X-ray photoelectron spectra and structure of polynuclear nickel complexes

Mono- and binuclear nickel complexes of different stoichiometry have been studied by X-ray photoelectron spectroscopy (XPS). The Ni2p, Ni3p, and N1s X-ray photoelectron spectra have been examined, and the role of a ligand in their formation has been determined. As distinct from a low-spin Ni(II) complex, the Ni2p spectra of high-spin Ni(II) compounds show strong satellite lines. For high-spin Ni(II) complexes, which have unpaired 3d electrons, the Ni2p _1/2-Ni2p _3/2 spin-orbit splitting is larger than that for a low-spin Ni(II) compound. The presence or absence of the satellite structure has made it possible to classify these complexes with regard to their magnetic properties. The difference between the Ni2p _3/2 and N1s binding energies has made it possible to estimate the covalence of the metal-ligand bond. The XPS results are consistent with X-ray crystallography data.     

Synthesis and crystal structure of a cyanide-bridged one-dimensional nickel complex with <Emphasis Type="Italic">trans</Emphasis>-Cn-Ni(En)<Subscript>2</Subscript>-CN structure

The synthesis and crystal structure of the cyano-bridged complex {Ni(En)₂[Ni(CN)₄]} _n are reported. The complex was synthesized by the reaction of [Ni(En)₂](ClO₄)₂ and K₂[Ni(CN)₄] in an H-shaped tube. The crystals are monoclinic, space group P2₁/c with a = 7.0917(4), b = 10.6629(5), c = 9.4975(5) Å, β = 108.193°, M = 170.85, Z = 4, V = 682.27(6) ų. The title complex reveals the trans-CN-Ni(En)₂-NC structure.     

Synthesis and crystal structure of a cyanide-bridged one-dimensional nickel(II) complex with alternating [Ni(En)<Superscript>2</Superscript>]<Superscript>2+</Superscript> and [Ni(CN)<Subscript>4</Subscript>]<Superscript>2−</Superscript> ions

The complex [Ni(En)₂][Ni(CN)₄] · 3.5H₂O (I) (En = ethylenediamine) was synthesized by the reaction of [Ni(En)₂](ClO₄)₂ and K₂[Ni(CN)₄] in an H-shaped tube. The crystal structure of I has been determined by single-crystal X-ray analysis. The crystal of complex I is orthorhombic, space group Pnna with a = 28.151(3), b = 8.3946(8), c = 14.5441(13)Å, M =404.76, Z = 8, V = 3437.0(5)ų. The structure of complex I reveals infinite zigzag chains shaped structure are formed by cis-Ni(En)₂-μ-(NC)₂, cis-μ-(NC)₂Ni(CN)₂, and trans-μ-(CN)₂Ni(En)₂.     

Solubility and Solution Thermodynamic Properties of 4-(4-Hydroxyphenyl)-2-butanone (Raspberry Ketone) in Different Pure Solvents

The solubility of 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone) in six pure solvents was experimentally determined at temperatures ranging from 283.15 to 313.15 K under the pressure 0.10 MPa by employing a gravimetrical method. The experimental results indicate that the solubility of raspberry ketone in all studied solvents is temperature dependent, a rise in temperature brings about an increase in solubility. The experimental solubility data of raspberry ketone in six pure solvents (acetone, ethanol, ethyl acetate, n-propyl alcohol, n-butyl alcohol, and distilled water) was correlated by using several commonly used thermodynamic models, including the Apelblat, van’t Hoff and λh equations. The results of the error analysis indicate that the van’t Hoff equation was able to give more accurate and reliable predictions of solubility with root-mean-square deviation less than 0.56%. Furthermore, the changes of dissolution enthalpies (Δ_diss H°), dissolution entropies (Δ_diss S°) and dissolution Gibbs energies (Δ_diss G°) of raspberry ketone in the solvents studied were estimated by the van’t Hoff equation. The positive value of Δ_diss H°, Δ_diss S°, and Δ_diss G° indicated that these dissolution processes of raspberry ketone in the solvents studied were all endothermic and enthalpy-driven.     

