A Quasi-Intramolecular Solid-Phase Redox Reaction of Ammonia Ligands and Perchlorate Anion in Diamminesilver(I) Perchlorate

The reaction of ammoniacal AgNO3 solution (or aq. solution of [Ag(NH3)2]NO3) with aq. NaClO4 resulted in [Ag(NH3)2]ClO4 (compound 1). Detailed spectroscopic (correlation analysis, IR, Raman, and UV) analyses were performed on [Ag(NH3)2]ClO4. The temperature and enthalpy of phase change for compound 1 were determined to be 225.7 K and 103.04 kJ/mol, respectively. We found the thermal decomposition of [Ag(NH3)2]ClO4 involves a solid-phase quasi-intramolecular redox reaction between the perchlorate anion and ammonia ligand, resulting in lower valence chlorine oxyacid (chlorite, chlorate) components. We did not detect thermal ammonia loss during the formation of AgClO4. However, a redox reaction between the ammonia and perchlorate ion resulted in intermediates containing chlorate/chlorite, which disproportionated (either in the solid phase or in aqueous solutions after the dissolution of these decomposition intermediates in water) into AgCl and silver perchlorate. We propose that the solid phase AgCl-AgClO4 mixture eutectically melts, and the resulting AgClO4 decomposes in this melt into AgCl and O2. Thus, the final product of decomposition is AgCl, N2, and H2O. The intermediate (chlorite, chlorate) phases were identified by IR, XPS, and titrimetric methods.

Compressibility Studies of Solvation Behaviour of Lithium and Sodium Ions in Nitromethane + Dimethylsulfoxide Binary Mixtures at 298.15 K

The isentropic compressibilities (Ks) and apparent molal isentropic compressibilities (Ks,φ) of lithium perchlorate (LiClO4), sodium perchlorate (NaClO4), sodium tetraphenylborate (NaBPh4), tetrabutylammonium tetraphenylborate (Bu4NBPh4) and tetrabutylammonium perchlorate (Bu4NClO4), have been calculated from measured ultrasonic velocity (u) and density (ρ) of these salts in the concentration range 0.001 to 0.60 mol Kg-1 in the mixed binary solutions of nitromethane (NM) and dimethyl sulfoxide (DMSO) containing 0, 20, 40, 60, 80 and 100 mol% of DMSO in NM at 298.15 K. Limiting values of apparent molal isentropic compressibilities (K°s,φ) for various salts were evaluated and split into the contributions (K°s,φ)± of the individual ions. Exceptionally large and negative (K°s,φ)± values were obtained whose variation with solvent composition shows strong solvation of both Li+ and Na+ in NM + DMSO mixtures at all compositions of the mixed binary solutions. Solvation of Li+ and Na+ increases as mol% of DMSO in NM increases. Solvation exhibited by Li+, however, is much stronger than Na+ in all compositions of the mixtures. Solvation exhibited by ClO4 – in NM + DMSO mixtures is weak which perchlorate ion shows by having some interactions with DMSO in the DMSO-rich compositions of the mixtures. The large and positive values for Bu4N+ and Ph4B– are indicative of some special type of interactions, mainly solvophobic with the solvent molecules.

Chemical stress contribution in bacterial biofilm formation

<p>Background: The use of different chemicals for agriculture, industry and mining has caused pollution of agrarian soils which provokes changes in rhizosphere microflora. We have studied 10 bacterial strains isolated from a winter wheat Cd-polluted field in Ukraine by their taxonomic position, biochemical properties and resistance to 3 classes of toxicants: heavy metals (Cu<sup>2+</sup>, Cd<sup>2+</sup>), non-metals (perchlorate-ion), organic xenobiotic (1-chloro-4-nitrobenzene, CNB).  </p> <p>Objectives: To study the effect of toxicants on the biofilm–formation ability of individual strains and a mixed community.</p> <p>Methods: Biofilm characteristics (total microcosm growth, biofilm strength and attachment to the microcosm walls) were studied by combined biofilm assay (n = 4) with four treatments including 100 mg/L Cu<sup>2+</sup>, 25 mg/L Cd<sup>2+</sup>, 300 mg/L ClO<sub>4</sub><sup>-</sup>, and 100 mg/L CNB, with correlations and Principal component analysis (PCA) used to investigate data.</p> <p>Results: We found that microbial community had a greater resistance to the toxicants compare to individual strains. The presence of heavy metals increased the strength of biofilms, and in most cases growth and biofilm strength were positively correlated. However, in the presence of Cd<sup>2+</sup> this correlation was lost. Perchlorate affected bacteria, increasing mucus production and biofilm strength though it also reduced attachment levels. Finally, we also found that CNB could be used as a source of Carbon and energy during biofilm–formation.</p>

