Two-step electrosynthesis and catalytic activity of CoO−CoO • xH2O-supported Ag,Au, and Pd nanoparticles

Russian Chemical Bulletin - Two-step electrosynthesis of CoO-CoO?xH2O-supported metal nanoparticles (MNPs, M = Au, Ag, Pd) was carried out in N,N-dimethylformamide in the absence and in...     

Mediated electrosynthesis of silver nanoparticles in a two-phase water—isooctane system

Russian Chemical Bulletin - Efficient electrosynthesis of silver nanoparticles (AgNPs) in bulk solution of a two-phase water—isooctane system is carried out by electrolysis in an undivided...     

Synthesis,characterization and antibacterial activity of a curcumin–silver(I) complex

The current study reports the synthesis of a curcumin–silver(I) complex and its preliminary tests against four bacterial strains viz. Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Bacillus cereus using agar well diffusion method. The results were compared with curcumin by testing it in parallel with the sample. Curcumin showed zones of inhibition against all tested strains of bacteria. Among all bacterial strains, S. aureus was the most sensitive to curcumin with zone of inhibition of 12.2 mm. However, the curcumin–Ag(I) complex did not show the expected enhanced activity against all bacteria. This is perhaps due to the replacement of curcumin phenolic protons by silver ions which might have suppressed the antibacterial property of curcumin. The current research findings suggest that while synthesizing curcumin–metal complexes, the phenolic heads may either be left unaltered or need to be replaced by better substituents than hydroxy groups. Based on the current findings, biologically enhanced models have been provided as future recommendations.     

Synthesis of CuO from CuCO3·Cu(OH)2 and its catalytic activity in the degradation of methylene blue

Research on Chemical Intermediates - A one-step route has been designed to synthesize CuO nanostructures using basic cupric carbonate (CuCO3·Cu(OH)2) as a precursor. The crystal structure and...     

Layer-by-layer electrosynthesis of Pt–Polyaniline nanocomposites for the catalytic oxidation of methanol

A new composite material based on the electrochemical generation of a layer-by-layer structure of polyaniline (PANI) and Pt particles has been prepared. The number of layers and the nature of the external layer (PANI or Pt) determine the electrocatalytic performance of the composite for the oxidation of methanol. We demonstrate that the layer-by-layer approach to form the nanocomposite and modification of the Pt particles with a layer of PANI leads to substantially higher catalytic efficiency.     

Electrocrystallization of silver nanoparticles from silver halides in polypyrrole evidenced by their SERS activity—thermodynamic and kinetic conditions

Journal of Solid State Electrochemistry - Silver(I) halide particles embodied in polypyrrole matrices are synthesized and further processed electrochemically to get nanoparticles of silver with...     

New silver(I)–monophosphine complex derived from chiral Ar-BINMOL: synthesis and catalytic activity in asymmetric vinylogous Mannich reaction

A new family of C₂-axially chiral monophosphines (Ar-NNPs) from Ar-BINMOLs was developed for silver-catalyzed asymmetric vinylogous Mannich reaction of (furan-2-yloxy)trimethylsilane with aromatic aldimines. It was found that the enantioselective vinylogous Mannich-type reactions of trimethylsiloxyfuran with aldimines are catalyzed efficiently by silver(I) complexes of the Ar-BINMOL-derived chiral monophosphine. This procedure displays wide aldimine versatility, excellent yields (up to 99% isolated yields), moderate to good enantioselectivity (up to 78%ee) and exceptional diastereoselectivity (>99:1 dr) in most cases examined. The molecular structure of silver–monophosphine complex was confirmed by X-ray analysis and revealed that the benzyl group on chiral monophosphine provided dual function with weak silver–π/π–π stacking and steric repulsion to favour the diastereoselective Re-nucleophilic addition of siloxyfuran to imine.     

