Ni-N Bond Research Articles

Molybdenum phosphide coupled with highly dispersed nickel confined in porous carbon nanofibers for enhanced photocatalytic CO2 reduction

Photoreduction of CO2 to chemical fuels offers a promising strategy for managing the global carbon balance using renewable solar energy. However, the decisive process of oriented photogenerated electron delivery presents a considerable challenge. The performance of most transition metal compounds, as photocatalysts for CO2 reduction, is largely limited by their inherent stacked structure, poor conductivity, and fast recombination of photogenerated electron-hole pairs. Herein, we report the construction of porous nitrogen-doped carbon nanofibers (NCPF) with highly dispersed Ni and molybdenum phosphide nanoparticles (Ni-MoP@NCPF) loaded for photocatalytic CO2 reduction. The porous carbon nanofibers with high conductivity and open ends can effectively promote charge/mass transfer and improve CO2 adsorption. The loaded Ni species exist at a highly dispersed state that are stabilized by formation of coordinating Ni-N bonds with N from pyrrolic nitrogen in NCPF. The incorporation of Ni and its electronic coupling with MoP can adjust the band structure of the resultant material and alter the transfer route of the photogenerated carriers. The Ni-MoP@NCPF exhibits a CO product selectivity up to 98.95% with a rate of 953.33 μmol g−1h−1 under visible light irradiation, which is 9.37 times faster than that of Ni-free MoP@NCPF. These findings provide new insights into photocatalytic CO2 reduction on cost-effective transition metal compounds through combined morphology, composition, and heterointerface engineering.

Construction of CoNiSSe-g-C3N4 nanosheets with high exposed conductive interface for boosting oxygen evolution reaction

Herein, the design and manufacture of electrocatalysts based on bimetallic CoNiSSe-g-C3N4 and monometallic CoSSe-g-C3N4 are reported. A comparative research of electron transfer from bimetallic Co/Ni and monometallic Co active sites to a large amount of pyridine-N in the potential g-C3N4 to promote oxygen evolution reactions. The CoNiSSe-g-C3N4 hybrid electrocatalysts exhibited nanosheet morphology and have an average thickness of 0.92 nm. XPS indicated that metal Ni-N bonds were formed between CoNiSSe and g-C3N4, which compared with no Ni-N covalent bonds between CoSSe and g-C3N4. Meanwhile, the integration of g-C3N4 provides a 2D g-C3N4 matrix for high-efficient interfacial charge transfer. The bimetallic CoNiSSe-g-C3N4 electrocatalysts demonstrated distinguished performance toward OER accompanied by an overpotential of 282 mV (1.512 V vs. RHE) at 10 mA cm–2, Tafel slope 59 mV dec–1, which exhibited excellent current densities, small overpotentials, and good stabilities. Theoretical calculations demonstrate that the DOS intensity of the Fermi level is closely related to the conductivity of the electrocatalysts, which indicates rapid charge transfer kinetics, electron transfer process.

Synthesis, X-ray structure, Hirshfeld analysis and DFT studies of Ni(II) complexes with pyridine-type ligands and monoanionic (SCN¯, N3¯ and NO3¯) ligands

The molecular and supramolecular structures of two self-assembled Ni(II) complexes with pyridine-type ligands (34Lut: 3,4-lutidine and 4Pic: 4-picoline) comprising different anions (SCN¯, N3¯and NO3¯) were presented. The dinuclear [Ni(34Lut)3(SCN)2]2(1) complexcomprises a hexa-coordinated Ni(II) with NiN5S coordination environment from three 34Lut, one isothiocyanate, in addition to two SCN¯ connecting the two Ni(II) centres via µ(1,3) coordination mode. Structure of complex 2 has the two complex units [Ni(4Pic)4(N3)2][Ni(4Pic)4(NO3)2], in which the two Ni(II) centers have also hexa-coordinated environments with NiN6 and NiN4O2 coordination spheres. In both units, there are four 4Pic ligand units coordinating the Ni(II) via the pyridine nitrogen atom and two anions in anti-positions to one another. In the first unit, the two azides have terminal coordination mode. In the second unit, there are two monodentate nitrate ions coordinating the Ni(II) ion via one oxygen atom. Molecular packing analysis using Hirshfeld calculations revealed the importance of the S…H (20.4%) and CH…π (25.2%) interactions in 1. For complex 2, the N…H (16.2%) and O…H (20.7%) contacts are the most important in [Ni(4Pic)4(N3)2] and [Ni(4Pic)4(NO3)2] complex units, respectively. The H…H contact percentages are 50.5, 54.6 and 51.3%, respectively which are the most common in all complex units. Using DFT calculations, the charge of the Ni(II) ion decreased to 0.7792, 0.8136 and 0.9377 e in the thiocyanato, azido and nitrato complexes, respectively. Using AIM calculations, the Ni-N, Ni-S and Ni-O bonds showed the characteristics of mainly closed shell interactions.

