29 resultados para Palladium(II) oxide


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A series of oligoaniline-functionalized mono- and bis-topic terpyridine ligands, i.e. C6H5[N(R)C6H4](n)TPY (R = H, butyl, tert-butyloxycarbonyl; n = 1-4; TPY = 2,2':6',2"-terpyridyl) and TPYC6H4[N(R)C6H4](m)TPY (R = H, tert-butyloxycarbonyl; m = 2, 4), and the corresponding monoand bis-nuclear ruthenium(II) complexes have been synthesized and verified. The spectroscopic results indicate that two kinds of pi-pi* transitions from TPY and oligoaniline fragments of ligands strongly shift to lower energy, and the metal-to-ligand charge-transfer transition ((MLCT)-M-1) bands of all obtained complexes are considerably red-shifted (Delta lambda(max) = 22-64 nm) and their intensities become much more intense (approximately 4-6 times), compared with those of the reported complex [Ru(TPY)(2)](2+). Moreover, the spectroscopic properties of the ligands and complexes with longer oligoaniline units (n = 3, 4) are markedly influenced by the external stimulus, such as the oxidation and proton acid doping.

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Four cyclometalated Pt(II) complexes, i.e., [(L-2)PtCl] (1b), [(L-3)PtCl] (1c), [(L-2)PtC CC6H5] (2b) and [(L-3)PtC CC6H5] (2c) (HL2 = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2'-bipyridine and HL3 = 4-[p(-N,N'-dibutyl-N'-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2'-bipyridine), have been synthesized and verified by H-1 NMR, C-13 NMR and X-ray crystallography. Unlike previously reported complexes [(L-1)PtCl] (1a) and [(L-1)PtC CC6H5] (2a) (HL1 = 4,6-diphenyl-2,2'-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer ((MLCT)-M-1) (d pi(Pt) -> pi*(L)) transitions (epsilon similar to 2 x 10(4) dm(3) mol (1) cm (1)) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c.

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CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

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A series of novel neutral nickel complexes 4a-e bearing modified beta-ketoiminato ligands [(2,6-(Pr2C6H3)-Pr-i)N=C(R-1)CHC(2 '-R2C6H4)O]Ni(Ph)(PPh3) (4a, R-1 R-2 = H; 4b, R-1 = H, R-2 = Ph; 4c, R-1 = H, R-2 = Naphth; 4d, R-1 = CH3, R-2 = Ph; 4e, R-1 = CF3, R-2 Ph) have been synthesized and characterized. Molecular structures of 4b and 4e were further confirmed by X-ray crystallographic analysis. Activated with B(C6F5)(3), all the complexes are active for the polymerization of ethylene to branched polyethylenes. Ligand structure, i.e., substituents R-1 and R-2, greatly influences not only catalytic activity but also the molecular weight and branch content of the polyethylene produced. The phenyl-substituted complex 4b exhibits the highest activity of lip to 145 kg PE/mol(Ni)center dot h center dot atm under optimized conditions, which is about 10 times more than unsubstituted complex 4a (14.0 kg PE/mol(Ni center dot)h center dot atm). Highly branched polyethylene with 103 branches per 1000 carbon atoms has been prepared using catalyst 4e.

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An enhanced electrochemiluminescence (ECL) efficiency is obtained from the ruthenium complex tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) by introduction of an ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF(4)). Upon addition of 1% (v/v) BMImBF(4) to 0.1 mm Ru(bpy)(3)(2+) solution, a maximum increase in ECL intensity is obtained both at an indium tin oxide (ITO) electrode (15-fold) and at a glassy carbon (GC) electrode (5- to 64old). Furthermore, upon addition of 1% (v/v) BMImBF4 to 5 pm Ru(bpy)(3)(2+)/100 mm co-reactant systems at a GC electrode, IL adsorption occurs at the electrode surface, which results in a change of the polarity of the electrode surface. Such functionalization greatly improves the functions of both Ru(bpy)(3)(2+) and ionic liquids, as is demonstrated in the sensitive and selective concentration enrichment of the Ru(bpy)(3)(2+) co-reactants.

