Open Access Published by De Gruyter Open Access

Volume 7 Issue 4

December 2009

Issue of Open Chemistry

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Contents
Journal Overview

Open Access October 6, 2009

Carbon paste electrodes in the new millennium

Ivan Švancara, Alain Walcarius, Kurt Kalcher, Karel Vytřas

Page range: 598-656

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Abstract

In this review (with 500 refs), both electrochemistry and electroanalysis with carbon paste-based electrodes, sensors, and detectors are of interest, when attention is focused on the research activities in the years of new millennium. Concerned are all important aspects of the field, from fundamental investigations with carbon paste as the electrode material, via laboratory examination of the first electrode prototypes, basic and advanced studies of various electrode processes and other phenomena, up to practical applications to the determination of inorganic ions, complexes, and molecules. The latter is presented in a series of extensive tables, offering a nearly complete survey of methods published within the period of 2001–2008. Finally, the latest trends and outstanding achievements are also outlined and future prospects given.

Open Access October 6, 2009

Atom transfer radical polymerization in aqueous dispersed media

Ke Min, Krzysztof Matyjaszewski

Page range: 657-674

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Abstract

During the last decade, atom transfer radical polymerization (ATRP) received significant attention due to its exceptional capability of synthesizing polymers with pre-determined molecular weight, well-defined molecular architectures and various functionalities. It is economically and environmentally attractive to adopt ATRP to aqueous dispersed media, although the process is challenging. This review summarizes recent developments of conducting ATRP in aqueous dispersed media. The issues related to retaining “controlled/living” character as well as colloidal stability during the polymerization have to be considered. Better understanding the ATRP mechanism and development of new initiation techniques, such as activators generated by electron transfer (AGET) significantly facilitated ATRP in aqueous systems. This review covers the most important progress of ATRP in dispersed media from 1998 to 2009, including miniemulsion, microemulsion, emulsion, suspension and dispersed polymerization.

Open Access October 6, 2009

Miniaturization of flow-through generation cells for electrochemical hydride generation in AAS

J. Hraníček, V. Červený, P. Rychlovský

Page range: 675-682

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Abstract

The construction and optimization of five new types of miniaturized flow-through electrolytic cells with lead cathode and platinum anode for electrochemical hydride generation in atomic absorption spectrometry (HG-QFAAS) were achieved during this research study. The ion-exchange membrane was not part of these cells and only one carrying electrolyte for both electrode chambers was used. Hydride generation efficiency achieved was either comparable or higher than the one recorded for the classic thin-layer generation cell. The inner volume of the cathode chamber was reduced to a quarter of the classic thin-layer flow-through cell. Compared to the commonly used thin-layer flow-through cell, higher sensitivity (7.32×103 dm3 µg−1) and better limit of detection (0.32 µg dm−3) were obtained for selenium determination using two of these new generators.

Open Access October 6, 2009

A theoretical study of the neutral and the double-charged cation of cyclo[8]pyrrole and its interaction with inorganic anions

Ibon Alkorta, Fernando Blanco, José Elguero

Page range: 683-689

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Abstract

A theoretical study of the complexation of cyclo[8]pyrrole dication, 2, and the corresponding system in neutral form, 3, with six anionic molecules has been carried out up to the B3LYP/6–311++G(2d,2p) computational level. The effect of the water solvation has been taken into account by means of the PCM method. The gas phase results correspond to the very large interaction energies expected for the interaction of molecules of opposite charge. In all the complexes, the analysis of the electron density by means of the Atoms In Molecules (AIM) methodology shows the presence of eight intermolecular interactions between the individual molecules. The results, using the water solvent model, indicate that the 2:SO42− complex is more stable than the 2:NO3−, in agreement with experimental results.

Open Access October 6, 2009

Polarized light spectroscopy of azobenzene or disperse red 1 with Mn12 single-molecule magnets in PMMA film hybrid materials

Takashiro Akitsu, Chiaki Ishioka, Tsubasa Itoh

Page range: 690-696

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Abstract

A series of organic/inorganic hybrid materials containing the single-molecule magnet [Mn12(CH3COO)16(H2O)4O12]·2CH3COOH·4H2O with the photochromic compounds azobenzene or disperse red 1 cast into polymethyl methacrylate films was prepared. To understand the photomodulation of analogous mixtures’ AC susceptibility, we investigated the molecular alignment based on Weigert’s effect accompanying cycles of cis-trans photoisomerization by alternate irradiations with polarized UV and visible light. Polarized electronic spectra of the hybrid materials demonstrated gradually increasing anisotropy. These features suggest interactions between photochromic compounds and the Mn12 complex in polymethyl methacrylate.

