Indirect electrochemical cyclization of bromoalkoxylated derivatives mediated by nickel(II) complex in environmental-friendly medium

An improved procedure has been developed using a catalytic amount of a nickel(II) complex in the efficient and selective electrochemical cyclization of propargyloxy and allyloxy bromo derivatives into substituted tetrahydrofurans using ethanol and ethanol-water mixtures as environmental-friendly systems. The reduction of the substrates proceeded via one-electron cleavage of the carbon-bromine bond to form a radical-type intermediate that undergoes cyclization to afford the tetrahydrofuran structures in good yields.     

Nonaqueous polymerization of vinyl chloride: An environmentally friendly process

Poly(vinyl chloride) (PVC) is produced via a nonaqueous polymerization process in which hexane is used as a diluent. This nonaqueous process can lead to significant energy savings, significant reductions in carbon dioxide emissions, and the elimination of wastewater. Various suspending agents have been used to evaluate their effects on the shape and morphology of PVC grains. The nonaqueous process leads to the formation of PVC grains with higher porosity than that of typical suspension PVC. The bulk density is slightly lower than that of suspension PVC, but the thermal stability seems to be similar. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A novel one-dimensional nickel(II) complex with a hydrogen-bond-link

A novel compound [Ni(L)(H₂O)₂]_0.5[Ni(L)(WO₄)₂]_0.5·4H₂O (1) (L=3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) has been structurally and magnetically characterized. The nickel(II) ions are shown to be in distorted octahedral environments with secondary amines of macrocycles in which two trans water molecules and two trans tungstate ions are assembled around each metal center. Two nickel(II) complexes are connected into a one-dimensional chain via hydrogen bonds. The magnetic susceptibility measurement for 1 indicates weak antiferromagnetic interaction (J=−1.01(2) cm⁻¹; H=−JΣS_i·S_i+1) between the S=1 nickel(II) paramagnetic centers.     

Synthesis,characterization and antibacterial activity of Pd(II), Pt(II) and Ag(I) complexes of 4-ethyl and 4-(p-tolyl)-1-(pyridin-2-yl)thiosemicarbazides

Pd(II), Pt(II) and Ag(I) ions were found to form stable complexes with 4-(p-tolyl)- or 4-ethyl-1-(pyridin-2-yl)thiosemicarbazides (Hp-TPTS or HEPTS). The complex structure was elucidated by analysis (elemental and thermal), spectroscopy (electronic, IR and ¹H NMR spectra) and physical measurements (magnetic susceptibility and molar conductance). The ligands coordinate to the metal ions as monobasic bidentate through nitrogen and sulfur atoms. The electronic spectra of the Pt(II) complexes in DMF showed a metal to ligand charge transfer transition at 11,935–13,260 cm^?1. The structural, electronic and vibrational features of HEPTS and Hp?TPTS were discussed on the basis of semi-empirical quantum mechanic calculations [ZINDO/S and semi-empirical parameterization (PM3)]. The simulated IR and electronic spectra are found reasonable in accordance with the experimental data. Finally, the antibacterial activities of the ligands and their complexes were investigated and some were found promising.     

Development of an environmentally friendly solventless process for electronic prepregs

The most common commercial processes for manufacturing prepregs for electronic applications use solvent‐based resin systems. Solvents are not environmentally friendly and contribute to voids in prepregs and laminates. The resin impregnation process is performed in an open resin bath. This low‐pressure impregnation is conducive to voids in prepregs. Voids cause product variability, which is a major source of scrap in board shops. To eliminate these drawbacks, a solventless process, based on the concept of injection pultrusion, has been developed. The impregnation is performed in a die under pressure to minimize voids. In previous work, chemorheological and kinetic measurements were used to identify a potential epoxy‐based resin system. In addition, flow visualization with model fluids was used to establish the basic flow mechanism. Here we use the previous results to develop a mathematical model for the B‐staging process. A prototype B‐staging die has been built and used to verify the mathematical model. The results show that the model agrees well with the experimental data for low pulling speeds and slightly underpredicts the runs at high pulling speeds. The properties of the prepregs, the dielectric constant (DK) and dielectric loss (DF), have also been measured in this research. The measurements show that the solventless prepregs have acceptable DK and DF values according to the Institute for Printed Circuits FR‐4 designation (a permittivity and tangent loss standard). A microscope has been used to observe the void contents of the prepregs. The solventless prepregs have been compared against standard FR‐4 prepregs and shown qualitatively to have fewer voids. Based on the mathematical model, two potential process alternatives for the manufacture of solventless prepregs have been developed and analyzed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1136–1146, 2004     