Coordination Ability of 10-EtC(NHPr)=HN-7,8-C2B9H11 in the Reactions with Nickel(II) Phosphine Complexes

The complexation reactions of nido-carboranyl amidine 10-PrNHC(Et)=HN-7,8-C2B9H11 with different nickel(II) phosphine complexes such as [(PR2R’)2NiCl2] (R = R’ = Ph, Bu; R = Me, R’ = Ph) were investigated. As a result, a series of novel half-sandwich nickel(II) π,σ-complexes [3-R’R2P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC2B9H10] with the coordination of the carborane and amidine components was prepared. The acidification of obtained complexes with HCl led to the breaking of the Ni-N bond with formation of nickel(II) π-complexes [3-Cl-3-R’R2P-8-PrNH=C(Et)NH-closo-3,1,2-NiC2B9H10]. The crystal molecular structure of [3-Ph3P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC2B9H10] was determined by single crystal X-ray diffraction.

Flower-like Ni/N-doped carbon composites with core–shell synergistic structure for broad-band electromagnetic wave absorption

The novel microstructure of magnetic-carbonaceous composites has become a prevalent route to improve electromagnetic wave absorption (EMWA) performance. Flower-like Ni/nitrogen-doped carbon (Ni/NC-X) composites with core–shell synergistic structure, N-doping and Ni-N bonds were rationally constructed and fabricated by hydrothermal methods and thermal decomposition with carbon reduction. The Ni cores were encapsulated within approximately 15 layers of the graphene shell, leading to the generation of a Ni/NC-X core–shell configuration. The EMWA performances of Ni/NC-X composites could be adjusted by modulating the acrylonitrile (AN) content. Benefiting from the synergistic effects of the core–shell configuration, a hierarchically flower-like architecture and the components (Ni and C), the flower-like Ni/NC-0.80 composite showed remarkable EMWA performance with a reflection loss (RL) of − 40.1 dB and a broad effective absorption bandwidth (EAB) of 10.05 GHz. The result of this study establishes a new strategy to prepare magnetic-carbonaceous composites by carefully designing the microstructure.

Liquid Structure and Thermophysical Properties of Ternary Ni-Fe-Co Alloys Explored by Molecular Dynamics Simulations and Electrostatic Levitation Experiments

The structure, thermodynamic and dynamic properties of normal and metastable liquid Ni2xFe50−xCo50−x alloys were systematically investigated by combining electrostatic levitation (ESL) experiments and molecular dynamics (MD) simulations. Their composition dependence and mutual interaction were explored in detail. The actual densities of liquid Ni90Fe5Co5, Ni80Fe10Co10, Ni70Fe15Co15 and Ni60Fe20Co20 alloys were measured by ESL experiments in a wide temperature range. The simulated densities of these liquid alloys are in good agreement with the corresponding experimental data. The thermodynamic properties show that all these alloys exhibit a negative excess volume and mixing enthalpy. Meanwhile, their pair distribution functions indicate that Fe and Co atoms easily bond with Ni atoms and have a similar characteristic to each other if compared with Ni atoms. Furthermore, the structure factors validate that there exist icosahedral short-range and medium-range orders of Ni-Ni, Fe-Fe, Fe-Co and Co-Co bonds in these liquid alloys. Additionally, the solute diffusion properties reveal that the correlation between dynamic behavior and alloy composition is determined by the diffusion of Fe and Ni atoms.

