Synthesis,structures and antimicrobial activities of nickel(II) and zinc(II) diaminomaleonitrile-based complexes

Three Ni(II) and Zn(II) complexes [Ni(L1)], [Ni(L2)], and [Zn(L3)(DMSO)] (L1 = 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile, L2 = 2,3-bis(2-hydroxy-3-methoxybenzylideneimino)-2,3-butenedinitrile, L3 = 2,3-bis(2-hydroxy-1-naphthylideneimino)-2,3-butenedinitrile) were obtained in DMSO by one-pot syntheses. The complexes were characterized by physicochemical and spectroscopic methods. Also, their solid-state structures were determined by single-crystal X-ray diffraction. The geometries of the Ni(II) and Zn(II) complexes were square planar and square pyramidal, respectively. The complexes were screened in vitro against a fungal species and eight species of bacteria, revealing their antimicrobial activity.     

Stable structures of oxocarbons and pseudooxocarbons of group VI

Density functional theory has been used to study the geometries, electronic structure and harmonic vibrational frequencies of the oxocarbons and the pseudooxocarbons of group VI. The ability of the maximum hardness principle for predicting the stable structures of oxocarbons and pseudooxocarbons of group VI is tested by analyzing the results of these calculations. To obtain the stable structure, the geometrical parameters and stability of molecules are compared and analyzed. Bond orders of candidate molecules are calculated by using natural bond orbital analysis. Except selenium derivatives, atoms in molecule calculations prove being useful for studying the nature of carbon heteroatom bond. Chemical hardness is also reported. This study reveals that (1) DFT gives very similar geometries and energies to ab-initio methods and (2) the maximum hardness principle (MHP) is not verified for some of these structures. Data for C₆Se₆, which are new, are presented in this work.     

Determination of aliphatic amines in water by gas chromatography using headspace solvent microextraction

The possibility of applying headspace microextraction into a single drop for the determination of amines in aqueous solutions is demonstrated. A 1 μl drop of benzyl alcohol containing 2-butanone as an internal standard was suspended from the tip of a micro syringe needle over the headspace of stirred sample solutions for extraction. The drop was then injected directly into a GC. The total chromatographic determination was less than 10 min. Optimization of experimental conditions (sampling time, sampling temperature, stirring rate, ionic strength of the solution, concentration of reagents, time of extraction and organic drop volume) with respect to the extraction efficiency were investigated and the linear range and the precision were also examined. Calibration curves yielded good linearity and concentrations down to 2.5 ng ml⁻¹ were detectable with R.S.D. values ranging from 6.0 to 12.0%. Finally, the method was successfully applied to the extraction and determination of amines in tap and river water samples. This system represents an inexpensive, fast, simple and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.     

The use of Cr (CO)6 as an alternative CO source in Pd‐catalyzed C‐N bond formation: Synthesis of benzamides

An efficient strategy for the synthesis of benzamides from acetamides and aryl iodides using 1 mol% Pd (OAc)₂ as catalyst and Cr (CO)₆ as CO‐precursor is described. This new synthetic methodology displays high functional group tolerance on both substrates and avoids the need for ligands, reducing agents, or other additives. The corresponding products were obtained in good to excellent yields at atmospheric pressure under mild reaction conditions.     

Nonlinear vibration analysis of isotropic cantilever plate with viscoelastic laminate

The nonlinear vibration of an isotropic cantilever plate with viscoelastic laminate is investigated in this article. Based on the Von Karman’s nonlinear geometry and using the methods of multiple scales and finite difference, the dimensionless nonlinear equations of motion are analyzed and solved. The solvability condition of nonlinear equations is obtained by eliminating secular terms and, finally, nonlinear natural frequencies and mode-shapes are obtained. Knowing that the linear vibration of this type of plate does not have exact solution, Ritz method is employed to obtain semi-analytical nonlinear mode-shapes of transverse vibration of this plate. Airy stress function and Galerkin method are employed to reduce nonlinear PDEs into an ODE of duffing type. Stability of plate and chaotic behavior are investigated by Runge–Kutta method. Poincare section diagrams are in good agreement with results of Lyapunov criteria.     

Separation optimization of quercetin,hesperetin and chrysin in honey by micellar liquid chromatography and experimental design

The chemometrics approach was applied for the separation optimization of flavonoid markers (quercetin, hesperetin and chrysin) in honey using micellar liquid chromatography (MLC). The investigated method combines SPE of flavonoids from honey using C₁₈ cartridge and their separation and quantification by micellar liquid chromatography. A two level full factorial design was carried out to evaluate the effect of four experimental factors including concentration of SDS, alkyl chain length of the alcohol used as the organic modifier (N), volume percentage of the organic modifier (V_m) and volume percentage of acetic acid (AcOH) in mobile phase on analytes retention times. Experiments for analytes retention times modeling and optimization of separation were performed according to central composite design. Multiple linear regression method was used for the construction of the best model based on experimental retention times. Pareto optimal method was used to find suitable compatibility between resolution and analysis time of analytes in honey. The optimum mobile phase composition for separation and determination of analytes in honey were [SDS]=0.124 mol/L; 7.8% v/v ethanol and 5.0% v/v AcOH. Limits of detection and linear range of flavonoid markers were 0.0079–0.0126, 0.05–50.0 mg/L, respectively.     

A theoretical study on the mechanism and thermodynamics of ozone-water gas phase reaction

Ozone water reaction including a complex was studied at the MP2/6-311++G(d,p) and CCSD/6-311++G(2df,2p)//MP2/6-311++G(d,p) levels of theory. The interaction between water oxygen and central oxygen of ozone produces stable H₂O-O₃ complex with no barrier. With decomposition of this complex through H-abstraction by O₃ and O-abstraction by H₂O, three possible product channels were found. Intrinsic reaction coordinate, topological analyses of atom in molecule, and vibrational frequency calculation have been used to confirm the preferred mechanism. Thermodynamic data at T = 298.15 K and atmospheric pressure have been calculated. The results show that the production of hydrogen peroxide is the main reaction channel with ΔG = ?21.112 kJ mol^-1.     

Aminoalkylation with Aldehydes Mediated by Solid Lithium Perchlorate

The solid LiClO₄-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature.