acids (especially histidine) and amines with relatively high stability constants for this paramagnetic metal ion were the most responsive (severe resonance broadenings were observed). However, at higher Ni(II) concentrations (140–670 µmol/L), weaker carboxylate O-donor ligands such as lactate, formate, succinate, and acetate were featured as major Ni(II) ligands, a consequence of their much higher WMSS concentrations, which were sufficient for them to compete for these higher Ni(II) availabilities. From these experiments, the metabolites most affected were found to be histidine ≈ methylamines > taurine ≈ lactate ≈ succinate > formate > acetate ≈ ethanol ≈ glycine ≈ N-acetylneuraminate, although they predominantly comprised carboxylato oxygen donor ligands/chelators at the higher added Ni(II) levels. Removal of the interfering effects arising from the differential biomolecular compositions of the WMSS samples collected from different participants and those from the effects exerted by a first-order interaction effect substantially enhanced the statistical significance of the differences observed between the added Ni(II) levels. The addition of EDTA to Ni(II)-treated WMSS samples successfully reversed these resonance modifications, an observation confirming the transfer of Ni(II) from the above endogenous complexants to this exogenous chelator to form the highly stable diamagnetic octahedral [Ni(II)-EDTA] complex (Kstab = 1.0 × 1019 M−1). Conclusions: The results acquired demonstrated the value of linking advanced experimental design and multivariate metabolomics/statistical analysis techniques to 1H NMR analysis for such speciation studies. These provided valuable molecular information regarding the identities of Ni(II) complexes in human saliva, which is relevant to trace metal ion speciation and toxicology, the in vivo corrosion of NiC-MADPs, and the molecular fate of ingested Ni(II) ions in this biofluid. The carcinogenic potential of these low-molecular-mass Ni(II) complexes is discussed.

The reactions of an aqueous solution of potassium dicyanoargentate with a mixture of nickel(II) or copper(II) chloride and ethylenediamine or 4,4'-bipyridyl in ethanol afford coordination polymers [Ni(Еn)2(Ag(CN)2)][Ag(CN)2] (I), [Cu(Еn)2(Ag(CN)2)][Ag(CN)2] (II), and [Cu(4,4'-Вipy)2(Ag(CN)2)2] (III) characterized by XRD (CIF files CCDC nos. 2225984 (I), 2214320 (II), and 2229270 (III)) and IR spectroscopy. According to the XRD data, the crystals of complexes I and II are formed by 1D chains {··NC–Ag–CN–M(Еn)2··}n (M = Ni (I), Cu (II)) linked with each other by the dicyanoargentate anions via argentophilic contacts (Ag···Ag 3.288(8) Å (I), 3.1616(14) Å (II)). The crystal of compound III consists of independent interpenetrating 3D networks built of polymer layers {Cu[Ag(CN)2]2}n bound to each other by the 4,4'-bipyridyl molecules. The bipyridyl linkers connect the Cu centers with the Ag centers of the [Ag(CN)2]– anions thus providing the tridentate coordination of the silver atoms. No Ag···Ag interactions are observed in the crystal of complex III. [ABSTRACT FROM AUTHOR]

Template condensation of S-methylisothiosemicarbazones of acetyl- or benzoylacetone with 8‑quinolinecarboxaldehyde in the presence of nickel(II) and copper(II) ions gave four new mononuclear coordination compounds [NiL1]I (I), [CuL1I] (II), [NiL2]I (III), and [CuL2I] (IV). The chemical composition of the products was confirmed by elemental analysis, IR spectroscopy, and mass spectrometry, and the crystal structure of compounds I and II was determined by X-ray diffraction analysis (CCDC nos. 2266386, 2266387). X-ray diffraction study revealed a square planar coordination environment of the central ion of the cationic Ni(II) complex and square pyramidal geometry for the molecular Cu(II) complex. [ABSTRACT FROM AUTHOR]