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Herein we report a simple electrochemical route for the controlled synthesis of a Cu2O microcrystal from perfect octahedra to monodisperse colloid spheres via control of the electrodeposition potential without the introduction of any template or surfactant. Perfect Cu2O octahedra and monodisperse colloid spheres have been obtained in high yield (similar to 100%).

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Two novel bis(amine anhydride)s, NN-bis(3,4-dicarboxyphenyl)aniline dianhydride (I) and N,N-bis(3,4-dicarboxyphenyl)-p-tert-butylaniline (II), were synthesized from the palladium-catalyzed amination reaction of N-methyl-protected 4-chlorophthalic anhydride with arylamines, followed by alkaline hydrolysis of the intermediate bis(amine-phthalimide)s and subsequent dehydration of the resulting tetraacids. The X-ray structures of anhydride I and II were determined. The obtained dianhydride monomers were reacted with various aromatic diamines to produce a series of novel polyimides. Because of the incorporation of bulky, propeller-shaped triphenylamine units along the polymer backbone, all polyimides exhibited good solubility in many aprotic solvents while maintaining their high thermal properties. These polymers had glass transition temperatures in the range of 298-408 degrees C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight loss recorded above 525 degrees C in nitrogen.The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 95-164 MPa, 8.8-15.7%, and 1.3-2.2 GPa, respectively.

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alpha-Diimine nickel catalyst hearing two allyl groups [ArN=C](2)C10H6NiBr2 (Ar = 4-allyl-2,6-(i-Pr)(2)C6H2)] (Cat-I) has been synthesized and characterized. The corresponding polymer-incorporated nickel catalysts PC and the SiO2-supported shell-core structure catalyst SC-1 were obtained by the co-polymerization of the olefin groups of Cat-1 with styrene in the presence of a radical initiator. Radical co-polymerizations with styrene in Solution were investigated in detail, and the compositions and molecular weight of the copolymers were determined. All three types of catalysts (Cat-1, PC and SC-1) have been investigated for ethylene polymerization. These catalysts were found to exhibit high activity in the presence of modified methylaluminoxane (MMAO) as a co-catalyst. Among them, the polymer-incorporated PC and SiO2 shell-core catalyst SC-1 displayed very high activity (similar to2.62 and similar to1.11 kg (mmol Ni)(-1) h(-1), respectively) with product molecular weights (M,) in the range 26 x 10(4) to 47 x 10(4) under 0.1 MPa ethylene pressure. The particle morphology of polyethylene produced by the shell-core structure catalyst SC-1 was improved.

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A sensitive electrochemiluminescent detection scheme by solid-phase extraction at Ru(bpy)(3)(2+)-modified ceramic carbon electrodes (CCEs) was developed. The as-prepared Ru(bpy)(3)(2+)-modified CCEs show much better long-term stability than other Nafion-based Ru(bpy)(3)(2+)-modified electrodes and enjoy the inherent advantages of CCEs. The log-log calibration plot for dioxopromethazine is linear from 1.0 x 10(-9) to 1.0 x 10(-4) mol L-1 using the new detection scheme. The detection limit is 6.6 x 10(-10) mol L-1 at a signal-to-noise ratio of 3. The new scheme improves the sensitivity by similar to 3 orders of magnitude, which is the most sensitive Ru(bpy)(3)(2+) ECL method. The scheme allows the detection of dioxopromethazine in a urine sample within 3 min. Since Ru(bpy)(3)(2+) ECL is a powerful technique for determination of numerous amine-containing substances, the new detection scheme holds great promise in measurement of free concentrations, investigation of protein-drug interactions and DNA-drug interactions, pharmaceutical analysis, and so on.