Open Access October 6, 2009

Modified silica surface by phenylboronic acid derivatives as effective sugar sensor

Joanna Kurczewska, Grzegorz Schroeder

Page range: 697-701

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Abstract

Silica surface was modified with phenylboronic acid derivatives. The structures of the functionalized supports were characterized by FT-IR spectroscopy, 13C CP/MAS NMR spectrometry, elemental and thermogravimetric analysis. The solid supports were effectively applied as artificial receptors for sugars in aqueous solutions. Alizarin Red S. (ARS) was used to detect colour change upon carbohydrate (sugar) binding. The association constants of the supports studied-ARS complex and the functionalized silica-sugar (glucose) complex were calculated. The parameters obtained were comparable with those for the phenylboronic acids used for the silica gel modification. The competitive binding of the functionalized silica surface with ARS and sugar were studied by UV/VIS measurements.

Open Access October 6, 2009

Organic / inorganic bioactive materials Part I: Synthesis, structure and in vitro assessment of collagen/silicocarnotite biocoatings

Vladimir Hristov, Lachezar Radev, Bisserka Samuneva, Georgi Apostolov

Page range: 702-710

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Abstract

The silicocarnotite, as an inorganic part of the coatings, has been synthesized using a polystep sol-gel method. The chemical composition of the prepared silicocarnotite sol is described as 58.12 CaO, 29.42 P2O5, 12.45 SiO2 (wt%), where Ca/P+Si = 1,67. The acid soluble type I collagen, as an organic part of the obtained coatings, was mixed with silicocarnotite powder in a weight ratio of 25:75 and 75:25 weight ratio without cross-linkage. The acidity of the obtained mixture was readjust with 25% NH4OH to pH = 9.0. The mixture was then dried at 37°C for 12 h. The growth of B-type carbonate containing hydroxyapatite (B-type CO3HA) in which CO3 2+→PO4 3− on the surface of collagen/silicocarnotite coatings soaked in 1.5 simulated body fluid (1.5 SBF) was observed. The nucleation of B-type CO3HA was estimated on the obtained coatings after 3 days immersion in 1.5 SBF. The negatively charged carboxylate groups from the collagen surface may be responsible for the HA deposition. This was confirmed by the “red shift” of carboxylate groups of collagen molecules in the FTIR spectra. After soaking in 1.5 SBF, the morphology of prepared coatings and HA formation was observed by SEM.

Open Access October 6, 2009

Organic/Inorganic bioactive materials Part II: in vitro bioactivity of Collagen-Calcium Phosphate Silicate/Wollastonite hybrids

Lachezar Radev, Vladimir Hristov, Bisserka Samuneva, Dimitrina Ivanova

Page range: 711-720

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Abstract

In the present study, novel hybrid materials of Collagen (C) and Calcium Phosphate Silicate/Wollastonite (CPS/W) were synthesized. The CPS/W ceramic was prepared via polystep sol-gel method. The dissolution test of CPS/W ceramic was filled with TRIS-HCl buffer. FTIR depicts that hydroxyl carbonate apatite (OHCO3HA) was observed after 3 days of immersion in TRIS-HCl buffer. Biohybrids of C-CPS/W were produced from diluted hydrochloric acid collagen type I and ceramic powder with different ratios of C and CPS/W equal to 25:75 and 75:25 wt.%. The synthesized hybrids were characterized by FTIR, XRD and SEM. FTIR depicts a “red shift” if amide I could be attributed to the fact that the collagen prefers to chelate Ca2+ from partial dissolution of CPS/W ceramic. The growth of B-type carbonate containing hydroxyapatite (B-CO3HA) on the C-CPS/W hybrids soaked in 1.5SBF was observed. The negatively charged carboxylate groups from the collagen may be responsible for hydroxyapatite (HA) deposition. This fact was confirmed by the “red shift” of carboxylate groups of collagen in FTIR spectra. The formation of HA was observed by FTIR, XRD and SEM.

Open Access October 6, 2009

Organic/Inorganic bioactive materials Part III: in vitro bioactivity of gelatin/silicocarnotite hybrids

Lachezar Radev, Maria Fernandes, Isabel Salvado, Daniela Kovacheva

Page range: 721-730

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Abstract

In this work we present our experimental results on synthesis, structure evolution and in vitro bioactivity assessment of new gelatin/silicocarnotite hybrid materials. The hybrids were obtained by diluting gelatin (G) and silicocarnotite (S) ceramic powder with G:S ratios of 75:25 and 25:75 wt.% in hot (40°C) water. The hybrids were characterized using XRD, FTIR, SEM/EDS and XPS. FTIR depicts that the “red shift” of amide I and COO− could be attributed to the fact that the gelatin prefers to chelate Ca2+ from S. The growth of calcium phosphates on the surface of the hybrids synthesized and then immersed in 1.5 SBF for 3 days was studied by using of FTIR, XRD and SEM/EDS. According to FTIR results, after an immersion of 3 days, A and B-type CO3HA can be observed on the surface. XRD results indicate the presence of hydroxyapatite with well defined crystallinity. SEM/EDS of the precipitated layers show the presence of CO3HA and amorphous calcium phosphate on the surface of samples with different G/S content when immersed in 1.5 SBF. XPS of the G/S hybrid with 25:75 wt.% proved the presence of Ca-deficient hydroxyapatite after an in vitro test for 3 days.