New macrocyclic Schiff bases, lower rim disubstituted imine derivatives of thia- and calix[4]arenes 7 and 8 adopted in a cone stereoisomeric conformation, bearing two tert-butyl substituents grafted to iminophenol coordinating sites, and containing a spacer composed of two methylene bridges were synthesized. The prepared compounds were characterized by a complex of physicochemical methods in solution (1H/13C NMR spectroscopy, MALDI TOF mass spectrometry) and in the crystalline phase (IR spectroscopy, single-crystal X-ray diffraction (XRD)). In crystals calix[4]arene 7 forms a solvate in which acetonitrile or methanol molecules are included into the macrocycle cavity, whereas the crystals of thiacalix[4]arene 8 contain no solvent molecules. The difference in the conformational behavior of the macrocyclic platform was evidenced when comparing the crystal structures of calix[4]arene 7 and thiacalix[4]arene 8. The stoichiometry and the logarithm and stability constant values of the corresponding complexes of the synthesized macrocyclic Schiff bases with 3d-metal cations (CoII, NiII) in solution were determined using spectrophotometry titration. When interacting with CoII cations, compound 7 forms complexes with stoichiometry Lig: M = 1: 1 and 1: 2 (Lig is ligand, and M is metal). In the case of compound 8, complexes with the stoichiometry Lig: M = 1: 4, as well as 1: 2, are observed, which presumably indicates the involvement of "soft" sulfur atoms in the interaction with the metal cations. The replacement of CoII cations by NiII resulted in the formation in the solution of complexes with the stoichiometry Lig: M = 2: 1, 1: 1 and Lig: M = 1: 1, 1: 2 for compounds 7 and 8, respectively. [ABSTRACT FROM AUTHOR]

In the title compound, [Ni(C13H13N4S)2]·0.33CH3OH·0.67H2O, the NiII atom is coordinated by two tridentate quinoline-2-carboxaldehyde 4-ethylthiosemicarbazonate ligands in a distorted octahedral shape. At 100 K, the crystal symmetry is monoclinic (space group P21/n). A mixture of water and methanol crystallizes with the title complex, and one of the ethyl groups in the coordinating ligands is disordered over two positions, with an occupancy ratio of 58:42. There is intermolecular hydrogen bonding between the solvent molecules and the amine and thiolate groups in the ligands. No other significant interactions are present in the crystal packing.

Reaction of isoquinoline (iQuin) with cobalt(II) and nickel(II) chloride and bromide produced a family of neutral coordination complexes: (iQuin)2CoX2 [X = Cl (1), Br (2)], (iQuin)4CoX2 (X = Cl (3), X = Br (4)], (iQuin)4NiX2 [X = Cl, (5), X = Br, (6)], and (iQuin)2NiBr2(CH3CN)2 (7). The crystal structures of 1–5 and 7 are reported. The majority of the compounds crystallize with some of the iQuin ligands undergoing a ∼2-fold rotational disorder, likely caused by the nearly equivalent space occupied by the two positions. The disorder is temperature independent and ∼50:50 in all cases but one. Magnetic measurements for all seven compounds indicate that their behavior is dominated by single-ion anisotropy effects with indications of antiferromagnetic exchange also present in 1 and 2. [ABSTRACT FROM AUTHOR]

Potentiometric and calorimetric study on mixed-ligand complexes of nickel(II) ion with histidine (His) and cysteine (Cys) has been carried out in aqueous solution at 298 K and the ionic strength of I = 0.5 mol·dm−3 (KNO3). Possible coordination modes of amino acid residues in ternary complexes are discussed using comparative analysis of thermodynamic parameters of complex formation. [ABSTRACT FROM AUTHOR]

A new complexes of Ni(II), Pd(II), and Pt(II) have been synthesized from the reaction of Azo-Schiff base ligand (L1) that was prepared by the condensation firstly of salicylaldehyde with ethylene diamine in a 1:2 molar ratio and the prepared imine compound (S1) reacted with 2,5-dichloro aniline, and were employed in the preparation of complexes containing the metal ions Ni(II), Pd(II), and Pt(II). The structural characteristics of the synthesized compounds were investigated using UV-Vis, IR and NMR, molar conductance, elemental analysis, and mass spectroscopy. The results of the elemental analysis point to a 1:1 [M:L] stoichiometry. According to molar conductance studies, none of the prepared end products are electrolytic in nature. The complexes of Ni(II), Pd(II), and Pt(II) may have square planer geometry, according to spectral investigations. Then Pd(II), Ni(II), and Pt(II) complexes were evaluated for antimicrobial activity against different types strains of Gram-negative [Escherichia coli (ATCC 25922)] and positive bacteria [Staphylococcus aureus (ATCC 25923)] and showed good significant against these bacteria. The cytotoxic effect of the palladium complex on the prostatic malignant cell was examined via the PC3 cell line studied against normal cell WRL-68. The molecular docking of target microorganisms of these complexes will be studied by using MOE software. [ABSTRACT FROM AUTHOR]

