Synthesis and characterization of poly(ethylene glycol) grafted poly(L-lactide)

Poly(ethylene glycol) grafted poly(L -lactide) was prepared by ring opening polymerization of L -lactide and epoxy-terminated poly(ethylene glycol) methyl ether (PEGME). Stannous octoate and Al(Et)₃·0.5 H₂O were tested as polymerization catalysts, and Al(Et)₃·0.5 H₂O was found to be more effective for the ring-opening of the epoxy group of the modified PEGME monomer. The synthesized polymers were characterized by NMR and the efficiency of the incorporation of epoxy-terminated PEGME in the copolymer was determined.     

A new approach to the preparation of lanthanide catalysts for the synthesis of 2-propyl-3-ethylquinoline based on the reactions of LnCl3 · 6H2O crystalline hydrates with triisobutylaluminum

A new approach to the preparation of lanthanide catalysts for the synthesis of nitrogen heterocycles (exemplified by 2-propyl-3-ethylquinoline) was developed based on the reactions of LnCl₃ · 6H₂O crystalline hydrates with alkylaluminums. It was found that the interaction of LnCl₃ · 6H₂O (Ln = Ce, Pr, Tb, and Eu) with iso-Bu₃Al in aromatic solvents (20°C) resulted in the formation of soluble (isobutane and the alumoxane (iso-Bu₂Al)₂O) and insoluble products (with the empirical formula LnCl₃ · xH₂O · y(iso-Bu₂Al)₂O (x = 0.4–0.7; y = 0.04–0.07)). The physiochemical properties of LnCl₃ · xH₂O · y(iso-Bu₂Al)₂O were studied, and these compounds were found to be highly efficient catalysts for the reaction of aniline condensation with butyraldehyde to form 2-propyl-3-ethylquinoline.     

Preparation of nanosheet Fe-ZSM-5 catalysts, and effect of Fe content on acidity, water, and sulfur resistance in the selective catalytic reduction of NO x by ammonia

Direct synthesis of nanosheet Fe-ZSM-5 catalysts and their use for selective catalytic reduction (SCR) of NO _x by ammonia were studied. XRD, BET, SEM, EPR, and NH₃-TPD were used to understand the properties of catalysts with different iron loading. XRD confirmed the presence of the ZSM-5 crystal phase, and there was no Fe₂O₃ phase on the surface of the crystals. SEM showed the Fe-ZSM-5 catalysts comprised microspheres made up of nanosheets. EPR indicated that the iron was present as isolated Fe³⁺and FeO _x oligomers uniformly dispersed throughout the crystals. NH₃-TPD indicated that Fe-ZSM-5 (20,1:1) had maximum acid sites and density at approximately 250 and 450 °C, respectively. Fe-ZSM-5 (20,1:1) had the highest activity in the SCR reaction with NH₃. It was also confirmed that Fe-ZSM-5 (20,1:1) had excellent resistance to SO₂ and H₂O under the SCR reaction conditions. The effects of water vapor and SO₂, iron loading, and the Si/(Fe + Al) ratio were also investigated for these catalysts.     

Effect of Ag-doping of nanosized FeMgO system on its structural, surface, spectral, and catalytic properties

The effects of Ag-doping on the physico-chemical, spectral, surface, and catalytic properties of the FeMgO system with various Fe₂O₃ loadings were investigated. The dopant (Ag) molar ratio varied between 0.01 % and 0.05 %. The techniques employed for characterisation of catalysts were TG/DTG, XRD, ESR, N₂ adsorption at ?196°C, and catalytic decomposition of H₂O₂ at 25?C35°C. The results obtained revealed that the investigated catalysts consisted of nanosized MgO as the major phase, apart from the MgFe₂O₄ and/or Fe₃O₄ phases. ESR result of the FeMgO system revealed the presence of paramagnetic species as a result of Ag-doping. The textural properties including SBET, porosity and St were modified by Ag-doping. The doping process with Ag-species improved the catalytic activity of the FeMgO system. Increasing the calcination temperature from 400°C to 800°C increased the catalytic activity (k*_{30 °C}) of 0.05 AgFeMgO in H₂O₂ decomposition by 21.2 times.     