Physicochemical properties and catalytic activity of metal–carbon carrier composite materials

Composite metal–carbon materials are created on the basis of different kinds of carbon (multiwall carbon nanotubes, carbon black, Sibunit carbon–carbon material) and metals (Ag, Ni, Co), and their physicochemical and catalytic properties are investigated. It is shown that interaction between metals and carbon carriers proceeds not only with the functional groups on the surfaces of the carriers, but also through a system of–C–C–conjugated bonds. Silver deposited on the surface of a carbon carrier has a crystalline structure (d _cr = 10–15 nm), while nickel has an amorphous lamellar structure. Based on quantum-chemical calculations using the density functional theory, it is shown that cumene oxidation occurs via a homogeneous–heterogeneous mechanism.     

Review: Multimetallic silver(I)–pyridinyl complexes: coordination of silver(I) and luminescence

This review highlights some structural features and luminescent properties of homo- and hetero-multinuclear silver(I)–pyridinyl complexes. It focuses on the coordination and geometry of the silver(I) ions to the pyridinyl-nitrogen. For this reason, we have considered only pyridinyl-N–Ag(I) complexes whose crystal data are available. In addition, this review does not consider mononuclear silver(I)–pyridinyl complexes as these have been reviewed elsewhere. This is motivated by the fact that multinuclear silver(I)–pyridinyl complexes have been shown to be more stable in solution, possess enhanced properties, and have fascinating structures compared to their mononuclear counterparts. The introduction highlights pyridinyl ligands used in complexation of silver(I) ions. The main body highlights complexation of silver(I) through pyridinyl nitrogen and the interactions found in the multinuclear silver(I)–pyridinyl complexes as well as the coordination number and geometry of silver(I) centers. Though silver(I) has been flaunted to prefer linear twofold coordination geometry, from this review, it is clear that higher coordination numbers in varied geometries are possible. These include distorted trigonal planar, T-shaped, distorted tetrahedral, trigonal bipyramidal, and octahedral geometries. Coordination of silver(I) to pyridinyl ligands and their metalloligands has been observed to impart or enhance luminescent properties in the ensuing complexes.     

Strategy to enhance catalytic activity and stability of sol–gel oxidoreductases

Journal of Sol-Gel Science and Technology - Oxidoreductases are widely recognized for their capability to degrade phenolic pollutants and versatile. However, the lack of enzyme stability makes this...     

Facile Synthesis and Catalytic Properties of β-Co(OH)2 and Mg(OH)2 Nanoplates

β-Co(OH)2 and Mg(OH)2 nanoplates were synthesized via a facile template-free hydrothermal approach. The different conditions of preparation and catalytic properties of the products were studied and discussed. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, selected area electron diffraction(SAED), and gas chromatograph.     

Deposition of silver nanoparticles into porous system of sol–gel silica monoliths and properties of silver/porous silica composites

Porous monolithic gels based on silica with pore size from 16 nm to 3–5 μm have been synthesized using sol–gel technology. Parameters of porous structure are determined by the components molar ratio in the reaction mixture. The reduction processes of silver ions by formamide in the synthesized porous gel were studied. It has been shown that at the initial stage of the reaction, silver particles with size up to 10 nm are formed in the absence of any stabilizers. The composites Ag/SiO₂ were synthesized by means of the threefold impregnation of porous monoliths using the solution of silver nitrate in the mixture of methanol and formamide. Their catalytic activity in the CO oxidation was studied. It was discovered that after activation in oxygen and hydrogen the samples display a low temperature activity, which depends on the number of Si–O-nonbridging oxygen groups on the surface of silica porous monoliths.     

Determination of the stability constants of Pb–(DIPSO)x–(OH)y and Pb–(AMPSO)x–(OH)y systems

In this work, complexation between lead ion and the ligands 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) and N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO), which are commercial pH buffers, is presented. Both ligands form complexes with lead in their pH buffer range (between pH 6.5 and 8.5 for DIPSO and between pH 8.0 and 9.0 for AMPSO). The final models and the overall stability constants, which are reported here, were determined by direct current polarography and glass electrode potentiometry [only for the Pb–(DIPSO)_x–(OH)_y system] at 25.0 °C and 0.1 M KNO₃ ionic strength. For the Pb–(DIPSO)_x–(OH)_y system, the proposed final model contains PbL, PbL₂, PbL₂(OH), and PbL₂(OH)₂ with stability constants, as log β, of 3.4 ± 0.1, 6.35 ± 0.15, 12.8 ± 0.2, and 18.0 ± 0.3, respectively. For the Pb–(AMPSO)_x–(OH)_y system, the species observed are PbL, PbL(OH), and PbL(OH)₂ with stability constants, as log β, of 2.9 ± 0.5, 9.4 ± 0.1, and 14.5 ± 0.2, respectively. For AMPSO, the possible adsorption of the ligand at the mercury electrode surface was evaluated by alternating current polarography through calculation of the capacitance of the double layer.     

