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NiO nanoparticles have garnered significant interest due to their diverse applications and unique properties, which differ markedly from their bulk counterparts. NiO nanoparticles are p-type semiconductors with a wide bandgap, high discharge capacity, and high carrier density, making them ideal for use in batteries, sensors, and catalysts. Their ability to generate reactive oxygen species also imparts disinfectant and antibiotic properties. Additionally, the higher Néel temperature of NiO compared with other antiferromagnetic materials makes it suitable for high-temperature applications in spintronic devices and industrial settings. This review focuses on the critical role of structure and composition in determining the magnetic properties of NiO nanoparticles. It examines how finite-size surface effects, morphology, crystallinity, and nickel distribution influence these properties. Fundamental physical properties and characterization techniques are discussed first. Various synthesis methods and their impact on NiO nanoparticle properties are then explored. Their magnetic phenomenology is examined in detail, highlighting the effects of finite size, particle composition and surface, and crystal quality. The review concludes with a summary of key insights and future research directions for optimizing NiO nanoparticles in technological applications. [ABSTRACT FROM AUTHOR]

Nickel coordination compounds featuring Ni–O bonds are key structural motifs in both bioinorganic and synthetic chemistries. They serve as precursors for organic substrate oxidation and are commonly invoked intermediates in water oxidation and oxygen reduction schemes. Herein, we disclose a series of well-defined dinuclear nickel complexes that, upon treatment with CO2 and H2O2, afford the first nickel-bound peroxycarbonate. This unprecedented nickel–oxygen intermediate is stabilized by hydrogen bonding templated across the bimetallic core. Contrasting copper and iron analogues, the nickel peroxycarbonate reversibly dissociates H2O2, a process that is shown to be accelerated by exogenous CO2. [ABSTRACT FROM AUTHOR]

We report herein a versatile method for synthesis of nickel-based inorganic compounds (i.e., Ni–O, Ni–S, Ni–Se, and Ni–P) from one basic nickel-cyanide-bridged coordination polymer (Ni-CP) flakes via a straightforward one-step annealing operation. Thus obtained Ni-based cocatalysts have been loaded over TiO 2 via facile incipient impregnation method to investigate performance towards H 2 production via H 2 O splitting reaction. Among examined compounds, the optimized 0.5Ni-P@TiO 2 exhibited the best photocatalytic activity with a hydrogen generation rate of 7.32 mmol h−1 g−1 compared with pristine TiO 2 (0.086 mmol h−1 g−1). While the 4Ni–Se@TiO 2 has revealed the strongest durability with cumulative hydrogen amount of 48.6 mmol g−1 upon a 5-h reaction, which is 81-fold higher than TiO 2 at identical conditions. On the other hand, Ni–S, Ni–P, and Ni–O, impregnated with 0.5 wt% of titania, show 13, 46, and 49-fold enhancement in evolved H 2 amount higher than the bare titanium dioxide. Additionally, the mixtures have been investigated again through photo-electrochemical measurements confirming the outperforming performance of Ni–P@TiO 2 (0.5% wt). The processed synthesis methodology is economical and easy opening a door to synthesizing various transition metal compound/semiconductor composites for efficient water photocatalytic hydrogen generation. [Display omitted] • Hydrogen extracted from water considered as a future fuel because of its sustainability and cleanliness. • The problem of huge energy required to split H–OH bond in water can be overcome through. • Among several approaches to produce green hydrogen from water, photocatalysis is the completely sustainable and eco-friendly approach. • Herein, we synthesized four nickel compounds from one parent Ni-CP, and investigated their influence on titania photocatalytic properties via water-splitting reaction. • 0.5Ni-P@TiO 2 composite provided the highest HGR (7.3 mmol h−1 g−1) with excellent electrical characteristics, while 4Ni–Se@TiO 2 composite gave the highest cumulative H 2 amount (48.6 mmol g−1), which indicated its distinguished stability. [ABSTRACT FROM AUTHOR]

Additive manufacturing (3D printing) is one of the most promising methods for creating complex metal parts and structures. It has already become a widespread industrial method in the production of coatings or various details of constructions and mechanisms made of pure metals and alloys. In this work, the mechanisms of the formation of intermetallic compounds based on nickel, aluminum and chromium by a dual-wire electron beam additive manufacturing were studied. The microstructure, phase composition, and microhardness of the intermetallic material strongly depend on the ratio of NiCr and Al wires deposited during the electron-beam melting. The intermetallic material based on the NiAl phase was obtained by the deposition of wires in the equal ratio NiCr:Al = 1:1. In the material obtained with a wire ratio of NiCr:Al = 3:1, ordered Ni3Al(Cr) and disordered Ni3Cr(Al) intermetallic compounds are predominantly observed, but the fraction of the Ni3Cr-based phase prevails. The microhardness of the NiAl-based alloy turns out to be higher (5.1 GPa) than that of the Ni3Al(Cr)-based material (4.3 GPa). These intermetallic alloys are developed for the production of intermetallic coatings using electron beam additive manufacturing method. [ABSTRACT FROM AUTHOR]

Herein we report an electrocatalyst for hydrogen evolution reaction (HER) by using cobalt-based zeolite imidazolate framework (ZIF67) as a synthesized precursor, along with its composites using Ni and Se nanoparticles. The morphology and structure of the samples were studied by using FESEM analysis, XRD diffraction method, IR spectra, and BET analysis. The final composite with Ni and Se doped ZIF 67 shows an over potential of 114 mV at a current density of 10 mA cm-2 and a Tafel slope of 46 mV dec-1 compared to that of commercial Pt/C catalyst. The metal-metal interaction on the ZIF 67 frame work were found to serve as an active site. The co-doping producing a synergetic effect helps in enhancing the activity of the optimized catalyst. [ABSTRACT FROM AUTHOR]

The synthesis is demonstrated for a heteroleptic Ni(II) complex, with a tridentate ligand bearing N-heterocyclic carbene (NHC), aryloxide, and picolyl donor groups. The compound was reacted with a variety of hydroxide sources, several of which resulted in complex mixtures. Reaction with [NH4]OH affords a bis-ligated nickel compound, in which the ligands are each bound in a bidentate fashion through the NHC and aryloxide donor groups. A desired nickel(II)-hydroxo product was not observed. DFT studies suggest that ligand redistribution is thermodynamically preferred over stabilization of a Ni-hydroxo in either a monomeric or dimeric form. [ABSTRACT FROM AUTHOR]

