Generalized Low‐Temperature Fabrication of Scalable Multi‐Type Two‐Dimensional Nanosheets with a Green Soft Template

Two‐dimensional nanosheets with high specific surface areas and fascinating physical and chemical properties have attracted tremendous interests because of their promising potentials in both fundamental research and practical applications. However, the problem of developing a universal strategy with a facile and cost‐effective synthesis process for multi‐type ultrathin 2 D nanostructures remains unresolved. Herein, we report a generalized low‐temperature fabrication of scalable multi‐type 2 D nanosheets including metal hydroxides (such as Ni(OH)₂, Co(OH)₂, Cd(OH)₂, and Mg(OH)₂), metal oxides (such as ZnO and Mn₃O₄), and layered mixed transition‐metal hydroxides (Ni‐Co LDH, Ni‐Fe LDH, Co‐Fe LDH, and Ni‐Co‐Fe layered ternary hydroxides) through the rational employment of a green soft‐template. The synthesized crystalline inorganic nanosheets possess confined thickness, resulting in ultrahigh surface atom ratios and chemically reactive facets. Upon evaluation as electrode materials for pseudocapacitors, the Ni‐Co LDH nanosheets exhibit a high specific capacitance of 1087 F g^?1 at a current density of 1 A g^?1, and excellent stability, with 103 % retention after 500 cycles. This strategy is facile and scalable for the production of high‐quality ultrathin crystalline inorganic nanosheets, with the possibility of extension to the preparation of other complex nanosheets.     

1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐2‐aryliminoacenaphthylylnickel halides highly polymerizing ethylene for the polyethylenes with high branches and molecular weights

A series of 1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐ 2‐aryliminoacenaphthylene derivatives ( L1–L5 ) and their halonickel complexes LNiX₂ (X = Br, Ni1–Ni5 ; X = Cl, Ni6–Ni10 ) are synthesized and well characterized. The molecular structures of representative complexes Ni2 and Ni4 are confirmed as the distorted tetrahedron geometry around nickel atom by the single crystal X‐ray diffraction. Upon activation with methylaluminoxane, all nickel complexes show high activities up to 1.49 × 10⁷ g of PE (mol of Ni)^?1 h^?1 toward ethylene polymerization, producing polyethylenes with high branches and molecular weights up to 1.62 × 10⁶ g mol^?1 as well as narrow polydispersity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1369–1378     

Magnetic Coupling in Enantiomerically Pure Trinuclear Helicate‐Type Complexes Formed by Hierarchical Self‐Assembly

Based on chiral, enantiomerically pure 7‐[(S)‐phenylethylurea]‐8‐hydroxyquinoline ( 1 ‐H), trinuclear helicate‐type complexes 2 – 5 are formed with divalent transition‐metal cations. X‐ray structural analyses reveal the connection of two monomeric complex units [M( 1 )₃]^? (M=Zn, Mn, Co, Ni) by a central metal ion to form a “dimer”. Due to the enantiopurity of the ligand, the complexes are obtained as pure enantiomers, resulting in pronounced circular dichroism (CD) spectra. Single‐ion effects and intra‐ and intermolecular coupling are observed with dominating ferromagnetic coupling in the case of the cobalt(II) and nickel(II) and dominating antiferromagnetic coupling in the case of the manganese(II) complex.     

Synthesis and Structural Characterization of a Novel Heterodinuclear Vanadium(IV)‐Nickel(II) Complex

A novel V^IV‐Ni^II heterodinuclear complex [VO(cat)₂][Ni(1, 2‐PDA)₂H₂O] ( 1 ) (cat = catechol; 1, 2‐PDA = 1, 2‐propane diamine) was synthesized at low temperature (10 °C) and characterized by IR spectroscopy and X‐ray diffraction. A novel Ni–O=V structure exists in the complex, the vanadyl–catechol moiety and the nickel–diamine moiety are connected by an oxygen bridge; all molecules are further assembled into crystallites by O–H ··· O hydrogen bonds.     

