Open Access Published by De Gruyter Open Access

Volume 11 Issue 4

April 2013

Issue of Open Chemistry

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Open Access January 23, 2013

Applicability of Gd-doped BaZrO3, SrZrO3, BaCeO3 and SrCeO3 proton conducting perovskites as electrolytes for solid oxide fuel cells

Wojciech Zając, Dariusz Rusinek, Kun Zheng, Janina Molenda

Page range: 471-484

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Abstract

Four proton conducting oxides of perovskite structure: BaZrO3, SrZrO3, BaCeO3 and SrCeO3 doped with 5 mol.% of gadolinium are compared in terms of crystal structure, microstructure, sinterability, water sorption ability, ionic transference number, electrical conductivity and stability towards CO2. Relations between proton conductivity, structural and chemical parameters: pseudo-cubic unit cell volume, lattice free volume, tolerance factor, crystal symmetry and electronegativity are discussed. The grain boundary resistance is shown to be the limiting factor of total proton-conductivity for the materials examined. The highest proton conductivity was observed for BaCeO3, however, it turned out to be prone to degradation in CO2-containing atmosphere and reduction at high temperatures. On the other hand, Ba and Sr zirconates are found to be more chemically stable, but exhibit low electrical conductivity. Electrical conductivity relaxation upon hydration is used to calculate proton diffusion coefficient. Selected materials were tested as electrolytes in solid oxide fuel cells.

Open Access January 23, 2013

Microstructures and electrode performances of Mg50Ni(50-X)Pdx alloys

Sydney Santos, José Castro, Edson Ticianelli

Page range: 485-491

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Abstract

Magnesium and several of its alloys can absorb large amounts of hydrogen. This feature is desirable for several technological applications such as solid state hydrogen storage tanks and anodes of nickel-metal hydride (Ni-MH) batteries. For the latter, Mg-Ni alloys are considered very promising due to their high discharge capacities. Conversely, the low stability of Mg-Ni alloys in alkaline electrolytes have hindered their practical use. In the present manuscript, the effects of palladium black addition on the structure and electrochemical properties of the Mg50Ni50 (in at.%) alloy were investigated. The studied ternary alloys have general composition of Mg50Ni(50-x)Pdx, with 0 ≤ x ≤ 5 (in at.%). These alloys were synthesized by mechanical alloying from pure elements. The alloy powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) while their electrode performances were evaluated by galvanostatic cycles of charge and discharge. The investigated alloys have multi-phase structures composed of amorphous and nanocrystalline phases, with nano-grain sizes of nearly 5 nm. Concerning the electrode performance, the best results were attained by the Mg50Ni47.5Pd2.5 alloy, which kept a high discharge capacity and improved the cycling stability.

Open Access January 23, 2013

Spectral properties of coumarin derivatives in various environments

Alzbeta Holubekova, Pavel Mach, Jan Urban

Page range: 492-501

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Abstract

The structural and spectral properties of coumarin derivatives in complex environments were investigated within the time-dependent density functional theory (TD DFT). Absorption spectra calculations were obtained at TD PBE0/6-31+G(d,p) level of theory for coumarin47 in the gas-phase and in various polar and non-polar organic solvents. The geometries of coumarins 6, 30, 47 and 522 in the gas phase and in inclusion complexes with the β-cyclodextrin (βCD) were determined by PM3 and DFT (HCTH/6-31G) calculations. Encapsulation of coumarin in βCD and associated changes in electronic structure produced either a red or blue shift in the absorption spectra of coumarins. A proposed cavity model for βCD-coumarin complex in water solution allowed identification of various contributions to the overall shift in the absorption spectra of coumarin upon complex formation in a solvent environment

Open Access January 23, 2013

Synthesis, reactions and antineoplastic activity of 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromene derivatives

Renata Gašparová, Pavol Koiš, Margita Lácová, Silvia Kováčová, Andrej Boháč

Page range: 502-513

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Abstract

The key 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromen-5-yl acetates 3 were synthesized in high yields by cyclocondensation of 4-oxo-4H-chromen-3-carbaldehydes 1 with coumarin-3-acetic acids 2 under mild conditions. The reaction pathway involves aldol condensation and subsequent intramolecular lactonization to afford 2-oxo-2H,5H-pyrano[3,2-c]chromene skeleton 3. Further treatment of acetates 3 with alcohols, water or nitrogen containing compounds led to 5-alkoxy-, 5-hydroxy- or 5-acylamino-2H,5H-pyrano[3,2-c]chromen-2-ones 4-6 via nucleophilic substitution of acetyloxy group at C-5. Acetates and hydroxyl derivatives 3 and 5 undergo facile rearrangement in an acid medium yielding 5-hydroxypyrano[2,3-b]chromen-2(10aH)-ones 7. Twelve prepared compounds were evaluated on their antineoplastic activities on 60 human tumour cell line panels in NCI USA. The obtained biological results confirmed that 3-(2-oxo-2H-chromen-3-yl)-2H,5H-pyrano[3,2-c]chromen-2-one represents a new leading skeleton suitable for further antitumour activity study.

Open Access January 23, 2013

Silver particles growth by pulse electrolysis in acetonitrile solutions

Orest Kuntyi, Yevhen Okhremchuk, Oleg Bilan’, Julia Hapke, Ivan Saldan

Page range: 514-518

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Abstract

The morphology of silver particles deposited on ITO-glass surface by pulse electrolysis in acetonitrile solutions of AgNO3 has been analyzed. The influences of potential value (E) as well pulse duration (τon) and pause (τoff) on the size and geometry of the particles has been discussed. It has been shown that in the range of 0.0 ≤ E ≤ −1.5 V at τon = 6 ms and 90 ≤ τoff ≤ 490 ms formation of silver particles (∼20–50 nm) and their agglomeration (∼0.2–2 µm) take place. The tendency to increase size of the particles in 3D has been observed with the increase of cathode potential. Decreasing of duty cycle leads to more discrete deposited particles.

Open Access January 23, 2013

Principal component analysis in interpretation of the results of HPLC-ELC, HPLC-DAD and essential elemental contents obtained for medicinal plant extracts

Pawel Konieczynski

Page range: 519-526

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Abstract

Principal component analysis (PCA) was applied to compare its usefulness with cluster analysis (CA), and factorial k-means analysis (fkm), for evaluating the results obtained using HPLC-DAD, HPLC-ELC and spectroscopic techniques (AAS and UV/VIS spectrometry for determining content of N, P, Fe and Cu) in aqueous extracts of seven medicinal plants. These represented the following plant species that are rich in flavonoids: Betula verrucosa Ehrh., Equisetum arvense L., Polygonum aviculare L., Viola tricolor L., Crataegus oxyacantha L., Sambucus nigra L. and Helichrysum arenarium (L.) Moench. The databases analyzed comprised four sets: 1) results obtained by the use of HPLC-DAD detection, 2) results obtained by the use of electrochemical detection (HPLC-ELC), 3) results for determining elements — total and water-extractable species, and 4) all data combined. Application of statistical methods allowed the samples to be classified into four groups: 1) Crataegus, Sambucus, 2) Equisetum, Polygonum and Viola, 3) Betula, and 4) Helichrysum, which were differentiated by characteristic patterns. PCA supported by CA, was the most suitable method, because it simultaneously allowed for reduction of multidimensionality of the databases, grouped the samples into four clusters, and made possible selection of the factors responsible for differentiation of the plant materials studied.

Open Access January 23, 2013

Fullerenes patched by flowers

Raluca Pop, Mihai Medeleanu, Mircea Diudea, Beata Szefler, Jerzy Cioslowski

Page range: 527-534

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Abstract

Stability measures, such as the total energy and the HOMO-LUMO gap, calculated at the Hartree-Fock and DFT levels of theory, and the aromatic character of five circulenes/flowers with a hexagonal core and petals consisting of 5-, 6- and 7-membered rings are investigated. Geometric (HOMA) and magnetic (NICS) criteria are used to estimate the local aromatic character of every ring of the investigated circulenes. The local aromaticity of the coronene and sumanene patches in two tetrahedrally spanned fullerenes were calculated and compared with the HOMA and NICS values of the corresponding isolated circulenes.

Open Access January 23, 2013

Effect of microwave irradiation on polyphenolic compounds from Satureja hortensis L.

Ildikó Lung, Maria Soran, Cristian Tudoran, Constantin Măruţoiu

Page range: 535-541

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Abstract

Summer savory (Satureja hortensis L.) is most often used as a culinary herb, but it also has medicinal benefits. The extracts from control and irradiated savory were obtained by ultrasound extraction for 30 minutes in an ethanol — water (80:20, v/v) mixture. Polyphenolic compounds from savory were identified and characterized by high-performance liquid chromatography coupled with a photodiode array detector and mass spectrometer. The separation was performed using an Altima C18 column (100×3 mm, 3 μm) and as mobile phase two solvent mixture: A — acetonitrile and B — water-formic acid (99.9:0.1, v/v). Peaks were identified with authentic standards in accordance to retention time, UV spectra and molecular mass. It was identified as caffeic acid, rosmarinic acid, luteolin, naringenin and apigenin. A quantitative determination of polyphenolic compounds was performed applying the external standard method. Our study showed large quantitative differences between the control plant and the irradiated plant.

Open Access January 23, 2013

Characteristics of polyurethane-based sustained release membranes for drug delivery

Mihaela Mândru, Constantin Ciobanu, Stelian Vlad, Maria Butnaru, Laurent Lebrun, Marcel Popa

Page range: 542-553

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Abstract

This paper is focused on the preparation and physicochemical characterization of two poly(ester ether urethane)s with rifampicin in their matrix and different molar concentrations of urethane groups. The polyurethanes with rifampicin were processed as asymmetrical microporous membranes by a phase inversion method and characterized by attenuated total reflection — Fourier transform infrared (ATR-FTIR) spectroscopy and differential scanning calorimetry (DSC). The influence of the surface morphology in the release of drug compounds was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle, and water uptake. The release of rifampicin depends on the molar concentration of urethane groups and also on the surface morphology of the polyurethane membranes. The antibacterial activity was evaluated with S. Epidermidis RP 62 A and P. Aeruginosa ATCC 1544. Finally, the biocompatibility of the polyurethane membranes was studied with human dermal fibroblasts (HDF) to evaluate the potential biomedical applications.

Open Access January 23, 2013

Spectrophotometric and voltammetric characterization of a novel selective electroactive chemosensor for Mg2+

Erhan Zor, Ahmet Saf, Haluk Bingol

Page range: 554-560

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Abstract

A novel azocalix[4]arene derivative, 5,11,17,23-tetrakis[(acetophenone)azo]-25,26,27,28-tetrahydroxycalix[4]arene (APC4), containing acetophenone azo groups at the upper rim was synthesized as a chemosensor. Its binding and sensing properties with alkali and alkaline earth metal ions (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+) were investigated by UV-vis spectrophotometric and voltammetric techniques. The stoichiometric ratio and the association constant were determined spectrophotometrically as 1:1 and (1.94±0.31)×105 L mol−1 for the complex between Mg2+ and the chemosensor, respectively. Moreover, it was shown that the interaction between Mg2+ and the APC4 occurred by means of the phenol groups at the lower rim by voltammetric methods. The results of spectrophotometric and voltammetric experiments showed that the chromogenic chemosensor has high selectivity towards Mg2+ among the other used metal ions, especially the interfering Ca2+ ion.

Open Access January 23, 2013

Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes

Thomas Borrmann, Andrew McFarlane, Uwe Ritter, James Johnston

Page range: 561-568

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Abstract

Rhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

Open Access January 23, 2013

P-Triazinylphosphonium chlorides as a new group of coupling reagents

Beata Kolesinska, Agnieszka Mrozek, Justyna Fraczyk, Zbigniew Kaminski

Page range: 569-583

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Abstract

Tertiary phosphines in reaction with 2-chloro-4,6-dialkoxy-1,3,5-triazines gave unstable quaternary P-triazinylphosphonium chlorides, which readily decomposed with a departure of the alkyl group of the triazine ring substituent. Stable quaternary P-triazinylphosphonium chlorides were obtained only in reaction of 2-chloro-4,6-diphenoxy-1,3,5-triazine. Both, stable quaternary P-triazinylphosphonium chlorides as well unstable analogues prepared in situ activated carboxylic acid yielding “superactive” triazine esters, useful as highly efficient reagents in peptide bond synthesis.

