Ethynylmonocarba-closo-dodecaborates: M[12-HCC-closo-1-CB11H11] and M[7,12-(HCC)2-closo-1-CB11H10] (M = Cs, [Et4N])

Cesium and tetraethylammonium salts of the ethynyl functionalized monocarba-closo-dodecaborate anions [12-HCC-closo-1-CB₁₁H₁₁]⁻ and [7,12-(HCC)₂-closo-1-CB₁₁H₁₀]⁻ were obtained by desilylation of [Et₄N][12-Me₃SiCC-closo-1-CB₁₁H₁₁] and [Et₄N][7,12-(Me₃SiCC)₂-closo-1-CB₁₁H₁₀], respectively. Their thermal properties were examined by differential scanning calorimetry. The compounds were characterized by multi-NMR, IR, and Raman spectroscopy, (−)-MALDI mass spectrometry, and elemental analysis. Single-crystals of Cs[12-HCC-closo-1-CB₁₁H₁₁] and [Et₄N][7,12-(HCC)₂-closo-1-CB₁₁H₁₀] were studied by X-ray diffraction. The discussion of the spectroscopic and structural properties is supported by data derived from theoretical calculations using density functional theory as well as perturbation theory.     

The ternary system cerium-rhodium-silicon

Phase relations have been established in the ternary system Ce-Rh-Si for the isothermal section at 800 °C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800 °C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: τ₇—Ce₃RhSi₃, (Ba₃Al₂Ge₂-type), τ₈—Ce₂Rh_3−xSi_3+x (Ce₂Rh_1.35Ge_4.65-type), τ₁₀—Ce₃Rh_4−xSi_4+x (U₃Ni₄Si₄-type), τ₁₁—CeRh₆Si₄ (LiCo₆P₄-type), τ₁₃—Ce₆Rh₃₀Si_19.3 (U₆Co₃₀Si₁₉-type), τ₁₈—Ce₄Rh₄Si₃ (Sm₄Pd₄Si₃-type), τ₂₁—CeRh₂Si (CeIr₂Si-type), τ₂₂—Ce₂Rh_3+xSi_1−x (Y₂Rh₃Ge-type) and τ₂₄—Ce₈(Rh_1−xSi_x)₂₄Si (Ce₈Pd₂₄Sb-type). For τ₂₅—Ce₄(Rh_1−xSi_x)₁₂Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for τ₃—CeRhSi₂ (CeNiSi₂-type) and τ₆—Ce₂Rh₃Si₅ (U₂Co₃Si₅-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of τ₄—Ce₂₂Rh₂₂Si₅₆, τ₅—Ce₂₀Rh₂₇Si₅₃ and τ₂₃—Ce_33.3Rh_58.2−55.2Si_8.5−11.5 are unknown. High temperature compounds with compositions Ce₁₀Rh₅₁Si₃₃ (U₁₀Co₅₁Si₃₃-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800 °C.     

Raman Spectra of Tungsten-Bearing Solutions

Raman spectroscopy at 25 °C was performed to analyze speciation in quenched solutions after experiments on sodium tungstates and sodium tungstate bronze dissolution at t=500 °C, p=1000 bar. The experiments were conducted under different oxidation-reduction conditions in sodium chloride solution media. The spectra of the quenched solutions were different from those of the reference solutions of 0.02 mol⋅kg⁻¹ W(VI) (H₂O) in the pH range 2.3–7.2. Thermodynamic models were established and the fields of predominance of different isopolytungstate species at 25–50 °C were determined. The experimental results of tungstate dissolution demonstrates that reduced tungstate solutions may contain a significant amount of tungsten species with valence states lower than W(VI).     

Preparation of pure hydrogen peroxide and anhydrous peroxide solutions from crystalline serine perhydrate

Hydrogen peroxide is one of the most versatile oxidation reagents, still it has not fully been exploited by synthetic chemists since anhydrous (let alone pure) hydrogen peroxide requires hazardous preparation protocols. We have recently reported on the crystallization of serine and other amino acid perhydrates, thus paving the way for a new method for laboratory-scale production of anhydrous hydrogen peroxide solutions. Serine is insoluble in most organic solvents (e.g., methanol, ethyl acetate, and methyl acetate) that readily dissolve hydrogen peroxide. Moreover, since the adduct of hydrogen peroxide and serine is unstable in these organic solvents, crystalline serine perhydrate readily decomposes to give anhydrous solutions of hydrogen peroxide and crystalline precipitate of the amino acid. This procedure can then yield an anhydrous hydrogen peroxide solution in a single step. Moreover, filtration of the amino acid, and room temperature evaporation of the volatile solvent (e.g., methyl acetate), yields over 99% hydrogen peroxide.     