Reduction of perchlorate ions by the sulfate-reducing bacteria Desulfotomaculum sp. and Desulfovibrio desulfuricans

The usage of microorganisms to clean the environment from xenobiotics, in particular chlorine-containing ones, is a promising method of detoxifying the contaminated environment. Sulfate-reducing bacteria Desulfovibrio desulfuricans Ya-11, isolated from Yavoriv Lake, and Desulfotomaculum AR1, isolated from the Lviv sewage treatment system, are able to grow under conditions of environmental contamination by aromatic compounds and chlorine-containing substances. Due to their high redox potential, chlorate and perchlorate ions can be ideal electron acceptors for the metabolism of microorganisms. To test the growth of the tested microorganisms under the influence of perchlorate ions, bacteria were cultured in modified Postgate C medium with ClO4–. Biomass was determined turbidimetrically, the content of sulfate ions and hydrogen sulfide – photoelectrocolorimetrically, the content of perchlorate ions – permanganatometrically. The study of the ability of sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 to grow in a medium with perchlorate ions as electron acceptors showed the inhibitory effect of ClO4– on sulfate ion reduction by bacteria. Bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 are able to grow in environments with aromatic hydrocarbons, in particular toluene. The possibility of the growth of sulfate-reducing bacteria in the presence of toluene as an electron donor and perchlorate ions as an electron acceptor was investigated. The efficiency of perchlorate ion utilization by sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 was about 90 %. The effect of molybdenum on the reduction of perchlorate ions by Desulfotomaculum AR1 is shown in the paper. Immobilization of bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 was carried out in 3% agar and on wood chips. The ability of bacteria, immobilized on these media, to purify the aqueous medium from perchlorate ions was investigated. Reduction of perchlorate ions is more efficiently performed by cells of Desulfotomaculum AR1 and D. desulfuricans Ya-11 bacteria immobilized in agar than on wood chips. Sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 are able to use perchlorate ions as electron acceptors, purifying the polluted aquatic environment from these pollutants.

Crystal structure of bis{μ2-2,2′-[(4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene)]bis(4-oxo-4H-pyran-3-olato)}dicobaltcalcium bis(perchlorate) 1.36-hydrate

The title compound, [CaCo2(C22H30N4O6)2](ClO4)2·1.36H2O or {Ca[Co(H–2L1)]2}·2ClO4·1.36H2O {whereL1is 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane}, is a trinuclear complex whose asymmetric unit comprises a quarter of the {Ca[Co(H–2L1)]2}2+trinuclear complex, half of a perchlorate ion and 0.34-water molecules. In the neutral [Co(H–2L1)] moiety, the cobalt ion is hexacoordinated in a trigonal–prismatic fashion by the surrounding N4O2donor set. A Ca2+cation holds together two neutral [Co(H–2L1)] moieties and is octacoordinated in a distorted trigonal–dodecahedral fashion by the surrounding O atoms belonging to the deprotonated oxide and carbonyl groups of two [Co(H–2L1)] units. The coordination of the CoIIcation preorganizesL1and an electron-rich area forms, which is able to host hard metal ions. The comparison between the present structure and the previously published ones suggests a high versatility of this ligand; indeed, hard metal ions with different nature and dimensions lead to complexes having different stoichiometry (mono- and dinuclear monomers and trinuclear dimers) or even a polymeric structure. The heterotrinuclear CoII–CaII–CoIIcomplexes are connected in three dimensionsviaweak C—H...O hydrogen bonds, which are also responsible for the interactions with the perchlorate anions and the lattice water molecules. The perchlorate anion is disordered about a twofold rotation axis and was refined giving the two positions a fixed occupancy factor of 0.5. The crystal studied was refined as a two-component inversion twin [BASF parameter = 0.14 (4)].