Three neutral nickel(II) complexes of 3,5–dibromo–salicylaldehyde (3,5–diBr–saloH) were synthesized in the presence or absence of 1,10–phenanthroline (phen) or its derivative 2,9–dimethyl–1,10–phenanthroline (neoc) as co–ligands, namely [Ni(3,5–diBr–salo)2(neoc)] (complex 1), [Ni(3,5–diBr–salo)2(phen)] (complex 2) and [Ni(3,5–diBr–salo)2(H2O)2] (complex 3), and were characterized by various techniques. The crystal structure of [Ni(3,5–diBr–salo)2(neoc)] was determined by single-crystal X-ray crystallography. According to employed studying techniques, the complexes interact tightly with calf-thymus DNA by an intercalative fashion. Furthermore, compounds 1–3 bind tightly and reversibly to human and bovine serum albumin. [ABSTRACT FROM AUTHOR]

Developing high-performance photocatalytic materials to remove contaminants from water sources is vital for health and environmental conservation. In this study, ZnO/Ni-doped Co3O4 heterojunction nanocomposites were successfully fabricated by sol-gel method and utilized as one of the most promising photocatalysts for the photocatalytic decolorization of reactive red 141 (RR141) dye. The concentration of Ni dopant was selected from 0 to 8 wt%. The prepared photocatalysts were characterized by X-ray diffraction (XRD) and field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray spectra (EDS), and UV-visible diffuse reflectance spectra (UV-vis DRS) analysis. The optical band gap of ZnO nanoparticles, Co3O4 nanoparticles, ZnO/Co3O4, ZnO/2Ni-Co3O4, ZnO/5Ni-Co3O4, and ZnO/8Ni-Co3O4 nanocomposites was found to be 3.25, 2.54, 2.9, 3.78, 2.71, and 2.56 eV, respectively. The photocatalytic results demonstrated robust performance for ZnO/5Ni- Co3O4 nanocomposite in the decolorization of RR141 dye, achieving output as high as 97.4% under 100 min light irradiation. This enhanced photocatalytic efficiency can be attributed to the synergistic effects of Ni doping into Co3O4 lattice and its coupling with ZnO to form an n-p heterojunction ZnO/Ni-Co3O4 nanocomposite, which effectively improves light absorption and separates photogenerated charge carriers on the surface of the nanocomposite. [ABSTRACT FROM AUTHOR]

A dinuclear nickel compound that features vanillin (van) and acetate (OAc) bridging ligands, [Ni2(μ-van)2(μ-OAc)(NCS)3(H2O)]·5H2O 1, was synthesized and characterized using various techniques. Crystal structure analysis revealed a pair of Ni(II) ions bridged by an acetate anion through a μ2-η1:η1 coordination mode. At the same time, vanillin bridges both nickel(II) centers through phenolic oxygen, separating the two Ni ions by a distance of 3.001(7) Å. The temperature-dependent magnetism indicates weak antiferromagnetic behaviour in compound 1, following the Curie–Weiss law with Curie constant C = 1.0145 cm3 K mol−1 and Weiss constant = −4.1 K. Compound 1 was evaluated for its ability to mimic the catechol oxidase enzyme using 3,5-di-tert-butylcatechol as a model substrate with a Kcat value of 157.1 × 102 h−1. Furthermore, compound 1 was tested for its cytotoxicity against HepG2 cancer cells and DNA cleavage properties. [ABSTRACT FROM AUTHOR]

Finding cost-effective electrocatalysts that can match the performance of noble metals like platinum is crucial for renewable hydrogen energy generation. In this study, the electrocatalytic properties of a nickel sulfide compound deposited on a porous copper network that is formed on a nickel foam substrate are investigated. To achieve this goal, the dynamic hydrogen bubble template method was employed. Copper and nickel sulfide electrodeposited in 5 s at 6 A cm−2. The presence of the copper layer resulted in a potential requirement of 98 mV, to achieve current densities of 10 mA cm−2, compared to 120 mV, when the porous copper substrate was not present. The ECSA was found to be significantly increased by the presence of the copper layer, as determined by examining the CV test and calculating the electrochemically active surface area. Ni 3 S 2 @Cu@NF is an excellent choice for electrocatalyst when it comes to HER in alkaline media. [Display omitted] • DHBT were used to electrodeposit coatings of Cu and Ni 3 S 2. • Presence of Cu layer increased electrocatalytic properties of Ni 3 S 2 @Cu@NF. • According to EIS, Ni 3 S 2 @Cu@NF had the best electrocatalytic properties with low R ct. [ABSTRACT FROM AUTHOR]

A review on the hydrogen reduction kinetics of NiO, NiCO3, and Ni(OH)2 hydrogen was conducted, and the most significant experimental values and results were summarized from the past two decades. Isothermal hydrogen reduction experiments of NiO, NiCO3, and, Ni(OH)2 experiments were carried out at 300 °C, 400 °C, and 500 °C, and the obtained data were fitted to multiple different solid-state kinetic models in order to compare the suitability of the models. Non-isothermal reduction in H2 (0 °C → 900 °C) showed the decomposition of NiCO3 at a temperature range of 230 °C to 300 °C and Ni(OH)2 at 220 °C to 300 °C. The calculated Ea values for NiCO3, Ni(OH)2, and NiO varied between 30 and 35, 36 and 37, and 21 and 26 kJ/mol, respectively. Most of the used models were well fitted making the choice of unequivocally the best suitable model difficult and the identification of the mechanism behind the reaction. It was concluded that an increase in temperature accelerates the reduction process, and the reaction rate-controlling mechanism requires more extensive investigation. [ABSTRACT FROM AUTHOR]

In this research, pure nickel chloride films (NiCl2) and doped with aluminum oxide (Al2O3) in proportions of (1,2,3)%. Using the method of thermal chemical spraying, where pure (NiCl2) was prepared and sprayed on glass slides, then the smearing process was carried out at the abovementioned proportions using a technique with a heating degree of the base (150)°C, a thin film of a certain thickness was obtained Then the films were annealed in degree (350)°C for one hour for each degree, and by making optical measurements ( UV visible spectrophotometer) and studying the surface on the prepared films ( Atomic Force Microscope) and matching them. With what was prepared in advance, fine Results have been obtained. [ABSTRACT FROM AUTHOR]