Structural studies of nickel(II) complexes with 1-<Emphasis Type="Italic">tert</Emphasis>-butylimidazole-2-thione and 3-phenyl-5-methyl-pyrazole ligands

The nickel(II) complexes dichlorobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂Cl₂] (1), dinitratobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂(NO₃)₂] (2), dichloro-bis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)Cl₂] (3) and dinitratobis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)(NO₃)₂] (4) have been synthesized and studied. The single crystal X-ray diffraction analysis was carried out for 1 and 4 {Bruker Kappa Apex-II CCD diffractometer, MoK _α radiation}. Crystal data for 1: monoclinic C2/c, a = 16.949(2) Å, b = 8.6647(10) Å, c = 15.461(3) Å, β = 117.662(4)°, V = 2011.1(5) ų, Z = 4, D _calc = 1.460 g/cm³. Crystal data for 4: triclinic P-1, a = 9.9775(7) Å, b = 11.2254(8) Å, c = 14.8068(10) Å, α = 75.401(4)°, β = 87.422(4)°, γ = 74.874(4)°, V = 1548.86(19) ų, Z = 2, D _calc = 1.405 g/cm³. Coordination core of complex 1 adopts distorted tetrahedral geometry whereas core 4 has distorted octahedral geometry. The bonded nitrates are of two types coordinating as monodentate and bidentate ligands.     

Crystal structure of a complex of nickel(II) with 2-amino-4-imino-2-pentene

The structure of a nickel(II) complex with 2-amino-4-iminopentane is determined by X-ray crystallography at 150 K. Crystal data for C₁₀H₁₈N₄Ni are: a = 10.9802(3)Å, b = 13.5780(4)Å, c = 8.0935(2)Å, β = 107.304(1)°, space group P2₁/c, V = 1152.04(5) ų, Z = 4, d _x = 1.459 g/cm³, R = 0.0283. The structure is molecular; the metal atom is coordinated by four nitrogen atoms of two β-diimine ligands. The Ni-N distances in Ni(NacNac)₂ fall within 1.8571–1.8623 Å. The molecules in the crystal are joined by only van der Waals interactions.     

Thermochemistry of glycyl-<Emphasis Type="Italic">DL</Emphasis>-α-alanine dissolution in water-alcohol solutions at 298.15 K

Integral enthalpies of glycyl-DL-α-alanine dissolution in aqueous solutions of ethanol, 1-propanol, and 2-propanol at concentrations of alcohols up to 0.4 mol fraction were measured by the calorimetry method. Standard values of the enthalpies of the peptide dissolution Δ_sol H ⁰ and transfer Δ_tr H ⁰ from water in mixed solvents were calculated. Dependences of the thermochemical characteristics of glycyl-DL-α-alanine dissolution on the concentration of cosolvents are of an extreme character. Within the limits of McMillan-Mayer’s theory enthalpy coefficients of pairwise interactions (h _xy ) of the studied compound with molecules of alcohols were calculated. They have positive values increasing in the series ethanol, 1-propanol, 2-propanol. The effect of the structure of dipeptides and composition of water-alcohol solvents on the dissolution enthalpy characteristics was considered on the basis of the obtained experimental and calculated data.     

Crystal structure of [(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>P][Ni(B<Subscript>9</Subscript>C<Subscript>2</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]·CCl<Subscript>4</Subscript>

A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C₆H₅)₄P][Ni(B₉C₂H₁₁)₂]·CCl₄, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C₂₉H₄₂B₁₈PCl₄Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) ų, Z = 2, d _calc = 1.348 g/cm³. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R ₁ = 0.0466 for 3055 I _hkl ≥ 2σ _I of 23,655 reflections collected and 5618 independent I _hkl (Bruker X8 APEX diffractometer, λMoK _α).     

Iridium–nickel composite oxide catalysts for oxygen evolution reaction in acidic water electrolysis

A series of Ir_1–xNi_xO_2–y (0 ≤ x ≤ 0.5) composite oxides have been prepared by a simple pyrolysis method in ethanol system and used as the electrocatalysts for OER in acidic medium. The materials have been characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). The electrochemical performances of these Ir_1–xNi_xO_2–y composite catalysts are evaluated by cyclic voltammetry (CV) and steady-state measurements. The resulting oxides with the Ni content (x) less than 0.3 have a complex nature of metal Ir and rutile structure IrO₂ which is similar to the Ir oxide prepared by the same approach and possess the contracted lattice resulted from the Ni-doping. Although the addition of Ni reduces the electroactive surface areas due to the coalescence of particles, the catalytic activity of the Ir_1–xNi_xO_2–y (0 < x ≤ 0.3) catalysts is slightly higher than that of the pyrolyzed Ir oxide. Regardless of the surface area difference, the intrinsic activity first increases and then decreases with the Ni content in Ir_1–xNi_xO_2–y catalysts, and the intrinsic activity of Ir_0.7Ni_0.3O_2–y catalyst is about 1.4 times of the Ni-free Ir oxide mainly attributed to the enhancement of conductivity and a change of the binding energy as increasing amount of the incorporated Ni with respect to the pure IrO₂. The Ir_0.7Ni_0.3O_2–y catalyst shows a prospect of iridium-nickel oxide materials in reducing the demand of the expensive Ir oxide catalyst for OER in acidic water electrolysis.     