Hybrid Polymeric Systems for Nano-Selective Counter Intervention in Virus Life Cycle

Self assembly of viral biopolymers to nano-complexes forming virions during virus delivery from infected cell and reverse disintegration to virus entry into new cells play a crucial role in viral life cycle and in viral diseases. Therefore artificial instruments for selective counter intervention into these processes are dramatically required for the high effective antiviral protection. Hybrid macromolecular systems (HMS) rationally integrating heterogeneous structure-functional factors for selective recognition - inhibition of viruses (nano-objects) without detriment for cells (micro-objects) can become a molecular basis for cardinal progress in this area. Here we discuss approaches to design and current experimental results of synthesis, and antiviral selectivity evaluations of the HMS, based on combinations of polyelectrolyte-grafted components constructed on principles of mimicry and/or complementarity to viral targets or virus-sensitive cell receptors. Particularly, the HMS generations strongly inhibiting the human immunodeficiency virus (HIV) were created as platform to novel drug development against HIV/AIDS and other sexually transmitted infections.     

IR and NMR spectra,intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10–20 cm^?1) red shift of the IR bands of the NH₂ stretching vibrations, which suggests rather weak NH?N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.     

Macroporous antimony film electrodes for stripping analysis of trace heavy metals

We report on the elaboration of macroporous antimony film electrodes. The strategy to create macroporous electrodes is based on the replication of colloidal crystal templates. These electrodes of controlled porosity show an increased internal electroactive area and a significantly improved electrochemical performance. The application of this novel electrochemical sensor for the sensitive quantification of traces of heavy metals has been demonstrated in combination with differential pulse anodic stripping voltammetry in model solutions.     

Kinetics of surface modification induced by submonolayer electrochemical oxygen adsorption on Pt(1 1 1)

Electrochemical oxygen adsorption/desorption below monolayer level leads to a disordering of platinum single-crystal surfaces vicinal to the (1 1 1) plane. The kinetics can be described by means of a consecutive reaction from (1 1 1)-terrace sites to (1 1 0)-defect sites, in which (1 0 0)-defects act as intermediates. The first oxidation of the electrode reflects independent contributions from terrace and step sites, the latter being structure sensitive. Oxygen adsorption charges amount to a mean value of one electron per step site.     

Bismuth modified Pd/C as catalysts for hydrogen related reactions

The electrocatalytic activity of bimetallic BiPd catalysts supported on Sibunit carbon towards hydrogen oxidation/evolution reactions (HOR/HER) was studied in a gas diffusion electrode (GDE) setup. Catalysts were synthesized by deposition of Pd on the carbon support, followed by impregnation of Pd/C precursor with Bi(NO₃)₃ solution and reduction in hydrogen. Transmission electron microscopy and local EDX elemental analysis revealed that BiPd/C catalysts contain bimetallic particles with narrow size distribution with maxima at 3.2–4.1 nm. X-ray diffraction evidenced that bimetallic particles are constituted by Pd–Bi solid solution. It was shown that modification of Pd/C by bismuth increases the specific activity of palladium towards HOR/HER by a factor of 3.     

Synthesis and characterisation of the water soluble bis-phosphine complex [Ru(η6-cymene)(PPh2(o-C6H4O)-κ2-P,O)(pta)]+ and an investigation of its cytotoxic effects

Metal complexes bearing phosphine ligands are attracting increasing attention for their applications in medicinal chemistry. In particular, organometallic ruthenium-phosphine complexes have been found to exhibit promising antitumour activity. The synthesis, anticancer activity and reactivity of a novel bis-phosphine complex, [Ru(η⁶-cymene)(PPh₂(o-C₆H₄O)-κ²-P,O)(pta)]Cl (pta = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1.]decane), is presented. The complex appears to exhibit its anticancer effect via a different mechanism to other ruthenium-arene pta complexes with labile co-ligands.