Electropolymerization of Ni(salen) on carbon nanotube carrier as a capacitive material by pulse potentiostatic method

The composites of poly[Ni(salen)] and multi-walled carbon nanotube(MWCNT) were synthesized by pulse potentiostatic method.The composites were characterized by field emission scanning electron microscopy,Fourier transform infrared spectra,and electrochemical impedance spectroscopy.The wrapping of carbon nanotubes with poly[Ni(salen)] varied significantly with anodic pulse duration.Variance of structure of poly[Ni(salen)] caused by anodic pulse duration affected the ability of absorption to solvent molecules or solvated ions,which was indicated by ν(C≡N) intensity.The ability to store/release charge of poly[Ni(salen)] caused by redox switching was evaluated in the form of low-frequency capacitance.Correlations of chargetransfer resistance/ionic diffusion resistance with potential and anodic pulse duration were investigated.     

Preparation and Characterization of NiO Nanoparticles via Solid-State Thermal Decomposition of Ni(II) Complex

Nickel(II) complex, Ni(Brsalph)(NO₃) was synthesized and characterized by elemental analyses and Fourier-transformed infrared (FT-IR) spectroscopy. Heating of Ni(Brsalph)(NO₃) at 550 °C for 3.5 h have resulted NiO nanoparticles. Fourier-transformed infrared spectrum confirmed the composition of products. The crystalline structures and morphology of NiO nanoparticles were studied by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy.     

Magnetic and Thermal Properties of Novel Poly(ether-amide)/Fe3O4 Nanocomposite Containing Phosphine Oxide Group

New poly(ether-amide) nanocomposite containing phosphine oxide was prepared via solution polymerization process from synthesized poly(ether-amide) and Fe₃O₄ nanoparticles in a solution of N,N-dimethylformamide. Uniform monodisperse Fe₃O₄ nanoparticles were synthesized at room temperature via a facile sonochemical reaction. Poly(ether-amide) (PEA) as the polymer matrix was synthesized from reaction of 1,4-(4-carboxy phenoxy)butane (1) and bis(3-amino phenyl)phenyl phosphine oxide (2) via a direct polycondensation reaction. Nanoparticle and nanocomposite were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared. The effect of the presence of Fe₃O₄ nanoparticles on the thermal properties of PEA was studied using thermogravimetric analysis in nitrogen atmospheres. The magnetic properties of the sample were also investigated using an alternating gradient force magnetometer. We found that the Fe₃O₄ nanoparticles exhibit a ferromagnetic behaviour with a saturation magnetization of 59 emu/g and a coercivity of 104 Oe at room temperature. The coercivity of PEA/Fe₃O₄ nanocomposites is found to be 126 Oe, higher than 104 Oe which is obtained for Fe₃O₄.     

Synthesis of Nickel Lysine Salen Complex and Its Catalytic Performance for Styrene Epoxidation

Nickel lysine salen complex was successfully synthesized via a stepwise procedure and applied as a heterogeneous catalyst for styrene epoxidation. For comparison, several other transition metal (Mn, Fe, Co, and Cu) lysine salen complexes were also synthesized. The prepared catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX). Data obtained by FT-IR and Raman spectroscopy indicated the formation of C=N bonds and the complexation of these bonds with metal ions. SEM analysis revealed that the complexation of metal ions with the C=N involves the change in surface morphology of samples. In addition, atomic percent composition of samples was obtained from EDX spectra, which was the complementary evidence for the formation of complexes. Results of catalytic measurements showed that a high conversion of styrene (91.51%) and selectivity to styrene oxide (91.99%) could be achieved over the nickel lysine salen complex with tert-butyl hydroperoxide as the oxidant. When the catalyst was reused the conversion of styrene decreased but the selectivity to styrene oxide still remained high.     

