Coulombic interactions,hydrogen bonding and supramolecular chirality in pyridinium trifluoromethanesulfonate

The title compound, C₅H₆N⁺·CF₃SO₃⁻, was serendipitously crystallized in the chiral space group P4₃2₁2. The component entities associate into hydrogen‐bonded helical chains, which propagate along the a and b axes of the crystal, with an alternating disposition of the cations and anions along the chain. N—H...O charge‐assisted hydrogen bonds, from each pyridinium cation to two adjacent trifluoromethanesulfonate anions and from every anion to two different cations, direct the formation of the supramolecular chiral arrays. The crystal packing exhibits nonconventional C—H...O and C—H...F hydrogen bonds between the components. The observed structure demonstrates induction of supramolecular chirality by a combination of Coulombic attractions and intermolecular hydrogen bonds.     

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Hydrogen‐bonded three‐dimensional network of a lanthanum(III) exocyclic complex with 5,10,15,20‐tetra‐4‐pyridylporphyrin

In the complex diaquatetranitrato[5‐(pyridinium‐4‐yl)‐10,15,20‐tri‐4‐pyridylporphyrin]lanthanum(III) 1,2‐dichlorobenzene trisolvate, [La(NO₃)₄(C₄₀H₂₇N₈)(H₂O)₂]·3C₆H₄Cl₂, the lanthanum ion is coordinated to one of the peripheral pyridyl substituents of the porphyrin entity. Units of the complex are interlinked to one another in three dimensions by a network of O—H...N, O—H...O and N—H...O hydrogen bonds between the water ligands, nitrate ions, and pyridyl and pyridinium groups of adjacent species. This is the first structural report of an exocyclic complex of the tetrapyridylporphyrin ligand with any lanthanide ion and its self‐assembly into a three‐dimensional architecture sustained by hydrogen bonds.     

Determination of foreign phases in Fe–As based superconducting systems

The recently discovered superconducting materials, containing Fe and As, have raised huge interest. However most materials prepared to date, suffer from a varying degree of content of foreign phases, Fe₂As, FeAs₂ and FeAs, which can lead to wrong conclusions concerning the properties of these materials. Mössbauer Spectroscopy determines quite easily the relative content of the foreign phases. This procedure is demonstrated by a study of eight samples of three Fe–As based families of materials, RAsFeO_1???x F _x , Sr_1???x K _x Fe₂As₂ and LiFeAs, prepared in three different laboratories.     

Mechanism by which Tungsten Oxide Promotes the Activity of Supported V2O5/TiO2 Catalysts for NOX Abatement: Structural Effects Revealed by 51V MAS NMR Spectroscopy

The selective catalytic reduction (SCR) of NO_x with NH₃ to N₂ with supported V₂O₅(‐WO₃)/TiO₂ catalysts is an industrial technology used to mitigate toxic emissions. Long‐standing uncertainties in the molecular structures of surface vanadia are clarified, whereby progressive addition of vanadia to TiO₂ forms oligomeric vanadia structures and reveals a proportional relationship of SCR reaction rate to [surface VO_x concentration]², implying a 2‐site mechanism. Unreactive surface tungsta (WO₃) also promote the formation of oligomeric vanadia (V₂O₅) sites, showing that promoter incorporation enhances the SCR reaction by a structural effect generating adjacent surface sites and not from electronic effects as previously proposed. The findings outline a method to assess structural effects of promoter incorporation on catalysts and reveal both the dual‐site requirement for the SCR reaction and the important structural promotional effect that tungsten oxide offers for the SCR reaction by V₂O₅/TiO₂ catalysts.     

Group IV complexes of a tetradentate amine mono(phenolate) ligand: a second side-arm donor stabilizes cationic species

An amine mono(phenolate) ligand bearing two side-arm donors led to octahedral trialkoxo and trialkyl group IV metal complexes, in which one of the donors was unbound, and to exceptionally stable cationic complexes in which the two side-arm donors were tightly bound.     

Colorimetric detection of thiol-containing amino acids using gold nanoparticles

This paper reports findings of an investigation of the unusual colorimetric change of gold nanoparticles in the presence of thiol-containing amino acids such as homocysteine, cysteine and glutathione. The colorimetric change for homocysteine exhibits a rate that is about two orders of magnitude higher than that for cysteine, and at least five orders of magnitude higher than that for glutathione. The reactivity is effectively reduced or suppressed by the coexistence of either cysteine or glutathione. It is believed that the reactivity involves encapsulation of the particles by the thiol-containing amino acids which is followed by crosslinking at the encapsulating shells. In comparison with cysteine and glutathione, homocysteine has a slower encapsulating rate but a faster crosslinking rate. Implications of the findings of the interfacial encapsulation and crosslinking reactivities of gold nanoparticles to potential nanoparticle-enhanced analytical detection of thiol-containing amino acids are also briefly discussed.