Synthesis,characterization, and catalytic properties of a cobalt(II) complex supported by an amine-bis(phenolate) ligand

A cobalt(II) complex [L′CoPy] 1 was prepared by the reaction of dimethylaminoethylamino-N,N-bis(2,4-dibromo)phenol (H₂L′) with CoCl₂. Electrochemical studies indicate that this complex is among the most efficient homogeneous catalysts for water reduction, with a turnover frequency of 917.7 mol of hydrogen per mole of catalyst per hour at an overpotential of 636.7 mV (pH 7.0). Additionally, under photoirradiation with blue light (λ _max = 469 nm), complex 1 in combination with [Ru(bpy)₃]Cl₂ and ascorbic acid (pH 4.0 in aqueous solution) also produces hydrogen with a turnover number of 4.9 × 10⁵ mol of H₂ per mol of catalyst.     

Mono- and dinuclear cyclopalladates as catalysts for Suzuki–Miyaura cross-coupling reactions in predominantly aqueous media

Suzuki–Miyaura cross-coupling reactions of aryl halides with arylboronic acids were performed in predominantly aqueous media employing two mono- and two dinuclear cyclopalladated complexes as catalysts. These complexes are [Pd(HL)Cl] (I), [Pd(L)(PPh₃)] (II), [Pd₂(μ-dppb)(L)₂] (III) and [Pd₂(μ-dppf)(L)₂] (IV); where H₂L, dppb and dppf represent 4-methoxy-N′-(mesitylidene)benzohydrazide, 1,4-bis(diphenylphosphino)butane and 1,1′-bis(diphenylphosphino)ferrocene, respectively. The reactions were conducted using potassium carbonate as base in presence of tetrabutylammonium bromide (TBAB) at 70/90 °C in dimethylformamide–water (1:20) mixture. Among the four catalysts used, the dinuclear complex IV turned out to be the most effective and afforded moderate to excellent yields with broad substrate scope.     

Synthesis of mesoporous Ca-MCM catalysts and their use in suitable multicomponent synthesis of polyfunctionalized pyrans

Mesoporous Ca-MCM catalysts were prepared using a mixture of CaCO₃, TEOS, cetyl trimethyl ammonium bromide (CTAB), triethanolamine (TEA), ethanol and H₂O. Three catalysts with different CaCO₃ contents, M-Ca 1 %, M-Ca 5 % and M-Ca 10 %, respectively, were prepared and characterized by N₂ physisorption, XRD, FT-IR, XPS, TPD-CO₂ and Pyridine-FTIR. A green and simple protocol was developed for the synthesis of 6-amino-4H-pyran scaffolds through a multicomponent coupling reaction of an aldehyde, malononitrile, and 1,3-dicarbonyl compound in different reaction solvents. This procedure was performed at room temperature (20 °C), obtaining good and excellent yields of 4H-pyran derivatives. The mesoporous materials are insoluble in polar media, which allows easy removal of the reaction products without affecting their catalytic activity. The leaching test showed an excellent stability, and Ca-MCM catalysts can be used three times without appreciable loss of their catalytic activity.     

Synthesis,characterization, and crystal structures of 2D cobalt(II) and nickel(II) coordination polymers containing flexible bis(benzimidazole) ligands

Three coordination polymers, namely {[Ni(L1)(nip)(H₂O)]·2H₂O} _n (1), [Co(L2)(tbip)] _n (2), and {[Co₂(L3)₂(bptc)]·3H₂O} _n (3) (L1 = 1,4-bis(5,6-dimethylbenzimidazole)butane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)-2-butylene, L3 = 1,3-bis(5,6-dimethylbenzimidazole)propane, H₂nip = 5-nitro-isophthalic acid, H₂tbip = 5-tert-butyl-isophthalic acid, H₄bptc = biphenyl-3,3′,4,4′-tetracarboxylic acid), have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single-crystal X-ray diffraction analysis. Complexes 1 and 2 both feature a two-dimensional (4,4) layer with (4⁴ × 6²) topology. Complex 3 possesses a uninodal 4-connected 2D htb network. The fluorescence spectra and catalytic properties of the complexes for the degradation of methyl orange by sodium persulfate in a Fenton-like process are reported.     

