Synthesis of new types of aminomethylenediphosphorus-containing acids and their derivatives

Convenient methods for synthesis of various aminomethylenediphosphorus-containing acids and their derivatives starting from available trimethylsilyl esters of hypophosphorous and phosphorous acids, ethoxymethyleneimine hydrochlorides, and N-substituted formamides have been proposed. Selected properties of the obtained compounds have been examined.

     

Clustering of gadolinium endofullerenols in aqueous solutions

Nature of structuring of aqueous solutions of paramagnetic endofullerenols Gd@C _n (OH)_38–40 was determined in relation to the concentration and pH factor from small-angle neutron scattering, viscometric, and conductometric data. Molecular fractal clusters of the type of branched polymers were found, with their correlation radius being about 20 nm and aggregation numbers reaching a value of 104. The clusterized systems obtained are promising as a basis for MRI-contrasting agents and other biomedical preparations for diagnostics and therapy.     

Metals in surface water of Ukraine: the migration forms,features of distribution between the abiotic components of aquatic ecosystems,and potential bioavailability

We have generalized the results of long-term studies of coexisting forms of a series of metals (Al, Fe, Mn, Zn, Cu, Cr, Pb, Mo, Cd, and V) in surface water bodies of Ukraine, differing in the hydrological regime and the water chemical composition (rivers, reservoirs, lakes, and ponds). The studied metals content has ranged widely, the concentrations of aluminum, iron, and manganese being typically the highest, and the concentration of molybdenum, vanadium, and cadmium being typically the lowest. The ratio between the suspended and the dissolved forms of the metals has been established. Iron and aluminum migrate mostly as part of the suspended matter, whereas the other metals mainly migrate in the dissolved state. The dissolved manganese form predominates in the water bodies under anaerobic conditions. Copper and molybdenum are present almost always in the dissolved state, regardless of the water body type. The data on the relative content of the labile metal fraction (potentially toxic to aquatic organisms) are reported. The relatively low content of this fraction has been found to be majorly owing to the metal ions complexing with natural organic ligands. The humic compounds, the most widespread group of natural organic compounds, play the primary role in the complexation. Even metals with variable oxidation state (Cr, Mo, and V) are found mainly in the form of anionic complexes with the humic substances. Carbohydrates are also involved in the metals binding in the highly bioproductive water bodies, thus increasing the mass fraction of the neutral complexes during the summer and autumn periods. The molecular weight distribution of anionic metal complexes has been discussed; the substantial part of the metals constitutes the compounds with the molecular weight of below 5.0 kDa.     

Synthesis and photochemical properties of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole derivatives

Method of synthesis has been developed for a series of 3,6-di-tert-butyl-9H-carbazole derivatives and their photochemical properties have been investigated. The dependence of the Steglich esterification reaction on the nature of the catalyst was studied. The synthesized compounds show fluorescent emission in the range 400–600 nm with a high quantum yield.     

Reaction of 1-germatranol hydrate with carboxylic acids

Reaction of 1-germatranol hydrate with carboxylic acids RCOOH (R = ClCH₂, PhCH=CH, Ph, 2-FC₆H₄, 3-BrC₆H₄, 3-HOC₆H₄, 3-EtOC₆H₄) in protic (CH₃OH, iso-C₅H₁₁OH) and aprotic polar solvent (CH₃CN) is studied. 1-Acyloxygermatranes RC(O)OGe(OCH{in2}CH{in2}){in3}N are formed in yields from 11 to ~100 % depending on the nature of the acid, solvent, duration of the process and the method of its completion. The reaction is the most effective in acetonitrile. Its topochemical completion (heating of the reaction residue in a vacuum) increases the yield of 1-acyloxygermatranes.     

Chalcogenation of 1,4-dichlorobut-2-yne with organic dichalcogenides in the system hydrazine hydrate–KOH

A reaction of organic dichalcogenides R₂Y₂ (R = Ph, Bn, Pr; Y = S, Se) with 1,4-dichlorobut-2-yne in the system hydrazine hydrate–KOH leads to four principal products: 1,4-bis(organylchalcogenyl)but-2-ynes, 1-organylchalcogenylbut-1-en-3-ynes, 4-organylchalcogenylbut-1-en-3-ynes, and 3(5)-methylpyrazole. The selectivity of the formation of individual products is determined by the ratio of the substrates used and the reaction temperature. A plausible mechanism of chalcogenation considered in the work agrees with the effect of the nature of chalcogene atoms and organic substituents R on stability of intermediates and products. The stabilization of carbanions by α chalcogene-containing groups corresponds to the following order: PhS > PhSe > BnS > BnSe > PrS.     

Application of polymethyl methacrylate in cathode materials of lithium-ion batteries

A study of the Li₂FeSiO₄/C cathode material doped with Mn demonstrated that introduction of polymethyl methacrylate results in a substantial decrease in the particle size and increase in the specific surface area of the cathode material. Polymethyl methacrylate strongly improves the cyclic stability of the cathode material. The discharge capacity after the first cycle was 218 mA h g^–1, and that upon stabilization of the structure of the cathode material, 170 mA h g^–1.     

Reaction of 2,3-dibromo-3-nitroacrylates with N-amino-N″-nitroguanidine

Russian Journal of Organic Chemistry -     

Observation of the multiple halogenation of peptides in the electrospray ionization source

The chlorination of peptides and proteins is an important posttranslational modification, which is a physiological signature of an enzyme myeloperoxidase and can serve as a potential biomarker of some diseases (Parkinson's disease, Alzheimer's disease, etc.). The quantification of the chlorinated peptides has been very challenging in part due to their low levels and artifacts associated with sample preparation. One of the most convenient and promising methods to detect and investigate the chlorinated peptides in the biological samples is the electrospray ionization (ESI) mass spectrometry coupled to the fragmentation techniques (collision‐induced dissociation and electron capture dissociation/electron transfer dissociation). We have shown that if the chlorine anions are present in the solution, then the peptide can undergo the chlorination during the ESI ionization. The effect was found to depend on the values of electric potentials of metal parts of the ESI interface. It was found that the grounding of ESI syringe results in the formation of an additional electric loop leading to the electrolytic production of Cl₂ and as a consequence the hypochlorous acid inside the ESI needle. Hypochlorous acid reacts with amino groups of peptides and proteins producing chloramine or causing the protein cleavage. In the paper, it is shown on the example of the solution of the several peptides in the presence of HCl that by manipulating the ESI syringe potential, it is possible to create complexes with up to five Cl atoms for sample peptides when the ESI is operated in the positive mode. Copyright © 2015 John Wiley & Sons, Ltd.