Copper(II) complexes of tetradentate N2S2 donor sets: synthesis, crystal structure characterization and reactivity

Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [Cu-II(L-1)Cl]ClO4 (1), [Cu-II(L-2)Cl]ClO4 (2) and [Cu-2(II)(L-3)(2)Cl-2](ClO4)(2) (3) were synthesized and isolated in pure form [where L-1 = 1,2-bis(2-pyridylmethylthio)ethane, L-2 = 1,3-bis(2-pyridylmethylthio)propane and L-3 = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [Cu-2(1)(L-3)(2)](ClO4)(2),0.5H(2)O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes I and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral. (C) 2008 Elsevier Ltd. All rights reserved.

Modelling small angle neutron scattering data from electrospun fibres

Electrospinning is a technique employed to produce nanoscale to microscale sized fibres by the application of a high voltage to a spinneret containing a polymer solution. Here we examine how small angle neutron scattering data can be modelled to analyse the polymer chain conformation. We prepared 1:1 blends of deuterated and hydrogenated atactic-polystyrene fibres from solutions in N, N-Dimethylformamide and Methyl Ethyl Ketone. The fibres themselves often contain pores or voiding within the internal structure on the length scales that can interfere with scattering experiments. A model to fit the scattering data in order to obtain values for the radius of gyration of the polymer molecules within the fibres has been developed, that includes in the scattering from the voids. Using this model we find that the radius of gyration is 20% larger than in the bulk state and the chains are slightly extended parallel to the fibre axis.

Isolation, structure, chemistry, and photochemistry of cis-bis(2,2'-bipyridyl)carbonylchlororuthenium(II) perchlorate

The molecular structure and chemical and photochemical reactions of [Ru(bpy)2(CO)Cl]+ClO4–, which has been isolated from the reaction of ruthenium trichloride and 2,2′-bipyridyl(bpy) in dimethylformamide, are described.

Structural and magnetic studies of Schiff base complexes of nickel(ii) nitrite: change in crystalline state, ligand rearrangement and a very rare μ-nitrito-1κO:2κN:3κO′ bridging mode

Four new nickel(II) complexes, [Ni2L2(NO2)2]·CH2Cl2·C2H5OH, 2H2O (1), [Ni2L2(DMF)2(m-NO2)]ClO4·DMF (2a), [Ni2L2(DMF)2(m-NO2)]ClO4 (2b) and [Ni3L¢2(m3-NO2)2(CH2Cl2)]n·1.5H2O (3) where HL = 2-[(3-amino-propylimino)-methyl]-phenol, H2L¢ = 2-({3-[(2-hydroxy-benzylidene)-amino]-propylimino}-methyl)-phenol and DMF = N,N-dimethylformamide, have been synthesized starting with the precursor complex [NiL2]·2H2O, nickel(II) perchlorate and sodium nitrite and characterized structurally and magnetically. The structural analyses reveal that in all the complexes, NiII ions possess a distorted octahedral geometry. Complex 1 is a dinuclear di-m2-phenoxo bridged species in which nitrite ion acts as chelating co-ligand. Complexes 2a and 2b also consist of dinuclear entities, but in these two compounds a cis-(m-nitrito-1kO:2kN) bridge is present in addition to the di-m2-phenoxo bridge. The molecular structures of 2a and 2b are equivalent; they differ only in that 2a contains an additional solvated DMF molecule. Complex 3 is formed by ligand rearrangement and is a one-dimensional polymer in which double phenoxo as well as m-nitrito-1kO:2kN bridged trinuclear units are linked through a very rare m3-nitrito-1kO:2kN:3kO¢ bridge. Analysis of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the nickel(II) ions in four complexes, with exchange parameters J of -5.26, -11.45, -10.66 and -5.99 cm-1 for 1, 2a, 2b and 3, respectively

Synthesis of novel hyperbranched polymers featuring oxazoline linear units and their application in fast-drying solvent-borne coating formulations