Synthesis and self-assembly behaviors of well-defined poly(lauryl methacrylate)-block-poly[N-(2-methacryloylxyethyl)pyrrolidone] copolymers

A series of structurally controllable poly(lauryl methacrylate)-b-poly[N-(2-methacryloylxyethyl)pyrrolidone], PLMA-b-PNMP, diblock copolymers were synthesized by reversible addition–fragmentation chain transfer polymerization. The self-assembly behaviors of PLMA-b-PNMP in a selective solvent, tetrahydrofuran (THF), were studied by employing static light scattering, dynamic light scattering, and transmission electron microscopy in detail. The relationships between the aggregation parameters, such as critical micelle concentration and the aggregation number (N _agg), and the molecular structure were established. It was found that spherical micelles can be formed once the solvophobic block length of poly[N-(2-methacryloylxyethyl)pyrrolidone] is larger than 215. Moreover, extremely small and monodisperse gold nanoparticles (<2 nm) were synthesized by employing PLMA-b-PNMP diblock copolymers in THF.     

Synthesis of high surface area NiO nanoparticles through thermal decomposition of mixed ligand Ni(II) Complex, [Ni(binol)(bpy)]∙CH<Subscript>3</Subscript>OH

The present work focuses on the synthesis of high surface area NiO nanoparticles through thermal decomposition of [Ni(binol)(bpy)]?CH₃OH complex as a new precursor. [Ni(binol)(bpy)]?CH₃OH (where binol = racemic-1,1′-bi-2-naphtholate and bpy = 2,2′-bipyridine) was synthesized from reaction of NiCl₂(bpy) with rac-Na₂(binol). The complex was characterized by elemental analysis and spectroscopy techniques of IR, UV-Vis, mass, ¹H and ¹³C NMR. The results revealed that [Ni(binol)(bpy)]?CH₃OH was a paramagnetic tetrahedral complex. The physicochemical properties of the nanoparticles were characterized by various analysis techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and BET specific surface area. The used synthetic rout is facile and economic that makes it suitable for large scale production of pure nickel oxide nanoparticles.     

Molybdenum Schiff base-polyoxometalate hybrid compound: A heterogeneous catalyst for alkene epoxidation with tert-BuOOH

The hybrid compound consisting of molybdenum(salen) [salen = N,N′-bis(salicylidene)ethylnediamine] complex covalently linked to a lacunary Keggin-type polyoxometalate, K₈[SiW₁₁O₃₉] (POM), was synthesized and characterized by elemental analysis, FT-IR, ¹H NMR and diffuse reflectance UV–Vis spectroscopic methods and BET analysis. The complex, [Mo(O)₂(salen)–POM], was studied, for the first time, in the epoxidation of various alkenes with tert-BuOOH and in 1,2-dichloroethane as solvent. This catalyst can catalyze epoxidation of various olefins including non-activated terminal olefins. The effect of the other parameters such as solvent, oxidant and temperature on the epoxidation of cyclooctene was also investigated. The interesting characteristic of this catalyst is that, in addition to being a heterogeneous catalyst, it gives higher yields towards epoxidation of olefins in comparison to the corresponding homogeneous [Mo(O)₂(salen)] complex.     

Preparation and Characterization of NiO Nanoparticles Via Solid-State Thermal Decomposition of Nickel(II) Schiff Base Complexes [Ni(salophen)] and [Ni(Me-salophen)]

This study focuses on the preparation and characterization of nickel oxide nanoparticles from nickel(II) Schiff base complexes as new precursors. At first nickel(II) complexes [Ni(salophen)] and [Ni(Me-salophen)] were synthesized and characterized by elemental analyses and FT-IR spectroscopy. Then NiO nanoparticles were prepared by solid-state thermal decomposition at 550 ºC for 3.5 h. The FT-IR spectrum confirmed the composition of products. The crystalline structures and morphology of products were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results revealed that the obtained products were nickel oxide. SEM and TEM images demonstrated that the NiO nanoparticles have uniform shape with size between 35 and 70 nm.     