Open Access October 6, 2009

The study of cyclooctene oxidation with molecular oxygen catalyzed by VSi2

Oksana Makota, Yuriy Trach, Roman Leboda, Jadwiga Skubiszewska-Zięba

Page range: 731-738

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Abstract

The catalytic effect of VSi2 on initial stages of the liquid-phase oxidation of cyclooctene by molecular oxygen was studied. The vanadium disilicide influences on the oxidation process in the presence of hydroperoxide. VSi2 takes part in a radical formation stage by catalysis of hydroperoxide decomposition reaction. The catalyst was investigated before and after reaction using FTIR spectroscopy. From the data obtained, the kinetic model of the catalytic oxidation process was proposed and the equation for the reaction rate was derived. The equation has described all observed dependences of reaction rate on the concentration of reactants and content of catalyst.

Open Access October 6, 2009

Rotating disk electrode study of electrocatalytic oxidation of ascorbate at Prussian blue modified electrode

Rūta Araminaitė, Rasa Garjonytė, Albertas Malinauskas

Page range: 739-744

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Abstract

Electrooxidation of ascorbate has been studied with the use of a rotating disk electrode. The results obtained show an efficient electrocatalytic oxidation of ascorbate at the Prussian blue (PB) modified electrode to proceed in solutions of pH 5.5 and 7.3. Depending on solution pH, the onset potential for ascorbate electrooxidation at PB modified electrode appears shifted by 0.1–0.2 V to lower values, as compared to an unmodified glassy carbon electrode. Within the electrode potential window of 0.3 to 0.5 V vs. Ag/AgCl, and electrode rotation velocity of 50–2000 rpm, the catalytic current obeys Koutecky-Levich equation at a submillimolar ascorbate concentration. Kinetic current densities, obtained from the data treatment, are higher for a pH 5.5 solution, and also at higher electrode potential.

Open Access October 6, 2009

Synthesis of hydroxyapatite by using calcium carbonate and phosphoric acid in various water-ethanol solvent systems

Arzu Engin, İsmail Girgin

Page range: 745-751

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Abstract

The purpose of the present study is to synthesize hydroxyapatite by using CaCO3 and H3PO4 in various water-ethanol solvent systems. It was observed from experiments that formation of ammonium phosphate compounds hindered the formation of calcium phosphates in ethanol medium. Although the reactivity was better in aqueous medium, the carbonate contents of the products obtained were above 8.5%. Best results with a carbonate content as low as 3.82% was obtained in 50% ethanol containing mixed-aqueous medium at 80°C and the FTIR analysis showed that the product was a carbonated apatite with a calculated composition of 14CaO·4.2P2O5·CO3·7.2H2O. The amorphous and porous phosphate compound obtained with a BET surface area of 106.6 m2 g−1 seems to be useful as adsorbent in wastewater treatment. Upon sintering of the amorphous product at 750°C, crystalline hydroxyapatite with a BET surface area of 25.9 m2 g−1 is obtained that may be used in biomedical applications.

Open Access October 6, 2009

Discrimination of GalNAc (4S/6S) sulfation sites in chondroitin sulfate disaccharides by chip-based nanoelectrospray multistage mass spectrometry

Corina Flangea, Alina Serb, Catalin Schiopu, Sorin Tudor, Eugen Sisu, Daniela Seidler, Alina Zamfir

Page range: 752-759

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Abstract

Sulfation pattern within chondroitin sulfate (CS) glycosaminoglycan (GAG) chains is an important post-translational modification that regulates their interaction with proteins. In this context, development of highly efficient and reproducible analytical methods for the investigation of CS sulfation patterns is of high necessity. In this study we report a novel method for straightforward determination of N-acetylgalactosamine (GalNAc) sulfation sites in chondroitin sulfate disaccharides. Our protocol involves combining fully automated chip-based nanoelectrospray (nanoESI) for analyte infusion and ionization in negative ion mode with multistage (MSn) collision-induced dissociation (CID) high capacity ion trap (HCT) mass spectrometry for generation of sequence ions diagnostic for identification of sulfate ester group position within GalNAc residues. The feasibility of this approach is here demonstrated on chondroitin 6-O-sulfate and chondroitin 4-O-sulfate disaccharides. Fragmentation patterns obtained by MS2 and MS3 sequencing stages provided first mass spectrometric data from which sulfation site(s) within GalNAc monosaccharide ring could be unequivocally deciphered. Hence, the method allowed discriminating 4S/6S sulfation sites solely on the basis of MS and multistage MS evidence.