A New Two‐Dimensional Manganese(II) Coordination Polymer Constructed from Trinuclear Molecular Building Block: Syntheses,Structure and Magnetic Property

A new manganese(II) coordination polymer, [Mn₃(atpt)₃(2, 2′‐bpy)₂]_n ( 1 ) (H₂atpt = 2‐aminoterephthalic acid; 2, 2′‐bpy = 2, 2′‐bipyridine), was synthesized by hydrothermal reaction of Mn(OAc)₂, H₂atpt, and 2, 2′‐bpy. It was structurally characterized by element analysis, IR spectroscopy, powder XRD, and magnetic measurements. X‐ray single‐crystal analysis was carried out for 1 , which crystallizes in the orthorhombic system, space group Pbca. The single X‐ray diffraction studies reveal that 1 consists of infinite layers of alternating trinuclear manganese subunits and H₂atpt ligands. There are two types of different coordination modes of H₂atpt in 1 . Magnetic susceptibility data for 1 were measured in the range 3–300 K. There are antiferromagnetic interactions between manganese ions of 1 .     

Nickel‐substituted cobalt ferrite nanoparticles supported on arginine‐modified graphene oxide nanosheets: Synthesis and catalytic activity

The amino acid arginine was used to modify the surface of graphene oxide nanosheets and then nickel‐substituted cobalt ferrite nanoparticles were supported on those arginine‐grafted graphene oxide nanosheets (Ni_0.5Co_0.5Fe₂O₄@Arg–GO). The prepared Ni_0.5Co_0.5Fe₂O₄@Arg–GO was characterized using flame atomic absorption spectroscopy, inductively coupled plasma optical emission spectrometry, energy‐dispersive spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The application of Ni_0.5Co_0.5Fe₂O₄@Arg–GO as a catalyst was examined in a one‐pot tandem oxidative cyclization of primary alcohols with o ‐phenylenediamine to benzimidazoles under aerobic oxidation conditions. The results showed that 2‐phenylbenzimidazole derivatives were successfully achieved using Ni_0.5Co_0.5Fe₂O₄@Arg–GO nanocomposite catalyst via the one‐pot tandem oxidative cyclization strategy.     

Mn‐[4‐Chlorophenyl‐Salicylaldimine‐Methylpyranopyrazole]Cl2 as a Novel Nanostructured Schiff Base Complex and Catalyst

Mn‐[4‐chlorophenyl‐salicylaldimine‐methylpyranopyrazole]Cl₂ ([Mn‐4CSMP ]Cl₂) as nano‐Schiff base complex was prepared and fully characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermal gravimetric analysis, derivative thermogravimetry, scanning electron microscopy, energy‐dispersive X‐ray analysis, and UV–vis spectroscopy. The reactivity of nano‐[Mn‐4CSMP ]Cl₂ as a catalyst was tested on the tandem cyclocondensation–Knoevenagel condensation–Michael reaction between phenylhydrazine and ethyl acetoacetate with various aromatic aldehydes to give 4,4′‐(arylmethylene)‐bis‐(3‐methyl‐1‐phenyl‐1H ‐pyrazol‐5‐ol)s derivatives.     

Synthesis and Crystal Structure of Two Succinato‐Bridged Macrocyclic Nickel(II) Complexes

Two dinuclear succinato‐bridged nickel(II) complexes [Ni(RR‐L)]₂(μ‐SA)(ClO₄)₂ ( 1 ) and [Ni(SS‐L)]₂(μ‐SA)(ClO₄)₂ ( 2 ) (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy. Single crystal X‐ray diffraction analyses revealed that the Ni^II atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central Ni^II atoms in a bis bidentate fashion to form dimers in 1 and 2 . The monomers of {[Ni(RR‐L)]₂(μ‐SA)}²⁺ and {[Ni(SS‐L)]₂(μ‐SA)}²⁺ are connected by O–H ··· O and N–H ··· O hydrogen bonds into a 1D right‐handed and left‐handed helical chain along the b axis, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy.     

Enhanced Pseudocapacitance in Multicomponent Transition‐Metal Oxides by Local Distortion of Oxygen Octahedra

Anomalously high pseudocapacitance of a metal oxide was observed when Ni, Co, and Mn were mixed in a solid solution. Analysis by X‐ray absorption near‐edge spectroscopy (XANES) identified a wider redox swing of Ni as the origin of the enlarged pseudocapacitance. Ab initio DFT calculations revealed that aliovalent species resulting from the copresence of multiple transition metals can generate permanent local distortions of [NiO₆] octahedra. As this type of distortion breaks the degenerate e_g level of Ni²⁺, the Jahn–Teller lattice instability necessary for the Ni^2+/3+ redox flip can be effectively diminished during charge–discharge, thus resulting in the significantly increased capacitance. Our findings highlight the importance of understanding structure–property correlation related to local structural distortions in improving the performance of pseudocapacitors.     