Co(II) and Ni(II) complexes incorporating <Emphasis Type="Italic">N</Emphasis>-acetimidoylacetamidine ligand: Synthesis and structures

Two new square planar complexes with the formula Co(L)₂ · CH₃OH (1) and Ni(L)₂ · CH₃OH (2) (HL = HN{C(Me)=NH}₂ = N-acetimidoylacetamidine) have been synthesized by solvothermal reactions in methanol/acetonitrile. N-acetimidoylacetamidine ligand was derived from the self-condensation reaction of acetonitrile, and the reaction was promoted by the cooperation of M(II) (M = Co in 1 and M = Ni in 2) with diphenylcarbazide. 1 and 2 are characterized by single crystal X-ray diffraction, elemental analysis and infrared spectrum. Both complexes crystallize in the monoclinic space group P2₁/c with a = 9.329(6) Å, b = 11.494(7) Å, c = 13.040(8) Å, β = 92.945(11)°, V = 1396.3(16) ų and Z = 4 for 1, and a = 9.323(4)Å, b = 11.512(5) Å, c = 13.020(6)Å, β = 92.819(7)°, V = 1395.7(10)ų and Z = 4 for 2.     

Enthalpy characteristics of the dissolution of L-valine in water/formamide mixtures at 298.15 K

The thermochemical dissolution of L-valine in solvent mixtures H₂O + (formamide, N-methylformamide, and N,N-dimethylformamide) is studied at an organic component concentration of x₂ = 0–0.35 molar fractions and a temperature of 298.15 K. The experimental data are used to calculate standard enthalpies of dissolution, the transferring of L-valine from water to a mixed solvent, and the enthalpy coefficients of pairwise interactions (h_xy) with organic solvent molecules. The correlation between the enthalpy characteristics of the dissolution of L-valine with the composition of aqueous organic mixtures and the nature of the organic solvent (its physicochemical properties) is determined. A comparative analysis of the values of h_xy of a number of aliphatic L-amino acids in similar solvent mixtures with the hydrophobicity parameters of their side chains is performed.     

Analysis of the fine structure of XANES spectra over Ni<Emphasis Type="Italic">K</Emphasis> edge in Ni(EtOCS<Subscript>2</Subscript>)<Subscript>2</Subscript>

The NiK edge X-ray absorption near edge spectra (XANES) of the Ni(EtOCS₂)₂ complex were measured. The theoretical NiK edge XANES spectra were calculated by the total multiple scattering and finite difference methods; the potential was calculated with a muffin-tin approximation and without it. It is shown that inclusion of the non-muffin-tin effects is important for modeling the NiK XANES spectrum for the Ni(EtOCS₂)₂ complex; good agreement with experiment was achieved only in the calculations with the total potential (without the muffin-tin approximation for the shape of the potential).     

Strontium nickel and barium nickel selenites: Synthesis and X-ray diffraction parameters

A new strontium nickel selenite, Sr₂Ni(SeO₃)₃, was prepared and structurally characterized. The compound crystallizes in triclinic system (space group P \(\bar 1\), a = 7.2860(10) Å, b = 7.581(2) Å, c = 8.722(2) Å, α = 103.02(2)°, β = 105.580(10)°, γ = 95.260(10)°, Z = 2) and is isostructural to cobalt and copper analogues. The structure of Sr₂Ni(SeO₃)₃ is a three-dimensional framework built of eight-vertex polyhedra [SrO₈] and distorted octahedra [NiO₆] sharing edges and vertices. The framework channels accommodate selenium atoms bonded to the framework oxygen atoms. The selenite groups SeO₃ are pyramidal, which is indicative of high stereochemical activity of the Se(IV) lone pair. The possibility of replacement of some Ni atoms by Cu in Sr₂Ni(SeO₃)₃ was studied. The search for analogous barium phases did not reveal such compounds, but BaM(SeO₃)₂ phases were found, where M = Co, Ni, or Cu. The unit cell parameters of the new selenite BaM(SeO3)2 were determined: space group Pnma, a = 14.989(5) Å, b = 5.439(2) Å, c = 7.161(3) Å, Z = 4.     