The stability constants of Glycine and Ni(II)Glyx complexes (x = 0-3) in aqueous solution were studied by potentiometric titration at 25°C. The data analysis afforded insight on speciation, which was further confirmed by measuring absorbance in the UV-VIS region, covering a pH range from 2 to 11 to establish the Ni(II)Gly complex extinction coefficients. The potentiometric and spectroscopic data were analyzed using the computer program ESTA. It was shown that the formation of Ni(II)/glycinate complexes are strongly pH dependent. The Ni(II) competes with the protons bound to Glycine at the amine and carboxylate moiety. The successive formation of the NiL, NiL2 and NiL3 was observed as the pH was increased. Free Ni(II) complexes with one Glycine ligand above pH 4 followed by further association of another Glycine ligand above pH 6 and again at pH 8 to form the NiL3 complex. The stability of the complexes is proportional to the number of glycine ligands bound. The analysis of the spectroscopic data supports this trend as an increase in Glycine bound to the Ni(II) center. However, it increases its stability in need of shorter wavelength (higher energy) to excite the electron, suggesting stronger field splitting exerted by the glycine ligand due to higher stability. Thermodynamics study proposed that the increase in stability of the Ni(II) complexes was in this direction: NiL3 > NiL2 > NiL Good correspondence between theoretical and experimental data, low standard deviations in the stability constants and low RH lend reasonable confidence in all obtained results. [ABSTRACT FROM AUTHOR]

Despite the Ni(II) α-diimine based ethylene polymerization catalysts were discovered almost 30 years ago, the mechanism of the ethylene polymerization over these catalysts still remains the subject of the numerous investigations. A significant progress in understanding the nature and role of the nickel compounds formed in real catalyst systems was made over the past 5–7 years. In present publication we summarized and analyzed the data on the nature and role of Ni(II) and Ni(I) species in the catalyst process. [ABSTRACT FROM AUTHOR]

Zinc plant filter cake contains valuable metals that can be reused as a source for obtaining these metals. This study describes an experimental two stage study on the extraction of zinc and nickel from waste zinc filter cake which includes acid leaching of zinc filter cake followed by organic phase aided extraction of metals from the leaching solution. To determine the optimum leaching condition a comprehensive study of the recovery of chemical elements from spent plant residues was experimentally studied at different levels of acid concentrations at different temperatures while measuring chemical elements concentration with respect to time. Experimental results showed that 99% recovery of Ni2+, Zn2+ and 89% recovery of Pb2+ can be achieved at following optimum conditions: 2M nitric acid, T= 358.15 K after 1.5 h of acid leaching at S/L=1/10. Then, the extraction of Zn2+, Ni2+, and Pb2+ was carried out by di-(2-ethylhexyl) phosphoric acid (D2EHPA) that was diluted with kerosene in equal phase ratio and the effect of extractant concentration and pH was studied at T = 298.15 K. Results showed that an increase in pH and extractant concentration can greatly increase zinc and nickel extraction to a maximum achievable amount of 95% and 90 % for Zn2+ and Ni2+, respectively by 25 (v/v%) D2EHPA at pH = 5.5 and organic to aqueous phase ratio (O/A) = 1/1. For modeling of equilibrium concentrations in organic and aqueous phases and activity coefficients calculation, Electrolyte-UNIQUAC-NRF, UNIQUAC-NRF, NRTL and NRTL-based local composition models were used. After that, adjusted parameters were successfully used for calculation of the equilibrium constant of the unknown parameters and the extraction reaction. The obtained results of thermodynamic modeling were in well agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The unique properties of nickel oxide nanoparticles distinguish it from classical nickel compounds, increasing its use in agriculture, industry, and many industrial areas. The aim of this study is to investigate the possible toxicity of nickel oxide and nickel oxide nanoparticles in the liver. For this purpose, Wistar rats were given nickel oxide and nickel oxide nanoparticles orally, intraperitoneally, and intravenously for 21 days. Liver organ weight, biochemical and hematological parameters, oxidative stress (malondialdehyde, catalase, superoxide dismutase, glutathione peroxidase, and glutathione S transferase), acetylcholinesterase activities, inflammation levels, apoptotic markers, and histopathological changes were evaluated comparatively. When the data obtained were examined in general, it was observed that nickel oxide nanoparticles caused more hepatotoxicity in liver tissue than nickel oxide in terms of oxidative stress parameters, apoptotic markers, inflammation indicators, and other parameters examined. The results suggest that toxicity induced by both nickel oxide and nickel oxide nanoparticles plays an important role in hepatocyte apoptosis. [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]

A facile synthesis for unprecedented stibastannene (10) featuring a Sn=Sb‐double bond together with the homologous arsa‐ (9) and phosphastannenes (8) is presented. Chloride abstraction from respective stannyl pnictinidenes [E=P (5), As (6), Sb (7)], which were made accessible by reduction of ECl3 addition products at an intramolecular phosphine‐stabilized stannylene, gave the pnictastannenes in moderate yields. The pnictastannenes coordinate Pd(PPh3)2 fragments (12–14) and the phosphastannene forms also a nickel coordination compound with the Ni(PPh3)2‐fragment (11). 2,3‐Dimethylbutadiene shows a [2+4]‐cycloaddition (15–17) in reaction with the pnictastannenes (8–10). Products of a [2+2]‐addition (18, 19) were isolated as the phosphaalkyne reaction products for 8 and 9. Addition of an O−H bond at the Sn=P‐bond was found in reaction of water with phosphastannene 8. Reaction with ammonia afforded the NH3‐adducts (21–23) at the tin atom for pnictastannenes 8–10. Only in the case of the arsastannene an azide reaction product featuring a three membered Sn−As−N‐ring was obtained. [ABSTRACT FROM AUTHOR]

Dust, both industrial and household, contains particulates that can reach the most distal aspects of the lung. Silica and nickel compounds are two such particulates and have known profiles of poor health outcomes. While silica is well-characterized, nickel compounds still need to be fully understood for their potential to cause long-term immune responses in the lungs. To assess these hazards and decrease animal numbers used in testing, investigations that lead to verifiable in vitro methods are needed. To understand the implications of these two compounds reaching the distal aspect of the lungs, the alveoli, an architecturally relevant alveolar model consisting of epithelial cells, macrophages, and dendritic cells in a maintained submerged system, was utilized for high throughput testing. Exposures include crystalline silica (SiO2) and nickel oxide (NiO). The endpoints measured included mitochondrial reactive oxygen species and cytostructural changes assessed via confocal laser scanning microscopy; cell morphology evaluated via scanning electron microscopy; biochemical reactions assessed via protein arrays; transcriptome assessed via gene arrays, and cell surface activation markers evaluated via flow cytometry. The results showed that, compared to untreated cultures, NiO increased markers for dendritic cell activation, trafficking, and antigen presentation; oxidative stress and cytoskeletal changes, and gene and cytokine expression of neutrophil and other leukocyte chemoattractants. The chemokines and cytokines CCL3, CCL7, CXCL5, IL-6, and IL-8 were identified as potential biomarkers of respiratory sensitization. [ABSTRACT FROM AUTHOR]