A 3d–4f heterometallic compound, namely [Ni6GdL4(ox)(H2O)12]⋅[NO3]⋅14.5H2O (1) (L=2,2'‐phosphinico‐dibenzoate and ox=oxalate), was obtained by self‐assembly of nickel nitrate, gadolinium nitrate, oxalic acid, and 2,2'‐phosphinico‐dibenzoic acid (H3L). Such compound has been structurally characterized via single‐crystal X‐ray diffraction analysis and infrared spectroscopy. This compound features a basic unit of {Ni4Gd} clusters and 2,2'‐phosphinico‐dibenzoate ligands. Each unit is connected by another Ni2+ through the axial coordination of benzoate oxygen to form a layer. Meanwhile, each oxalate ligand bridges the expanded Ni4Gd‐Ni4 net, constructing a 3‐D framework. From the viewpoint of network topology, this compound can be simplified as a sqc6 topology. Magnetic analysis shows ferromagnetic interactions between the Ni(II) and Gd(III) centers in Ni4Gd nodes and antiferromagnetic coupling with oxalate bridges in this compound. [ABSTRACT FROM AUTHOR]

In the title complex, [Ni(C19H13N5)2](CF3SO3)2·(CH3CH2)2O, the central NiII atom is sixfold coordinated by three nitrogen atoms of each 2,6-bis(2-benzimidazolyl)pyridine ligand in a distorted octahedral geometry with two trifluoromethanesulfonate ions and a molecule of diethyl ether completing the outer coordination sphere of the complex. Hydrogen bonding contributes to the organization of the asymmetric units in columns along the a axis generating a porous supramolecular structure. The structure was refined as a two-component twin with a refined BASF value of 0.4104 (13).

A possibility of extracting nickel(II) complex with 1-(2-allylamino-1-methylethyl)thiocarbamide in the presence and absence of hydrophobic amines, diphenylguanidine and triphenylguanidine, was studied. It was found that, in the presence of hydrophobic amines, mixed ligand complexes formed, which are readily soluble in 1-butanol. The extraction of complexes occurred within 60 s, phase separation took 80 s. A single extraction recovered up to 96.7 and 98.0% nickel(II) in the presence of diphenylguanidine and triphenylguanidine, respectively. The optimal conditions for the formation and extraction of nickel(II) complexes in the presence and absence of hydrophobic amines were found. The ratio of components in the composition of the complexes was determined, the linearity range of the calibration curve for the determination of nickel(II) (0.10–2.80 μg/mL) was established, and the equations of calibration curves were obtained using the least-squares technique. The effect of foreign ions and masking substances on the extraction–spectrophotometric determination of nickel(II) was studied and it was found that the reaction selectivity increased significantly because of the formation of mixed-ligand complexes. A procedure was developed for the extraction–spectrophotometric determination of trace nickel in the waters of the Akstafa and Dzhogaz rivers of the Kazakh region of the Republic of Azerbaijan. [ABSTRACT FROM AUTHOR]

Coordination compounds of cobalt and nickel with an azomethine ligand (a product of 4-benzoyl-3-methyl-1-phenylpyrazol-5-one and 2-aminophenol condensation) are prepared and studied by XRD. It is established that Co(II) ions under the reaction conditions are oxidized to Co(III) to form (Et3NH)[CoL2]·2H2O complexes, whereas Ni(II) ions form the (Et3NH)(H3L)[NiL(HL)]·H2O·Solv compound. The anionic part of the nickel complex is a supramolecular dimer assembled due to hydrogen bonds. The complexes are studied by static magnetic susceptibility techniques. It is shown that the Co compound is diamagnetic; this is confirmed by the oxidation of this compound and indicates that the metal ion occurs in the low-spin state. Weak ferromagnetic interactions of Ni(II) ions through bridging hydrogen bonds are discovered. [ABSTRACT FROM AUTHOR]