In‐situ XAFS Studies of Mn12 Molecular‐Cluster Batteries: Super‐Reduced Mn12 Clusters in Solid‐State Electrochemistry

In situ X‐ray absorption fine structure (XAFS) analyses were performed on rechargeable molecular cluster batteries (MCBs), which were formed by a lithium anode and cathode‐active material, [Mn₁₂O₁₂(CH₃CH₂C(CH₃)₂COO)₁₆(H₂O)₄] with tert‐pentyl carboxylate ligand (abbreviated as Mn12tPe), and with eight Mn³⁺ and four Mn⁴⁺ centers. This mixed valence cluster compound is used in an effort to develop a reusable in situ battery cell that is suitable for such long‐term performance tests. The Mn12tPe MCBs exhibit a large capacity of approximately 210 Ah kg⁻¹ in the voltage range V=4.0–2.0 V. The X‐ray absorption near‐edge structure (XANES) spectra exhibit a systematic change during the charging/discharging with an isosbestic point at 6555 eV, which strongly suggests that only either the Mn³⁺ or Mn⁴⁺ ions in the Mn12 skeleton are involved in this battery reaction. The averaged manganese valence, determined from the absorption‐edge energy, decreased monotonically from 3.3 to 2.5 in the first half of the discharging (4.0>V>2.8 V), but changed little in the second half (2.8>V>2.0 V). The former valence change indicates a reduction of the initial [Mn12]⁰ state by approximately ten electrons, which corresponds well with the half value of the observed capacity. Therefore, the large capacity of the Mn12 MCBs can be understood as being due to a combination of the redox change of the manganese ions and presumably a capacitance effect. The extended X‐ray absorption fine structure (EXAFS) indicates a gradual increase of the Mn²⁺ sites in the first half of the discharging, which is consistent with the XANES spectra. It can be concluded that the Mn12tPe MCBs would include a solid‐state electrochemical reaction, mainly between the neutral state [Mn12]⁰ and the super‐reduced state [Mn12]⁸⁻ that is obtained by a local reduction of the eight Mn³⁺ ions in Mn12 toward Mn²⁺ ions.     

Formation of CaCO3 deposits on OMS‐2 surface to synergistically promote peroxymonosulfate activation and organic dyes degradation

The development of green and efficient catalysts for peroxymonosulfate (PMS) activation and organic pollutants degradation has received widespread attention. In this study, the hybrid CaCO₃/OMS‐2 catalysts were prepared by a simple precipitation approach and characterized by X‐ray powder diffraction, N₂ adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and cyclic voltammetry. It was found that deposition of CaCO₃ on OMS‐2 surface can weaken the Mn‐O bond by formation of Ca‐O‐Mn bond. The interactions between CaCO₃ and OMS‐2 significantly enhanced Acid Orange 7 degradation in the presence of PMS with a pseudo‐first‐order kinetic constant of 0.21 min^?1, which was much higher than those of OMS‐2 (0.026 min^?1) and CaCO₃ (0.021 min^?1). The CaCO₃/OMS catalysts were also much more efficient than other reported OMS‐2 hybrid catalysts, and could be performed over a wide solution pH and for other organic dyes degradation. Sulfate and hydroxyl radicals were formed from the oxidation of low valent manganese species by PMS as the active species in the system. This study can provide a simple method for the design of efficient manganese‐based hybrids for wastewater remediation via PMS activation.     