Thermochemical study of the complex formation of copper(II) and nickel(II) iminodiacetates with amino acids in aqueous solutions

The formation of mixed-ligand complexes in the M(II)–Ida–L systems (M = Cu, Ni, L = His, Orn, Lys), where Ida is the iminodiacetic acid residue, was studied by pH-metry, calorimetry, and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of formation of the complexes were determined at 298.15 K and the ionic strength I = 0.5 (KNO₃). The most probable mode of coordination of the chelating agent and the amino acid in the mixed-ligand complexes was elucidated.     

Microwave-assisted Ni–La/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for benzene hydrogenation

A series of Ni–La/γ-Al₂O₃ catalysts were prepared by adopting the methods of isometric impregnation and microwave impregnation. The catalysts were characterized with XRD, BET, and SEM, respectively. Inspecting the effects of adding La and the methods of impregnation on the hydrogenation activity of catalysts. The results show that adding a moderate amount of La promotes the dispersing of Ni on the carrier, the methods of microwave impregnation weaks the interaction between Ni and the carrier further, inhibits the formation of NiAl₂O₄, and the activity of catalyst prepared by the methods of microwave impregnation was significantly higher than that prepared by the methods of isometric impregnation. The hydrogenation activity of the Ni–La/γ-Al₂O₃ (WB) dipped with n(Ni): n(La) = 4: 1, microwave irradiation time 30 min with power 600W as well as calcined at 400°C exhibited the best performance. The conversion rate is 91.21% with reaction conditions: T = 160°C, p = 0.8 MPa, air speed 5 h^–1, n(H₂): n(benzene) = 2: 1.     

Micromechanism of Cu and Fe alloying process on the martensitic phase transformation of NiTi-based alloys: First-principles calculation

Using first-principles pseudo-potential plane wave method, the formation enthalpy ΔH, binding energy ΔE, elastic constants, and electronic structure were calculated and analyzed carefully for NiTiX (X = Cu, Fe) shape memory alloy. The results show that the Cu or Fe element prefers to occupy the Ni site in the NiTi matrix phase respectively. Compared with the NiTi matrix phase, the ΔH, ΔE, c ₄₄ and c′ of NiTi (Cu) are similar to each other. However, the structural stability of the NiTi phase is improved obviously by the Fe alloying process. Simultaneously, the shear modulus c ₄₄ and c′ of NiTi (Fe) are larger than those of the NiTi matrix phase. Furthermore, Milliken population results indicate that Q _Cu–Ti is smaller than Q _Ni–Ti after the Cu alloying process, but Q _Fe–Ti is larger than Q _Ni–Ti. The electron density difference shows that some covalent bonding exists between Fe and Ti elements. Based on the upward analysis, the difference in the phase stability and elastic constants of NiTiX (X = Cu, Fe) is the substantial mechanism for the different M _s of NiTiX (X = Cu, Fe) although Cu or Fe substitutes for the same atom Ni elements in the NiTi matrix phase.     

Solvothermal synthesis and crystal structure of a 1d coordination polymer: [Ni(1,4-BDC)(N-MIM)<Subscript>2</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (1,4-BDC = 1,4-benzenedicarboxylic acid,N-MIM = <Emphasis Type="Italic">N</Emphasis>-methylimidazole)

A new metal-organic coordination polymer, namely [Ni(1,4-BDC)(N-MIM)₂] _n (I) (1,4-BDC = 1,4-benzenedicarboxylic acid and N-MIM = N-methylimidazole), has been synthesized under solvothermal conditions by using N-MIM as solvent and characterized by elemental analysis, IR, and X-ray single-crystal diffraction. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic system, space group C2/c. The 1,4-BDC ligand adopts a bis(bidentate) chelating mode to connect two adjacent Ni(II) centers to form a one-dimensional (1D) zigzag chain. The adjacent chains are further linked through hydrogen bonds and π-π stacking interactions, forming a three-dimensional (3D) supramolecular framework. The unit cell parameters for I: a = 17.250(10), b = 7.214(4), c = 16.506(7)Å, β = 125.53(4)°, V = 1671.6(15)ų, Z = 4.     