A series of Ni2+‐sensitized LiGa5O8 nanocrystals doped with varying amounts of Sn4+ were synthesized via a high‐temperature solid‐state method. X‐ray diffraction and scanning electron microscopy were employed to investigate the microstructure of the LiGa5O8 host, and optical spectroscopy was used to examine the effects of Sn4+ addition on the emission spectra and persistent luminescence (PersL) properties, which indicated a homogeneous distribution of the constituent elements in the phosphor. The Sn4+ incorporation led to an approximately sixfold enhancement of photoluminescence intensity at room temperature and decrease in the energy transition of Ni2+(3T2(3F)→3A2(3F)), which resulted in ∼65 nm bathochromic shift in the photoluminescence emission maxima. However, the addition of Sn4+ dopant led to a decrease in the quantum yield of luminescence compared to that of the original phosphor. Temperature‐dependent thermoluminescence measurements revealed that doping of LiGa5O8 with Sn4+ interfered with the Ni2+ trap centers. Moreover, Ni2+‐sensitized Sn4+‐doped LiGa5O8 nanocrystals exhibited an afterglow effect that persisted for up to 300 s. [ABSTRACT FROM AUTHOR]

The two heteroligand Ni(II) complexes were synthesized: tetranuclear ionic complex (NBu4)4[Ni4(OH)2(Bzmal)4(H2O)6]-(OAc)2·8H2O and mononuclear neutral complex [Ni(Bzmal)2(4-ampyH)2]. 2H2O·2DMF (where NBu4+ is the tetrabutylammonium cation, Bzmal2− are benzylmalonate dianions, and 4-ampyH+ is the 4-(ammoniummethyl)pyridine). The structure of the complexes was determined by single-crystal X-ray diffraction analysis. The simultaneous thermal analysis of [Ni(Bzmal)2(4-ampyH)2] ·2H2O·2DMF was performed. [ABSTRACT FROM AUTHOR]

There are six different linearized models of the pseudo-second-order kinetic model found in the literature. The pseudo-second-order kinetic model's linearized model count was expanded to eight in this study by deriving two newly linearized models. This study used experimental data from the literature for creating plots of these two new models. In the type 7 model, the slope of the line obtained by plotting 1/(qe - qt) vs. t graph gives 1/k2, and its shift gives [-1/k2qe]. In the type 8 model, the slope of the line obtained by plotting t vs. t/qt graph gives qe, and its shift gives [-1/k2qe]. Regression analysis was performed based on R² values, which revealed that the concordance of the kinetic data's degree was type 3 = type 4 < type 2 = type 5 < type 1 = type 7 < type 6 = type 8. It was discovered that the regression coefficients of type 6 and newly derived type 8 models are equal and have the highest value. It was determined that the highest qe value belonged to type 6 with 12.594 mg·g-1, and the highest k2 value belongs to type 2 as 0.0175 g·mg-1·min-1. It was also understood that the k2 and qe constants are close in the six models. On the other hand, the constants of types 1 and 7 are almost half the value of the constants in other models. Different constants offer alternatives in adsorption affinity, uptake in equilibrium, and degree of coherence. Since the k2 constants are also used in the Arrhenius equation, it is understood that different k2 constants will provide a wide range of alternatives for calculating the activation energy. [ABSTRACT FROM AUTHOR]

Ionic complexes [(κ4−PP3)P(OCH2PPh2)3NiX]BF4 (2 (X=Cl) and 3 (X=Br)) were formed when P(OCH2PPh2)3 ligand (1) was reacted with mixtures of salts NiX2/Ni(BF4)2 (X=Cl or Br). Single crystal X‐ray characterizations performed on complexes 2 and 3 established that metal centers are in pseudo‐trigonal bipyramidal ligand geometries formed by the phosphorus centers from coordinated 1 and the halide ligand. Reactions of 1 with other nickel(II) salts (acetate, nitrate or tetrafluoroborate) proceeded in 2 : 1 (ligand‐salt) ratio yielding complex 4, [(κ3−PP2)((−O−P)(OCH2PPh2)2)(κ2−PP)(−O−P)(OCH2PPh2)(OCH2P(=O)Ph2)Ni]. The formation of this complex required hydrolysis of one of the P−O ester bonds in ligand P(OCH2PPh2)3 thus forming O‐anionic phosphite/diphosphine fragment [−O−P(OCH2PPh2)2]. One of such fragments is coordinated to the metal center as a tridentate (κ3−PP2) ligand, whereas the other is in bidentate (κ2−PP) coordination via phosphorus centers of the −O‐P‐OCH2PPh2 chelating pocket; the remaining ‐OCH2P(=O)Ph2 arm is P‐oxidized and uncoordinated. Nickel center in 4 is in distorted trigonal‐bipyramidal geometry, with O‐anionic‐phosphite groups coordinated at the axial positions, and the three ‐PPh2 groups located in the equatorial plane. Compounds 2–4 were characterized by multinuclear NMR spectroscopy, elemental analyses, electron absorption spectroscopy, cyclic voltammetry, and single crystal X‐ray crystallography. Their electronic structures were also investigated by DFT methods. [ABSTRACT FROM AUTHOR]