Syntheses,Structures and Electrochemistry Properties of Two Dicyanamide Manganese(III) Complexes [Mn(5‐Brsalen)(dca)]·CH3OH and [Mn(3‐Meosalphen)(dca)(H2O)]

Two manganese(III)‐dicyanamide compounds, [Mn(5‐Brsalen)(dca)] · CH₃OH ( 1 ) and [Mn(3‐Meosalphen)(dca)(H₂O)] ( 2 ) (dca = dicyanamide anion, [N(CN)₂]^–), were synthesized and characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray structure analysis, and cyclic voltammetry. The structure of complex 1 is an infinite zigzag chain of hexacoordinate Mn^III ions, in which the adjacent manganese atoms are connected by dca in μ_1,5‐bridging mode. The molecular structure of complex 2 consists of a hexacoordinate Mn^III atom, which generates a slightly distorted octahedral arrangement, and a dimer structure is formed by intermolecular hydrogen bonding interactions. The electrochemical properties of the two complexes were measured by cyclic voltammetry.     

Functionalization and Dispersion of Hexagonal Boron Nitride (h‐BN) Nanosheets Treated with Inorganic Reagents

A mixture of bulk hexagonal boron nitride (h‐BN) with hydrazine, 30 % H₂O₂, HNO₃/H₂SO₄, or oleum was heated in an autoclave at 100 °C to produce functionalized h‐BN. The product formed stable colloid solutions in water (0.26–0.32 g L ^?1) and N,N‐dimethylformamide (0.34–0.52 g L ^?1) upon mild ultrasonication. The yield of “soluble” h‐BN reached about 70 wt %. The dispersions contained few‐layered h‐BN nanosheets with lateral dimensions in the order of several hundred nanometers. The functionalized dispersible h‐BN was characterized by IR spectroscopy, X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV/Vis spectroscopy, X‐ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). It is shown that h‐BN preserves its hexagonal structure throughout the functionalization procedure. Its exfoliation into thin platelets upon contact with solvents is probably owing to the attachment of hydrophilic functionalities.     

Achieving branched polyethylene waxes by aryliminocycloocta[b]pyridylnickel precatalysts: Synthesis,characterization, and ethylene polymerization

Cycloocta[b ]pyridin‐10‐one was prepared to form the corresponding imino derivatives, which then reacted with (DME)NiBr₂ to form 10‐aryliminocycloocta[b ]pyridylnickel bromides ( Ni1 – Ni5 ). The new compounds were characterized by means of FT‐IR spectroscopy as well as elemental analysis and the organic ligands were also analyzed by the NMR measurements. Furthermore, the molecular structure of a representative complex Ni3 was determined by the single crystal X‐ray diffraction, indicating the distorted tetrahedral geometry around the nickel atom. Upon the activation with either methylaluminoxane (MAO) or diethylaluminium chloride (Et₂AlCl), the title nickel complexes exhibited high activity in ethylene polymerization and produced polyethylene of low molecular weight (1.43–6.78 kg mol^?1) and low dispersity (1.7–2.4), which suggests a single‐site catalytic system. More importantly, the microstructure of the resultant polyethylene (especially degree of branching) and certain physical properties, such as T _m values, can easily be modulated by selecting the proper substituents within the ligands and adjusting the polymerization conditions. This finding demonstrates that it is plausible to use a single catalyst for synthesizing different types of polyethylene on demand.10‐Aryliminocycloocta[b ]pyridylnickel bromides ( Ni1–Ni5 ), upon activation with either MAO or Et₂AlCl, exhibited high activity towards ethylene polymerization and produced polyethylenes with low molecular weight (1.43–6.78 kg mol^?1) and low dispersity (1.7–2.4). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2601–2610     

Valence Interconversion of Octahedral Nickel(II/III/IV) Centers

Three oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuclear complex, [Ni{Rh(apt)₃}₂]^{n +} (apt=3‐ aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox‐inert fac ‐[Rh^III(apt)₃] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single‐crystal X‐ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn–Teller distortion.     