Nickel (II) dibenzotetramethyltetraaza[14]annulene supported on DFNS nanoparticles catalyst in carbonylative sonogashira coupling

In this study, the carbonylative sonogashira coupling reaction was performed in the presence of CO (2 MPa) and Nitmtaa@DFNS as NPs. Nickel(II)dibenzotetramethyltetraaza[14]annulene complex (Nitmtaa) prepared and immobilized on amino-fucntionnalized DFNS (N-DFNS) via NiN (NH2) bond to obtain a stable and reusable new nanocatalyst named as Nitmtaa@DFNS. Good to superb performance products were provided deploying Nitmtaa@DFNS nanocatalyst. In addition, the anatomy of Nitmtaa@DFNS has been distinguished by various methods, including XRD, VSM, FT-IR, SEM, EDX, TEM, and TGA. In addition, the hot filtration test provided complete insight into the heterogeneity of the catalyst. The reuse and recycling of the catalyst were repeatedly investigated for coupling reactions. In addition, the mechanism of the coupling reactions was thoroughly studied.

Effect of different point-defect energetics in Ni80X20 (X=Fe, Pd) on contrasting vacancy cluster formation from atomistic simulations

Recent irradiation experiments have shown that smaller vacancy clusters are observed in Ni80Pd20 compared to Ni80Fe20. Using atomistic calculations, we find that the vacancy energetics are significantly different between the two alloys. Ni80Pd20 has lower vacancy migration barriers and lower vacancy-vacancy binding energies than Ni80Fe20. The consequence of these energetic differences is observed in molecular dynamics (MD) simulations, where despite higher vacancy diffusivity that would help in cluster formation, significantly reduced vacancy clusters are observed in Ni80Pd20 than Ni80Fe20. Calculations show that binding energy decreases and formation energy increases with increasing Ni-Ni bond lengths, and larger Ni-Ni bond lengths are observed in Ni80Pd20 than Ni80Fe20. Thus, the reduced vacancy-vacancy binding and higher formation energy due to longer Ni-Ni bonds in Ni80Pd20 are possibly the underlying reasons for smaller vacancy clusters in Ni80-Pd20 than Ni80Fe20. This study illustrates the unique effects of alloying elements on defect energetics and microstructural evolution in random alloys.

Triply Carbonyl-Bridged Ni2(CO)5 Featuring Triple Three-Center Two-Electron Ni-C-Ni Bonds Instead of Ni≡Ni Triple Bond.

Motivated by the predicted unusual short Ni-Ni bond length that is comparable to the intermetallic distance anticipated for the triple bond, the nature of Ni-Ni bonding interaction in the triply carbonyl-bridged geometry of the neutral Ni2(CO)5 complex has been investigated using a range of state-of-the-art quantum chemistry methods. The elaborate analyses manifest that the tribridged Ni2(CO)5 features triple three-center two-electron Ni-C-Ni bonds instead of Ni≡Ni triple bond. The electron pair donated by the bridging carbonyl ligand should be shared by both nickel centers to achieve the favored (18, 18) configuration.

Influence of Interatomic Interactions on the Mechanical Properties of Face-Centered Cubic Multicomponent Co-Ni-Cr-Mo Alloys

The composition of a multicomponent solid solution has a significant influence on its mechanical and microstructural properties. Herein, the microstructures, phase stabilities, mechanical properties, and interatomic interactions of multicomponent Co-(5-55)Ni-19Cr-9Mo (mass%) alloys with varying Ni contents were investigated based on correlative experimental and computational methods. First-principles calculations were performed to predict the mechanical properties, electron distributions, atomic bonding states, and density of states (DOS) of the alloy system. The local charge distribution revealed that the alloying elements exhibit stronger bonds with Co atoms than with Ni atoms, and the Ni-Ni bond is the weakest; accordingly, an increase in the Ni content generally diminishes the interatomic interactions in the Co-Ni-Cr-Mo alloy system, which is consistent with the experimental results. Meanwhile, significant augmentations in the strength, hardness, and elastic modulus were observed at 45 mass% Ni. This can be attributed to the additional interactions between the second-nearest Ni atoms with vacant 3d-states, which are prevalent in 45-55 mass% Ni alloys, in the unit form of quartets of four Ni atoms or three Ni atoms and one Co atom. An axial next-nearest-neighbor Ising (ANNNI) model was employed to calculate the stacking fault energies (SFEs) and elucidate the strain-hardening behaviors. A similar trend in the SFE variations was obtained using a parameter-updated thermodynamic model under special consideration of the concentration dependence of the Co-Ni interaction, which indicated the significant influence of interatomic interactions at elevated temperatures.