Synthesis of Ni/Al2O3 catalysts via alkaline polyol method and hydrazine reduction method for the partial oxidation of methane

Nickel catalysts supported on γ-Al₂O₃ were synthesized in the presence of polyvinylpyrrolidone (PVP) using both alkaline polyol method and hydrazine reduction method while fixing the weight ratio of [(PVP)]/[Ni(CH₃COO)₂·4H₂O] at 2. The effects of hydrazine [N₂H₅OH]/[Ni] and [NaOH]/[Ni] molar ratios on the structural properties of the catalysts were characterized by transmission electron microscopy (HRTEM) and by X-ray diffraction (XRD). The average of monodispersed Ni nanoparticles ranged between 8.0 and 13.0 nm. The catalytic tests were performed for the partial oxidation of methane in the temperature range of 600–800 °C under a flow rate of 157,500 L kg^–1 hr^–1 with CH₄/O₂= 2. At the molar ratio of [NaOH]/[Ni] = 2, the resultant nickel nanoparticles on alumina was established completely without impurities; thus, it demonstrated the highest catalytic activity, 88% for CH₄ conversion, and H₂ selectivity, 90.60%. The optimum [N₂H₅OH]/[Ni] ratio was determined as 4.1, which means a good catalytic performance and 89.35% selectivity to H₂ for the partial oxidation of methane.     

A Facile Sonochemical Method for Synthesis of Mercury Selenide Nanostructures

Mercury selenide (HgSe) nanostructures has been achieved from N–N′-bis(salicylaldehyde)-1,2-phenylenediimino mercury [Hg(salophen)] as a new precursor. Cubic phase HgSe nanoparticles with the size of mostly 20–40 nm were produced by sonication of the Hg(salophen) precursor. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, photoluminescence, energy dispersive X-ray spectroscopy and Fourier transformed infrared spectroscopy. The results of this paper show that the shape and size of mercury selenide nanostructures can be controlled systematically by adjusting reaction parameters, such as the ultrasonic power, temperature, capping agent and reaction time.     

Planting of bis(1,5‐cyclooctadiene) nickel upon silica to harvest NiO (<5 nm) nanoparticles in a silica matrix

Bis(1,5‐cyclooctadiene) nickel [Ni(COD)₂] was employed as a nickel precursor to prepare nickel oxide nanoparticles upon high‐surface‐area mesoporous silica. Under protection of argon, Ni(COD)₂ was dissolved in tetrahydrofuran (THF) to react with surface silanols of mesoporous silica SBA‐15, which formed a black powder after completion of the surface reaction. Calcination of the powder produced ultrafine NiO inside the mesoporous silica matrix, which was evidenced by X‐ray diffraction, N₂ adsorption–desorption, transmission electron microscopy and thermogravimetric analysis. The thermogravimetric analysis suggests that NiO formation is a result of surface nickel species calcination, whereas structural characterization clearly show that NiO nanoparticles of <5 nm are evenly distributed inside the silica SBA‐15 matrix and mesoporosity is well preserved upon calcinations and NiO formation. The surface reaction between Ni(COD)₂ and surface silanols was found for the first time, and the method used here may be extended conveniently to prepare other metal oxide nanoparticles upon high‐surface‐area supports as well. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of nickel metal nanoparticles via a chemical reduction of nickel ammine and alkylamine complexes by hydrazine

Nickel nanoparticles were prepared from their coordination compounds, such as [Ni(NH₃)₆]Cl₂, [Ni(N₂H₄)₂Cl₂], [Ni(HNEt₂)₆]Cl₂, and [Ni(H₂NBu)₆]Cl₂ in aqueous solution by chemical reduction. The reaction of nickel ammine and alkylamine complexes with hydrazine monohydrate as a reducing agent was carried out at 90 °C and pH = 10–12. Depending on the influencing parameters such as oxidizing agent, pH, and temperature, the hydrazine reaction can be carried out in different pathways. The chemical reduction method is a simple procedure and also is the best one in the controlling of composition, size, and shape of Ni powder. The reduction of nickel complexes into the metallic Ni powder occurs via the dissociation of complexes and reduction by hydrazine in alkaline solution. Therefore, complexing agents have the most effect on the reduction reaction. The results show that, when the ligands in complexes were changed from ammine to diethylamine and butylamine, respectively, the crystalline size and morphology of nickel metal nanoparticles are changed. The chemical reduction of nickel complexes into metallic nickel can be accompanied with a change in the crystalline system. The pure nickel crystalline has a face-centered cubic structure. The nickel nanoparticles were characterized using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and vibrating sample magnetometer analyses.     

