ResonanceRaman spectra of Iron(II) complexes with 4,4′-didodecyloxy-2,2′-bipyridine and 4,4′-dioctadecyloxy-2,2′-bipyridine

The resonanceRaman spectra of Fe(LC ₁₂)₃Cl₂ and Fe(LC ₁₈)₃Cl₂ (whereLC ₁₂ andLC ₁₈ denote 4,4′-didodecyloxy-2,2′-bipyridine and 4,4′-dioctadecyloxy-2,2′-bipyridine, respectively) have been measured along with their excitation profiles. The exciting lines of an Ar⁺ laser have been used. The bands appearing in theRR spectra within 1 200–1 600cm^?1 (expected to arise from thebipy moiety C-N and C-C vibrations) suffer the greatest resonance enhancements. Both depolarization ratios of theRaman bands and excitation profiles reveal the interaction of the resonant electronic states.     

Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

The Co–Mg–Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600–800 °C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV–vis-DRS) and their redox properties (H₂-TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700 °C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO₂, were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800 °C. High activity of this catalyst was likely connected with the presence of a Co–Mg–Al spinel-type phases, containing easy reducible Co³⁺ cations, formed during high-temperature treatment of the hydrotalcite-like precursor.     

Impedance studies of porous lanthanum-phosphate-bonded nickel electrodes in concentrated sodium hydroxide solution

The hydrogen evolution reaction (HER) was investigated on a lanthanum-phosphate-bonded nickel (LPBN) powder electrode in 30 wt.% NaOH at 70°C using ac impedance and steady-state polarization techniques. Circuits containing one or two constant-phase elements (CPEs) in parallel with a resistance and corresponding to fractal and porous electrode models were tested in order to interpret the ac impedance data. The experimental impedance spectra were well described by the porous electrode model and the circuit containing two CPEs. The results obtained from the ac impedance and steady-state measurements allowed the mechanism and kinetics of the HER to be evaluated. Comparison of these parameters with those obtained on the polycrystalline nickel electrode in 1 M alkaline solution at 25°C indicates that an increase in activity is principally due to an increase in the real surface area.     

Cumulative atomic multipole representation of the molecular charge distribution and its basis set dependence

A simple procedure to decompose the theoretical molecular charge distribution into cumulative atomic multipoles supplementing any population analysis scheme has been described and tested for a number of molecules in extended basis sets. This approach may be applied to describe local charge distributions in neutral as well as charged systems and also leads to a simplified point-charge model conserving the local anisotropy of the atomic charge distribution in molecules. Such an approach may be useful in estimating intermolecular interactions, representing the molecular environment in solvent effect or enzyme catalytic activity studies, evaluation of molecular electrostatic potentials or tracing the quality of basis set functions.     

Analytical quality solid-state composite reference electrode manufactured by injection moulding

An injection moulding method was used for fabricating solid-state reference electrodes (Ag/AgCl type) based on a polymer/inorganic salt composite. In this method, a silver/silver chloride wire was placed inside a mould into which the mixture of polymer and inorganic salt was injected. The obtained solid-state composite reference electrodes were extensively tested to study the influence of different parameters such as solution composition, the concentrations and mobility of ions and pH on the potential stability of the electrodes. These experiments revealed that the composite reference electrodes are insensitive to the matrix effect, have excellent potential readings stability and considerably reduced leakage of inorganic salt. The composite reference electrodes were compared favourably to high-quality commercial reference electrodes. It was concluded that the composite reference electrodes obtained by injection moulding are of analytical quality allowing for continuous, prolonged and intensive usage.     

Unusual potassium-oxalate coordination in the two-dimensional trimetallic [CoCl(NH3)5][KCr(C2O4)3]·0.5H2O complex

A new heterometallic compound, [CoCl(NH₃)₅][KCr(C₂O₄)₃]·0.5H₂O (1), has been synthesized and characterized by elemental analysis, IR and electronic spectra, thermal analysis, variable temperature magnetic susceptibility measurements, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional [{KCr(C₂O₄)₃}_n]^2n? layers, [CoCl(NH₃)₅]²⁺ ions and water molecules. Within the 2-D layer, three different types of oxalate coordination modes are present. Each K cation is coordinated by eight oxygen atoms from oxalate groups and also weakly interacts with the ninth oxygen atom. The extensive network of hydrogen bond is formed between the [KCr(C₂O₄)₃]^2? layer and the [CoCl(NH₃)₅]²⁺ ions. These interactions involve all hydrogen atoms of ammonia ligads and water molecule.     

Evolution and potential of the BiAS procedure for the determination of non-ionic surfactants

The evolution of the BiAS procedure is reviewed and its standard recommended version was compared with the modified version combined with the indirect tensammetric method (BiAS-ITM). New applications of the use of BiAS-ITM for the determination of nonionic surfactants (in the presence of hydrocarbons or adsorbed on particles) and polyethylene glycols were discussed.