Anchoring of Cu (II)-Schiff base complex on magnetic mesoporous silica nanoparticles: catalytic efficacy in one-pot synthesis of 5-substituted-1H-tetrazoles,antibacterial activity evaluation and immobilization of α-amylase

Magnetic mesoporous silica nanocomposite, Fe₃O₄@MCM-41, was prepared and functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS). Then Schiff base grafted nanoparticles were synthesized by the condensation of 5,5'-methylene bis (salicylaldehyde) and then benzhydrazide with Fe₃O₄@MCM-41-AEAPS. Finally, by adding Cu (CH₃COOH)₂.H₂O, the magnetic nanoparticles (MNPs) functionalized with Cu (II) Schiff base complex were synthesized. The new organic–inorganic hybrid nanocomposite was characterized by FT-IR, PXRD, AAS, BET, TGA, VSM, FE-SEM, HRTEM and EDX techniques. Then, the performance of this copper based magnetic nanocatalyst was investigated for the synthesis of 5-substituted 1H-tetrazole derivatives using one pot three-component reactions of various aldehydes, hydroxyl amine hydrochloride and sodium azide. The catalyst can be easily isolated from the reaction mixture by applying an external magnet and reused for at least 5 times without significant loss in catalytic activity. Also, the antibacterial activity of the streptomycin loaded magnetic nanoparticles against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria in the presence and absence of a magnetic field were studied. Results revealed that when these materials exposed to the magnetic field, bacteriostatic activity of nanocomposites was increased. Furthermore, the enzyme immobilization ability of the synthesized compounds was investigated and the results showed that these nanoparticles efficiently immobilized amylase enzyme.     

[Cu(bpdo)2·2H2O]2+-supported SBA-15 nanocatalyst for efficient one-pot synthesis of benzoxanthenone and benzochromene derivatives

A novel [Cu(bpdo)₂·2H₂O]²⁺-supported SBA-15 catalyst (bpdo = 2,2′-bipyridine,1,1′-dioxide) was prepared by the impregnation method. The catalyst was characterized by XRD, TEM, and BET nitrogen adsorption–desorption method, FT-IR, UV–vis, and chemical analysis. XRD patterns and TEM analysis of [Cu(bpdo)₂·2H₂O]²⁺/SBA-15 showed highly ordered hexagonal mesoporous silica, even after immobilization. Also, nitrogen adsorption–desorption isotherms exhibited type-IV isotherms and H1 hysteresis loops according to the IUPAC classification of mesoporous materials. This green support was tested for the synthesis of benzoxanthenone and benzochromene derivatives under solvent-free conditions, with high yield of products via a simple experimental and work-up procedure.     

The preparation of conducting polyaniline–silver and poly(p-phenylenediamine)–silver nanocomposites in liquid and frozen reaction mixtures

The oxidation of aniline with silver nitrate in 1 mol L⁻¹ acetic acid at 20 °C yielded a composite of two conducting components, polyaniline and silver; the acceleration with 1 mol% of p-phenylenediamine is needed for efficient synthesis. The yield and molecular weight increased when aniline was copolymerized with 10 mol% p-phenylenediamine. Such product displayed metallic conductivity below 180 K and semiconductor type above this temperature. As the result, the conductivity was the same at 100 and 300 K. The oxidation of p-phenylenediamine alone with silver nitrate also produced a conducting composite having the conductivity of 1,750 S cm⁻¹ despite the assumed nonconductivity of poly(p-phenylenediamine). The present study demonstrates that all oxidations proceeded also in frozen reaction mixtures at −24 °C, i.e., in the solid state. In most cases, molecular weights of polymer component increased, the conductivity of composites with silver improved, to 2,990 S cm⁻¹ for poly(p-phenylenediamine)–silver, and remained high after deprotonation with 1 mol L⁻¹ ammonium hydroxide.

