Novel aromatic polyimides derived from benzofuro[2,3-b]benzofuran-2,3,8,9-tetracarboxylic dianhydride (BBTDA)

Benzofuro[2,3-b]benzofuran-2,3,8,9-tetracarboxylic dianhydride (BBTDA) is introduced as a monomer for the synthesis of a series of novel polyimides with enhanced high thermal stability. Polyimides derived from BBTDA and aromatic diamines showed high glass transition (T_g>296 °C) and degradation (T₅>455 °C) temperatures, and were soluble in organic solvents (i.e. N-methyl pyrrolidone (NMP), N,N^′-dimethylformamide (DMF), N,N^′-dimethylacetamide (DMAc)). The polymerization yielded high-molecular-weight polyimides with inherent viscosities ranging from 1.75 to 2.14 dl/g. The polymers were characterized by IR and elemental analysis.     

Kinetic-Spectrophotometric Determination of Trace Quantities of Thiocyanate Based on Its Landolt Effect on the Reaction of Bromate with Hydrochloric Acid1

A new method for the rapid and sensitive determination of trace quantities of thiocyanate based on its Landolt effect on the bromate-hydrochloric acid reaction was developed. The induction period of the reaction is proportional to the SCN^– concentration. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. We were able to determine thiocyanate in the range 2 × 10^–7–4 × 10^–5 M by this method. The relative standard deviation for 10 determinations of 1.5 × 10^–6 M thiocyanate ion is 0.19% and the detection limit of the method was 7.00 × 10^–8 M. The method was applied to the determination of thiocyanate in human blood serum and of saliva samples with satisfactory results.     

Acidic ionic liquids catalyst in homo and graft polymerization of ε-caprolactone

Biodegradable polycaprolactone was prepared by ring-opening polymerization in presence of ionic liquids as efficient, inexpensive, nontoxic, and easily handled acid catalysts. The resulting polymer exhibited good yield and inherent viscosity between 0.10 and 0.18 dL/g. The chemical structure of obtained polymer was verified by the ¹H-NMR and Fourier transform infrared spectroscopy (FT-IR) spectra. In continuation, the obtained polymer was applied to improve quality level and mechanical properties and also to reduce the hydrophilic properties of the starch, so the ring-opening polymerization of ε-caprolactone was investigated in the presence of starch hydroxyl groups as initiator and ionic liquid as catalyst. The obtained starch-grafted-polycaprolactone was verified by ¹H-NMR, FT-IR spectra, and field emission scanning electron microscopy analysis.     

Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

Synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones using nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl2 nanoparticles

Nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl₂ (nano‐[Zn‐2BSMP]Cl₂) as a nanoparticle Schiff base complex and a catalyst was introduced for the solvent‐free synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones by the multicomponent condensation reaction of various aromatic aldehydes, β‐naphthol, ethyl acetoacetate, and phenyl hydrazine at room temperature.     

Pyridine-2,6-Dicarboxylic Acid (Dipic): Crystal Structure from Co-Crystal to a Mixed Ligand Nickel(II) Complex

Abstract  

Pyridine-2,6-dicarboxylic acid (dipic) was used for the synthesis of a co-crystal with 1,10-phenanthroline-5,6-dione (phen-dione) and a nickel(II) complex. The co-crystal dipic·phen-dione·4H₂O (1) has been synthesized and studied by X-ray crystallography. The structure is stabilized with hydrogen bonds between dipic, H₂O and phen-dione. It is surprising that there is no direct hydrogen bonding between phen-dione and dipic and yet the molecules co-crystallize in aqueous solution. A new complex of nickel(II), [Ni(phen)(dipic)(H₂O)]·4H₂O (2), (where phen = 1,10-phenanthroline) has been synthesized and characterized by elemental and thermogravimetric analyses, FT-IR, UV–Vis and ¹H-NMR spectroscopy. The structure of (2) has been studied by X-ray crystallography. The coordination around Ni(II) is a distorted octahedron. The crystal packing shows that the dimensionality of (2) is enlarged to 3D, through hydrogen bonds and π–π interactions. Cyclic voltammetry of (2) shows that the Ni(II/I) couple is irreversible.     

Certain monomial ideals whose numbers of generators of powers descend

Archiv der Mathematik - This paper studies the numbers of minimal generators of powers of monomial ideals in polynomial rings. For a monomial ideal I in two variables, Eliahou, Herzog, and Saem...     

Electro-oxidation of methanol catalysed by porous nanostructured Fe/Pd-Fe electrode in alkaline medium

Nanostructured Fe/Pd-Fe catalysts are prepared first by the deposition of Fe-Zn onto the Fe electrode surface, followed by replacement of the Zn by Pd at open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of coatings are determined by scanning electron microscopy and energy dispersive X-ray techniques. The results show that the Fe/Pd-Fe coatings are porous structure and the average particle size of Pd-Fe is low, in the range of 30–80 nm. The electrocatalytic activity and stability of Fe/Pd-Fe electrodes for oxidation of methanol are examined by cyclic voltammetry and chronoamperometry techniques. The new Fe/Pd-Fe catalyst has higher electrocatalytic activity and better stability for the electro-oxidation of methanol in an alkaline media than flat Pd and smooth Fe catalysts. The onset potential and peak potential on Fe/Pd-Fe catalysts are more negative than that on flat Pd and smooth Fe electrodes for methanol electro-oxidation. All results show that the nanostructured Fe/Pd-Fe electrode is a promising catalyst towards methanol oxidation in alkaline media for fuel cell applications.     

Synthesis,crystallographic and spectroscopic studies,evaluation as antimicrobial and cytotoxic agents of a novel mixed-ligand nickel(II) complex

A new mononuclear mixed-ligand complex of Ni(II) has been synthesized and structurally characterized by single-crystal X-ray diffraction as [Ni(4-Cl-pydc)(apym)(H₂O)₂], where 4-Cl-pydc and apym are 4-chloropyridine-26-dicarboxylate and 2-aminopyrimidine, respectively. Spectroscopic studies such as FT-IR, UV-vis, ¹H-NMR, and thermal analysis (TGA/DTA) were carried out. The fluorescence properties were studied in solvents with different dipole moments. Antimicrobial activities of 4-chloropyridine-26-dicarboxylic acid (1), 2-aminopyrimidine (2), complex (3), and nickel(II) nitrate hexahydrate (4) were investigated by disk diffusion and broth microdilution methods against three Gram-positive bacteria, Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis and three Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa, S. marcescens; also antifungal effect was evaluated on Aspergillus niger and Saccharomyces cerevisiae in vitro. The highest antibacterial activity of complex was observed nearly equal to gentamicin as a standard drug toward S. epidermids with IZD of 18 mm. The in vitro antiproliferative activity of 1–4 on H1299 (a human non-small cell lung carcinoma), HepG2 (a human liver hepatocellular carcinoma), and β-TC3 (a mouse beta pancreatic) cell lines was evaluated by MTT (3-(45-dimethylthiazol-2-yl)-25-diphenyl-2H-tetrazolium bromide) assay and, effect of complex on depolarization of mitochondrial membrane (MMP) of all three cell lines was measured by rhodamine 123. The highest cytotoxic effect of complex was exhibited toward H1299 cell line with IC₅₀ value equal to 10 μM.