BackgroundMetallic nickel and nickel compounds are classified as possibly carcinogic and carninogic to humans respectively, but the exact carcinogenic mechanism has not been clarified.ObjectiveTo analyze the carcinogenic research trend and hotspots of nickel and nickel compounds, and provide research directions for this topic.MethodsLiterature search on the carcinogenesis of nickel and nickel compounds was conducted through authoritative databases at home and abroad: Wanfang, China National Knowledge Infrastructure, PubMed at the US National Library of Medicine, and Elsevier’s biomedical research database EMBASE. VOS viewer 1.6.17 visual analysis software was applied to perform the bibliometric analysis and present results with charts on annual number of publications, distribution of author’s affiliations, country/region distribution, journal distribution, and keywords of literature that meet a predetermined inclusion criteria.ResultsA total of 242 Chinese documents and 878 foreign documents (languages included English, German, and Japanese) related to the carcinogenic research of nickel and nickel compounds were found. In terms of Chinese articles, the earliest publication of relevant research was in 1974; Guangzhou Medical University (including Guangzhou Medical College and Institute of Chemical Carcinogenesis of Guangzhou Medical College) was the institution that published most articles in this field (35 articles); Industrial Health and Occupational Diseases was the journal that published the most articles (19 articles). In terms of foreign articles, the earliest publication was in 1950; the United States ranked the country having the highest number of published articles (304 articles), and China took the second place (83 articles); Cancer Research was the journal that published the most articles (40 articles). The keyword co-occurrence analysis showed that the domestic studies on the carcinogenesis of nickel and nickel compounds mainly focused on nickel smelting fume, nickel sulfate, nickel chloride, and other nickel and its compounds in association with DNA damage, DNA methylation, induction of human bronchial epithelial cell transformation, and other carcinogenic mechanisms. The international studies focused on population epidemiological studies on occupational risk factors, incidence, and mortality on carcinogenesis of nickel and nickel compounds, and studies on histone modification, oxidative stress, DNA damage, cell transformation, and other carcinogenic mechanisms.ConclusionStudies have shown that the hotspots of carcinogenic research on nickel and nickel compounds involved studies on carcinogenic mechanisms related to DNA damage, DNA methylation, histone modification, oxidative stress, and induction of human bronchial epithelial cell transformation, and population epidemiological studies on occupational risk factors, incidence, and mortality. In recent years, the number of published articles on the carcinogenesis of nickel and its compounds in China has been decreasing. In view of the large number of occupational nickel-exposed population in China, more efforts should be made to study the carcinogenesis of nickel and nickel compounds in the future.

Inhalation studies with nickel (Ni) subsulfide (Ni3S2) and Ni sulfate hexahydrate (NiSO4·6H2O) investigated differences in mode of action that could explain why the former induced lung tumors in rats and the latter did not. Male rats were exposed to ≤0.22 mg Ni/m3 NiSO4·6H2O or 0.44 mg Ni/m3 Ni3S2, 6 h/day, 5 days/week for 3 and 13 weeks; subsets of the rats exposed for 13 weeks were held for an additional 13 weeks. Analyses of bronchoalveolar lavage fluid, isolated cells, and whole lung tissue were conducted to compare the extent and persistence of any induced lung effects. Histological findings were qualitatively identical for both compounds and consistent with lesions reported in earlier studies. After 13 weeks of exposure, the incidence and severity of pulmonary inflammation and epithelial cell hyperplasia were greater among Ni3S2‐exposed rats, whereas the reverse response was seen for apoptosis. Only Ni3S2 exposure significantly increased epithelial and non‐epithelial cell proliferation after 13 weeks of exposure. Both compounds induced DNA damage in isolated lung cells and DNA hypermethylation of whole lung tissue after 13 weeks of exposure at the highest exposure concentrations. Increases in cell proliferation, DNA damage, and tissue DNA hypermethylation did not persist during the 13‐week recovery period. In summary, the highest concentrations of each compound produced marked pulmonary toxicity, but the lowest concentrations produced minimal or no effects. Differences in the proliferative and apoptotic responses between the two compounds may help explain differences in carcinogenicity, whereas the identification of no observed adverse effect concentrations (NOAECs) contributes to the risk characterization for inhalation exposure to nickel compounds. A comprehensive study comparing rat responses to 3‐ and 13‐week inhalation exposure to NiSO4 and Ni3S2 indicated some differences (e.g., stronger apoptotic response for NiSO4 and a stronger effect on cell proliferation for Ni3S2); these responses did not persist after cessation of exposure. These findings add to our understanding of the mode of action for lung carcinogenicity by nickel compounds. Our study also contributes to the risk characterization for inhalation exposure to nickel compounds. [ABSTRACT FROM AUTHOR]

Spectrophotometric methods are used to study the reaction of the nickel complex with 2.4- tyazolidindico (L) and its derivatives {5- (gasilysiliden) -2,4-tyazolidindio (L1), 5- (2-chlorbenzyliden) -2,4- tyazolidindion (L2), 5-(2-hydroxybenzylide) -2,4-tiazoleader (L3), 5- (4-hydroxybenzylide)-2,4- tyazolidindion(L4),5-(2-Brom-5-methoxybenzyiliden)-2,4-tiazolyidinedion (L5). With a single extraction, the chloroform is extracted by 97.8-98.4 % of the nickel. The study of the dependence of complexation on pH showed that the optimal range of acidity, at which the optical density is maximum and constant, is at pH 2.3- 8.0. The optimal condition for the formation and extraction of the nickel complex of these compounds is (2.0- 2.5) × 10-4 M concentration L. Nickel complexes with L are stable in water and organic solvents and do not decompose for three days, and after extraction for more than a month. The maximum optical density is achieved within 5 minutes. The maximum analytical signal during the complex of nickel L is observed at 470-482 nm/ molar absorption coefficients (1.37-1.61)×104 . The comprehensive form of nickel is Ni2*while the number of protons supplanted by it from one molecule L turned out to be equal to 1. Nickel and its complexes in the organic phase are not polymerized and are in a monomeric form (γ = 1.01-1.07). The proposed method under already established optimal conditions is used to determine Ni (II) in wastewater, bottom deposits, as well as in oil and oil products. [ABSTRACT FROM AUTHOR]