Synthesis and characterization of Co3O4 nanoparticles by a simple method

Using solid complex molecular precursor [bis(salicylaldehyde)ethylenediiminecobalt(II)], [Co(salen)], a simple and surfactant-free method to synthesize Co₃O₄ nanoparticles was proposed. Cubic-phase Co₃O₄ nanoparticles of size 30–50-nm could be produced by thermal treatment of the Co(salen) in the air at 500 °C for 5 h. The as-prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical absorption spectrum indicates that the direct band gaps of Co₃O₄ nanoparticles are 1.53 and 2.02 eV. The optical property test indicates that the absorption peak of the nanoparticles shifts towards short wavelengths, and the blue shift phenomenon might be ascribed to the quantum effect. The hysteresis loops of the obtained samples reveal their ferromagnetic behavior, an enhanced coercivity (H_c) and a decreased saturation magnetization (M_s) as compared to their respective bulk materials.     

Syntheses and characterization of nickel(II) dithiocarbamate complexes containing NiS4 and NiS2PN moieties: Nickel sulphide nanoparticles from a single source precursor

In this study, ammonium N-benzyldithiocarbamate was synthesized and used to prepare homoleptic Ni(II) bis(N-benzyldithiocarbamate) (1) and heteroleptic Ni(II) complexes involving isocyanate (2) and cyanide (3) ions. The complexes were characterized by elemental analysis, Fourier transform infra-red (FTIR), and NMR (¹H and ¹³C) spectroscopic techniques. Complex 2 was further characterized by single crystal X-ray diffraction analysis. The FTIR showed bidentate co-ordination for all the complexes as the v(CN) stretching frequency were in the 980–1050 cm^?1 region without any splitting. Thermal decomposition profile of the complexes showed decomposition resulting in the formation of nickel sulphides. The homoleptic complex 1 was utilized as single source precursor (SSP) to prepare Nickel sulphide nanoparticles. The synthesis of the nanoparticles was conducted using different capping molecules (with various alkyl chain lengths), and at different reaction temperature and time. Pure phase Heazlewoodite (Ni₃S₂) nanoparticles were obtained from the X-ray diffraction study. The TEM analysis showed that the type of capping agent, reaction temperature, and time of reaction have significant effect on the morphology and size of the nanoparticles. The optical properties of the nanoparticles were studied using absorption and fluorescence spectroscopies, and they displayed evidence of quantum confinement effect.     

Multi-walled carbon nanotube bound nickel Schiff-base complexes as reusable catalysts for oxidation of alcohols

Nickel salen and salophen complexes have been covalently anchored on multi-walled carbon nanotubes (MWNTs). The MWNT-supported nickel complexes have been characterized by inductive coupled plasma spectroscopy, FT-IR spectroscopy, UV-Vis spectrophotometry, transmission electron microscopy, and X-ray diffraction. The catalytic performance for the oxidation of primary and secondary alcohols was evaluated using periodic acid as oxidant. Reaction conditions have been optimized for MWNT-supported salen and salophen complexes by considering the effect of parameters such as solvent, reaction time, concentration of catalyst, amount of oxidant, etc. The catalytic activity was higher for supported catalysts than similar homogeneous ones. These supported catalysts were highly stable and reused several times without the loss of catalytic activity.     

Ni (II) schiff base complex immobilized on graphene oxide nano-sheets catalyzed epoxidation of alkenes

Ni (II) schiff base complex was synthesized by the reaction of nickel acetate tetrahydrate with N, N’-Bis(2,4-di-hydroxybenzaldehyde)-1,2-cyclohexanediamine and supported on modified grapheme oxide nano-sheets using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous nano-catalyst was characterized by Fourier transform infrared spectra, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, nitrogen adsorption–desorption isotherms and atomic absorption spectroscopy. This catalyst was used for the epoxidation of alkenes using tert-butyl hydroperoxide as oxidant, giving excellent conversions and selectivity. The catalyst showed great reusability and selectivity without significant loss of activity in the epoxidation reactions.     