Enhancing easy-plane anisotropy in bespoke Ni(II) quantum magnets

We examine the crystal structures and magnetic properties of several S = 1 Ni(II) coordination compounds, molecules and polymers, that include the bridging ligands HF2−, AF62− (A = Ti, Zr) and pyrazine or non-bridging ligands F−, SiF62−, glycine, H2O, 1-vinylimidazole, 4-methylpyrazole and 3-hydroxypyridine. Pseudo-octahedral NiN4F2, NiN4O2 or NiN4OF cores consist of equatorial Ni-N bonds that are equal to or slightly longer than the axial Ni-Lax bonds. By design, the zero-field splitting (D) is large in these systems and, in the presence of substantial exchange interactions (J), can be difficult to discriminate from magnetometry measurements on powder samples. Thus, we relied on pulsed-field magnetization in those cases and employed electron-spin resonance (ESR) to confirm D when J ≪ D. The anisotropy of each compound was found to be easy-plane (D > 0) and range from ≈ 8–25 K. This work reveals a linear correlation between the ratio d(Ni-Lax)/d(Ni-Neq) and D although the ligand spectrochemical properties may play an important role. We assert that this relationship allows us to predict the type of magnetocrystalline anisotropy in tailored Ni(II) quantum magnets.

Unsaturated binuclear homoleptic nickel carbonyl anions Ni2(CO)n- (n = 4-6) featuring double three-center two-electron Ni-C-Ni bonds.

The homoleptic homodinuclear nickel carbonyl anions Ni2(CO)n- (n = 4-6) are mass-selected in the gas phase and examined with anion photoelectron velocity-map imaging spectroscopy combined with density functional calculations. The doubly carbonyl-bridged structures are found to be favorable for Ni2(CO)n- (n = 4-6). The nature of Ni-Ni bonding in these complexes is analysed with the aid of a range of state-of-the-art quantum chemistry methods. Despite the absence of direct multiple Ni-Ni bonds, the two nickel atoms in Ni2(CO)n- (n = 4-6) complexes are joined by two bridging carbonyl ligands via the sharing three-center two-electron Ni-C-Ni bond in turn to achieve the (16,16), (16,18), and eventually the favored (18,18) configurations.

Highly dispersed nickel anchored on a N-doped carbon molecular sieve derived from metal-organic frameworks for efficient hydrodeoxygenation in the aqueous phase.

ZIF-8 was employed as a template to synthesize HD-Ni/N-CMS containing highly dispersed Ni at the atomic level anchored on a N-doped carbon molecular sieve for vanillin hydrodeoxygenation. The ZIF-8 structure was inherited and Ni-N bonds were formed by the coordination of Ni with N-rich defects, therefore it exhibited a high turnover frequency (1047.1 h-1) and good stability.

An unusual partial occupancy of labile chloride and aqua ligands in cocrystallized isomers of a nickel(II) complex bearing a tripodal N4-donor ligand.