In this work, carbon-supported nickel catalysts with different Ni content (1, 2.5, 5, 10, and 20 wt%) were tested in the oxidation of alpha-pinene in solvent-free reaction conditions. The process of catalyst preparation consisted of two stages. In the first stage, the activated carbon from spent coffee grounds was obtained. In the second stage, the active phase in the form of nickel compounds was applied using two methods: (1) the impregnation of the material with the nickel salt solution, and next reduction in H2, and (2) the hydrothermal method in the autoclave using the reductor and the reaction stabilizer. The obtained catalysts were subjected to the following instrumental studies: FT-IR, XRD, SEM, and N2 adsorption at −196 °C. The performed catalytic tests showed that the catalysts containing 5 wt% of Ni (porous material obtained by the impregnation method) and 1 wt% of Ni (porous material obtained by the hydrothermal method) were the most active in the oxidation of alpha-pinene, and the main oxidation products were alpha-pinene oxide, verbenol, and verbenone. Ultimately, the hydrothermal method of catalyst preparation turned out to be more advantageous because it allows one to obtain higher selectivities of the epoxide compound, probably due to the greater stability of this organic compound in pores. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of Au-intercalation on the magnetic coupling between a sub-monolayer of Co-Tetraphenylporphyrin molecules and a graphene-covered Ni(111) single crystal. Using x-ray absorption spectroscopy and x-ray magnetic circular dichroism, the element-specific magnetization and its field dependence were probed. Cobalt strongly couples antiferromagnetically to the nickel substrate, also through the graphene layer. The intercalation of graphene with gold leads to a complete removal of this coupling. [ABSTRACT FROM AUTHOR]

The triangular spin lattice of NiBr 2 is a canonical example of the frustrated helimagnet that shows a collinear commensurate antiferromagnetic to an incommensurate spin helix phase transition on cooling. Herein, we have studied a self-flux grown NiBr 2 single crystal by neutron diffraction and low temperature magnetization measurements at fields up to 14 T. Experimental findings enable the deduction of the driving force responsible for the spin spiral ordering. The neutron diffraction data reveal satellite peaks representing characteristic features of an incommensurate magnetic state. The satellites develop symmetrically below T N = 44.0 (1) K , replacing the main magnetic reflections. Interestingly, a field-induced incommensurate to commensurate spin phase transition has been successfully demonstrated, which enforces the spin helix to restore the high temperature compensated antiferromagnetic structure. This reorientation can be described by a spin-flop in the (a–b) basal plane of a triangular spin lattice system. The findings offer a novel way for spin helix control of incommensurate phases, having immense scientific and technological implications in the next-generation data storage devices. [ABSTRACT FROM AUTHOR]

The functional stability of a shape memory alloy (SMA) may be related to its structural compatibility between the parent-phase and the martensitic-phase structures. In this study, we perform systematic first-principles calculations for 276 Ni–Ti-based ternary alloys to investigate their energetic stability as well as their structural compatibility between the parent- and the martensitic-phase structures. We analyze in detail the dependences of the energetics and structural properties on the additional element X, on X concentration, and on the replaced chemical element. Some X are found to energetically stabilize the B19 structures more than the B19′ structures at X concentrations above 6.25 at. %. It is also found that the B19–B2 martensitic transformation shows better structural compatibility than the B19′–B2 transformation for most of the investigated ternary Ni–Ti–X alloys. These alloys also tend to have better structural compatibility than binary equiatomic NiTi. Moreover, we screen the investigated alloys on the basis of their energetic stability and structural compatibility, and we identify 26 Ni–Ti–X alloys as possible SMAs with good functional stability. In this study, we reveal a strong potential of the computational design for improving the functional stability of Ni–Ti SMAs by alloying additional elements. [ABSTRACT FROM AUTHOR]

The dissociation of water on a transition-metal catalyst is a fundamental step in relevant industrial processes such as the water-gas shift reaction and steam reforming. Although many theoretical studies have been performed, quantitative agreement between theoretical simulations and molecular beam experiments has not yet been achieved. In this work, we present a predictive ab initio molecular dynamics study on the dissociation of mono-deuterated water (HOD) on Ni(111). The analysis of the trajectories gives useful insight into the full-dimensional dynamics of the process and suggests that rotational steering plays a key role in the dissociation. The computed reaction probability suggests that, in combination with accurate molecular beam experiments, the specific reaction parameter density functional developed for CHD3 (SRP32-vdW) represents a good starting point for developing a semi-empirical functional able to achieve chemical accuracy for HOD on Ni(111). [ABSTRACT FROM AUTHOR]

Abstract NiOx thin films were prepared on an Au substrate using the electrodeposition (ED), spin‐coating (SP), and ED after SP (SP/ED) techniques to realize their application as an electrochemical sensor for the selective detection of trace substances. The results indicated that the electrodeposited films had nanoparticles formed as coarse‐grain morphology, and the spin‐coated films had a uniform layer with ∼60 nm thickness. The thin film prepared by the SP/ED technique showed the highest electrochemical activity, and it was used to record a linear sweep voltammogram to measure the target substance, monosodium glutamate (MSG), and glucose, from low concentrations (2 nM) to high concentrations (200 μM). Within the range of concentrations, high R2 values of ≥0.99 were observed for both target substances, confirming that the SP/ED thin films can be used as an electrochemical sensor with high reliability.

The atomically dispersed Ni metal on two-dimensional (2D) monolayer species have exhibited impressive catalytic properties towards oxygen evolution and oxygen reduction reactions (OER/ORR). In this work, nickel boride and nickel carbide monolayers, which is inspired by the more different active sites of monolayer surface, such as Ni atom, that efficiently catalyze the reduction of OOH to O 2 to some extent, while B/C atom can work in the reduction of H∗ to H 2 , are theoretically reported. Remarkably, the density functional theory (DFT) calculations showed that the random combination of Ni atom to two free-metal atoms such as B and C to form catalytically active double sites lead to a remarkable reduction of the first or last hydrogenation free energy barrier step. The resulting Ni 2 B 5 and NiC 3 exhibited ultra-low Gibbs free energy (Δ G H∗) of only 0.096 V and 0.018 V for HER and lower onset potentials of only 0.39 V (0.62 V) and 0.60 V (0.31 V) for OER (ORR), respectively, while the NiB 6 exhibited appropriate OER and ORR electrocatalytic activity. The superior bifunctional even multifunctional catalytic performance in the overall water splitting is mainly attributed to both the electron donation from the Ni metal atoms to the key intermediates, which significantly polarizes and weakens the O–H bond, and to the synergistic effect of the B/C atoms that moderates the binding strength of terminal top of H atoms. This work constitutes the DFT study of the water electroreduction processes on diverse nickel compounds monolayer catalytic sites and, consequently, paves the way towards the rational design of highly efficient bifunctional even multifunctional electrocatalysts. [Display omitted] • Nickel-based materials have unique advantages in the application of electrocatalysts. • The three kinds of nickel-based materials studied are all excellent bifunctional or even multifunctional catalysts. • The Ni 2 B 5 monolayer with dual active centers can effectively reduce the theoretical overpotential of OER and ORR. • The dual active centers mechanism breaking the traditional scaling relationship of single active center. [ABSTRACT FROM AUTHOR]

