Highly efficient and enantioselective cyclopropanation of styrene with diazoacetates using a new copper-(Schiff-base) catalyst

A new copper-(Schiff-base) complex, derived from (S)-2-amino-1,1-di(3,5-di-t-butylphenyl)propanol, 2-hydroxy-5-nitrobenzaldehyde and copper acetate monohydrate, was used as an efficient catalyst for the cyclopropanation of styrene with diazoacetates, affording ees of up to 98%. (C) 2000 Elsevier Science Ltd. All rights reserved.

Anodic Stripping Voltammetry at Bismuth-Coated and Uncoated Carbon Microdisk Electrodes:Application to Trace Metals Analysis in Flood Samples

This article reports on the performance of a bismuth-coated carbon microdisk electrode (BiFμE) for the determination of trace heavy metals by anodic stripping voltammetry (ASV). The BiFμE was prepared by electrodeposition of a metallic bismuth film onto the microdisk, by applying an in-situ electroplating procedure. To test the performance of the BiFμE, ASV measurements were performed on synthetic solutions containing Cd2+, Pb2+, and Cu2+ as target ions. The results indicated that cadmium and lead gave well-defined ASV peaks with no interference, and their quantitative determination could be carried out straightforwardly. In particular, linear calibration curves over the range 5.0 x 10-8-1.0 x 10-6M for both ions, and detection limits of 7.8 and 2.9 nM, for cadmium and lead, respectively, after applying a 60 sec preconcentration step, were obtained. The reproducibility was also satisfactory, the relative standard deviation (RSD) being within 2.5% for both ions. Copper, instead, gave an ASV response that. in most experimental conditions, overlapped with that of bismuth. This circumstance made the determination of copper at the BiFμE difficult. Since the latter element could be detected reliably at the uncoated carbon microdisk electrode (CμE), both BiFμE and CμE were employed, respectively, for the determination of lead and copper ions in drinking water, wine, and tomato sauce.

Nontoxic electrodes of solid amalgams

This is a review of electrodes based on nontoxic solid amalgams (MeSAE) (prepared by amalgamation of soft metal powders) in connection with some other kinds of voltammetric electrodes is given. Information is summarized on various types of MeSAEs (esp. AgSAE, CuSAE, AuSAE), pretreatment of their surfaces, their hydrogen overvoltage in aqueous solutions, conditions for their testing, electroanalytical parameters and use, in compared with the hanging mercury drop electrode (HMDE). Although the solid amalgam electrodes do not reach the quality of the HMDE, in many cases they represent its possible alternative. The broad range of voltammetric applications of the MeSAEs, especially of the AgSAEs, their good mechanical stability, simple handling, and new aspects of their use in electrochemical techniques are documented by numerous examples.

Preparation and characterization of a novel macrocyclic ligand—dinitro-tetraazacyclotetradeca-tetraene—and application as a highly selective extractant for copper(II)

A novel tetraaza macrocyclic Schiff base ligand, 6,13-dinitro-5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,-12-tetraene, was prepared and its copper(II) and nickel(II) complexes were characterized. This ligand was found to be an excellent extractant for copper(II).

Efficient One-Pot Synthesis of Highly Substituted Thiophene Library from 1,3-Dicarbonyl Compounds

A faccile and efficient one-pot synthesis of highly substituted thiophenes has been developed and employed for the preparation of a small focused library. Treatment of 1,3-dicarbonyl compounds 1 with CS2 in the presence of K2CO3 in DMF at room temperature, followed by stepwise addition of alkyl bromides 2 and methylene active bromides 3, provided via intramolecular cyclization 2,3,4,5-tetrasubstituted thiophenes 4 in yields of 77-94%. This protocol, combining construction and modification of the thiophene ring, increases the structural diversity of final products from readily available materials. A mechanism for the one-pot synthesis of thiophenes of type 4 has been proposed. A small focused library of thiophenes is prepared using the sequential addition of reagents to achieve unique substitution in the 2 and 5 position of the thiophene ring