A novel Ni2+ complex with the N4-donor tripodal ligand bis[(1-methyl-1H-imidazol-2-yl)methyl][2-(pyridin-2-yl)ethyl]amine (L), namely, aqua{bis[(1-methyl-1H-imidazol-2-yl-κN3)methyl][2-(pyridin-2-yl-κN)ethyl]amine-κN}chloridonickel(II) perchlorate, [NiCl(C17H22N6)(H2O)]ClO4 or [NiCl(H2O)(L)Cl]ClO4 (1), was synthesized and characterized by spectroscopic and spectrometric methods. The crystal structure of 1 reveals an interesting and unusual cocrystallization of isomeric complexes, which are crystallographically disordered with partial occupancy of the labile cis aqua and chloride ligands. The Ni2+ centre exhibits a distorted octahedral environment, with similar bond lengths for the two Ni-N(imidazole) bonds. The bond length increases for Ni-N(pyridine) and Ni-N(amine), which is in agreement with literature examples. The bond lengths of the disordered labile sites are also in the expected range and the Ni-Cl and Ni-O bond lengths are comparable with similar compounds. The electronic, redox and solution stability behaviour of 1 were also evaluated, and the data obtained suggest the maintenance of structural integrity, with no sign of demetalation or decomposition under the studied conditions.

Catalytic Conversion of Atmospheric CO2 into Organic Carbonates by Nickel(II) Complexes of Diazepane-Based N4 Ligands.

Activation of CO2 and conversion into value-added products is an effective option to mitigate CO2 emission. The nickel(II) complexes [Ni(L1)](ClO4)2 1, [Ni(L2)](ClO4)2 2, and [Ni(L3)(CH3CN)2](Ph4B)2 3 of diazepane-based ligands [1,4-bis[(pyridin-2-yl-methyl)]-1,4-diazepane (L1), 1,4-bis[2-(pyridin-2-yl)ethyl]-1,4-diazepane (L2), and 4-bis[2-(quinoline-2-yl)-methyl]-1,4-diazepane (L3)] have been synthesized and structurally characterized. The complexes were employed as the catalysts for the conversion of atmospheric CO2 into organic carbonates in the absence of cocatalyst at 1 atm pressure. The single-crystal X-ray structures of 1 and 2 exhibit distorted square-planar geometry with almost identical Ni-N bond distances (1.891-1.946 Å). The geometry of the complexes rearranged into octahedral in acetonitrile, which was studied by paramagnetic 1H NMR and electronic spectra. The complexes selectively captured CO2 from the atmospheric air and readily converted epoxides into cyclic carbonates without any cocatalyst. They showed a maximum yield of 25% (TON, 500) using 1 atm air, which is drastically enhanced up to 89% (TON, 1780) using 1 atm pure CO2 gas. This is the highest catalytic efficiency reported for CO2 fixation using nickel-based catalysts to date. The CO2 fixation reaction without organic substrate showed the formation of carbonate-bridged dinuclear nickel(II) complexes. They showed characteristic absorption bands around 571-612 nm and were further confirmed by electrospray ionization mass spectrometry, IR, and single-crystal X-ray structures. The molecular structure of carbonate-bridged intermediates exhibited two Ni2+-centers with distorted square pyramidal geometries for 2a and 3a but distorted octahedral and square pyramidal geometries for 1a. The CO2 fixation reactions possibly proceeded via the formation of CO2-bound nickel species.

An efficient high-frequency electromagnetic wave absorber: Nickel-N@Carbon composite

The nickel-N@carbon composite (Ni-N@C) with size of 4.0–5.0 μm was prepared, in which the Ni-N bonds were formed in the carbonization process. The Ni-N bonds between metallic Ni and N provide different surface electron distribution and contribute to the high-frequency electromagnetic wave absorption (EMWA) of Ni-N@C composite. The Ni-N bonds in the Ni-N@C composite have been confirmed by X-ray diffraction, Raman spectrum, X-ray photoelectron spectroscopy. Compared with Ni@C composite and reported Ni-based materials, the Ni-N@C composite shows the stronger reflection loss (RL = −32.31 dB) and wider effective absorption band (EAB, RL < −10 dB) at the high frequency (12.79–18 GHz), which can be ascribed to Ni-N bonds. Besides, the EMWA characteristics of Ni-N@C composites are flexibly adjusted by tuning the pyrrole monomers to obtain optimized impedance matching, which is beneficial for broadening the EAB. All C, X and Ku bands (3.90–18.0 GHz) can be covered through changing the Ni content and layer thickness for Ni-N@C composites.

The 4-Electron Cleavage of a N═N Double Bond by a Trimetallic TiNi2 Complex.