Open Access January 23, 2013

Facile ultrasensitive monitoring of mercury ions in water by fluorescent ratiometric detection

Bogdan Dereka, Denis Svechkarev, Andrey Doroshenko

Page range: 584-593

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Abstract

Prospects for analytical application of 2,5-diphenyloxazole-substituted 3-hydroxychromone for detection of mercury ions are presented. Sensitivity and selectivity for a number of metal ions both in methanol solution and in the plasticized polymer are outlined. Ultrasensitive and highly selective fluorescent ratiometric response of the polymer film containing the title compound for mercury ions in water media is revealed. Reversibility of ratiometric response to mercury ions and influence of plasticizer’s content in the polymer film on the optical feedback are also discussed.

Open Access January 23, 2013

A novel 2-(2-methyl-2-nitrovinyl)-furan ectoparasitic drug: physicochemical characterization and determination of the raw material by gas chromatography mass spectrometry

Zenaida Negrin, Yoslainy Valdés, Tania Pouron, Edell López, Keyller Borges

Page range: 594-603

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Abstract

2-(2-methyl-2-nitrovinyl)-furan (NVF) has recently been synthesized and the pharmaceutical industry interest in this compound has grown due to its antibacterial, fungicidal and anti-ectoparasitic activities. Therefore, the physicochemical characterization of new drug was conducted. In addition, two rapid, simple and suitable GC methods were developed for determination of NVF. Analyses were carried out with an Agilent DB-5ms capillary column (60 m × 0.25 mm i.d., 0.25 µm film thickness). The GC-FID analysis employed splitless mode of injection, oven/injector/detector temperature of 160/230/280°C and nitrogen carrier at the flow of 5.0 mL min−1. The GC-MS analysis employed splitless mode of injection, helium carrier at the flow of 1.5 mL min−1, column temperature program with 2 min at 100°C, ramp at 50°C min−1 to 260°C and injector and detector temperature of 250 and 290°tC, respectively. The MS conditions were ionization voltage, 70 eV; mass range, m/z 40–350; and ion source temperature, 200°C. The analysis time took less than 6 min. The results obtained in the validation of the methods suggest that these methods are economic, precise, accurate and linear over the range of analysis. The methods were successfully employed during the synthesis of NVF in order to ensure the quality of the raw material.

Open Access January 23, 2013

Phase equilibria in the Er-Co-In system and crystal structure of Er8CoIn3 compound

Mariya Dzevenko, Andriy Hamyk, Yuriy Tyvanchuk, Yaroslav Kalychak

Page range: 604-609

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Abstract

Isothermal section of the Er-Co-In system at T = 870 K was constructed by means of X-ray powder diffraction, microstructure, and EDX-analyses. Twelve ternary compounds, namely ErCoIn5 (HoCoGa5-type), Er6Co17.92In14 (Lu6Co17.92In14-type), ErCo4In (MgCu4Sn-type), Er2CoIn8 (Ho2CoGa8-type), Er10Co9In20 (Ho10Ni9In20-type), Er3Co1.87In4 (Lu3Co1.87In4-type), ErCoIn, Er11Co4In9 (Nd11Pd4In9-type), Er11Co3In6, Er8CoIn3 (Pr8CoGa3-type), Er6Co2.19In0.81 (Ho6Co2Ga-type), and Er13.83Co2.88In3.10 (Lu14Co2In3-type) exist in the Er-Co-In system at this temperature. The crystal structure of the Er8CoIn3 compound was determined by means of X-ray powder method (Pr8CoGa3-type, P63mc space group, a = 1.02374(2) nm, c = 0.68759(2) nm). Almost none of the binary compounds dissolve the third component. The exception is the existence of the solid solution based on ErCo3 binary compound, which dissolves up to 8 at.% of In.

Open Access January 23, 2013

Selection of mineralised methods to analyse different types of matrices. Applying the Box-Cox transformation to chemometrics study the coexistence of heavy metals in natural samples

Marcin Sajdak, Celina Pieszko

Page range: 610-618

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Abstract

Chemometric methods are mostly used to optimise technological processes and analytical procedures. Applying chemometric methods in environmental tests may reveal relationships among chemical elements in biomes. Cluster analysis and principal component analysis (PCA) are very helpful for detecting relationships among studied parameters. However, large amounts of data may have a negative effect on this analysis and can lead to misinterpretation of the results. This situation was observed when the samples, taken from several places in the Silesian Province, were used to test the relationship between heavy metals contained in various environmental matrices. Samples were collected from a small area and were characterised by a single biome (pine forest) because direct interpretation of PCA and CA was insufficient to correctly describe such data. The solution to this problem was the use of the Box-Cox transformation, which is a rapid method to normalise input data. The application of chemometric tools enabled the relationships between sampling sites (industrialised and non-industrialised) to be examined and was very helpful in illustrating the relationship between the methodologies of plant preparation samples. Furthermore, the results may indicate the need for further data analysis. The tools described in this paper can be useful for choosing the optimal mineralisation method according to the type of test matrix.