Structure and stability of a clathrate of bis(dibenzoylmethanato)-dipyridine-nickel(II) with acetone (1:2)

An inclusion compound of constant composition [Ni(DBM)₂Py₂]·2(CH₃COCH₃) is synthesized, Ni = Ni(II), DBM is dibenzoylmethanate-anion (C₆H₅CO)₂CH^?, Py is pyridine. The compound and its dissociation products are examined by structural and thermal analysis, as well as vapor pressure measurements. The crystal structure of the clathrate is solved in the monoclinic space group P2₁/n (temperature 173 K, a = 11.8617(9) Å, b = 10.0096(6) Å, c = 17.2895(9) Å, β = 96.72(1)°, V = 2038.7(2) ų, Z = 2, final R ₁ = 0.032). The host molecule [Ni(DBM)₂Py₂] is an uncharged octahedral complex, the central Ni(II) atom being surrounded by two DBM-anions in the equatorial plane and two terminal pyridines in the axial positions. Pairs of guest molecules are located in the voids of the molecular crystal. Calculated packing coefficients of the clathrate and the stable form of the host complex are 0.685(2) and 0.668(1) at 173 K, respectively. Isochoric melting of the clathrate has incongruent nature and occurs at 58–60°C to yield the solid phase of the host complex, while in air the complex decomposes in gaseous acetone and a metastable form of the host (apohost). The collapse of the metastable form of [Ni(DBM)₂Py₂] to the stable one takes place at 131°C with the release of 11 kJ/mol. The equilibrium vapor pressure of acetone over the clathrate is measured with the spoon gauge technique in a temperature interval from 292 K to 310 K (at 298 K the pressure is 0.48P ₀, P ₀ is the saturated vapor pressure of liquid acetone at this temperature). The experimental dependence logP ? 1/T is used to derive thermodynamic parameters of the process of clathrate dissociation 1/2[Ni(DBM)₂Py₂]· 2(CH₃COCH₃)(s) = 1/2[Ni(DBM)₂Py₂](s) + CH₃COCH₃(gas): ΔH _av ⁰ = 53±3 kJ/mol, ΔS _av ⁰ = 160±10 J/(mol·K), ΔG ₂₉₈ ⁰ = 4.74±0.07 kJ/mol.     

Hydrothermal synthesis and crystal structure of a novel nickel(II) complex: [Ni(H<Subscript>2</Subscript>Bibzim)<Subscript>3</Subscript>Cl<Subscript>2</Subscript> · 2H<Subscript>2</Subscript>O] (H<Subscript>2</Subscript>Bibzim = 2,2-Bibenzimidazole)

A novel organic-inorganic hybrid compound based on weak intermolecular interactions formulated as Ni(H₂Bibzim)₃Cl₂ · 2H₂O (H₂Bibzim = 2,2-bibenzimidazole, formula, C₁₄H₁₀N₄) has been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction analyses, and IR spectra. It crystallizes in the orthorhombic system, space group Pbcn, Z = 2, a = 20.8530(19), b = 15.7838(14), c = 12.3159(11) Å, V = 4053.7(6) ų, M _r = 1736.84, ρ_c = 1.423g/cm³, λ = 0.71073 Å, μ(MoK _α) = 0.664 mm^?1, F(000) = 1792, R = 0.0283 and wR = 0.0707 for 3746 observed reflections with I > 2σ(I). The complex is composed of mononuclear cations [Ni(H₂Bibzim)₃]²⁺, chlorine anions, and lattice water molecules, which are linked into a two-dimensional supramolecular architectures via hydrogen bonds and π-π-stacking interactions.     

Thermodynamic characteristics of the dissolution of glycine,glycylglycine, and glycylglycylglycine in aqueous solutions of sodium dodecyl sulfate at <Emphasis Type="Italic">Т</Emphasis> = 298.15 K

the enthalpies of dissolution of glycine (Gly), glycylglycine (GlyGly), and glycylglycylglycine (GlyGlyGly) are measured in aqueous solutions of sodium dodecyl sulfate (SDS) at SDS concentrations m = 0–0.7 mol kg^?1 and Т = 298.15 K by means of calorimetry. The obtained data are used to calculate the standard values of enthalpies of dissolution (Δ_sol H ^m ) and enthalpies of transfer (Δ_tr H ^m ) of glycine and its oligomers from water to SDS aqueous solutions. The dependences of Δ_sol H ^m and Δ_tr H ^m on SDS concentration in an aqueous solution at a constant concentration of glycine and its oligomers are determined. A comparative analysis of the thermodynamic characteristics of Gly, GlyGly, and GlyGlyGly transfer within the studied range of SDS concentrations is performed. The results are interpreted in terms of ion–ion, ion–polar, and hydrophobic interactions between SDS and molecules of glycine and its oligomers.