Nickel(II) complexes of whole set of the simple ethylenediaminetetracarboxylate ligands: DFT study of complexes invoking molecular orbital and configurational analysis

The whole set of the nickel(II) complexes with no derivatized edta-type hexadentate ligands has been investigated from their structural and electronic properties. Two more complexes have been prepared in order to complete the whole set: trans(O₅)-Mg[Ni(ed3ap)]·8H₂O and trans(O₅O₆)-Ba[Ni(eda3p)]·4H₂O complexes. trans(O₅) geometry has been verified crystallographicaly and trans(O₅O₆) geometry of the second complex has been predicted by the DFT theory and spectral analysis. Mutual dependance has been established between: the number of the five-membered carboxylate rings, octahedral/tetrahedral deviation of metal-ligand/nitrogen-neighbour-atom angles, charge-transfer energies (CTE) calculated by the Morokuma’s energetic decomposition analysis and energy of the absorption bands and HOMO–LUMO gap.     

A review of environmentally friendly rubber production using different vegetable oils

Vegetable oils were investigated as plasticizers to improve the sustainability of rubber compounding. The potential use of different vegetable oils as an alternative to petroleum-based rubber process oils was reviewed. This article presents a literature review on the current understanding of the influence of vegetable oil properties on natural rubber (NR) compounding. Hansen solubility parameters of the vegetable oils were determined to assist with the selection of vegetable oil for NR. We believe that the use of Hansen parameters could make the use of vegetable oils in rubber more convenient and cost-effective.     

The Effect of the Synthetic Conditions on the Deposition and Distribution of Copper Complexes on Polymer Supports

The influence of conditions (e.g., ratios of components, temperature etc.) on the reaction of Cu(OCOCH₃)₂·2H₂O with polyethylene grafted-polyacrylic on the amount of the metal and the composition of the immobilized Cu(II) complexes was studied. The concentration dependence obeys the Langmuir law. Analysis of the data leads to an evaluation of the stability constant for the Cu(II) complexes (K=300 l/mole at 333 K). The constant corresponds to a Cu(II) fixation value, k=0.35 mole/l (22.22 mg Cu(II)/g). The multistage fixation mechanism for Cu(II) complex formation was demonstrated by the marked atom technique. Cu(II) is fixed by one carboxylate group (to 16 mol% of the supported Cu(II), K ₁=16×10^–2 mole/g) and by two carboxylate groups (K ₂=2.54×10^–3 mole/g) of the grafted ligands. The PE-gr-PAA–Cu(II) system mimics the situation-insoluble support-soluble functional polymer covering and realizes the advantages of both the soluble and the three-dimensional crosslinked polymer. Steady-state magnetic susceptibility measurements and ESR spectroscopy were used to study the distribution of cupric ion attached to a polyethylene-grafted poly(acrylic acid) support. The existence of three types of cupric ion complexes was demonstrated: (1) isolated complexes, (2) complexes bonded by dipole–dipole interactions, and (3) clusters with strong exchange interactions. The mean distances between the isolated ions (¯r22–15 Å) and between the dipole–bound complexes (¯r _agreg7 Å) were estimated. The results obtained were compared to the data for other immobilized catalysts. Preliminary results on the fixation of bimetallic Cu(II) and Pd(II) complexes to the polymers as well as on their distributions were obtained.     

A voltammetric study of α- and β-hydroxides over nickel alloys

The hydrogen evolution reaction (HER) is one of the most studied electrochemical process due to the alternative energy conversion and the importance in some chemical process. The search for new electrocatalytic materials lead to investigate metals and alloys with particular characteristics/properties. This paper describes aspects of hydrogen adsorption and Ni-hydroxide formation over nickel alloys (SAF2205, INCONEL625 and MONEL400) utilizing cyclic voltammetry. The SAF2205 (6.4% Ni) alloy present behavior analogue to pure Ni electrodes to hydroxide species, and can bring some advantages to HER compared with the carbon steel (SAE1020) electrode commonly utilized in industrial process.     

Development of environmentally friendly antifouling paints using biodegradable polymer and lower toxic substances

The development of new antifouling coatings with respect to the marine environment is actually crucial. The aim of the present work is to concept an erodible paint formulated with biodegradable polyester as binders and which combines two modes of prevention: chemical and physical repelling of biofouling. This system is principally dedicated to disturb durable settlement of microfouling. Each component was chosen according to its specific properties: chlorhexidine is a bisdiguanide antiseptic with antibacterial activity, zinc peroxide is an inorganic precursor of high instable entities which react with seawater to create hydrogen peroxide, Tween 85 is a non ionic surfactant disturbing interactions between colonizing organisms and surface. Obtained results highlighted the interest on mixing such molecules to obtain a promising coating with lower toxicity than traditional systems.     