Open Access January 23, 2013

Solubilisation of camptothecin by nonionic surfactants and alkyldimethylamine oxides

Martin Pisárčik, Mája Polakovičová, Ferdinand Devínsky

Page range: 619-628

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Abstract

The solubilisation of poorly soluble antineoplastic drug camptothecin by nonionic surfactants (polysorbates and octylphenol ethoxylates) and alkyldimethylamine oxide surfactants with the alkyl chain length 8 to 16 carbon atoms was investigated. The hydrophobicity of the solubilising agent turned out to be the primary structural parameter controlling the solubility efficiency of camptothecin in an aqueous solution. The quantitative parameter of solubilisation (drug loading coefficient) provided values in the range of 0.1–1.2% and 0.1–1.0% for alkyldimethylamine oxides and nonionic surfactants, respectively. The decreasing number of oxyethylene units and the extension of the hydrophobic part of nonionic surfactant molecule resulted in the increase of camptothecin solubility. From the dynamic light scattering measurements, the hydrodynamic diameter values of camptothecin-loaded alkyldimethylamine oxide and nonionic micelles were found in the range of 4–42 nm and 5–120 nm, respectively. The experimental values confirmed the increase in micellar size with the increasing alkyl chain length. The values of the packing parameter of camptothecin-loaded dodecyldimethylamine oxide micelles indicate their spherical shape at all the investigated surfactant concentrations. A simple computer model of camptothecin-loaded dodecyldimethylamine oxide micelle provided the diameter of the structure cross section which is consistent with the experimental values.

Open Access January 23, 2013

The influence of process conditions on the formation of thallium sulfide layers on polyethylene by the use of higher polythionic acid H2S33O6

Ingrida Bružaitė, Vitalijus Janickis

Page range: 629-635

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Abstract

Thallium sulfide layers of varying composition form on the surface of low-density polyethylene (PE) when the PE films have been sulfurized in a solution of higher polythionic acid H2S33O6, and then immersed in the alkaline solution of thallium (I) sulfate. The concentration of sulfur sorbed-diffused into PE surface increases with the increase of the sulfurization time and concentration of higher polythionic acid solution. The concentration of thallium in the Tlx Sy layers depends on the sulfur concentration sorbed-diffused into PE, the concentration, and temperature of thallium (I) sulfate solutions. By chemical analysis of the obtained sulfide layers it was determined that the values of x and y in the TlxSy layers varies in the intervals: 1xy2S2 were identified by X-ray diffraction analysis in thallium sulfide layers. Scanning Electron (SEM) and Atomic Force (AFM) microscopies were used to characterize surface morphology of thallium sulfide layers. The films deposited on the PE surface have a non-homogeneous structure, and consist of separated islands.

Open Access January 23, 2013

Comparison characterization of copper selenide thin layers prepared on polyamide 6 films by sorption-diffusion method

Remigijus Ivanauskas, Vitalijus Janickis, Vitalija Jasulaitienė

Page range: 636-643

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Abstract

Some earlier synthesized copper selenide (Cux Se) layers formed on the surface of polyamide 6 by sorption-diffusion method using potassium selenotrithionate (K2SeS2O6) as precursor of selenium were characterized by the XRD, XPS and SEM methods. According to the results of the SEM studies, the most uniform Cux Se layers form at the 2.5 h polyamide seleniumized duration at the temperature of 60°C. The thickness of layers, which dependeds on the duration of seleniumization, changed in the range of 0.8–3.2 µm. The XRD patterns of not previously studied Cux Se layers showed their phase composition of six copper selenides: Cu2Se, two phases of CuSe2, Cu3Se2, berzellianite, Cu2-x Se, and bellidoite Cu2Se. Analysis of the XRD and XPS data shows that the macrostructure and composition of the CuxSe layers depend on the conditions of formation of these layers.

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.

Aims and Scope

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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