Synthesis of palladium complexes derived from imidazolidin‐2‐ylidene ligands and used for catalytic amination reactions

N‐Aryl amination and the Buchwald–Hartwig reaction are of great synthetic and industrial interest and scientists accept their usefulness and versatility for obtaining arylamines. In this study Ag–N‐heterocyclic carbene complexes were used as transmetallation reagents for the synthesis of Pd–N‐heterocyclic carbene complexes. The new Pd–N‐heterocyclic carbene complexes were characterized using elemental analysis and ¹H NMR, ¹³C NMR and infrared spectroscopies. The crystal structure of one, namely dichlorobis[1,3‐bis(2‐methylbenzyl)imidazolidin‐2‐yliden]palladium(II), is presented. The activity of the Pd(II) complexes in the coupling reaction of anilines or amines with bromobenzene was investigated. These complexes exhibited high catalytic activities in the direct synthesis of triarylamines and secondary amines in a single step. Copyright © 2016 John Wiley & Sons, Ltd.     

Aqua­di­chloro­(di‐2‐pyridyl­di­azene)copper(II) monohydrate

The crystal structure of the mononuclear title complex, [CuCl₂(C₁₀H₈N₄)(H₂O)]·H₂O, shows an s‐cis/E/s‐trans‐configured di‐2‐pyridyl­diazene ligand, with the square‐pyramidal Cu^II ion coordinated to one pyridyl and one diazene N atom together with two Cl atoms and one aqua ligand. The crystal packing involves both hydrogen‐bonding and π–π interactions. The solvent water mol­ecule links three monomers to one another through hydrogen‐bonding interactions in which two monomers are linked via chloro ligands and the third via the aqua ligand. Face‐to‐face and weak slipped π–π interactions also occur between di‐2‐pyridyl­diazene moieties, and these interactions are responsible for the interchain packing.     

On Pointwise Convergence of q-Bernstein Operators and Their q-Derivatives

Pointwise convergence of q-Bernstein polynomials and their q-derivatives in the case of 0 < q < 1 is discussed. We study quantitative Voronovskaya type results for q-Bernstein polynomials and their q-derivatives. These theorems are given in terms of the modulus of continuity of q-derivative of f which is the main interest of this article. It is also shown that our results hold for continuous functions although those are given for two and three times continuously differentiable functions in classical case.     

Synthesis and characterization of new air stable primary amido substituted diborane(4) derivatives

Three new diborane(4) derivatives, 1,2-bis(2,4,6-trimethylanilide)-1,2-bis(dimethyamido)diborane(4) (1), 1,2-bis(2,4,6-trimethylanilide)-1,2-bis(duryl)diborane(4) (2) and 1,2-bis(anilide)-1,2-bis(duryl)diborane(4) (3), have been synthesized and characterized by means of elemental analysis, IR, ¹H, ¹³C and ¹¹B NMR spectroscopy. Additionally, the structures of compounds 1 and 2 have been determined by the single crystal X-ray diffraction technique. The compounds 1 and 2 crystallize in the monoclinic P21/c space group. All of the compounds were found to be air stable.     

Tunability of the optical properties in the Y6(W,Mo)(O,N)12 system

New fluorite-type solid solution domains have been evidenced in the system Y₆(W,Mo)(O,N)₁₂ using precursors prepared by the amorphous citrate route. The oxynitrides as well as the low temperature oxides (600 °C) crystallize in a cubic-type symmetry while the oxides annealed above 1200 °C exhibit a rhombohedral symmetry. Either cationic (W/Mo) or anionic (O/N) substitutions bring the possibility to tune the optical absorption of the yttrium tungstate Y₆WO₁₂, which potential as inorganic UV absorbers is discussed.     

Screening the oxidative potential of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes

The present study was designed to investigate the potential of reactive oxygen species (ROS) generating and subsequent ROS-mediated lipid peroxidation (LPO) inducing effect of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes in vitro. For this aim, 4-chloro- and 4-bromo biphenyl (4-CB and 4-BB), 4-OH, 4'-BB, 4-bromo diphenylether (4-BDE), 4,4'-dichlorobiphenyl (4,4'-DCB), 4,4'-dibromobiphenyl (4,4'-DBB), and 3,4-dichlorobiphenyl (3,4-DCB) were incubated with freshly isolated rat hepatocytes. Their oxidative potential was evaluated by detecting the intracellular ROS formation by oxidant-sensing fluorescent probes (2',7'-dichlorofluorescein diacetate and C(11)-BODIPY(581/591)) using a multiplate reader and determining the levels of eight LPO products (formaldehyde, malondialdehyde, propanal, butanal, pentanal, hexanal, octanal, and nonanal) by a gas chromatography-electron capture detection. 4-BDE was found to be active both in cytoplasm and in the cell membrane in terms of inducing the formation of ROS. Another important finding was the increase in ROS-inducing potential of 4-BB when the same concentration of the hydroxylated derivative, 4-OH,4'-BB, was incubated with hepatocytes. 4-BDE was also found to be the most effective among all tested compounds in inducing LPO where 4-OH, 4'-BB was again more potent than its unmetabolized form, 4-BB. Lactate dehydrogenase leakage analyses indicated that all tested compounds are cytotoxic; 4-BDE caused the highest LDH leakage compared to other mono-halogenated biphenyls tested. Our results suggest that ROS formation by chlorinated biphenyls and mono-hydroxylated bromobiphenyls, and concomitant induction of LPO might be involved in the cytotoxic effects of these industrial pollutants. Similar effects of mono-BDE are also reported, which is a novel observation.     

A note on Baskakov-Kantorovich type operators preserving e−x

In this paper, we give a generalization of the Baskakov-Kantorovich type operators that reproduce functions e₀ and e^−x. We discuss uniform convergence of this generalization by means of the modulus of continuity and establish quantitive asymptotic formula.     

A note on Szász–Mirakyan–Kantorovich type operators preserving $$e^{-x}$$

In the present article, we study modified form of Szász–Mirakyan–Kantorovich operators, which reproduce constant and \(e^{-x}\) functions. We discuss a uniform convergence result along with a quantitative estimate for the modified operators.     

Use of amidoximated hydrogel for removal and recovery of U(VI) ion from water samples

Poly(acrylamidoxime-co-2-acrylamido-2-methylpropane sulfonic acid) (PAMSA) hydrogel was prepared by copolymerization of acrylonitrile and 2-acrylamido-2-methylpropane sulfonic acid as monomer, N,N′-methylenebis(acrylamide) as crosslinking agent and potassium peroxodisulfate as initiator. Amidoximated copolymer network was prepared by the reaction of copolymer network with hydroxylamine hydrochloride. A batch procedure was used for the determination of the characteristics of the U(VI) solid phase extraction from the amidoximated hydrogel. The determination of U(VI) was performed by spectrophotometric method using arsenazo-III as complexing agent. Optimal pH value for the quantitative preconcentration was 3, and full desorption was achieved with 3 mol L⁻¹ HClO₄. The adsorption process can be well described by the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm was closely fitted with the Langmuir model. A preconcentration factor of 20 and the three sigma detection limit of 2.8 μg L⁻¹ (n = 20) were achieved for uranium(VI) ions. The PAMSA hydrogel was used for separating and preconcentrating the uranyl ion existing in sea water samples, thermal spring water samples and the certified reference materials (TMDA 64; fortified lake water sample).     

$$K_{a}$$-convergence and Korovkin type approximation

In the present paper, we study a Korovkin type approximation theorem in the setting of \(K_{a}\)-convergence that contains the classical result. We also study the rate of \(K_{a}\)-convergence and afterwards, we give some concluding remarks.