The selective extraction of metals from aqueous solutions is a very important stage in the hydrometallurgical processing of metallic waste. Leach solutions are usually a multicomponent mixture. The main impurity of aqueous solutions obtained after leaching using inorganic acids is iron. In this work, the membrane separation of iron(III) from nickel(II), cobalt(II), and lithium(I) was studied. The facilitated transport of metal ions using polymer inclusion membranes (PIMs) with tetrabutylammonium bromide (TBAB) as an ion carrier under various conditions was analyzed in detail. Several factors, such as the ion carrier concentration in the membrane as well as the effect of the inorganic acid concentration in the source/receiving phases on the kinetic parameters, were investigated. The results show that ionic liquid TBAB is a very selective ion carrier of Fe(III) towards Ni(II), Co(II), and Li(I). [ABSTRACT FROM AUTHOR]

Nickel(II) complexes with pyridine-2-carbaldehyde 2,4-dichlorophenoxy acetylhydrazone (HL) are studied by elemental and thermogravimetric analyses, IR and electron spectroscopy, and X-ray diffraction analysis. It is established that ligands in the complex occur in deprotonated or molecular forms, depending on the synthesis conditions, thus forming [NiL2]·2H2O (I) and [Ni(HL)L](NO3)·2H2O (II) compounds. The nickel(II) coordination environment is an octahedron with tridentate chelating ligands. Compound II contains intermolecular stacking interactions of aromatic systems. [ABSTRACT FROM AUTHOR]

Permeable nickel metallic and nickel oxide ceramic materials with nanostructured surface and multilevel hierarchical porosity were created by cyclic redox post-treatment of biporous nickel(II) consolidated in the sintering–dissolution process. Additional levels of intraparticle porosity—Kirkendall pores and shrinkage nanopores—were formed during the stages of high-temperature oxidation in air and reduction in hydrogen, respectively. [ABSTRACT FROM AUTHOR]

Two metal coordination polymers [Ni(oba)(Py2TTz)1.5(H2O)]·2H2O·DMF (1) and [Co(oba)(Py2TTz)(H2O)4]·2H2O (2) have been synthesized under solvothermal conditions [H2oba = 4,4′-oxybis(benzoic acid) and Py2TTz = 2,5-di(pyridine-4-yl)thiazolo[5,4-d]thiazole]. Crystals of compound 1 belong to the orthorhombic system, space group Ibam, with a = 38.928(8), b = 7.7113(14), c = 28.508(6) Å, V = 8558(3) Å3, Z = 8. Compound 2 crystallizes in the monoclinic crystal system, space group C2/c, with a = 33.816(3), b = 6.2697(6), c = 13.5821(13) Å, β = 96.393(3)°, V = 2861.7(5) Å3, Z = 4. The oba2− dianions link two Ni atoms through unidentate carboxylate moieties in a μ1 − η1:η0 coordination mode. Compound 1 features a three-dimensional (3D) framework structure with Py2TTz and oba2− ligands. In compound 2, the central cobalt ion is in an octahedral geometry, which is defined by four oxygen atoms from four different coordinated water molecules and two nitrogen atoms from two different Py2TTz ligands. It is noteworthy that the dicarboxylate ligands oba2− with four oxygen atoms do not directly coordinate with the cobalt ion, and only act as a counter-anion. The luminescence properties of 1 and 2 were also investigated. [ABSTRACT FROM AUTHOR]

The title compound, {[Ni(C12H14O4)(C11H9N3O)(H2O)]·H2O}n, contains octahedrally coordinated NiII ions ligated by adamantane-1,3-dicarboxylate (adc) and N-(pyridin-3-yl)isonicotinamide (3-pina) ligands forming coordination polymer layers with a (4,4) grid topology. These diperiodic layer motifs aggregate in an AAA pattern mediated by supramolecular C—H...O interactions to form the full triperiodic crystal structure of the title compound.