Synthesis,structure, and magnetic properties of heterotrimetallic tetranuclear complexes

Two novel heterotrimetallic tetranuclear complexes [Cu(H₂L)(CH₃OH)]₂Gd(DMF)Fe(CN)₆·2H₂O·DMF (1) and [Cu(H₂L)(CH₃OH)]₂Tb(H₂O)_0.57(DMF)_0.43Fe(CN)₆·5.5H₂O (2) are reported (H₄L = N,N′-ethylenebis(3-hydroxysalicylidene)). The central Ln(III) ion is surrounded by two neutral [Cu(H₂L)(CH₃OH)] moieties, forming a Cu₂Ln trinuclear unit. The [Fe(CN)₆]^3? anion is weakly coordinated to one Cu(II) ion of [Cu(H₂L)(CH₃OH)] through a cyanide nitrogen atom with the N–Cu distance of ca. 3.2 Å. Magnetic susceptibility measurements indicate the presence of overall ferromagnetic interactions in complexes 1 and 2. The magnetic coupling constant in complex 1 is J _Cu1Gd1 = 4.54 cm^?1 and J _Cu2Gd1 = 7.97 cm^?1 based on \( \hat{H} = - 2J_{\text{Cu1Gd1}} \hat{S}_{\text{Cu1Gd1}} - 2J_{\text{Cu2Gd1}} \hat{S}_{\text{Cu2Gd1}} \) . Dynamic AC magnetic susceptibility studies reveal that complex 2 shows frequency-dependent out-of-phase signals, typical of single molecule magnet behavior. The energy barrier for complex 2 under a 2 kOe applied DC magnetic field is 13 K.     

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds and their morphology and application in catalysis: III. Catalytic properties of massive Ni-Mo sulfide catalysts synthesized using mechanochemical activation

The precursors of massive Ni-Mo catalysts for hydrotreating processes, which were synthesized by the mechanochemical activation of a mixture of nickel hydroxocarbonate NiCO₃·2Ni(OH)₂·nH₂O and ammonium paramolybdate (NH₄)₆Mo₇O₂₄ · 4H₂O, were sulfidized. Their structure was studied by X-ray diffraction analysis and high-resolution electron microscopy. It was found that MoS₂ packets, which are characterized by the presence of structural defects and geometric curvature, are the constituents of the massive catalysts. The catalyst also includes a phase of Ni₃S₂ and regions containing a complex Ni-Mo-S phase. The catalytic tests of the synthesized catalysts in the model reactions of 1-methylnaphthalene and dibenzothiophene conversions showed that the catalyst whose precursor was a heteropoly compound with the Anderson structure after the stage of mechanochemical activation exhibited the highest activity.     

Controllable synthesis of MnO2/iron mesh monolithic catalyst and its significant enhancement for toluene oxidation

A series of monolithic MnO₂/iron mesh (IM) catalysts for oxidation of toluene were successfully prepared by using in situ hydrothermal growth. MnO₂ can grow firmly on the IM substrates surface with a shedding rate of only 0.14%. Due to the highest O_ads and high-valent Mn⁴⁺ and Fe³⁺ elements, the temperature at 50% and 90% toluene conversion (T_50% and T_90%) was 252 and 265 °C, respectively for the best performance catalyst (hydrothermal temperature of 80 °C, hydrothermal time of 12 h, and precursor manganese ion concentration of 0.03 mol/L). The catalysts also presented good water resistance and cycle performance. In-situ DRIFTS results suggesting that toluene was first rapid transformed into the reaction intermediate species (benzoate species) and then converted to CO₂ and H₂O. Therefore, this work provides a new direction for the research and application of IM-based monolithic catalysts.     

Preparation and catalytic activity for ammonia synthesis of several ruthenium supported catalysts

Ruthenium supported catalysts were prepared from RuCl₃ · 3H₂O and K₄[Ru(CN)₆] · 3 H₂O solutions, upon several acid/base pretreated γ-Al₂O₃ samples, using water and acetone as solvents. Metallic adsorption was found to be dependent on solvent and precursor used. An increasing final ruthenium content of the catalysts with increasing acid site content of the support is observed, when K₄[Ru(CN)₆] · 3 H₂ is used as a precursor. The catalytic activity was followed at atmospheric pressure and 593 K (N₂/H₂ = 1/3). Catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O were about ten fold more active than those prepared from RuCl₃ · 3 H₂O. The catalytic activity of catalysts prepared from K₄[Ru(CN)₆] · 3 H₂O was found to be sensitive to the acid-pretreatment of γ-Al₂O₃, while the activity of those prepared from RuCl₃ · 3 H₂O was not sensitive to the pretreatment of the support.     