Open Access October 6, 2009

Equilibrium isotherm analysis of the sorption of congo red by palm kernel coat

Nurudeen Oladoja, Isaac Ololade, Justice Idiaghe, Emmanuel Egbon

Page range: 760-768

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Abstract

The ability of Palm Kernel Coat (PKC), a waste agricultural product, in the abstraction of Congo Red (CR), an anionic dye, from aqueous solution was studied. The effects of sorbent dose and temperature were studied using batch sorption system. Isotherm experiments were conducted and the data obtained were fitted with different equilibrium isotherm equations namely, Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura and Halsey isotherm equations. The Langmuir isotherm equation gave the best description of the sorption process and the maximum saturated monolayer sorption capacity of the PKC for CR was 79.37 mg g−1. Harkins-Jura isotherm equation gave the poorest description of the sorption process. The linear form of the Langmuir equation was used to analyze the data obtained when the sorbent dosage was optimized by method of continuous variation. The results obtained showed that the equilibrium monolayer sorption capacity, qm, of the PKC for CR decreased (79.37–17.07 mg g−1) with an increase in sorbent dosage. The relationship between the dimensionless parameter, KR, and initial concentration, Co, showed that the sorption of CR was favored at higher initial dye concentration and PKC dosages than the lower ones. The thermodynamic parameters, such as change in the free energy, the enthalpy and the entropy, were also evaluated. The thermodynamic analysis showed that the sorption is spontaneous and exothermic.

Open Access October 6, 2009

Investigation of electrical properties of PANI/chalcogenide junctions

Vinodini Shaktawat, Dinesh Patidar, Kananbala Sharma, Narendra Saxena, Thansewar. Sharma

Page range: 769-773

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Abstract

Pure Polyaniline (EB) and Polyaniline doped with different protonic acids (ESs) were chemically synthesized using ammonium peroxydisulphate (APS) as an oxidant. Junctions have been prepared by evaporating chalcogenide materials (ZnSe, CdSe) on conducting polyaniline (EB & ESs) pellets using a vacuum evaporation technique. I–V characteristics of junctions have been studied at room temperature using the Keithley electrometer 6517A. I–V measurements show the rectification effect. A junction of ES[PO43−] may be preferred over the other junctions due to its low ideality factor and maximum rectification ratio.

Open Access October 6, 2009

Calorimetric study of melts in the system KF - K2TaF7

Ivan Nerád, Eva Mikšíková, Zuzana Balogová

Page range: 774-779

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Abstract

Enthalpy increment measurements on melts in the system KF-K2TaF7 were carried out by drop calorimetry at temperatures between 298 K and 1063, 1103 and 1143 K for selected compositions. Heat capacities of the melted mixtures and enthalpies of mixing have been determined. Careful calorimetric experiments showed small but distinct non-ideality of the melt. The molar heat capacity of melt exhibits small positive divergence from additivity. The molar enthalpy of mixing shows negative deviation from ideality which decreases with increasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing more complex fluorotantalate anions. The formation of complex anions with lower coordination number of Ta may not be excluded.

Open Access October 6, 2009

Effects of doping with CeO2 and calcination temperature on physicochemical properties of the NiO/Al2O3 system

Waleed Shaheen, A. El-Hendawy

Page range: 780-786

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Abstract

The effects of doping with CeO2 and calcination temperature on the physicochemical properties of the NiO/Al2O3 system have been investigated using DTA, XRD, nitrogen adsorption measurements at −196°C and decomposition of H2O2 at 30–50°C. The pure and variously doped solids were subjected to heat treatment at 300, 400, 700, 900 and 1000°C. The results revealed that the specific surface areas increased with increasing calcination temperature from 300 to 400°C and with doping of the system with CeO2. The pure and variously doped solids calcined at 300 and 400°C consisted of poorly crystalline NiO dispersed on γ-Al2O3. Heating at 700°C resulted in formation of well crystalline NiO and γ-Al2O3 phases beside CeO2 for the doped solids. Crystalline NiAl2O4 phase was formed starting from 900°C. The degree of crystallinity of NiAl2O4 increased with increasing the calcination temperature from 900 to 1000°C. An opposite effect was observed upon doping with CeO2. The NiO/Al2O3 system calcined at 300 and 400°C has catalytic activity higher than individual NiO obtained at the same calcination temperatures. The catalytic activity of NiO/Al2O3 system increased, progressively, with increasing the amount of CeO2 dopant and decreased with increasing the calcination temperature.

Open Access October 6, 2009

Activity and kinetics studies of yeast alcohol dehydrogenase in a reverse micelle formulated from functional surfactants

Yun Zhang, Xirong Huang, Guanglei Ji, Ying Li, Weifeng Liu, Yinbo Qu

Page range: 787-793

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Abstract

Yeast alcohol dehydrogenase (YADH) showed substantial decrease in its catalytic activity due to the strong electrostatic interaction between the head groups of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and YADH in AOT reverse micelles. However, the catalytic activity of YADH in a nonionic reverse micellar interface (GGDE/TX-100) obtained from a functional nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) and Triton X-100 (TX-100) was higher than that in AOT reverse micelle under the respective optimum conditions. A comparison of the kinetic parameters showed that the turnover number kcat in GGDE/TX-100 reverse micelle was 1.4 times as large as that in AOT reverse micelle, but the Michaelis constants in AOT reverse micelle for ethanol K mB was twice and for coenzyme NAD+ K mA was 5 times higher than their counterparts in GGDE/TX-100 reverse micelle. For the conversion of ethanol, the smaller K mB and larger kcat in GGDE/TX-100 reverse micelle resulted in higher catalytic efficiency kcat/K mB. The stability of YADH in GGDE/TX-100 reverse micelle was also found to be better than that in AOT reverse micelle. They were mainly attributed to the absence of electric charge on the head groups of GGDE and TX-100 in the GGDE/TX-100 reverse micelle.