Mononuclear Carbene Dithiolate [Ni(NHX)(′S2C ′)] Complexes with HNX = HNPiPr3 or HNSPh2 Coligands (′S2C ′ 2– = 1,3‐ImidazolidinylN,N′‐bis(2‐benzenethiolate)(2–))

Cleavage reactions of the dinuclear [{Ni(′S₂C ′)}₂] · DMF (′S₂C ′ ^2– = 1,3‐imidazolidinyl‐N,N′‐bis(2‐benzenethiolate)(2–)) with HNPiPr₃ or HNSPh₂ yielded the mononuclear complexes [Ni(NHPiPr₃)(′S₂C ′)] ( 1 ) and [Ni(NHSPh₂)(′S₂C ′)] ( 2 ) which have been completely characterized. The nickel‐carbene‐dithiolate [Ni(′S₂C ′)] moiety is one of the very rare complex fragments that are able to coordinate both HNPR₃ or HNSR₂. IR spectra and X‐ray structure determinations show that 1 and 2 exhibit intramolecular N–H…S(thiolate) hydrogen bonds. Geometric parameters and NMR spectroscopic data of 1 and 2 are compatible with N–X single bonds and ylidic structures of the HNPiPr₃ and HNSPh₂ ligands. Comparison of Ni–N distances in diamagnetic and paramagnetic [Ni(NHSPh₂)] complexes was rendered possible through the X‐ray structure determination of the homoleptic [Ni(NHSPh₂)₆]Cl₂ ( 3 ) which formed as minor by‐product in the synthesis of 2 .     

Preparation of Monodisperse Ferrite Nanocrystals with Tunable Morphology and Magnetic Properties

The synthesis of monodisperse magnetic ferrite nanomaterials plays an important role in several scientific and technological areas. In this work, dibasic spinel MFe₂O₄ (M=Mg, Ni, Co, Fe, Mn) and polybasic spinel ferrite MCoFeO₄ (M=Mg, Ni, Mn, MgNi) nanocrystals were prepared by the calcination of layered double hydroxide (LDH) precursors at 900 °C, which was confirmed by X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate that the as‐obtained spinel ferrites present a single‐crystalline nature with uniform particle size and good dispersibility. The composition, morphology, and particle size can be effectively tuned by changing the metal ratio, basicity, reaction time, and temperature of the LDH precursors. In addition, these spinel ferrites show high magnetic saturation values in the range 21.7–84.3 emu g^?1, which maintain a higher level than the previously reported magnetic nanoparticles. Therefore, this work provides a facile approach for the design and fabrication of spinel ferrites with controllable nanostructure and improved magnetism, which could potentially be used in magnetic and biological fields, such as recording media, sensors, drug delivery, and intracellular imaging.     

Evolution of Oxygen–Metal Electron Transfer and Metal Electronic States During Manganese Oxide Catalyzed Water Oxidation Revealed with In Situ Soft X‐Ray Spectroscopy

Manganese oxide (MnO_x) electrocatalysts are examined herein by in situ soft X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) during the oxidation of water buffered by borate (pH 9.2) at potentials from 0.75 to 2.25 V vs. the reversible hydrogen electrode. Correlation of L‐edge XAS data with previous mechanistic studies indicates Mn^IV is the highest oxidation state involved in the catalytic mechanism. MnO_x is transformed into birnessite at 1.45 V and does not undergo further structural phase changes. At potentials beyond this transformation, RIXS spectra show progressive enhancement of charge transfer transitions from oxygen to manganese. Theoretical analysis of these data indicates increased hybridization of the Mn?O orbitals and withdrawal of electron density from the O ligand shell. In situ XAS experiments at the O K‐edge provide complementary evidence for such a transition. This step is crucial for the formation of O₂ from water.     

Synthesis of 2‐(N‐arylimino)pyrrolide nickel complexes and polymerization of methyl methacrylate

The synthesis, characterization and methyl methacrylate polymerization behaviors of 2‐(N‐arylimino)pyrrolide nickel complexes are described. The nickel complex [NN]₂Ni ( 1 , [NN] = [2‐C(H)NAr‐5‐tBu‐C₄H₂N]^?, Ar = 2,6‐iPr₂C₆H₃) was prepared in good yield by the reaction of [NN]Li with trans‐[Ni(Cl)(Ph)(PPh₃)₂] in THF. Reaction of [NN]Li with NiBr₂(DME) yielded the nickel bromide [NN]Ni(Br)[NNH] ( 2 ). Complexes 1 and 2 were characterized by ¹H NMR and IR spectroscopy and elemental analysis, and by X‐ray single crystal analysis. Both complexes, upon activation with methylaluminoxane, are highly active for the polymerization of methyl methacrylate to give high molecular weight polymethylmethacrylate with narrow molecular distributions. Copyright © 2009 John Wiley & Sons, Ltd.