Micron‐granula polyolefin with self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups

Self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArN?C]₂(C₁₀H₆)NiBr₂ [Ar = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₂] ( 1 ), [ArN?C(Me)][Ar′N? C(Me)]C₅H₃NFeCl₂ [Ar = Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃, Ar = 2,6‐(i‐Pr)₂C₆H₃, and Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArN?C]₂C₁₀H₆NiBr₂ (Ar = 2,6‐(i‐Pr)₂C₆H₂)], but also greatly improved the morphology of polymer particles to afford micron‐granula polyolefin. The self‐immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self‐immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018–1024, 2004     

Bioprocessing of Biodiesel Industry Effluent by Immobilized Bacteria to Produce Value-Added Products

Biodiesel industrial effluent rich in crude glycerol (CG) was processed to produce value-added product. Under continuous culture system, Bacillus amyloliquefaciens strain CD16 immobilized within its biofilm, produced 3.2 L H₂/day/L feed, over a period of 60 days at a hydraulic retention time of 2 days. The effective H₂ yield by B. amyloliquefaciens strain CD16 was 165 L/L CG. This H₂ yield was 1.18-fold higher than that observed with non-biofilm forming Bacillus thuringiensis strain EGU45. Bioprocessing of the effluent released after this stage, by recycling it up to 25% did not have any adverse effect on H₂ production by strain EGU45; however, a 25% reduction in yield was recorded with strain CD16. Biofilm forming H₂ producers thus proved effective as self-immobilizing system leading to enhanced process efficiency.     

Syntheses and crystal structures of phthalato-, succinato-, maleato-, acetylenedicarboxylato-bridged [bis(2-pyridylcarbonyl)amide]copper(II) complexes

Self-assemblies of the 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) and Cu(OH)₂ in the presence of dicarboxylate ligands yielded four new complexes, [Cu₄(bpca)₄(L1)₂(H₂O)₂]·5H₂O (1), [Cu₂(bpca)₂(L2)(H₂O)₂]·2H₂O (2), [Cu₂(bpca)₂(L3)(H₂O)₂]·H₂O (3), and [Cu₂(bpca)₂(L4)(H₂O)₂]·3H₂O (4) (bpca = bis(2-pyridylcarbonyl)amide anion, H₂L1 = phthalic acid, H₂L2 = succinic acid, H₂L3 = maleic acid, H₂L4 = acetylenedicarboxylic acid). Their structures were determined by single-crystal X-ray diffraction analyzes and further characterized by IR spectra and thermogravimetric analyzes. The five-coordinate Cu ions in 1 are bridged by phthalate to form 1-D chains, which are assembled into 3-D frameworks by extensive hydrogen bonds. Compounds 2–4 possess similar structures, built up of [Cu₂(bpca)₂(L)(H₂O)₂] (L = L2 for 2, L3 for 3, L4 for 4) and lattice molecules. The 3-D frameworks of 2–4 are completed by hydrogen bond interactions.     

Two cobalt(II) metal–organic frameworks based on mixed 1,2,4,5-benzenetetracarboxylic acid and bis(benzimidazole) ligands

Two cobalt(II) metal–organic frameworks constructed from 1,2,4,5-benzenetetracarboxylic acid and flexible bis(5,6-dimethylbenzimidazole) ligands, namely {[Co_1.5(Hbtec)(L1)_1.5(H₂O)₂]·(H₂O)} _n and {[Co(H₂btec)(L2)]·(L2)_0.5(H₂O)₂} _n [L1 = 1,4-bis(5,6-dimethylbenzimidazole-1-ylmethyl)benzene, H₄btec = 1,2,4,5-benzenetetracarboxylic acid, L2 = 1,4-bis(5,6-dimethylbenzimidazole)butane], have been hydrothermally synthesized and characterized by physicochemical and spectroscopic methods and by single-crystal X-ray diffraction. The cobalt atoms present different coordination environments, with trigonal-bipyramidal and octahedral geometries in 1, and a tetrahedral geometry in 2. Complex 1 has a 2D (6,3) wave like layer structure, which is further linked by hydrogen bonding to generate a 3D supramolecular architecture. It is a trinodal (4,4,4)-connected topology with a point symbol of {4²·6·8³}₂{4²·6²·8²}{4³·6³}₂. Complex 2 is a 2D (6,3) honeycomb net, further linked into a 3D supramolecular network via two modes of π–π stacking interactions. The degradation of methyl orange in a Fenton-like process using complexes 1 and 2 as catalysts has been investigated.     