Open Access October 6, 2009

Synthesis of novel mesoporous Al2O3 microspheres with flower-like structure

Huiping Liu, Guanzhong Lu, Yun Guo, Yanqin Wang, Yanglong Guo

Page range: 794-802

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Abstract

Using glucose as a structuring additive and aluminium nitrate as the Al precursor, a novel kind of mesoporous Al2O3 microspheres with flower-like structure were synthesized hydrothermally at 180°C for 20 h. When the synthesis temperature was lowered to 140°C, the carambola-like Al2O3 can be synthesized. This approach is convenient and simple, and flower-like Ce-Al2O3 and La-Al2O3 spheres have also been prepared in this way. It may be applied to synthesize other metal oxides when suitable precursor salts are used. From an analysis of the experimental results, a mechanism for the formation of the flower-like Al2O3 spheres has been proposed and discussed.

Open Access October 6, 2009

“Bubble Bunch” phenomenon in operation of a bubble column

Dariush Bastani, Ali Baghaei, Amir Sarrafi

Page range: 803-808

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Abstract

While studying the operation of a rectangular bubble column in laboratory scale, it was observed that under certain circumstances tiny bubbles attach to larger bubbles without causing them to coalesce. In other words, bubbles with large diameters (d > 5 mm) swept tiny bubbles (d

Open Access October 6, 2009

High surface area nano-sized La0.6Ca0.4MnO3 perovskite powder prepared by low temperature pyrolysis of a modified citrate gel

Meysam Soleymani, Ahmad Moheb, Ezatolah Joudaki

Page range: 809-817

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Abstract

Single phase nanocrystalline La0.6Ca0.4MnO3 powder was synthesized by both the usual and a modified citrate gel precursor method, and the effects on the formation of homogeneous nano-sized powder with a perovskite structure were investigated. In the modified method, single phase La0.6Ca0.4MnO3 powder with an average particle size of 17.2 nm was obtained when the powder was pyrolyzed at 520°C for 2 h. Its specific surface area was 40.7 m2 g−1, about 4-fold larger than that of powder made by the usual citrate gel method.

Open Access October 6, 2009

One step synthesis of Diflunisal using a Pd-diamine complex

Tuula Kylmälä, Jan Tois, Youjun Xu, Robert Franzén

Page range: 818-826

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Abstract

Diflunisal and Felbinac, two FDA-approved NSAIDs and other biphenyl carboxylic acids were prepared in one step by a simple and clean Suzuki cross-coupling reaction using an easily synthesized, air and moisture stable, palladium-diamine complex. The yield (93%) for the one-step preparation of Diflunisal is the best reported without using a glovebox and a phoshine-based catalyst.

Open Access October 6, 2009

Silver sorption on acrylic copolymers functionalized with amines. Equilibrium and kinetic studies

Rodica Buhaceanu, Ioan Sarghie, Adriana Barsanescu, Viorica Dulman, Ioan Bunia

Page range: 827-835

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Abstract

The sorption capacity of three weak base ion exchangers based on acrylic copolymers functionalized with ethylenediamine, triethylenetetramine and N, N- dimethylamino propylamine for Ag(I) ions was evaluated. Adsorption experiments were carried out by batch method. The effect of pH, crosslinking degree of copolymers, amount of sorbent, initial ion concentration, contact time and temperature was studied. The parameters which characterize the retention process were estimated using Langmuir and Freundlich isotherm models, the best fitting being for the first model. Kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models. Experimental data were in good agreement with the pseudo second order.

Open Access October 6, 2009

Investigation of FIrpic in PhOLEDs via LC/MS technique

Varatharajan Sivasubramaniam, Florian Brodkorb, Stephanie Hanning, Hans Loebl, Volker Elsbergen, Herbert Boerner, Ullrich Scherf, Martin Kreyenschmidt

Page range: 836-845

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Abstract

The commercial breakthrough of phosphorescent organic white light sources is presently hampered due to the unavailability of a stable blue phosphorescent emitter material. Moreover, only few analytical investigations have been made regarding the chemical degradation of the phosphorescent emitter materials during the processing or the operation of the devices. Organic light emitting devices (OLEDs) containing phosphorescent metal complexes with iridium as central ion were investigated. Special attention was paid to the chemical degradation of the material. The devices were analyzed by means of high performance liquid chromatography coupled with mass spectrometry (HPLC/MS). Electron spray ionization (ESI) was employed as ionization source. Isomerization phenomena of the blue-green emitting heteroleptic iridium complex FIrpic could be observed after the device manufacture and after operation. These findings could give hints on the mechanisms that influence the lifetime of PhOLEDs based on FIrpic or similar blue emitters.