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A series of binuclear neutral nickel and palladium complexes [(XC6H2CH=NC6H3-iPr(2))MRL](2) 4b-f (X=NO2, M=Ni, R=Ph, L=PPh3, 4b; X=H, M=Pd, R=Me, L=PPh3,4c; X=H,M=Pd, R=Me, L=Py, 4d; X=NO2,M=Pd, R=Me, L=PPh3, 4e; X=NO2, M=Pd, R=Me, L=Py, 4f) and [(C10H7CH=NC6H3-iPr(2))MRL](2) 8a-c (M=Ni, R=Ph, L=PPh3, 8a; M=Pd, R=Me, L=PPh3, 8b; M=Pd, R=Me, L=Py, 8c) have been synthesized and characterized. The structures of complexes 4e and 8b have also been confirmed by X-ray crystallographic analysis. With modified methylalummoxane (MMAO) as cocatalysts, these complexes and complex [(C6H3CH=NC6H3-iPr(2))NiPh(PPh3)](2) 4a are capable of catalyzing the addition polymerization of norbomene (NBE) with the high activity up to 2.3 x 10(8) g PNBE/(mol(M) h). The structure of complexes affects considerably catalytic activity towards norbomene polymerization. The polymers obtained with nickel complexes are soluble, while those obtained with palladium complexes are insoluble. Palladium complexes 4c, 4e and 8b bearing PPh3 ligands exhibit much higher activities than the corresponding complexes 4d, M and 8c bearing pyridine ligands under the same conditions.

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Tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection in a capillary electrophoresis separation system was used for the determination of diphenhydramine. In this study, platinum disk electrode (300 mum in diameter) was used as a working electrode and the influence of applied potential and buffer conditions were investigated. Under optimal conditions: 1.2 V applied potential, pH 8.50, 15 kV separation voltage and 10 mmol l(-1) running buffer, the calibration curve of diphenhydramine was linear over the range of 4 x 10(-8) to 1 x 10(-5) Mol l(-1). This technique gave satisfactory precision, and relative standard deviations of migration times and chemiluminescence peak intensities were less than 1 and 6%, respectively. The technique was applied to animal studies for determination of diphenhydramine extracted from rabbit plasma and urine samples, and the extraction efficiency were between 92 and 98.5%.

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Poly(ethylene glycol)-block-poly(butyl acrylate) synthesized by radical polymerization in a one-step procedure were characterized by gel permeation chromatography, infrared, IH-NMR spectroscopy, and differential scanning calorimetry (DSC). The crystalline property, emulsifying property, and phase transfer catalytic effect in the Williamson reaction were studied. It was found that the crystallinity of the copolymer increased with an increase in both the content and molecular weight of poly( ethylene oxide) (PEO) sequences. DSC curves showed two distinct crystallization temperature due to the heterogeneous nucleation and homogeneous nucleation crystallization. The casting solvent significantly affected the morphology and crystallinity of the solvent cast films. Both the emulsifying volume and the phase transfer catalytic efficiency in the Williamson reaction increased with the amount and PEO content of the block copolymers used, but decreased with an increase in the molecular weight of PEO sequences. (C) 1998 John Wiley & Sons, Inc.

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The electro-oxidation of PtCl42- was studied on a glassy carbon (GC) electrode. A Pt(IV) complex was formed on the electrode surface through coordination to the oxygen atom of an oxide functional group on the electrode, which results in its deactivation. The ferri/ferrocyanide redox couple was used as a probe to examine the activity of the GC electrode. X-ray photoelectron spectroscopy was employed to characterize the platinum on the electrode surface, and showed that the oxidation state of the Pt element changes depending on the electrochemical treatment of GC electrode. The platinum complex on the surface of the GC electrode can be transformed to Pt-0 by cycling the electrode between -0.25 and +1.65 V/SCE in 0.1 M H2SO4 solution. The above procedure can be used to disperse platinum ultramicroparticles on the surface of a GC electrode.

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Amperometic flow measurements were made at +0.55 V (vs. Ag/AgCl) in 0.1 mol l-1 KOH electrolyte with an Ni(II) chemically modified electrode (CME) with an Eastman-AQ polymer film. The use and characteristics of a Ni(II)-containing crystalline and polymer-modified electrode obtained by a double coating step as a detector for amino acids in a flow-injection system using reversed-phase liquid chromatography are described. The detection of these analytes is based on the higher oxidation state of nickel (NiOOH) controlled by the applied potential. The electroanalytical parameters and the detection current for a series of amines and amino acids were investigated. The use of such a CME in the flow-injection technique was found to be suitable in a solution at low pH. The linear range for glycine is 5 X 10(-6)-0.1 mol 1-1 with a detection limit of 1.0 X 10(-6) mol l-1. A 1 X 10(-4) mol 1-1 mixture of serine and tyrosine was also detected after separation on an Nucleosil C18 column.