Ferrocene as a Reference Redox Couple for Aprotic Ionic Liquids

The electrochemical behavior of ferrocene has been studied in a number of room temperature ionic liquids. Diffusion‐controlled, well‐defined anodic and cathodic peaks were found for the Fc/Fc⁺ (ferrocene/ferrocenium) oxidation/reduction on the gold electrode. Ohmic resistance R between working and auxiliary electrodes was deduced from impedance measurements. Cyclic voltammograms were corrected for the base line current as well as for the ohmic drop (IR). The formal potential 1/2(E_pa+E_pc) for ferrocene reduction/oxidation in aprotic ionic liquids tested is within a relatively narrow range and may be approximated by the value of 0.527±0.018 V (against the cryptate Ag/Ag⁺222 in acetonitrile reference). Ferrocene diffusion coefficients, calculated from the peak current dependence on the sweep rate, were of the order of 10^?7 cm² s^?1.     

The relationship between chemical structure and antimicrobial activity of selected nicotinates, p-iodobenzoates, picolinates and isonicotinates

Alkaline metal, calcium and magnesium p-iodobenzoates and alkaline metal nicotinates, as well as sodium and potassium picolinic and isonicotinates were investigated by means of their antimicrobial and chemical properties. The quality estimation of the influence of metal cation coordinated to the carboxylic anion of the series of studied compounds on their antimicrobial activity as well as on the vibrational structure of whole complex in water solution was done. The changes in antimicrobial properties and in charge distribution of the complex along the position of nitrogen atom in the aromatic ring in sodium and potassium complexes were investigated. The analysis of influence of iodine substituent in para position on the change of electronic charge distribution of carboxylate anion and aromatic ring was done. The relationship between electronic properties estimated by vibrational spectroscopy and antimicrobial activity of studied complexes was investigated.     

Branching fractions and CP asymmetries in B0-->pi0pi0, B+-->pi+pi0, and B+-->K+pi0 decays and isospin analysis of the B-->pipi system

Based on a sample of 227 x 10(6) BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the branching fraction B(B0-->pi(0)pi(0))=(1.17+/-0.32+/-0.10)x10(-6), and the asymmetry Cpi(0)(pi(0))=-0.12+/-0.56+/-0.06. The B0-->pi(0)pi(0) signal has a significance of 5.0 sigma. We also measure B(B+-->pi(+)pi(0))=(5.8+/-0.6+/-0.4)x10(-6), B(B+-->K+pi(0))=(12.0+/-0.7+/-0.6)x10(-6), and the charge asymmetries Api(+)(pi(0))=-0.01+/-0.10+/-0.02 and AK+(pi(0))=0.06+/-0.06+/-0.01. Using isospin relations, we find an upper bound on the angle difference |alpha-alpha(eff)| of 35 degrees at the 90% C.L.     

Synthesis and properties of waterborne self‐crosslinkable sulfo‐urethane silanol dispersions

A novel type of crosslinkable waterborne polyurethane ionomer was prepared by the acetone process. Two new types of sulfonated diols compatible with this process were synthesized from dimethyl 5‐sodium sulfo isophthalate using a one‐ or two‐stage method. Isocyanate‐terminated polyurethane oligomers were prepared from the sulfonated diols with various combinations of diols and diisocyanates and subsequently reacted with amino silane derivatives. Stable, low‐volatile organic chemical, waterborne dispersions of the sulfo‐urethane silanol polymers spontaneously crosslink upon drying without extra additives or processing steps. Despite the lack of organic coalescing solvents, the dispersions have minimum film‐forming temperatures below 10 °C, regardless of glass‐transition temperature. Tensile strengths up to 6000 psi with elongations between 300 and 600% were obtained for the crosslinked films. The hard‐segment content of the films can be controlled to produce films with a Sward–Rocker hardness value up to 42. Through silane end‐group modification, the crosslinking density of the films can also be modified to produce polyurethanes with a wide range of physical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3037–3045, 2002     