Open Access October 6, 2009

QSPR modelling of the octanol/water partition coefficient of organometallic substances by optimal SMILES-based descriptors

Andrey Toropov, Alla Toropova, Emilio Benfenati

Page range: 846-856

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Abstract

Usually, QSPR is not used to model organometallic compounds. We have modeled the octanol/water partition coefficient for organometallic compounds of Na, K, Ca, Cu, Fe, Zn, Ni, As, and Hg by optimal descriptors calculated with simplified molecular input line entry system (SMILES) notations. The best model is characterized by the following statistics: n=54, r2=0.9807, s=0.677, F=2636 (training set); n=26, r2=0.9693, s=0.969, F=759 (test set). Empirical criteria for the definition of the applicability domain for these models are discussed.

Open Access October 6, 2009

Catalytic reduction of NO by CO over Pd — doped Perovskite-type catalysts

Mariana Khristova, Srdjan Petrović, Ana Terlecki-Baričević, Dimitar Mehandjiev

Page range: 857-863

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Abstract

The perovskite type oxides (nominal formula LaTi0.5Mg0.5O3) with addition of Pd were prepared by annealing the ethanol solution of precursors in nitrogen flow at 1200°C and characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of NO (NO-TPD). Their activity was evaluated for NO reduction by CO under stoichiometric and oxidizing conditions and for direct decomposition of NO. Pd substituted samples exhibited high NO reduction activity and selectivity towards N2. Nearly complete elimination of NO was achieved at 200°C. Two simultaneous reactions, NO reduction by CO and direct decomposition of NO as well as two forms of NO adsorption were observed on the surface of Pd substituted perovskite samples. The distribution of Pd in different catalytically active sites or complexes on at the catalyst surface may be responsible for the proceeding of two reactions: NO reduction with CO and direct NO decomposition.

Open Access October 6, 2009

Comparison of the efficacy of sulfurization agents in decreasing the sheet resistance of polyamide and polyethylene with copper sulfide layers and influence of their compositions

Remigijus Ivanauskas, Ingrida Ancutienė, Vitalijus Janickis, Rūta Stokienė

Page range: 864-869

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Abstract

The process of obtaining semiconductive and electrical conductive layers of copper sulfides by the sorption — diffusion method on polymers (polyamide 6 and low density polyethylene) using solutions of potassium pentathionate, K2S5O6, and higher polythionic acids, H2Sn O6 (n = 21, 33), was investigated. The layers were characterized for compositional and electrical properties by X-ray diffraction (XRD) analysis and sheet resistance measurements. The thickness of copper sulfides layers on polyamide and polyethylene increased with increasing time of polymer sulfurization and varied from 10 to 43 µm. The variations of the sheet resistance of copper sulfides layers formed on the surface of polymers on sulfurization agent used, the conditions of sulfurization, chemical and phase composition of the obtained layers were established. Sheet resistance of copper sulfides layers decreases with increasing time of the duration of sulfurization and the number of sulfur atoms in the polythionate anion. The sheet resistance values for copper sulfide layers formed on the polyamide surface are much lower than those of Cux S formed on the polyethylene surface. XRD showed the predomination of Cux S phases with low x values.

Open Access October 6, 2009

Two charge-transfer complex spectrophotometric methods for the determination of sulpiride in pharmaceutical formulations

Sayed Zayed

Page range: 870-875

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Abstract

Two simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of sulpiride. They are based on charge transfer complexation between the drug as n-electron donor and p-chloranilic acid as π acceptor or iodine as σ-acceptor. These give highly coloured complexes with absorption maxima at 518 and 363, 294 nm, respectively. Beer’s law linear ranges were 13.7–341.4 and 1.7–20.5 µg mL−1 for the p-chloranilic acid and iodine methods. The methods were successfully applied to the determination of the drug in Dogmatil® Fort tablets and the results compared with the official method. The complex association constants and standard free energy changes were calculated using Benesi-Hildebrand plots.

Open Access October 6, 2009

Acid-base behaviour of sanguinarine and dihydrosanguinarine

Helena Absolínová, Luděk Jančář, Irena Jančářová, Jaroslav Vičar, Vlastimil Kubáň

Page range: 876-883

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Abstract

Acid-base and optical properties of sanguinarine and dihydrosanguinarine were studied in the presence of HCl, HNO3, H2SO4, H3PO4, CAPSO and acetic acid (HAc) of different concentrations and their mixtures. The equilibrium constants pKR+ of the transition reaction between an iminium cation Q+ of sanguinarine and its uncharged QOH (pseudo-base, 6-hydroxy-dihydroderivative) form were calculated. A numerical interpretation of the A-pH curves by a SQUAD-G computer program was used. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to alkaline medium were observed. The shifts depend on the type and concentration of inert electrolyte (the most remarkable for HNO3 and HCl). The corresponding pKR+ values ranged from 7.21 to 8.16 in the same manner (ΔpKR+ = 0.81 and 0.73 for HNO3 and HCl, respectively). The priority effect of ionic species and ionic strength was confirmed in the presence of NaCl and KCl. The strength of interaction of SA with bioactive compounds (i.e. receptors, transport proteins, nucleic acids etc.) may be affected because of the observed influence of both cations and anions of the inert electrolytes.