Ternary Ni(II) complexes formed with 1,10-phenanthroline (Phen) and the amino acids glycine (Gly, HL), α-alanine (Ala, HL), β-alanine (βAla, HL), proline (Pro, HL), phenylalanine (Phe, HL), methionine (Met, HL), serine (Ser, HL) and threonine (Thr, HL) were studied in aqueous solution using 1.0 M NaCl at 25 °C as an ionic medium. The systems were studied by potentiometric measurements. Analysis of the potentiometric data was done with the least-squares-based program LETAGROP, supporting the formation of species Ni(Phen)(HL)2+, Ni(Phen)(L)+, Ni(Phen)(L)(OH), Ni(Phen)2(L)+ and Ni(Phen)(L)2. Species distribution diagrams were generated and the relative stabilities were analyzed using Δ log10 K, log10 X and % RS values. [ABSTRACT FROM AUTHOR]

Two novel acetato complexes with NNN type planar bdmpp ligand, [Ni(OAc)(H2O)2(bdmpp)]OAc (1) and [Co(OAc)(H2O)2(bdmpp)]OAc (2) (bdmpp: 2,6-bis(3,5-dimethylpyrazolyl)pyridine) were synthesized and characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction analysis. Thermal stabilities of these complexes were studied by thermogravimetric and differential thermal analyses. The crystal structures of both complexes were also determined using single-crystal X-ray diffraction. It was found that complexes 1 and 2 possessed smilar octahedral coordination environment in which metal ions were coordinated by N donor atoms of bdmpp, two oxygens of aqua ligands and one oxygen atom from terminal bonding acetato ligand. [ABSTRACT FROM AUTHOR]

The electrochemical sensing potential of two isostructural one-dimensional nickel(II) and cobalt(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy) and 6-oxonicotinate (6-Onic), namely, {[Ni(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n and {[Co(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n, was investigated along with the polymers' potential applications in the catalytic oxidation of methanol. The highly oxidative species from redox pairs Ni(II)/Ni(III) and Co(II)/Co(III) in these compounds represent catalytically active centres for oxidation of small molecules. A glassy carbon electrode (GCE) modified with a Ni polymer showed stability and reproducibility in 0.1 M NaOH, while the oxidation current inc 2reased with the increasing methanol concentration, suggesting that the Ni-polymer-modified electrode possess good sensing ability with respect to methanol. The GC electrode modified with the Co polymer is not reproducible and cannot be used for electroanalytical purposes under these experimental conditions. The GC electrode modified with the Ni polymer was successfully applied in the determination of methanol. This method showed favourable linear concentration dependence with a good sensitivity of 2.65 and 11.0 mA mM−1, a wide concentration range (0.001–4 mM), and a detection limit of 0.8 μM, which indicates its excellent application potential for methanol oxidation and thus its determination. [ABSTRACT FROM AUTHOR]

The reaction of hydroxybenzoates with divalent first row transition metal ions afforded four mononuclear complexes, [M(OH2)6](dhbzc)2·2H2O (M = Co2+, 1 or Mn2+, 2), [Ni(OH2)6](hbzc)2·2H2O (3) and [Ni(OH2)5(hbzc)](hbzc)·3H2O (4) (where dhbzc− = 2,6-dihydroxybenzoate and hbzc− = 4-hydroxybenzoate). The complexes were characterized by single crystal and powder X-ray diffraction analyses, infrared spectroscopy, and thermogravimetric analysis. Results showed that the hydrogen bonds present in dhbzc− impaired its coordination to Co2+ and Mn2+. Thereafter, Hirshfeld surface analyses (HS) and 2D fingerprint plots were used to investigate the intermolecular contacts in 1–4. The offset π···π stacking of the dhbzc− counterions in 1 and 2 lead to C···C close contacts over C···H/H···C ones. Complexes 3 and 4 presented the usual herringbone aromatic-based packing for the hbzc− rings with a predominance of C···H/H···C close contacts. The existence of water molecules in the crystal lattices of 1–4 was determined by TG analyses, which proved the presence of coordinated and uncoordinated water molecules. The thermal decomposition patterns were analyzed in light of the percentage of the strongest intermolecular close contacts. [ABSTRACT FROM AUTHOR]