Calcium complex of 2,5-dihydroxybenzoic acid (gentisic acid): synthesis,crystal structure,and spectroscopic properties

The synthesis, crystal structure, and spectral characteristics (IR, Raman, and ¹H and ¹³C NMR) of a monomeric hexa(aqua)calcium compound, viz. [Ca(C₇H₅O₄)₂(H₂O)₆]·H₂O (C₇H₅O₄ = 2,5-dihydroxybenzoate), are reported. The central Ca(II) located on a twofold axis is eight coordinate in an approximate square antiprismatic environment, bonded to two monodentate 2,5-dihydroxybenzoate ligands via the carboxylate oxygen, and six waters. The adjacent monomeric units are linked with the aid of several O–H?O hydrogen bonds.     

Reactions of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone: A convenient route to trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides

A new series of six 3-aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides were synthesised in one-step in high yields by the reaction of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone in the presence of hydrochloric acid. The hydrochloride salts were easily converted to the respective new series of free trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazoles using triethylamine in anhydrous diethyl ether. X-ray structure and NMR data from the pyrazole hydrochlorides are reported.     

Adsorption studies and release of selected dyes from functionalized mesoporous MCM-41 silica

Functionalized mesoporous MCM-41 silica was subjected to adsorption and release studies of encapsulated guest molecules of three chosen dyes. These mesoporous systems were composed of three different capping reagents introduced by grafting method on the silica surface to control the release of dye molecules at two different pH values. The amounts of dyes adsorbed on the silica surface were measured using ultraviolet-visible (UV-VIS) spectrophotometry. The efficiency of grafting was calculated on the basis of differential thermal analysis (TG) results and elemental analysis. The release profiles were determined for all obtained systems using USP Dissolution Apparatus 2. Adsorption of the two azo dyes used was the most efficient after the positively charged functionalization and lower after functionalization with neutral and negatively charged capping reagents, while the phthalocyanine dye adsorption was almost functionalization-independent. Grafting efficiency was the highest for neutral capping reagent and much lower for electrically charged molecules of other reagents. Release studies showed clearly that desorption was pH-dependent for azo dyes and pH independent for Alcian Blue. The adsorption and release seem to be connected with the electrical charge of all constituents of these systems. Results obtained can be used for further analysis of different electrically charged molecules.      

Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect

The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions [1]. The vibrational FT-IR (in KBr and ATR techniques) and ¹H and ¹³C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg → Ba were compared with series of univalent metal Li → Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.     

Dynamic analysis of frames with viscoelastic dampers modelled by rheological models with fractionalderivatives

Frame structures with viscoelastic dampers mounted on them are considered in this paper. Viscoelastic (VE) dampers are modelled using two, three-parameter, fractional rheological models. The structures are treated as elastic linear systems. The equation of motion of the whole system (structure with dampers) is written in terms of state-space variables. The resulting matrix equation of motion is the fractional differential equation. The proposed state space formulation is new and does not require matrices with huge dimensions. The paper is devoted to determine the dynamic properties of the considered structures. The nonlinear eigenvalue problem is formulated from which the dynamic parameters of the system can be determined. The continuation method is used to solve the nonlinear eigenvalue problem. Moreover, results of typical calculations are presented.     

From Crystalline to Amorphous Germania Bilayer Films at the Atomic Scale: Preparation and Characterization

A new two‐dimensional (2D) germanium dioxide film has been prepared. The film consists of interconnected germania tetrahedral units forming a bilayer structure, weakly coupled to the supporting Pt(111) metal‐substrate. Density functional theory calculations predict a stable structure of 558‐membered rings for germania films, while for silica films 6‐membered rings are preferred. By varying the preparation conditions the degree of order in the germania films is tuned. Crystalline, intermediate ordered and purely amorphous film structures are resolved by analysing scanning tunnelling microscopy images.