     

Synthesis and catalytic activity of DI-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)] and m-xylylenediamine Zn(OAc)2

Compound I, [di-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)], was obtained by two different synthetic routes. In synthetic route 1, we first obtained intermediate by the addition of two equivalents of o-aminopyridine to copper chloride in an ethanolic solution, and then we recrystallized the intermediate from methanol and n-hexane to give compound I. Synthetic route 2 involved the reaction of o-aminopyridine with copper chloride in a methanol solution directly. The crystal structure of compound I was obtained. The reaction of m-xylylenediamine with Zn(OAc)₂ · 2H₂O in THF resulted in the production of one novel zinc complex C₁₂H₁₈N₂O₄Zn, bis(m-xylenediamine)zinc (II) and its structure was determined by X-ray diffraction analysis. Complexes I and II were also characterized by elemental analysis, and IR. Then they were applied as catalysts for the Henry reaction, and they achieved good conversions (64 and > 99%, respectively).     

Synthesis and evaluation of antibacterial and anti-oxidant activity of small molecular chitosan–fucoidan conjugate nanoparticles

Research on Chemical Intermediates - Low-molecular weight chitosan (LMWC) and low-molecular weight fucoidan (LMWF) have been reported to possess diverse biological activity. In this study, LMWC and...     

Electrochemical preparation of α-Ni(OH)2 ultrafine nanoparticles for high-performance supercapacitors

Well-dispersed nanoparticles of nickel hydroxide were prepared via a simple electrochemical method. Electrodeposition experiments were performed from 0.005 M Ni(NO₃)₂ bath at a constant current density of 0.1 mA cm^?2 on the steel cathode for 1 h. Recording the potential values during the deposition process revealed that the reduction of water has major role in the base electrogeneration at the applied conditions. The obtained deposit was characterized by the X-ray diffraction (XRD), infrared (IR), differential scanning calorimeter–thermogravimetric analysis, carbon–nitrogen–hydrogen (CHN), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The CHN, XRD, and IR analyses showed that the obtained deposit has α phase of Ni(OH)₂ with intercalated nitrate ions in its structure. Morphological characterization by SEM and TEM revealed that the prepared α-Ni(OH)₂ is composed of well-dispersed ultrafine particles with the size of about 5 nm. The supercapacitive performance of the prepared nanoparticles was analyzed by means of cyclic voltammetry and galvanostatic charge–discharge tests. The electrochemical measurements showed an excellent supercapacitive behavior of the prepared α-Ni(OH)₂ nanoparticles. It was also observed that the α-Ni(OH)₂ ultrafine particles have better electrochemical characteristic and supercapacitive behavior than β-Ni(OH)₂ ultrafine nanoparticles, including less positive charging potential, lower E _a???E _c value, better reversibility, higher E _OER???E _a, higher utilization of active material, higher proton diffusion coefficient, greater discharge capacity, and better cyclability. These results make the α-Ni(OH)₂ nanoparticles as an excellent candidate for the supercapacitor materials.     

Synthesis and structure of an air-stable binuclear complex of bis(ethylcyclopentadienyl)zirconium perfluorooctanesulfonate and its catalytic application in one-pot three-component aza-Friedel–Crafts reactions

An air-stable Lewis acidic binuclear complex of bis(ethylcyclopentadienyl)zirconium perfluorooctanesulfonate (1a) was successfully synthesized by the reaction of (CH₃CH₂Cp)₂ZrCl₂ with C₈F₁₇SO₃Ag. The complex 1a was characterized by different techniques and found to have the nature of air-stability, water tolerance, thermal-stability, and strong Lewis-acidity. In addition, its solubility was higher than that of our previously reported uninuclear zirconocene bis(perfluorooctanesulfonate). This complex showed high catalytic efficiency, good recyclability, and reusability in the one-pot three-component aza-Friedel–Crafts reactions of indoles with aldehydes and N,N-dimethylaniline. The yields of the corresponding 3-diarylmethyl indoles are higher than those from the traditional Lewis acidic catalysts.