Novel acid-terminated hyperbranched polymers (HBPs) containing adipic acid and oxazoline monomers derived from oleic and linoleic acid have been synthesized via a bulk polymerization procedure. Branching was achieved as a consequence of an acid-catalyzed opening of the oxazoline ring to produce a trifunctional monomer in situ which delivered branching levels of >45% as determined by 1H and 13C NMR spectroscopy. The HBPs were soluble in common solvents, such as CHCl3, acetone, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide and were further functionalized by addition of citronellol to afford white-spirit soluble materials that could be used in coating formulations. During end group modification, a reduction in branching levels of the HBPs (down to 12–24%) was observed, predominantly on account of oxazoline ring reformation and trans-esterification processes under the reaction conditions used. In comparison to commercial alkyd resin paint coatings, formulations of the citronellol-functionalized hyperbranched materials blended with a commercial alkyd resin exhibited dramatic decreases of the blend viscosity when the HBP content was increased. The curing characteristics of the HBP/alkyd blend formulations were studied by dynamic mechanical analysis which revealed that the new coatings cured more quickly and produced tougher materials than otherwise identical coatings prepared from only the commercial alkyd resins.

The role of solvent on the doping of polyaniline with Fe(III) ions

The products formed from the reaction of emeraldine base polyaniline (EB-PANI) with Fe(III) ions in N-methyl-pyrrolidone (NMP), dimethylacetamide (DMA), dimethylformamide (DMF) and m-cresol media have been investigated using UV-VIS-NIR and resonance Raman (lambda(0) = 632.8 and 1064 nm) spectroscopies. Through these results it was verified that the different PANI forms in solution can be formed by the suitable choice of the solvent. The behavior of Fe(III)/EB-PANI in different solvents was rationalized in terms of the interactions among Fe(III) ions, EB-PANI and solvent. In basic NMP, DMA and DMF media, the reaction of Fe(III) with EB-PANI yields EB-PANI doping giving ES-PANI and/or the EB-PANI oxidation to PB-PANI. The formation of ES-PANI is favored in DMF while PB-PANI is formed in a greater extension in NMP and DMA. In acidic m-cresol, only ES-PANI is produced in Fe(III)/EB-PANI solutions indicating the important role played by the solvent in the nature of the product. (C) 2010 Elsevier B.V. All rights reserved.

Optical and structural properties of PbI(2) thin films

Lead iodide thin films were fabricated using the spray pyrolysis technique. Milli-Q water and N.N-dimethylformamide were used as solvents under varying deposition conditions. Films as thick as 60 mu m were obtained. The optical and structural properties of the samples were investigated using Photoluminescence, Raman scattering, X-ray diffraction, and Scanning electron microscopy. In addition, the study included also the electronic properties which were investigated by measuring the dark conductivity as a function of temperature. The deposition technique seems to be promising for the development of thick films to be used in medical imaging.

Solubilizacao e interacao de pigmentos com solventes organicos e agentes tenso-ativos