The synthesis and reactivity of a new trimetallic complex Ti(NP)4Ni2 (NP = 2-diphenylphosphinopyrrolide) (3) is reported. Single-crystal X-ray diffraction and X-ray absorption studies point to a unique bonding motif: a d10-d10, Ni0-Ni0 bond stabilized by a proximal d0 TiIV metal center. The coordination chemistry of 3 with a variety of L (L = isocyanide and alkyne) donors has also been explored. In the case of isocyanide coordination, the Ni-Ni bond is broken, while diphenylacetylene binding results in a symmetric butterfly μ2-κ2-alkyne bridge across the Ni-Ni moiety. Finally, complex 3 is capable of the 4-electron cleavage of the N═N double bond in benzo[c]cinnoline, the first example of N═N bond cleavage by Ni. The resulting product, 7, has been characterized structurally and spectroscopically, and the mechanistic implications are discussed in the context of metal-metal cooperativity.

Mechanistic Study on Decarbonylative Phosphorylation of Aryl Amides by Nickel Catalysis.

The phosphorylation of amide represents an unprecedented environmentally friendly and easily achievable method to constitute C-P bonds in organic synthesis. In this study, the mechanisms for the nickel-catalyzed direct decarbonylative phosphorylation of amides recently reported by Szostak's team were systematically studied with density functional theory calculations. The reaction mainly undergoes four steps: oxidative addition (rate-determining step), phosphorylation, decarbonylation, and reductive elimination. The structures of the substrate and Na2CO3 were found to be critical for the reaction efficiency. Substrates bearing electron-withdrawing groups like carbonyl groups near the amide bond facilitate the reaction by weakening the C-N bond, and Na2CO3 can not only neutralize the H atom in the phosphate ligand as an alkali but also activate the Ni-N bond through the coordination bond with the adjacent carbonyl of the amide group.

Influence of hydrogen environment on dislocation nucleation and fracture response of 〈1 1 0〉 grain boundaries in nickel

The segregation of solute H has a profound effect on mechanical properties of grain boundaries (GBs). In this work, systematic molecular dynamics (MD) simulations have been performed to elucidate the influence of H environment on dislocation nucleation process and fracture response of different Ni GBs. The results show that the effect of H on dislocation nucleation depends strongly on GB structures. The presence of H decreases the yield stress required to nucleate dislocations from GBs with C and D structural units (SUs), while increases the yield stress of GBs with E SUs. This difference is attributed to different deformation mechanisms related to the dislocation nucleation from various GBs with H. By analysing the decohesion results, it is found that H has stronger embrittling effect on GBs with E SUs than C and D SUs, originating from the fact that H significantly elongates the Ni-Ni bonds around the open E SUs while slightly expands the compact C and D SUs. These findings present fundamental understanding on H embrittlement mechanism and provide mechanistic insights for engineering microstructure against H embrittlement in metallic materials.

Crystal structure of bis-{μ-2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}bis-({2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}nickel(II)) involving different coordination modes of the same Schiff base ligand.

The structure of the title compound, [Ni2(C9H10NO2)4], is built up by discrete centrosymmetric dimers. Two nitro-gen and three oxygen atoms of two Schiff base ligands singly deprotonated at the phenolate site form a square-pyramidal environment for each metal atom. The ligands are bonded differently to the metal centre: one of the phenolic O atoms is bound to one nickel atom, whereas another bridges the two metal atoms to form the dimer. The Ni-N/O distances fall in the range 1.8965 (13)-1.9926 (15) Å, with the Ni-N bonds being slightly longer; the fifth contact of the metal to the bridging phenolate oxygen atom is substanti-ally elongated [2.533 (1) Å]. A similar coordination geometry was observed in the isomorphous Cu analogue previously reported by us [Sydoruk et al. (2013 ▸). Acta Cryst. E69, m551-m552]. In the crystal, the [Ni2 L 4] mol-ecules form sheets parallel to the ab plane with the polar meth-oxy groups protruding into the inter-sheet space and keeping the sheets apart. Within a sheet, the mol-ecules are stacked relative to each other in such a way that the Ni2O2 planes of neighbouring mol-ecules are orthogonal.