Novel 2-aminoimidazole-4-one complexes of copper(II) and cobalt(II): Synthesis,structural characterization and cytotoxicity

A series of 2-aminosubstituted (5Z)-3-phenyl-5-(pyridine-2-ylmethylene)-3,5-dihydro-4H-imidazole-4-ones (L) was prepared by the reaction of the corresponding 2-alkylthio-3,5-dihydro-4H-imidazole-4-ones with morpholine or piperidine in the presence of ytterbium(III) triflate. The resulting ligands were subsequently reacted with CuCl₂·2H₂O and CoCl₂·6H₂O to give the corresponding copper(II) and cobalt(II) complexes, respectively. Analysis revealed that the complexes were formed with an LMCl₂ (M = Cu, Co)-type composition in all cases. The structures of the three cobalt complexes prepared in this way were determined by X-ray crystallography. The results revealed that the cobalt ions in these complexes were tetrahedrally coordinated to two chloride anions and two nitrogen atoms from the pyridine and imidazole moieties of the ligand. The electrochemical properties of the ligands and their complexes were evaluated by cyclic voltammetry, and the results revealed that the first stage in the reduction of the Co(II) and Cu(II) complexes involved the reversible formation of the corresponding Co(I) and Cu(I) complexes, respectively. The cytotoxicity activities of the organic ligands and their complexes were evaluated against several cancer cell lines, including MCF-7, A549 and HEK293 cells. The copper complexes of the organic ligands bearing a phenyl or allyl moiety at their N(3) position together with a piperidine substituent at the 2-position of their imidazolone ring exhibited the greatest cytotoxicity of all of the compounds tested in the current study.     

Runge-Kutta collocation methods for differential-algebraic equations of indices 2 and 3

Stiffly accurate Runge-Kutta collocation methods with explicit first stage are examined. The parameters of these methods are chosen so as to minimize the errors in the solutions to differential-algebraic equations of indices 2 and 3. This construction results in methods for solving such equations that are superior to the available Runge-Kutta methods.     

Hochschild cohomology of the Weyl algebra and Vasiliev’s equations

We propose a simple injective resolution for the Hochschild complex of the Weyl algebra. By making use of this resolution, we derive explicit expressions for nontrivial cocycles of the Weyl algebra with coefficients in twisted bimodules as well as for the smash products of the Weyl algebra and a finite group of linear symplectic transformations. A relationship with the higher-spin field theory is briefly discussed.     

Stabilization of propane combustion in a supersonic air flow using a nonequilibrium longitudinal discharge and a coaxial local low-pressure zone

The results of the experimental investigation of the flow in the vicinity of an electric-discharge module having a low aerodynamic drag and intended for igniting hydrocarbon fuel and stabilizing its burning in a supersonic flow at low initial static temperature and pressure are presented. The distinctive feature of the module is that the combustion zone is not attached to the combustion chamber walls. Due to a certain geometric connection between different regions of the module anode, an interference of shock and expansion waves occurs in its vicinity. This leads to the formation of a local longitudinal low-pressure zone behind the anode, the convergence of individual fuel jetlets injected through orifices in the anode in this zone, the formation precisely there of a longitudinal nonequilibrium discharge, and the intensification of fuel mixing and plasmochemical reactions. The gasdynamic features of supersonic flow past the module are numerically investigated. The dynamics of electrical discharge formation and the combustion zones thus formed are studied under particular conditions. The data on the stagnation temperature distribution in the discharge wake are obtained.     

Postmetallocene lanthanide-hydrido chemistry: A new family of complexes [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] (Ln = Y, Nd, Sm, Gd, Yb) supported by guanidinate ligands-synthesis, structure, and catalytic activity in olefin polymerization

The new family of Lewis base free hydrido complexes of rare-earth metals supported by guanidinate ligands [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] (Ln = Y, Nd, Sm, Gd, Yb) was synthesized and structurally characterized. Single-crystal X-ray and solution NMR studies revealed that these complexes are dimeric in both solid state and in [D6]benzene. The dimeric hydrido complexes can adopt eclipsed (Nd, Sm, Gd) or staggered (Y, Yb, Lu) conformations depending on the metal-atom size. Catalytic activity of these [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] complexes in the polymerization of ethylene, propylene, and styrene has been investigated. Complexes of Sm and Y have high catalytic activity in ethylene polymerization (1268 and 442 g mmol(-1) atm(-1) h(-1), respectively).     

Implicit Runge–Kutta Methods with Explicit Internal Stages

The main computational costs of implicit Runge–Kutta methods are caused by solving a system of algebraic equations at every step. By introducing explicit stages, it is possible to increase the stage (or pseudo-stage) order of the method, which makes it possible to increase the accuracy and avoid reducing the order in solving stiff problems, without additional costs of solving algebraic equations. The paper presents implicit methods with an explicit first stage and one or two explicit internal stages. The results of solving test problems are compared with similar methods having no explicit internal stages.     

Cis-trans-conversion of the bicycle in pyrrolizidines: The effect of the preferred conformations on the properties of the bases and the thermodynamics of conformational transformation of the ring fusion type. (Review)

The cis-trans conversion in pyrrolizidines and the deciding effect of steric factors on their conformational equilibrium are discussed. Work on the synthesis and characteristics of sterically strained pyrrolizidines is analyzed and discussed. It is shown that such compounds (predominantly trans-fused) have a series of features in their properties that greatly distinguish them from unstrained pyrrolizidines. The first results from study of the thermodynamics of cis-trans conversion of the pyrrolizidine bicycle are summarized. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1466, October, 2006.     

The h-measure of M-sets for a Walsh system

For any nondecreasing function h(t), given on the positive semiaxis and tending to zero as t 0, we construct an example of a perfect M-set for a Walsh system, having a zero h-measure.Translated from Matematicheskie Zametki, Vol. 21, No. 3, pp. 335–340, March, 1977.     

Reaction of 5,5-dimethyl-4-cyanomethylene-1,3-oxathiolan-2-one with amines and ammonia

A simple method for the synthesis of 5,5-dimethyl-4-cyanomethylene-2-cyanomethyl-2-[1-methyl-1-(carbamoyloxy)ethyl]-1,3-dithiolanes was developed on the basis of the reaction of 5,5-dimethyl-4-cyanomethylene-1,3-oxathiolan-2-one with amines (primary and secondary) and ammonia.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 335–338, March, 1992.