A polymeric inclusion membrane (PIM) consisting of matrix CTA (cellulose triacetate), ONPPE (o-nitrophenyl pentyl ether) and phosphonium salts (Cyphos 101, Cyphos 104) was used for separation of Cu(II), Zn(II) and Ni(II) ions. Optimum conditions for metal separation were determined, i.e., the optimal concentration of phosphonium salts in the membrane, as well as the optimal concentration of chloride ions in the feeding phase. On the basis of analytical determinations, the values of parameters characterizing transport were calculated. The tested membranes most effectively transported Cu(II) and Zn(II) ions. The highest recovery coefficients (RF) were found for PIMs with Cyphos IL 101. For Cu(II) and Zn(II), they are 92% and 51%, respectively. Ni(II) ions practically remain in the feed phase because they do not form anionic complexes with chloride ions. The obtained results suggest that there is a possibility of using these membranes for separation of Cu(II) over Zn(II) and Ni(II) from acidic chloride solutions. The PIM with Cyphos IL 101 can be used to recover copper and zinc from jewellery waste. The PIMs were characterized by AFM and SEM microscopy. The calculated values of the diffusion coefficient indicate that the boundary stage of the process is the diffusion of the complex salt of the metal ion with the carrier through the membrane. [ABSTRACT FROM AUTHOR]

Over the preceding years, nickel (Ni) and its compounds have been increasingly employed in various aspects of human social life, metallurgical/industrial manufactures, healthcare and chemical processes. Although Ni is considered as an essential trace element in biological system, excessive intake or metabolic deficiency of Ni2+ ions may cause detrimental health effects to the living organisms. Therefore, a facile and accurate detection of Ni2+, especially in environment and biological settings, is of huge significance. As an efficient detection method, assaying Ni2+ using optical (colorimetric and/or fluorogenic) sensors has experienced quite a vigorous growth period with large number of excellent researches. Nanomaterial-based optical sensors including metal nanoparticles (MNPs), quantum dots (QDs), and carbon dots (CDs) offer distinct advantages over conventional small-molecule organic and inorganic sensors. This study mainly provides an overview of the recent advancements and challenges related to the design strategies of various optical nanosensors to selectively detect Ni2+ ion. Emphasis has also been placed on comparing the sensing performance of various nanosensors along with exploring future perspectives. [Display omitted] • This study covers nanomaterials based sensors for optical detection of Ni(II) ion. • Various metal-based nanoparticles (MNPs) and quantum dots (QDs) have been exloited. • Recent developments and challenges in the design and fabrication of nanosensors are emphasized. [ABSTRACT FROM AUTHOR]

The removal of nickel(II) and lead(II) ions from aqueous solutions was investigated using pumpkin peel biochar (PPB) prepared with sulfuric acid at ambient temperature. The effects of pH, contact time, dosage, and initial concentration of nickel(II) and lead(II) on the removal of the metal ions were studied. The removal of nickel(II) and lead(II) was highly dependent on the pH of aqueous solutions and the maximum adsorption occurred at pH 5.0. Nickel(II) and lead(II) adsorption reached to equilibrium conditions at 120 min. Increasing the initial concentration of nickel(II) and lead(II) resulted in an enhancement in the adsorbed quantities of the metal ions per gram of PPB, but the percentage of nickel(II) and lead(II) adsorbed decreased. The adsorption equilibrium of nickel(II) and lead(II) was compatible with the Langmuir isotherm model providing maximum monolayer adsorption capacities of 64.1 and 178.6 mg g−1 for nickel(II) and lead(II), respectively. The nickel(II) and lead(II) adsorption kinetics represented well fit with pseudo-second-order kinetic model. It was concluded that the pumpkin peel carbon activated with sulfuric acid was highly effective for the removal of nickel(II) and lead(II) ions from aqueous solution. [ABSTRACT FROM AUTHOR]