Cyclometalated complexes containing ferrocenyl Schiff base: Preparation,characterization, DFT calculations,application in cancer and biological researches and MOE studies

A series of transition metal (II/III) complexes containing organometallic Schiff base ligand (H₂L) had been synthesized and characterized by using elemental analysis (C, H, N, M), molar conductivity, IR, UV–Vis, ¹H NMR and mass spectral analysis. Also, their TG and DTG behaviors were investigated. The ligand was prepared by condensation of 4-aminosalicylic acid with 2-acetylferrocene in 1:1 M ratio. The data of elemental analysis indicated that the prepared complexes were synthesized also in a 1:1 M ratio. The ligand behaved as neutral bidentate ligand that coordinated to metal ions through protonated O-phenolic and protonated carboxylic-OH groups. All complexes had octahedral structure. DFT calculations for H₂L ligand were determined with some parameters such as HOMO-LUMO energy gab, electronegativity and chemical hardness–softness. Antimicrobial activity of both H₂L Schiff base ligand and its metal complexes was tested against different strains of bacteria and fungi species. Furthermore, all compounds had been screened for their anticancer activities against breast cancer (MCF-7) cell line. [Cu(H₂L)(H₂O)₂Cl₂]·2H₂O complex had the lowest IC₅₀ value = 47.3 µg/mL. For determining the more effective and probable binding mode between the H₂L ligand, Co(II) and Zn(II) complexes with different active sites of 4K3V, 2YLB and 3DJD receptors, so molecular docking studies were investigated.     

Solution Equilibria of Ternary Systems Involving Nickel(II) Ion,Picolinic Acid,and the Amino Acids Histidine,Cysteine, Aspartic and Glutamic Acids

Solution equilibria of the ternary systems Ni(II)–picolinic acid (Hpic) and the amino acids aspartic acid (H₂asp), glutamic acid (H₂glu), cysteine (H₂cys) and histidine (Hhis), where the amino acids are denoted as H _i L, have been studied pH-metrically. The formation constants of the resulting mixed ligand complexes have been determined at 25 °C using a ionic strength 1.0 mol·dm^?3 NaCl. In the Ni(II)–Hpic–H₂asp and Ni(II)–Hpic–H₂glu systems, the complexes [Ni(pic)H₂L]⁺, Ni(pic)HL, [Ni(pic)L]^? and [Ni(pic)L(OH)]^2? were detected. In the Ni(II)–Hpic–H₂cys system the complexes [Ni(pic)H₂L]⁺ and [Ni(pic)L]^? are present. Additionally, in the Ni(II)–Hpic–Hhis system the species [Ni(Hpic)HL]²⁺, Ni(pic)L and [Ni(pic)L(OH)]^? were identified. The species distribution diagrams as functions of pH are briefly discussed.     

Nickel(II) complexes bearing pyrazolylpyridines: synthesis,structures and ethylene oligomerization reactions

Reactions of 2‐bromo‐6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine ( L1 ) and 2,6‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine ( L2 ) with NiCl₂ and NiBr₂ led to the formation of their respective metal complexes [NiCl₂(L1)] ( 1 ), [NiBr₂(L1)] ( 2 ) and [NiBr₂(L2)] ( 3 ) in moderate to high yields. The complexes were characterized using elemental analyses, mass spectrometry and single‐crystal X‐ray diffraction for 2 . The solid‐state structure of 2 confirmed the bidentate coordination mode of L1 and formation of a monometallic compound. Activation of the nickel(II) pre‐catalysts with methylaluminoxane afforded active catalysts in the ethylene oligomerization reaction to produce mainly butenes (84–86%). In contrast, activation of nickel(II) pre‐catalyst 2 with ethylaluminium dichloride resulted in partial Friedel–Crafts alkylation of the toluene solvent by the preformed oligomers. Complex structure, nature of co‐catalyst employed, type of solvent and reaction conditions influenced the catalytic behaviour of these pre‐catalysts. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrogen Peroxide Sensor Based on Hemoglobin Immobilized on Glassy Carbon Electrode with SiO2 Nanoparticles/Chitosan Film as Immobilization Matrix

Abstract

A novel amperometric sensor of hydrogen peroxide was constructed. Hemoglobin (Hb) was successfully immobilized on nanometer‐sized SiO₂, which was supported by chitosan. Chitosan was acted as dispersant. The determination of hydrogen peroxide was performed in the presence of an electron mediator hydroquinone. Hb immobilized on the SiO₂/chitosan composite film displayed excellent electrocatalytical activity to the reduction of H₂O₂. The linear range of detection towards H₂O₂ was from 6.25×10^?7 to 1.63×10^?4mol/L with a detection limit of 1.8×10^?7mol/L (S/N=3). The apparent Michaelis‐Menten constant (K ^app _M) was found to be 0.75mmol/L.