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A series of new zinc complexes containing the 2,2′-dipyridylamine (dipya) ligand and anions of four benzenepolycarboxylic (BPC) acids, namely phthalic (H 2 pht), isophthalic (H 2 ipht), terephthalic (H 2 tpht) and pyromellitic (H 4 pyr), have been synthesized by ligand exchange reactions. The complexes were characterized based on elemental analysis, FTIR spectroscopy and thermal (TG/DSC) analysis. The complexes were found to have the formulae [Zn(dipya)(pht)] ( 1 ), [Zn(dipya)(ipht)] n ( 2 ), {[Zn(dipya)(tpht)]·H 2 O} n ( 3 ) and [Zn 2 (dipya) 2 (pyr)] ( 4 ). Compounds 2 and 3 have been obtained as single crystals and their crystal structures were determined from X-ray diffraction data. In both structures the coordination number of the Zn atoms is five and they are linked by bridging BPC ligands. In 2 , the ipht ligand is coordinated in a tridentate manner via chelate and monodentate COO groups, whereas two crystallographically different tpht ligands in 3 are coordinated as bis-chelate and bis-monodentate ligands, respectively. These combined modes of ipht and tpht anions resulted in zigzag chains of 2 and 3 . Two-dimensional pseudo-layers in 2 and a three-dimensional network in 3 are governed by hydrogen bonds and C–H⋯O interactions which are formed between the zigzag chains, and by additional C–H⋯ π interactions in 3 . The antimicrobial activity of complexes 1 – 4 was screened in vitro against some Gram-positive bacteria ( Bacillus subtilis , Enterococcus faecalis , Listeria monocytogenes and Staphylococcus aureus ), some Gram-negative bacteria ( Escherichia coli , Pseudomonas aeruginosa and Salmonella enteritidis ) and yeast Candida albicans . Complex 2 showed the most potent inhibitory effect against the tested microorganisms. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a combined experimental and theoretical study on the structures of methoxy substituted 5-phenylazo-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones has been reported. The dyes under the investigation have been thoroughly characterized. X-ray single-crystal analysis shows that 5-(4-methoxyphenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridone crystallizes in the hydrazone form. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of the investigated dyes have been performed using density functional theory. The optimized geometrical parameters obtained by density functional theory calculations are in good conformity with the single-crystal data. The fundamental vibrational wavenumbers, as well as their intensities have been calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Vibrational, nuclear magnetic resonance and natural bond orbital analysis confirm that the prepared dyes exist in the hydrazone tautomeric form in the solid state and dimethyl sulfoxide solution. [Copyright &y& Elsevier]

Zirconium carbide ceramics were prepared by carbothermal reduction of ZrO 2 and C that were mixed by high-energy ball milling. Powders were milled for times from 0 to 120 min in air. As milling time increased, the surface area of the powders increased, indicating significant particle size reduction. Milled powders were reacted at 1600 °C and then densified by spark plasma sintering at 2000 °C, which was sufficient to convert the starting powders to zirconium carbide. Unmilled powders did not reach full density. Milled powders reached full density, but ZrO 2 impurities were found for specimens prepared from powders milled for 60 and 120 min. Microstructure analysis showed that grain size was less than 2 µm for ceramics produced from powder milled for 15 min. Based on densification onset temperature and impurity levels, a milling time of 15 min gives the best balance of particle size reduction to promote densification while minimizing impurity levels. [ABSTRACT FROM AUTHOR]

Crystal structure of the title compound: [Cu 2 (bipy) 2 (pht) 2 ]·4H 2 O (bipy = 2,2'-bipyridine, pht = dianion of phthalic acid), CuBP·4H 2 O, consists of dinuclear entities, which are further connected by π–π stacking interactions between bipy ligands. In this way small channels (micropores) oriented parallel to the [0 0 1] direction and containing loosely hydrogen bonded water molecules are formed. The structural changes during dehydration–rehydration have been thoroughly investigated using TG/DSC analysis, FT-IR spectroscopy, X-ray powder diffraction, optical and scanning electron microscopy, and sorption experiments. In addition, dehydration process was analyzed from the aspect of kinetics. A complete reversibility of the dehydration–rehydration CuBP·4H 2 O(s) ⇌ CuBP(s) + 4H 2 O(g) process was confirmed by all means. Therefore, CuBP·4H 2 O can be classified as molecular sieve with quite unexpected zero-dimensional structure. [ABSTRACT FROM AUTHOR]

Abstract: A series of polycrystalline samples containing sillenite-like (doped γ-Bi2O3) phases were prepared by high-temperature reactions from α-Bi2O3 powder and different oxides in six pseudo-binary Bi2O3–M x O y (M = Mn, Ti, V) and six pseudo-ternary Bi2O3–M1 x O y –M2 x O y (M1 = Pb, Zn, Ti and M2 = Zn, Ti, Si) systems. The products were characterized by XRD, SEM/EDX, HRTEM, SAED and DTA techniques. It is shown that for pseudo-binary systems, the phase composition of specimens depends on dopant content, while, for pseudo-ternary systems, depends on dopants radii, as well. In pseudo-binary systems, single-phase sillenites are obtained if the dopant content is in accordance with formula Bi12M4+O20, for M = Mn and Ti, and , for M = V. However, two coexisting sillenite-like phases, doped compound and nominally undoped solid solution, are found if a half of that dopant quantity is applied. In pseudo-ternary systems, the phase-pure double-doped sillenite specimens are identified if ionic radii of dopants differ less than 40%. Otherwise, two coexisting sillenites were obtained. The possibility to prepare the undoped γ-Bi2O3 phase was also discussed. [Copyright &y& Elsevier]

Abstract: Alumina nanofibers are very suitable materials for use as reinforcement in a great variety of high performance composite materials. Nanosized alumina fibers were prepared from the aluminum chloride hydroxide/poly (vinyl alcohol)/water precursor using the electrospinning technique. The mass ratio of aluminum chloride hydroxide/polymer was 5/1. The fibers were calcinated at 1100°C. The fibers were characterized by the TGA/DTA, XRD and FESEM methods. Calcinated fibers had a mean diameter of 470nm and corundum well defined crystal structure. [Copyright &y& Elsevier]