Sorption of heavy metal ions from aqueous solution by a novel cast PVA/TiO2 nanohybrid adsorbent functionalized with amine groups

Sorption of Cd(II), Ni(II) and U(VI) ions onto a novel cast PVA/TiO₂/APTES nanohybrid adsorbent with variations in adsorbent dose, pH, contact time, initial metal concentration and temperature has been investigated. The adsorbent were characterized by SEM and FTIR analysis. BET surface area, pore diameter and pore volume of adsorbent were 35.98 m² g⁻¹, 3.08 nm and 0.059 cm³ g⁻¹, respectively. The kinetic and equilibrium data were accurately described by the double-exponential and Freundlich models for all metals. The maximum sorption capacities were 49.0, 13.1 and 36.1 mg g⁻¹ for Cd(II), Ni(II) and U(VI) ions with pH of 5.5, 5 and 4.5, respectively. Thermodynamic studies showed that the sorption process was favored at higher temperature. The adsorbent can be easily regenerated after 5 cycles of sorption–desorption.     

Bis[4-(methylthio)phenylmethyleneaminophenyl] disulfide, 2-[4-(methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole,and its nickel(II) and cobalt(II) complexes: Synthesis,adsorption on gold surface and electrochemical characterization

2-[4-(Methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole (1) and bis[4-(methylthio)phenylmethylene-aminophenyl] disulfide (2) were synthesized. Novel coordination compounds of Ni(II) and Co(II) with 2-[4-(methylthio)phenylmethyleneamino]thiophenol, M(1)₂ (M=Co (3); M=Ni (4)), were prepared by reacting 1 with M(OAc)₂·6H₂O or MCl₂·6H₂O in EtOH solution. The structure of 2 was proved by X-ray crystallography. Electrochemical behavior of 1–4 in CH₃CN solution and at the surface of a gold electrode was studied by cyclic voltammetry. The modification of the electrode by ligand 1 and its complexes with Ni²⁺ and Co²⁺ is described in detail. Two procedures were used to obtain a self-assembled monolayer of a metal complex on the gold surface: the adsorption of prepared coordination compound 3 or 4 on the electrode and the initial modification of the electrode with ligand 1 followed by the formation of a coordination complex between the ligand adsorbed on the electrode and a metal salt occurring in solution. On the basis of the electrochemical data, it was found that the structure of complexes formed on the surface differs from that of the complexes produced in solution.     

DNA-Binding Study of Tetraaqua-bis(p-nitrobenzoato)cobalt(II) Dihydrate Complex: [Co(H2O)4(p-NO2C6H4COO)2]·2H2O

The interaction of [Co(H₂O)₄(p-NO₂C₆H₄COO)₂]^· 2H₂O with sheep genomic DNA has been investigated by spectroscopic studies and electrophoresis measurements. The interaction between cobalt(II) p-nitrobenzoate and DNA has been followed by gel electrophoresis while the concentration of the complex was increased from 0 to 14 mM. The spectroscopic study and electrophoretic experiments support the fact that the complex binds to DNA by intercalation via p-nitrobenzoate into the base pairs of DNA. The mobility of the bands decreased as the concentration of complex was increased, indicating that there was increase in interaction between the metal ion and DNA.     

Reduction of nitroaromatics with poly(vinylpyridine) complexes of palladium(II) and platinum(II)

Palladium(II) and platinum(II) anchored to 2- and 4-vinylpyridine polymers of different molecular weights were used for the dihydrogen reduction of various nitroaromatics and benzaldehyde in ethanol at 50°C. Palladium(II) complexes were far more effective than their platinum(II) analogues and the activity decreased with increasing molecular weights of the polymers. The nitroaromatics were selectively and almost completely reduced to the corresponding anilines. During reduction, the orange palladium(II) complexes changed to voluminous green precipitates, which could be used repeatedly and preserved for a long time without any loss of activity. A rate equation of the type: rate = K[Cat] [H₂] has been derived and a reduction mechanism has been proposed on the basis of experimental results and kinetic data.     

Synthesis and characterization of resins with ligands containing guanidinine derivatives. Cu(II) sorption and coordination properties

A new modification direction of acrylonitrile, vinyl acetate and divinylbenzene terpolymers (A, B) are presented. The aminolysis of nitrile groups of the terpolymers using ethylenediamine or hydroxylamine hydrochloride was a first stage of the modification. The resulting amine groups reacted with dicyandiamide (DCDA), cyanamide (CA) and sodium dicyanimide (SDC) in order to obtain the biguanidyl, guanidyl or nitrilguanidyl derivatives in the polymer side chain, respectively. The properties of all obtained resin such as water regain, nitrogen content, amine and carboxyl group concentration and sorption properties towards Cu(II) from nitric acid solutions were determined. The studies of IR spectra of all the resins were performed. Structures of ligand complexes with Cu(II) were studied using electron paramagnetic resonance spectroscopy.     