This paper describes the specific features of the formation of an unsupported nickel-tungsten sulfide nanosize catalyst in situ in a hydrocarbon feedstock from oil-soluble precursors—nickel and tungsten compounds in the presence of elemental sulfur additive. The catalysts formed at different times of the catalytic experiment (2, 5, 7 and 10 h) were analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. According to STEM-EDX elemental spectra, the formation of tungsten and nickel sulfides was established, with a further increase in the amount of active Ni-W-S phase on the surface of the crystalline nickel sulfide. It was found that the time of catalyst formation affects its morphology and phase composition. Evaluation of the hydrogenating catalytic activity confirms that an increase in the time of catalyst formation leads to an increase in its activity, which is associated with the peculiarities of the morphology of sulfide particle aggregates as well as an increase in the degree of promotion of tungsten disulfide crystallites by nickel atoms. [ABSTRACT FROM AUTHOR]

The microstructural evolution and corrosion behavior of Ni62Nb33Zr5 bulk metallic glasses (BMGs) after annealing treatment (AT) at different crystallization temperatures and cryogenic treatment (CT) at −100◦C are experimentally investigated. Appropriate AT and CT can both improve the thermal stability and comprehensive corrosion resistance of as-cast BMG in 3.5 wt.% NaCl solution. The annealed and cryo-treated BMGs exhibit one more finite diffusion layer loop in the electrical equivalent circuit than the as-cast BMG, indicating the complexity of the corrosion behavior. Superior corrosion resistance is obtained in the cryo-treated BMG because the high degree of amorphization caused by CT reduces the structural inhomogeneity. Lower Cd and higher Rd values are obtained for the cryo-treated BMG, revealing the formation of a more stable passive film. Among the annealed BMGs, the fully crystallized sample exhibits a higher anti-corrosion performance owing to the existence of Nb-rich oxides in the crystallization products. The passive film is found to be composed mainly of Nb2O5 and ZrO2, demonstrating that Nb and Zr are conducive to reacting with oxygen to form a passive film. Based on the goal of maintaining a fully amorphous phase, appropriate CT causing structural homogeneity of the BMG is a simple and effective means to improve the comprehensive corrosion resistance. [ABSTRACT FROM AUTHOR]

The electrocatalyzed ammonia oxidation reaction (AOR) is a potential pathway toward waste ammonia remediation, energy generation, and the synthesis of value‐added products. To date, mechanistic studies have focused on elucidating the progress of AOR on Pt‐based catalysts with an established pathway for N2$\mathrm{N_2}$ only. In this work, density functional theory was applied to determine the lowest energy intermediates toward nitrogen gas, nitrite, and nitrate formation on β$\beta$‐Ni(OH)2$\mathrm{Ni(OH)_2}$, a promising electrocatalyst material for AOR. It was found that dinitrogen formation progresses via NH‐NH coupling, whereas nitrite and nitrate formation occurs via deprotonation of ammonia to form adsorbed N and subsequent hydroxylation to form oxygenated intermediates. This work is the first to report a mechanism for nitrite and nitrate formation and will also serve as a benchmark for future studies on Ni‐based materials. [ABSTRACT FROM AUTHOR]

This paper investigates the application of a mixture of three types of fuels, namely urea, glycine and hydrazine, for the synthesis of Ni-10 wt. % Al2O3 nanocomposite using the solution combustion method. Nickel and aluminum nitrates are used as an oxidizer. The fuels are used at two different fuel to oxidizer ratios. DSC-TGA diagrams prove hydrazine-nitrate reaction system can ignite before nitrate decomposition in contrary to urea-nitrate and glycinenitrate systems. The results showed synthesized alumina at combustion temperatures less than 500 °C is amorphous and the combustion temperatures more than 600 °C made alumina crystalline. The measured surface area for the synthesized nanocomposite in air and less than 10 min was 207 m² g-1. SEM and FESEM images prove the presence of small porosities in the synthesized nanocomposites. TEM image shows synthesized alumina in the nanocomposite has a mean particle size of less than 25 nm. [ABSTRACT FROM AUTHOR]

Nickel compounds nanoparticles have great potential for optoelectronic devices. In this study, we investigate the structural, morphological, optical, and electrical properties of (PET/ITO/NiO/Ag) and (PET/ITO/ β -Ni(OH) 2 /Ag) heterojunction obtained by chemical bath deposition and spin coating, which are low-cost techniques. The crystal size was obtained by XRD diffraction; the structural analysis showed crystal dimensions in the 2–7 nm intervals. An enhanced conductivity of 0.86 (Ω /cm) and an increment in the lifetime carriers compared with samples without annealing treatment were observed. The I–V characteristics measured at room temperature, the height of the Schottky barriers, were estimated in the range of 0.56–0.60 eV. This method leads to an affordable application in optoelectronic devices. • Facile and cost-effective chemical synthesis is used to obtain Ni(OH) 2 and NiO nanocrystals. • Thermal annealing improved lifetime carriers and photoconductivity of Nickel compunds • Optical studies demonstrates optimal temperature annealing at 300 °C have most desirable optoelectronic properties. • The electrical characterization of (PET/ITO/NiO/Ag) and (PET/ITO/β-Ni(OH) 2 /Ag were analyzed. [ABSTRACT FROM AUTHOR]

The quantum size effect is a well-known fundamental scientific phenomenon. Due to quantum confinement, downscaling a system to small sizes should increase the bandgap of a solid state material. However, in this work, we present an exception: monolayers of nickel hydroxide have smaller bandgaps than their bulk analogues, due to the surface states appearing at energies within the bandgap region. Our findings are obtained by several state-of-the-art first principles calculations. [ABSTRACT FROM AUTHOR]