A Mg e Mn-Ftalocianina (Mg e Mn-Pc) foram solubilizados à 25°C em dimetilsulfóxido (DMSO); N, N-dimetilacetamida (DMA); N,N-dimetilformamida (DMF); N-metil-formamida, formamida, piridina, o-diclorobenzeno, monoclorobenzeno, tolueno, metanol, etanol, propanol-1, propanol-2, butanol-1 e octanol-1. Alguns valores representativos obtidos para o logarítimo da absortividade molar (E) da Mn-Pc, são os seguintes: o-diclorobenzeno (E = 4,94); DMSO (E = 4,39); octanol-1 (E = 3,90). Valores correspondentes para Mg-Pc são: o-diclarobenzeno (E = 4,93); DMSO (E = 5,22) e Octanol-1 ( E = 5,06). Em função de interação com solventes, pode-se classificar a Mg-Pc como um indicador básico e a Mn-Pc como indicador ácido. Os pigmentos Mg e Mn-Pc foram também solubillzados em soluções aquosas contendo vários surfatantes à 25°C. A Mg-Pc apresentou solubilidade significativa em água contendo brometo de cetiltrimetilamônio (CTAB), Brij-35, cloreto de cetilpiridinio (CPC1), brometo de cetilpiridínio (CPBr,) Triton X-100, cloreto de metildodecilbenziltrimetilamônio, brometo de cetildimetiletilamõnio e brometo de laurilisoquinolínio. A Mn-Pc foi solúvel em soluções aquosas de Brij-35 e Triton X-100. Em função de sua interação com surfatantes a Mg-Pc é classificada como corante catiônico e a Mn-Pc como corante aniônico. O corante comercial quinóide Oil Blue A [1,4-di(isopropilarnina)-antraquinona - 9,10 foi solubilizado à 25°C em DMF, DMSO, DMA, monoclorobenzeno, benzeno, tolueno, piridina, metanol, etanol, propanol-1, propanol-2, butanol-1 e octanol-1. Foi também solubilizado em soluções aquosas de surfatantes, tais como sódio lauril-sulfato (NaLS), cloreto de cetiltrimetilamônio (CTAB), brometo de cetildimetiletilamônio, Triton X-100, cloreto de cetilpiridínio (CPCl), Brij-35, cloreto de rnetildodecilbenziltrimetilamônio e brometo de laurilisoquinolínio. Em função de suas interações com os solventes o corante é um indicador ácido-básico pouco sensível e em função de sua interação com surfatantes é um corante catiônico. 0s resultados experimentais apresentam importância teórica e prática considerando sistemas que envolvem armazenamento e transferência de energia, compostos porfirínicos, fotossíntese, fotocondutores, coletores solares, semi-condutores e processos de embelezamento e proteção de superficies de vários materiais.

Rapid determination of desorption efficiency, and analysis of solvent mixtures for occupational exposure studies

An analytical procedure has been developed for simultaneous determination of solvent mixture vapors to enable evaluation of occupational exposure. To determine the desorption efficiency the volatile components of the solvent mixtures were generated from a glass tube filled with glass wool. This device is easy to prepare and use. These vapors were then collected in activated charcoal tubes and analyzed by capillary gas chromatography. The method was tested with a mixture of 22 solvents, including aliphatic and aromatic hydrocarbons, alcohols, ethers, esters, and ketones, oil at low concentrations. All the components were defected. When a 99: 1 mixture of carbon disulfide-dimethylformamide was used for desorption the efficiency was > 75% for most of the solvents.

Effect of the doping medium on blends of polyurethane and polyaniline

Flexible and free-standing films from blends of polyurethane, based on castor oil, and polyaniline were obtained with various compositions by casting. Significant increase on conductivity followed by a considerable decrease on doping time was obtained by doping the films in N,N-dimethylformamide (DMF) solution with p-toluene sulphonic acid (TSA) or HCl instead of the conventional doping in aqueous solution. This doping efficiency is proposed to be due to an improved swelling of the blend structure caused by the solvent. The electrical conductivity increases significantly upon polyaniline content increase reaching 10(-2) S/cm for a polyaniline content of about 10% (w/w).

Monte Carlo investigations of intermolecular interactions in water-amide mixtures

Monte Carlo simulations of water-amides (amide=fonnamide-FOR, methylfonnamide-NMF and dimethylformamide-DMF) solutions have been carried out in the NpT ensemble at 308 K and 1 atm. The structure and excess enthalpy of the mixtures as a function of the composition have been investigated. The TIP4P model was used for simulating water and six-site models previously optimized in this laboratory were used for simulating the liquid amides. The intermolecular interaction energy was calculated using the classical 6-12 Lennard-Jones potential plus a Coulomb term. The interaction energy between solute and solvent has been partitioned what leads to a better understanding of the behavior of the enthalpy of mixture obtained for the three solutions experimentally. Radial distribution functions for the water-amides correlations permit to explore the intermolecular interactions between the molecules. The results show that three, two and one hydrogen bonds between the water and the amide molecules are formed in the FOR, NMF and DMF-water solutions, respectively. These H-bonds are, respectively, stronger for DMF-water, NMF-water and FOR-water. In the NMF-water solution, the interaction between the methyl group of the NMF and the oxygen of the water plays a role in the stabilization of the aqueous solution quite similar to that of an H-bond in the FOR-water solution. (c) 2005 Elsevier B.V. All rights reserved.