Diastereoselective and Highly Enantioselective Henry Reactions using C1‐Symmetrical Copper(II) Complexes

Catalytic Henry reactions of aliphatic aldehydes and prochiral nitro compounds were investigated using copper(II) complexes of 14 C₁‐symmetrical ligands derived from (1R,2R)(−)‐diaminocyclohexane. β‐Nitro alcohols with syn:anti ratios of up to 5.7 and excellent ee values for both diastereosimers were obtained.     

Direct synthesis and characterization of novel homo- and heterometallic mixed-ligand tetrazolate complexes, Cu(en)(tz)2 and Cu(en)2Zn(tz)4 [en = ethylenediamine, tz = tetrazolate]

For the first time, tetrazolate complexes have been prepared by direct synthesis. Two novel homo- and heterometallic mixed-ligand complexes, Cu(en)(tz)₂ and Cu(en)₂Zn(tz)₄, have been synthesized using tetrazole (Htz), ethylenediamine (en), metallic copper and zinc oxide as starting materials. Both tetrazolates were characterized by single-crystal X-ray diffraction, IR spectroscopy and thermal analysis. The complexes present 1D coordination polymers, with tetrazolate anions acting as both monodentate and bridging ligands.     

Cationic Peptides and Their Cu(II) and Ni(II) Complexes: Coordination and Biological Characteristics

Antimicrobial peptides are a promising group of compounds used for the treatment of infections. In some cases, metal ions are essential to activate these molecules. Examples of metalloantibiotics are, for instance, bleomycin and dermcidin. This study is focused on three new pseudopeptides with potential biological activity. The coordination behavior of all ligands with Cu(II) and Ni(II) ions has been examined. Various analytical methods such as potentiometric titration, UV-Vis and CD spectroscopies, and mass spectrometry were used. All compounds are convenient chelators for metal ion-binding. Two of the ligands tested have histidine residues. Surprisingly, imidazole nitrogen is not involved in the coordination of the metal ion. The N-terminal amino group, Dab side chains, and amide nitrogen atoms of the peptide bonds coordinated Cu(II) and Ni(II) in all the complexes formed. The cytotoxicity of three pseudopeptides and their complexes was evaluated. Moreover, their other model allowed for assessing the attenuation of LPS-induced cytotoxicity and anti-inflammatory activities were also evaluated, the results of which revealed to be very promising.     

Water-Soluble Monoamineplatinum(II) Complexes Bound to Polyaspartamide Carriers by a Poly(ethylene Oxide) Spacer

In continuation of earlier work in this laboratory comprising the synthesis of water-soluble polyaspartamide-monoamineaquadichloroplatinum conjugates as potential antineoplastic agents, the presently described project is concerned with related conjugates in which the same type of monoamineplatinum complex unit is bound to polyaspartamide carriers via main chain-attached poly(ethylene oxide) (PEO) spacers introduced here in order to improve certain biomedical performance features. The conjugates are synthesized by aqueous-phase platination of amine terminals on the PEO side chains of the carriers, brought about by treatment with tetrachloroplatinate(II) anion under closely controlled conditions of time, temperature, and acidity, followed by dialysis. The target polymers, separated by freeze-drying, are completely water soluble upon isolation, yet undergo slow intermolecular interaction in the solid state with a gradual loss of solubility unless stored in (frozen) aqueous solution at –30°C.     

The Influence of Alkyl Chain Length and Steric Effect on Extraction of Zinc(II) Complexes with 1‐Alkyl‐2‐Methylimidazoles

Abstract

The extraction of Zn(II) complexes with six 1‐alkyl‐2‐methylimidazoles (alkyl is from C₅H₁₁ up to C₁₂H₂₅) from nitric solution was studied as a function of pH of the aqueous phase. As the organic solvents toluene, p‐xylene and 1,2,3,4‐tetrahydronaphthalene were used. The stability constants of the complexes in the aqueous phase as well as partition constants of the extractable species were determined. It was demonstrated that both the stability constants (β_c) and the partition constants (P_c) of the complexes increased with increasing alkyl chain length. Pseudo‐tetrahedral complexes were found to dominate at the second and third complexation steps, thus increasing the stability constants and facilitating extraction of the Zn(II) complexes with 1‐alkyl‐2‐methylimidazoles.