Solution-processable highly efficient yellow- and red-emitting phosphorescent organic light emitting devices from a small molecule bipolar host and iridium complexes

A bipolar transport compound, 2,5-bis(4-(9-(2-ethylhexyl)-9H-carbazol-3-yl) phenyl)-1,3,4-oxadiazole (CzOXD), incorporating both electron-and hole-transport functionalities, was synthesized and fully characterized by H-1 NMR, C-13 NMR, elemental analysis and mass spectrometry. Its thermal, electrochemical, electronic absorption and photoluminescent properties were studied

Highly efficient white organic light-emitting devices based on a multiple-emissive-layer structure

Characteristics of white organic light-emitting devices based on phosphor sensitized fluorescence are improved by using a multiple-emissive-layer structure, in which a phosphorescent blue emissive layer is sandwiched between red and green&yellow ones. In this device, bis[(4,6-difluorophenyl)-pyridinato-N,C-2] (picolinato), bis(2,4-diphenyl-quinoline) iridium (III) acetylanetonate, fac bis (2-phenylpyridine) iridium, and 5,6,11,12-tetraphenylnaphthacene are used as blue, red, green, and yellow emitters, respectively.

Highly ordered mesoporous carbons as electrode material for the construction of electrochemical dehydrogenase- and oxidase-based biosensors

In this work, the excel lent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors.

The characteristics of highly ordered mesoporous carbons as electrode material for electrochemical sensing as compared with carbon nanotubes

In this paper, the unique properties of highly ordered mesoporous carbons modified glassy carbon electrode (OMCs/GE) are illustrated from comparison with carbon nanotubes modified glassy carbon electrode (CNTs/GE) for the electrochemical sensing applications.

Stripping voltammetric determination of Pb(II) and Cd(II) based on the multiwalled carbon nanotubes-Nafion-bismuth modified glassy carbon electrodes

In this work, a new method for the simultaneous determination of Pb(II) and Cd(II) on the multiwalled carbon nanotubes (MWNT)-Nafion-bismuth modified glassy carbon electrode (GCE) using square-wave anodic stripping voltammetry has been studied. Scanning electron microscopy was used to investigate the characteristics of the MWNT-Nafion-bismuth modified GCE.

Sensitive determination of Cd and Pb by differential pulse stripping voltammetry with in situ bismuth-modified zeolite doped carbon paste electrodes

Here we investigated the analytical performances of the bismuth-modified zeolite doped carbon paste electrode (BiF-ZDCPE) for trace Cd and Pb analysis. The characteristics of bismuth-modified electrodes were improved greatly via addition of synthetic zeolite into carbon paste. To obtain high reproducibility and sensitivity, optimum experimental conditions for bismuth deposition Were Studied.

Phase Behavior and self-assembly of poly[N-vinylformamide-co-(acrylic acid)] copolymers under highly acidic conditions

Copolymers of N-vinylformamide and acrylic acid were synthesized by conventional aqueous free-radical polymerization. The phase behavior of the copolymer solutions was investigated through the addition of hydrochloric acid and the variation of the temperature. With a moderate content of N-vinylformamide, the copolymers showed complex phase behaviors. Under low-acidity conditions, a suspending liquid was formed, whereas under high-acidity conditions, the random copolymers could assemble into round nanoparticles with a broad particle size distribution.

Synthesis of carbon nanofibers for mediatorless sensitive detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 mu M with a low detection limit of 20 nM was obtained with the CNF-modified carbon paste electrode (CNF-CPE).

Ionic liquids Supported Growth of Highly Ordered Microdroplets Induced by Fluidic Leakage at Poly(dimethylsiloxane) Interfaces

"Fluidic leakage" caused by vacuum force at the reversible sealing poly(dimethylsiloxane) (PDMS) interfaces was converted to one useable avenue, which led to formation of highly ordered surfactant microdroplets functionalized with ionic liquids (ILs). Vacuum force is the prerequisite to lead constant microsolutions to diffuse to the PDMS interfaces. Imidazolium ions of ILs rendered structural rearrangement of the surfactant aggregates and the ordered droplets formation.