A thermionic energy converter with a nickel collector and cesium vapor as a working gas was studied, and an abnormally low value of the surface work function of ≈1 eV was obtained if the collector was covered by a thin carbon layer. Scanning electron microscopy x-ray microanalysis data of the elemental composition of the collector's surface after its long exposure to plasma indicate that the carbon structure was intercalated with cesium atoms, and this change to surface structure can be a reason for the anomalously low work function ∼1 eV. The thermionic energy converter with such a collector demonstrated high heat-to-electric power conversion efficiency up to ∼20%. [ABSTRACT FROM AUTHOR]

The critical behaviors of polycrystalline Ni2MnGa and Ni2Mn0.85Cu0.15Ga have been examined through high-resolution bulk magnetization measurements. The critical exponents, β and γ, were derived from modified Arrott plots using the Kouvel-Fisher method. The values of the extracted critical exponents satisfied the scaling equation of state and associated exponent relations, indicating self-consistency of the extracted values. In Ni2MnGa, the critical exponents (β = 0.401 ± 0.003, γ = 1.27 ± 0.02) indicate a deviation from the 3D-Heisenberg values toward the mean-field values, likely due to the presence of long-range Ruderman-Kittel-Kasuya-Yosida interactions. However, the critical exponents of Ni2Mn0.85Cu0.15Ga (β = 0.389 ± 0.004, γ = 1.39 ± 0.02) are closer to the 3D-Heisenberg values. This indicates a weakening of the long-range exchange interactions due to the substitution of Cu in the Mn site. [ABSTRACT FROM AUTHOR]

In this work, hydrolysis lignin with nickel compounds deposited on the surface was prepared. The resulting material was introduced into the process of carbon dioxide assisted conversion and the catalytic activity of the deposited nickel compounds in this reaction was evaluated. Use of the obtained catalytic system increases CO2 conversion by more than 30% in the temperature range 450–800 °C. After the conversion process, the material was subjected to a study using a variety of physico-chemical analysis methods (TEM, SEM-EDX, and X-ray phase analysis). Physico-chemical methods of analysis of a sample calcined at 300 °C to decompose nickel nitrate revealed NiO nanoparticles with an average particle size of 16.9 nm. [ABSTRACT FROM AUTHOR]

The teaching laboratory remains an important environment for developing undergraduate chemists, but the inherent diversity of inorganic chemistry results in less standardised undergraduate curricula than other sub-disciplines. This study surveys the content of advanced (third-year) inorganic chemistry across Australia and reviews experimental materials from 15 universities that offer inorganic laboratory programmes at this level. All institutions offer at least one traditional inorganic experiment, the most common being the preparation and acetylation of ferrocene, spectroscopy and magnetochemistry of nickel coordination compounds and palladium-catalysed cross-couplings. These inorganic classics are complemented by a breadth of non-traditional offerings that often align with institutional research strengths. Academic unit coordinators were also surveyed and their responses interpreted using ASELL (Advancing Science and Engineering through Laboratory Learning) tools. Advanced inorganic laboratory programmes were found to develop students' practical and transferrable skills. Students generally receive guidance from teaching staff in all aspects of experimental work, including planning, development, analysis and communicating conclusions. Academic unit coordinators identified potential improvements that included diversifying student activities in the lab and how they are being assessed. This study investigates the content, scope and approaches to learning in advanced (third-year) inorganic chemistry laboratory curricula at Australian universities. Staff at 19 of the 23 Australian institutions that offer undergraduate degrees with a Chemistry major participated in this study. [ABSTRACT FROM AUTHOR]

Abstract The state of the ampere‐hour capacity of the battery depends on the condition of materials used in it. Large reduction of capacity ends with maintenance or replacement of the battery. Modern battery materials include application of nanomaterials and nanotechnology in various stages of production. This article attempts to monitor the capacity of battery used for vehicles which are made of different types of materials using switching transients. The analytical part was done using wavelet‐based decompositions. Data sets of large number of coefficients have been developed for learning. Their statistical behaviour has been studied, and monitoring was initially carried out by some selective parameters. Then the artificial neural network‐based algorithm was developed which includes all features of statistical variation for better monitoring. Case studies have been carried out followed by comparison. The study ends with a satisfactory monitoring.

To develop the structural and functional modeling chemistry of [NiFe]-H2ases, we have carried out a study regarding the synthesis, structural characterization and reactivity of a new series of [NiFe]-H2ase model complexes. Thus, treatment of diphosphine dppb-chelated Ni complex (dppb)NiCl2 (dppb = 1,2-(Ph2P)2C6H4) with (dppv)Fe(CO)2(pdt) (dppv = 1,2-(Ph2P)2C2H2, pdt = 1,3-propanedithiolate) and NaBF4 gave dicarbonyl complex [(dppb)Ni(pdt)Fe(CO)2(dppv)](BF4)2 ([A](BF4)2). Further treatment of [A](BF4)2 with Me3NO and Bu4NCN or KSCN afforded t-cyanido and t-isothiocyanato complexes [(dppb)Ni(pdt)Fe(CO)(t-R)(dppv)]BF4 ([1]BF4, R = CN; [2]BF4, R = NCS), respectively. While azadiphosphine MeN(CH2PPh2)2-chelated t-hydride complex [MeN(CH2PPh2)2Ni(pdt)Fe(CO)(t-H)(dppv)]BF4 ([3]BF4) was prepared by treatment of dicarbonyl complex [MeN(CH2PPh2)2Ni(pdt)Fe(CO)2(dppv)](BF4)2 ([B](BF4)2) with Me3NO and 1.5 MPa of H2, treatment of dicarbonyl complex [B](BF4)2 with Me3NO (without H2) in pyridine resulted in formation of a novel monocarbonyl complex [MeN(CH2PPh2)2Ni(SCHCH2CH2S)Fe(CO)(dppv)]BF4 ([4]BF4) via the unexpected sp3 C-H bond activation reaction. Furthermore, azadiphosphine PhN(CH2PPh2)2-chelated µ-mercapto complex [PhN(CH2PPh2)2Ni(pdt)Fe(CO)(µ-SH)(dppv)]BF4 ([5]BF4) was prepared by treatment of dicarbonyl complex [PhN(CH2PPh2)2Ni(pdt)Fe(CO)2(dppv)](BF4)2 ([C](BF4)2) with Me3NO and H2S gas, whereas treatment of azadiphosphine Ph2CHN(CH2PPh2)2-chelated dicarbonyl complex [Ph2CHN(CH2PPh2)2Ni(pdt)Fe(CO)2(dppe)](BF4)2 ([D](BF4)2, dppe = 1,2-(Ph2P)2C2H4) with Me3NO⋅2H2O gave rise to µ-hydroxo complex [Ph2CHN(CH2PPh2)2Ni(pdt)Fe(CO)(µ-OH)(dppe)]BF4 ([6]BF4). All the possible pathways for formation of the new model complexes are briefly discussed, and their structures were fully characterized by various spectroscopic techniques and for six of them by X-ray crystallography. [ABSTRACT FROM AUTHOR]