Open Access October 6, 2009

Temperature-induced phase transition; Polymorphism in BP2 SAMs on Au(111)

Waleed Azzam

Page range: 884-899

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Abstract

Self-assembled monolayers (SAMs) of ω-(4′-methylbiphenyl-4-yl)ethanethiol (CH3(C6H4)2(CH2)2SH, BP2) prepared at different temperatures on Au(111) substrates were investigated using scanning tunneling microscopy (STM). Also, the effect of the incubation time of the gold substrate in the thiol solution was examined. The STM results showed that samples prepared at room temperature were significantly different from those prepared at elevated temperatures in their surface morphology, space group and size of unit cell. The micrographs of samples prepared at higher temperatures revealed a pronounced and progressive increase in the size of the well-known etch-pits at the expense of their density with increasing preparation temperature (but the increase did not continue for SAMs prepared at 348 K). The average domain size was found to increase significantly with increasing preparation temperature. In addition, polymorphism was observed in BP2 SAMs at all investigated temperatures. This study has demonstrated that solution temperature and incubation time are key factors controlling the two-dimensional SAM structure of BP2 molecules.

Open Access October 6, 2009

Use of the sulfide minerals pyrite and chalcopyrite as electrochemical sensors in non-aqueous solutions. The potentiometric titration of weak acids in alcohols

Ljiljana Mihajlović, Snežana Nikolić-Mandić, Branislav Vukanović, Ranđel Mihajlović

Page range: 900-908

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Abstract

Natural monocrystalline pyrite and chalcopyrite were examined as new indicator electrodes for the potentiometric titration of weak acids in tert-butanol and iso-propanol. The electrodes investigated demonstrated a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 48 mV per decade for pyrite in tert-butanol. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be suitable titrating agents. The response time was less than 12 s and the lifetime of the electrodes was higher than 1 year. The advantages of the electrodes are long-term stability, rapid response, reproducibility, easy preparation and low cost.

Open Access October 6, 2009

CP-MLR directed QSAR study of carbonic anhydrase inhibitors: sulfonamide and sulfamate inhibitors

Brij Sharma, Pradeep Pilania, Prithvi Singh, Susheela Sharma, Yenamandra Prabhakar

Page range: 909-922

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Abstract

The inhibition activities of sulfonamide and sulfamate derivatives for human carbonic anhydrases have been quantitatively analyzed using DRAGON descriptors. QSAR models have been obtained through combinatorial protocol-multiple linear regression (CP-MLR) computational procedure. For the hCA I inhibition activity, a higher value of information content index of the 1-order neighborhood symmetry (IC1) and a lower value of the Moran autocorrelations, MATS2v and MATS1p, along with a lower number of sulfur atoms in a molecular structure (nRSR) is beneficial to the activity. A higher number of 5-membered rings (nR05), a bigger distance between nitrogen and sulfur T(N..S), and a higher value of van der Waals volume weighted descriptor (GATS6v), are helpful to improve the hCA II inhibition activity. For the inhibition of hpCA, a lower value of the descriptors Jhetv and PW5, and higher values of the eigenvalue sum from Z weighted distance matrix, SEigZ, the Moran autocorrelation of lag 8 weighted by atomic van der Waals volumes, MATS8v and the Moran autocorrelation of lag 4 weighted by atomic Sanderson electronegativities, MATS4e are favorable. The derived significant models in such descriptors may further be used to synthesize new potential compounds and to decipher the mode of their actions at molecular level.

Open Access October 6, 2009

Synthesis, structures, and spectroscopic properties of copper(I) complexes bearing 7-acetamido-4-methyl-1,8-naphthyridin-2-carbaldehyde azine and 1,2-bis(diphenylphosphino)ethane ligands

Shao-Ming Chi, Yu-Fei Wang, Xin Gan, De-Hui Wang, Wen-Fu Fu

Page range: 923-928

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Abstract

A new ligand napaa (napaa = 7-acetamido-4-methyl-1,8-naphthyridin-2-carbaldehyde azine) and its two dinuclear copper(I) complexes, Cu2(napaa)(dppe)2(ClO4)2 (1) and Cu2(napaa)(PPh3)4(BF4)2 (2) (dppe = 1,2-bis(diphenylphosphino)ethane) and PPh3 = triphenylphosphine) were synthesized and characterized, and the structure of 1 was determined by X-ray crystal analysis. Each copper atom in 1 has a distorted tetrahedral geometry in which the metal center is associated to napaa and dppe ligands displaying chelating coordination modes and the naphthyridine rings of napaa are almost coplanar. The two complexes exhibit similar electronic absorption spectra with λmax at about 366 nm, which can be tentatively assigned to metal-to-ligand charge-transfer (MLCT) transition. The assignment was further supported by density functional theory (DFT) calculations.