A new route to obtain PVDF/PANI conducting blends

Electrically conductive poly(vinylidene fluoride)(PVDF) - polyaniline blends of different composition were synthesized by chemical polymerization of aniline in a mixture of PVDF and dimethylformamide (DMF) and studied by electrical conductivity measurement, UV-Vis-NIR and FTIR spectroscopy. The samples were obtained as flexible films by pressing the powder at 180 degrees C for 5 min. The electrical conductivity showed a great dependence on the syntheses parameters. The higher value of the electrical conductivity was obtained for the oxidant/aniline molar ratio equal to 1 and p-toluenesulfonic acid-TSA/aniline ratio between 3 and 6. UV-Vis-NIR and FTIR spectra of the blend are similar to the doped PANI, indicating that the PANI is responsible for the high electrical conductivity of the blend. The electrical conductivity of blend proved to be stable as a function of temperature decreasing about one order at temperature of 100 degrees C. The route used to obtain the polymer blend showed to be a suitable alternative in order to obtain PVDF/PANI-TSA blends with high electrical conductivity. (c) 2006 Elsevier Ltd. All rights reserved.

Influence of semen storage and cryoprotectant on post-thaw viability and fertility of stallion spermatozoa

The aim of the current study was to verify that stallion, spermatoza could be cooled for 24 hours and then frozen. In experiment I, one ejaculate from each of 13 stallions was used. Semen was collected and split into two parts; one part immediately frozen using standard cryo-preservation techniques and the other diluted, stored in an Equitainer for 24 hours, and then frozen. In experiment II, one ejaculate from each of 12 stallions was collected, diluted with Botu-Semen, and split into two parts: one cooled in an Equitainer and the other in Max-Semen Express without prior centrifugation. After 24 hours of cooling, the samples were centrifuged to remove seminal plasma and concentrate the sperm, and resuspended in Botu-Crio (R) extender containing on e of three cryoprotectant treatments (1% glycerol + 4% dimethylformamide, 1% glycerol + 4% dimethylacetamide and 1% glycerol + 4% methylformamide), maintained at 5 degrees C for 20 minutes, then frozen in nitrogen vapour. No difference was observed between the two cooling systems. The association of 1% glycerol and 4% methylformamide provided the best post-thaw progressive motility. For experiment III, two stallions were used for a fertility trial. Forty three inseminations were performed using 22 mares. No differences were seen in semen parameters and pregnancy rates when comparing the two freezing protocols (conventional and cooled/frozen). Pregnancy rates for conventional and cooled/frozen semen were, respectively, 72.7% and 82.3% (stallion A), and 40.0% and 50.0% (stallion B). We concluded that cooling equine-semen for 24 hours before freezing while maintaining sperm viability and fertility is possible.

Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fast Screening for Antioxidant Properties of Flavonoids from Pterogyne nitens Using Electrochemical Methods

A fast, low-cost, convenient, and especially sensitive voltammetric screening approach for the study of the antioxidant properties of isoquercitrin and pedalitin from Pterogyne nitens is suggested in this work. These flavonoids were investigated for their redox properties using cyclic voltammetry in nonaqueous media using N,N-dimethylformamide and tetrabutylammonium tetrafluorborate as the supporting electrolyte, a glassy carbon working electrode, AglAgCl reference electrode, and Pt bare wire counter electrode. The comparative analysis of the activity of rutin has also been carried out. Moreover, combining HPLC with an electrochemical detector allowed qualitative and quantitative detection of micromolecules (e.g., isoquercitrin and pedalitin) that showed antioxidant activities. These results were then correlated to the inhibition of p-carotene bleaching determined by TLC autographic assay and to structural features of the flavonoids.