It is difficult to design a new single‐component photocatalyst to simultaneously possess a bandgap small enough to absorb most of sunlight and strong redox ability to reduce CO2 into value‐added chemical fuels. Herein, bandgap engineering of nickel vanadate compounds (NixV2O5+x, x = 1, 2, 3) is rationally designed to overcome the above challenge. Through changing the Ni:V ratio, the bandgap and band edge positions of nickel vanadates can be regulated, enabling Ni2V2O7 and Ni3V2O8 to reduce CO2 in the presence of water under visible light irradiation that do not exist in NiV2O6. Ni 3d orbitals of Ni2V2O7 and Ni3V2O8 replace V 3d orbitals of NiV2O6 and hybridize with O 2p orbitals to form the valence band maximums, resulting in their negative shifts. Meanwhile, the relatively weaker effect of the crystal field in VO4 tetrahedron over Ni2V2O7 and Ni3V2O8 results in less V 3d split, thus making the conduction band edges to shift upward. In addition, higher concentration of oxygen vacancies over Ni2V2O7 can further enhance its photocatalytic activity for CO2 conversion into CO with nearly 100% selectivity by prolonging the lifetime of photogenerated carriers and improving the chemisorption of CO2. [ABSTRACT FROM AUTHOR]

The physicochemical and catalytic properties of low-cost metal mixed oxide catalysts have been researched and characterized. To explore catalysts, various characterization techniques such as BET and X-ray diffraction (XRD) have been utilized. Three distinct catalysts, C1(NiO-Co3O4/Silica), C2(NiO- Co3O4-ZnO/ Silica), and C3(NiO- Co3O4-BaO/ Silica), are synthesized with 20 wt% mixed oxide (NiO- Co3O4) supported on silica and doped with zinc/barium oxide, and then dried at 110°C overnight and calcined at 350°C All three catalysts have been tested in an ethyl acetate saponification reaction, and the conversion of reactants is calculated. In comparison to the other catalysts, C2 (NiO-Co3O4-ZnO/ Silica), which is a combination of NiO-Co3O4/SiO2 doped with zinc oxide, show good catalytic activity. In terms of catalyst doping, the addition of zinc oxide to the Silica supported original composition boosted the catalytic activity for the saponification reaction compared to barium oxide and without doped. [ABSTRACT FROM AUTHOR]

Developing low‐cost and high‐efficiency catalysts for sustainable hydrogen production through electrocatalytic hydrogen evolution reaction (HER) is crucial yet remains challenging. Here, a strategy is proposed to fill Ni‐vacancy (Niv) sites of dual‐deficient NiO (D‐NiO‐Pt) deliberately created by Ar plasma with homogeneously distributed Pt atoms driven by oxygen vacancies (Ov). The incorporated Pt atoms filling the Niv reduce the formation energy to increase crystal stability, and subsequently combine with additional Ov to tune the electronic structure of the surrounding Ni sites. Thus, a more ideal hydrogen adsorption free energy (ΔGH*) closer to 0 of Ni sites and Pt sites can be achieved. As a result, the D‐NiO‐Pt electrode achieves superior mass activity of ≈1600 mA mg−1 (normalized by platinum) and nearly negligible loss of activity during long‐term operation, which is much better than as‐prepared Pt‐containing NiO catalysts without plasma treatment. A low overpotential of 20 mV is required for the D‐NiO‐Pt at 10 mA cm−2 in alkaline HER, outperforming that of the commercial Pt/C. In addition, the universal access to the other Ni‐based compounds including nickel phosphide (Ni2P), nickel sulfide (Ni0.96S), and nickel selenide (NiSe2) is also demonstrated by employing a vacancy‐driven Pt filling mechanism. [ABSTRACT FROM AUTHOR]

Three square planar nickel(II) complexes of a new asymmetric tetradentate redox-active ligand H3L2 in its deprotonated form, at three redox levels, open-shell semiquinonate(1−) π radical, quinone(0) and closed-shell dianion of its 2-aminophenolate part, have been synthesized. The coordinated ligand provides N (pyridine) and N′ and N′′ (carboxamide and 1,2-phenylenediamide, respectively) and O (phenolate) donor sites. Cyclic voltammetry on the parent complex [Ni(L2)] 1 in CH2Cl2 established a three-membered electron-transfer series (oxidative response at E1/2 = 0.57 V and reductive response at −0.32 V vs. SCE) consisting of neutral, monocationic and monoanionic [Ni(L2)]z (z = 0, 1+ and 1−). Oxidation of 1 with AgSbF6 affords [Ni(L2)](SbF6) (2) and reduction of 1 with cobaltocene yields [Co(η5-C5H5)2][Ni(L2)] (3). The molecular structures of 1·CH3CN, 2·0.5CH2Cl2 and 3·C6H6 have been determined by X-ray crystallography at 100 K. Characterization by 1H NMR, X-band EPR (gav = 2.006 (solid); 2.008 (CH2Cl2–C6H5CH3 glass); 80 K) and UV-VIS-NIR spectral properties established that 1, 2 and 3 have [NiII{(L2)˙2−}], [NiII{(L2)−}]+/1+ and [NiII{(L2)3−}]−/1− electronic states, respectively. Thus, the redox processes are ligand-centred. While 1 possesses paramagnetic St (total spin) = 1/2, 2 and 3 possess diamagnetic ground-state St = 0. Interestingly, the variable-temperature (2–300 K) magnetic measurement reveals that 1 with the St = 1/2 ground state attains the antiferromagnetic St = 0 state at a very low temperature, due to weak noncovalent interactions via π–π stacking. Density functional theory (DFT) electronic structural calculations at the B3LYP level of theory rationalized the experimental results. In the UV-VIS-NIR spectra, broad absorptions are recorded for 1 and 2 in the range of 800–1600 nm; however, such an absorption is absent for 3. Time-dependent (TD)-DFT calculations provide a very good fit with the experimental spectra and allow us to identify the observed electronic transitions. [ABSTRACT FROM AUTHOR]