Intermolecular Interactions in Systems Containing Bi(III) – ClO−4 – H2O – Selected Amino Acids in the Aspect of Catalysis of Bi(III) Electroreduction

The paper describes recent results of studies on the accelerating effect of sulfur‐containing protein amino acids and water activity on multistep Bi(III) ion electroreduction at mercury electrode. The catalytic effect of methionine (Mt), cystine (CY) and cysteine (CE) was analyzed based on kinetic and thermodynamic parameters, which correlated with water activity. Investigations of adsorption of those amino acids at the electrode/solution interface provided information for the analysis of the electrical double layer and its influence on the kinetics of the electrode process. The multistep Bi(III) electroreduction process is controlled by the kinetics of active complexes formation, which precedes transfer of consecutive electrons.     

Thermoanalytical,magnetic and structural investigation of Co(II) complexes with dipyridylamine and 2-hydroxyphenones

The simultaneous TG/DTG–DTA technique was used for three new cobalt(II) complexes with dipyridylamine (dpamH) and the anion of a 2-hydroxyphenone ligand (phenone), with the general formula [Co(dpamH)₂(phenone)]Br, in order to determine their thermal degradation in static air and dynamic nitrogen atmospheres, which was found to be a multi-step decomposition related to the release of the ligand molecules. The complexes were characterized by elemental analyses, FT-IR and UV–Vis spectroscopy, magnetic and conductivity measurements. All structures were determined by X-ray crystallography revealing octahedral coordination of cobalt(II) and monomeric nature of the compounds, [Co(dpamH)₂(2-OH-acetophenone)]Br (1), [Co(dpamH)₂(2-OH-propiophenone)]Br (2) and [Co(dpamH)₂(2-OH, 5-CH₃-acetophenone)]Br·EtOH (3). The variable temperature (76–303 K) magnetic susceptibility measurements showed a paramagnetic nature of the complexes, in accordance with their molecular structure.     

Modification of niobium surfaces using plasma electrolytic oxidation in silicate solutions

Herein, a study of the plasma electrolytic oxidation (PEO) of niobium in an anodising bath composed of potassium silicate (K₂SiO₃) and potassium hydroxide (KOH) is reported. The effects of the K₂SiO₃ concentration in the bath and the process voltage on the characteristics of the obtained oxide layers were assessed. Compact, barrier-type oxide layers were obtained when the process voltage did not exceed the breakdown potential of the oxide layer. When this threshold was breached, the morphology of the oxide layer changed markedly, which is typical of PEO. A significant amount of silicon, in the form of amorphous silica, was incorporated into the oxide coatings under these conditions compared with the amount obtained with conventional anodising. This surface modification technique led to an improvement in the corrosion resistance of niobium in Ringer’s solution, regardless of the imposed process conditions.     

A novel polynuclear donor complex based on helical peptides with aligned electroactive moieties

Two newly synthesised 21-amino acid peptides substituted with ferrocene groups preserve the helical structure of the peptide and behave as multi-centre donor systems with six electroactive reversible redox centres per molecule. The formal potential of the hexaferrocene compound is slightly less positive than that of its single centre analogue.     

Global attractor for heat convection problem in a micropolar fluid

The article is devoted to describe asymptotics in the heat convection problem for a micropolar fluid in two dimensions. We show the existence and the uniqueness of global in time solutions and then prove the existence of a global attractor for considered model. Next, the Hausdorff dimension of the global attractor is estimated. Copyright © 2006 John Wiley & Sons, Ltd.     

Two thia­zolino­[2,3-a]­iso­quinolinone S-oxides

The structures of two racemic thia­zolino­[2,3-a]­isoquinolinone S-oxides, i.e. 8,9-di­methoxy-2,3,5,6-tetra­hydro-10bH-thia­zolo­[2,3-a]­isoquinolin-3-one 1-oxide [C₁₃H₁₅NO₄S, (IIa)] and 8,9-di­methoxy-10b-methyl-2,3,5,6-tetra­hydro-10bH-thia­zolo­[2,3-a]­isoquinolin-3-one 1-oxide [C₁₄H₁₇NO₄S, (IIb)], are described. The thia­zolinone ring in (IIa) exists in an envelope conformation, while in (IIb), it assumes a half-chair conformation. In (IIa) and (IIb), the six-membered heterocyclic ring adopts an envelope conformation. The O atom at sulfur is oriented in a pseudo-axial position, whereas the H atom in (IIa) and the methyl group in (IIb), linked to the stereogenic C centre, occupy a bisectional position with respect to the partially saturated pyridine ring and a pseudo-axial position with respect to the thia­zolinone ring. In both structures, the S=O group and the substituent at the stereogenic C centre are trans with respect to one another. Intermolecular C—H⋯O hydrogen bonds are observed in the crystal lattice of (IIa) and (IIb).     

Polyketanils. Polymers protonated with Bronsted acid

New luminescent materials—aromatic polyketanils (PKs) containing p‐phenylene and biphenylene linkages in the backbone and electron‐donating, side‐group substitutions—were synthesized via melt polycondensation with the goal of studying the interactions between the polymer chains (PKs), primary dopant [1,2‐(di‐2‐ethylhexyl)ester of 4‐sulfophthalic acid (PSA)], and secondary dopant [m‐cresol (MC)] with ¹H NMR, ¹³C NMR, Fourier transform infrared (FTIR), ultraviolet–visible, and photoluminescence measurements. Spectral changes were observed for the PKs after primary and secondary doping, and they supported ionic‐ and hydrogen‐bond formation between the PKs and the PSA and MC, respectively. This specific interaction of the dopant with the host polymer influenced the PK properties, and the following observations were made: (1) HOMO/LUMO energy gap of the protonated PKs; (2) bathochromic/hypsochromic photoluminescence shifts observed after protonation with PSA; (3) a downfield chemical shift of the labile proton in the protonating agent OH group in the ¹H NMR spectra of the protonated polymers; (4) a protonation decrease in the intensity of the C?N stretching band in the FTIR spectrum; and (5) a spherulite‐like morphology, detected by atomic force microscopy and polarized optical microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5645–5660, 2006