Open Access October 6, 2009

Mechanistic aspects of oxidation on L-tyrosine by diperiodatocuprate(III) complex in alkali media: a kinetic model

Nagaraj Shetti, Rajesh Hegde, Sharanappa. Nandibewoor

Page range: 929-937

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Abstract

Oxidation of an amino acid, L-tyrosine (L-Tyr) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.1 mol dm−3 was studied spectrophotometrically at different temperatures (288.1–313.1 K). The reaction between DPC and L-Tyr in alkaline medium exhibits 1:4 stoichiometry (L-Tyr:DPC). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidence, a mechanism involving monoperiodatocuprate(III) (MPC) as the reactive oxidant species has been proposed. A suitable mechanism is proposed through the formation of a complex and free radical intermediate. The products were identified by spot test and characterized by spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and are discussed. The thermodynamic quantities were determined for different equilibrium steps. Isokinetic temperature was also calculated and found to be 252.3 K.

Open Access October 6, 2009

Cloud point extraction-preconcentration and flame atomic absorption spectrometric determination of low levels of zinc in water and blood serum samples

Ardeshir Shokrollahi, Mojtaba Shamsipur, Fahimeh Jalali, Hamid Nomani

Page range: 938-944

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Abstract

A simple, sensitive and selective flotation method is described for the preconcentration and atomic absorption spectrometric determination of zinc ion in water and blood samples. At a solution pH of 5.2, 4-(2-pyridylazo-resorcinol) and Triton X-114 were used as hydrophobic ligand and non-ionic surfactant, respectively. The chemical variables affecting the preconcentration process were optimized. Under the optimized experimental conditions, the selective preconcentration and determination of as low zinc concentration as 6.5 µg L−1 can be made. The proposed method was successfully applied to the preconcentration and low-level determination of zinc in different water and blood serum samples.

Open Access October 6, 2009

Solid phase selective separation and green preconcentration of Cu, Zn, Pb and Cd in drinking water by using novel functionalized resin

Nagwa Burham, Sami Azeem, Mohamed El-Shahat

Page range: 945-954

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Abstract

A new solid — phase extraction sorbent was developed based on stepwise anchoring of two ligand molecules for the determination of copper, zinc, lead and cadmium in drinking water by flame AAS. Amberlite XAD-2 functionalized with 4′-(2-hydroxyphenylazo)-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one (HPAPyr) was utilized for preconcentration/separation of these elements. The sorbent was prepared by two successive azo coupling reactions. First, 2-aminophenol was anchored to the amino groups in the resin resulted from nitration followed by reduction. Then, the resulted 2-aminophenol functionalized resin was further diazotized and coupled to the pyrazolone compound and the final product HPAPyr-XAD-2 was characterized by IR and elemental analysis. The optimum pH range for sorption, shaking time, exchange capacity, sample flow rate, preconcentration factor and interference from co-existing ions were investigated. All metal ions were quantitatively desorbed from the resin by 4.5 mol L−1 nitric acid solution. The sorbent provides limit of detection within the range 0.9–3.3 µg L−1 and concentration factor up to 250. The procedure was validated by analysis of certified material NIST-SRM 1577b. Application to drinking water showed satisfactory results with relative standard deviation RSD ≤ 8.5%.

About this journal

Open Chemistry is a peer-reviewed open access journal that publishes original research, reviews, and communications in the fields of chemistry in an ongoing way. Our central goal is to provide a hub for researchers working across all subjects to present their discoveries, and to be a forum for the discussion of the important issues in the field.

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Open Chemistry aims to publish high quality research in the following areas:

Biological Chemistry/Biochemistry including bioanalytical chemistry, biochemistry and biological chemistry, biophysics and chemical physics in biology

Analytical Chemistry including electrochemistry, environmental chemistry, spectroscopy
Physical Chemistry including catalysis, chemical kinetics and reactivity, chemical physics, computational chemistry, chemometrics and QSAR, hydrogen technologies, hydrogen storage, nanochemistry, photochemistry, physical chemistry and physical organic chemistry, radiochemistry and nuclear chemistry, supramolecular chemistry, surface chemistry and colloids, theoretical chemistry, thermodynamics
Inorganic Chemistry including coordination chemistry, crystallography, materials and solid- state chemistry
Organic Chemistry including macromolecules and polymers, natural product chemistry, organic chemistry, organometallic chemistry, phytochemistry
Interference with other sciences including clinical chemistry, marine chemistry, medicinal chemistry, pharmaceutical chemistry

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