Substituted salen–Ru(II) complexes as catalysts in the asymmetric cyclopropanation of styrene by ethyl diazoacetate: the influence of substituents and achiral additives on activity and enantioselectivity

A series of alkyl-, halogen- and nitro-substituted salen ligands, 1, have been employed in the asymmetric cyclopropanation of styrene with ethyl diazoacetate by its ruthenium(II) complex with [RuCl₂(p-cymene)]₂ or RuCl₂(PPh₃)₃ as precursors. The introduction of appropriate electron withdrawing groups in the salen ligands benefited the enantioselectivity of the reaction. Some additives, including O-donor, N-donor and P-donor ligands, were added to the reaction to improve the enantioselectivity and activity, and e.e.s of up to 80% were achieved. In the salen/[RuCl₂(p-cymene)]₂ system, the (1R,2S)-isomer was obtained in 80.2% e.e. by using the salen ligand 1f derived from 3,5-dibrominated salicylaldehyde with Et₃N as additive. E.e.s of up to 81.3% for (1S,2R)-isomers were achieved by using the complex 2 synthesized from the nitro-substituted ligand 1m and RuCl₂(PPh₃)₃. A possible mechanism was also discussed.     

Synthesis,crystal structure,and electrochemical properties of Ni(II) and Cu(II) complexes with two unsymmetrical N2O2 Schiff base ligands

Nickel(II) and copper(II) complexes of two unsymmetrical tetradentate Schiff base ligands [Ni(Me-salabza)] (1), [Cu(Me-salabza)] (2) and [Ni(salabza)] (3), {H₂salabza = N,N′-bis[(salicylidene)-2-aminobenzylamine] and H₂Me-salabza = N,N′-bis[(methylsalicylidene)-2-aminobenzylamine]}, have been synthesized and characterized by elemental analysis and spectroscopic methods. The crystal structures of 2 and 3 complexes have been determined by single crystal X-ray diffraction. Both copper(II) and nickel(II) ions adopt a distorted square planar geometry in [Cu(Me-salabza)] and [Ni(salabza)] complexes. The cyclic voltammetric studies of these complexes in dichloromethane indicate the electronic effects of the methyl groups on redox potential.     

Synthesis of nickel nanoparticles supported on metal oxides using electroless plating: Controlling the dispersion and size of nickel nanoparticles

Nickel nanoparticles supported on metal oxides were prepared by a modified electroless nickel-plating method. The process and mechanism of electroless plating were studied by changing the active metal (Ag) loading, acidity, and surface area of metal oxides and were characterized by UV–vis spectroscopy, transmission electron microscopy, scanning electron microscopy, and H₂ chemisorption. The results showed that the dispersion of nickel nanoparticles was dependent on the interface reaction between the metal oxide and the plating solution or the active metal and the plating solution. The Ag loading and acidity of the metal oxide mainly affected the interface reaction to change the dispersion of nickel nanoparticles. The use of ultrasonic waves and microwaves and the change of solvents from water to ethylene glycol in the electroless plating could affect the dispersion and size of nickel nanoparticles.     

Improved procedures for the synthesis of (S)-2-[N-(N′-benzylprolyl)amino]benzophenone (BPB) and Ni(II) complexes of Schiff's bases derived from BPB and amino acids

(S)-N-Benzylproline (BP) was obtained by the reaction of (S)-proline and benzylchloride in high chemical yield (89%). (S)-2-[N-(N′-Benzylprolyl)amino]benzophenone (BPB) was synthesized in amounts greater than 100 g by the SOCl₂ promoted condensation of BP with 2-aminobenzophenone (yield 82%). Ni(II) complexes of Schiff's bases derived from BPB and amino acids were prepared by an improved procedure involving the use of KOH as a base and MeOH as solvent (yield 90–91%).