Non-covalent dendrimer-based liquid crystalline complexes: Synthesis and characterization

The synthesis and structural characterization of dendritic macromolecules based on 3,5-dihydroxybenzoic acid are described. The molecular structures and purity of all new compounds were confirmed by ¹H NMR, ¹³C NMR spectroscopy and elemental analysis. The dendritic non-covalent liquid crystalline complexes were prepared through the formation of hydrogen bonds between different generation of dendritic acids (proton donor) and stilbazole derivative containing bipyridyl units (proton acceptor). We found that, the hydrogen-bonded dendritic liquid crystals supramolecules (G1-2py, G2-2py and G3-2py) exhibits nematic and semectic phase. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) were used for investigation of the liquid crystalline properties of the hydrogen-bonded dendritic supramolecular complexes.     

DC-Pulsed Plasma for Dry Reforming of Methane to Synthesis Gas

The carbon dioxide reforming of methane to synthesis gas under DC-pulsed plasma was investigated. The effects of specific input energy and feed ratio on the product distribution and also feed conversion was studied. At the input energy of about 11 eV/molecule per methane and/or carbon dioxide the feed conversion of 38% for CH₄ and 28% for CO₂ and product selectivity of 74% has been attained for H₂ and CO at feed flow rate of 90 ml/min. The energy consumption in this work displays potential to further study and optimization of the process. The importance of the electron impact reactions in the process was discussed. The results show that by prudent tuning of system variables, the process be able to run in the way of synthesis gas, instead of hydrocarbon production.     

Synthesis,characterization, electrochemical behaviour and X-ray crystal structures of nickel(II) complexes with a N2O4 donor set macrocyclic Schiff base ligand

Two nickel(II) complexes of [1 + 1] macrocyclic Schiff base ligand (L) have been prepared by cyclocondensation reactions between 1,3-diamino-2-propanol and 2-[3-(2-formylphenoxy)-2-hydroxypropoxy] benzaldehyde, using NiX₂ (X = Br, and I) salts as template agents, and characterized by elemental analyses, IR, molar conductivity and electronic spectra in both solid and solution states. The single-crystal X-ray diffractions of the complexes are also reported that contain nickel(II) ion in a distorted octahedral geometry coordination of N₂O₃X (X = Br, I and NO₃). In all complexes the ligand behaves as a pentadentate ligand. Cyclic voltammetric studies of nickel(II) complexes indicate a quasi-reversible redox wave in the negative potential range.     

New Re(I) tricarbonyl-diimine complexes with N,N′-bis(substituted benzaldehyde)-1,2-diiminoethane Schiff base ligands: Synthesis,spectroscopic and electrochemical studies and crystal structures

The syntheses, structures and spectroscopic properties of tricarbonylrhenium(I) complexes with N,N′-bis(2-bromo, 4-bromo, 4-chloro and 3-methoxybenzaldehyde)-1,2-diiminoethane Schiff base ligands have been investigated in this paper. Characterization of these complexes was carried out with FTIR, NMR, UV–Vis spectroscopy, elemental analysis and X-ray crystallography. The electrochemical behavior of the investigated complexes has been studied by cyclic voltammetry. The crystal structures of the 4-chloro, 4-bromo and 4-methoxy substituted complexes are stabilized by intermolecular C–H?Cl and C–H?O hydrogen bonds. The remarkable features of the 2-bromo, 4-bromo and 4-chloro substituted complexes are short intermolecular halogen–oxygen contacts. In the 4-bromo complex, short intermolecular Br?O and O?O contacts link neighboring molecules along the [1 0 0] direction, which are further stabilized by short intermolecular π?π interactions. In 2-bromo complex, intermolecular Br?O interactions link neighboring molecules into 1D extended chains along the [0 1 0] and [0 0 1] directions, forming a 2D network which is parallel to the bc-plane.     

Protic ionic liquid [TMG][Ac] as an efficient,homogeneous and recyclable catalyst for Boc protection of amines

An efficient and practical protocol for the chemoselective N-Boc protection of various structurally different aryl, aliphatic and heterocyclic amines was carried out with (Boc)₂O using protic 1, 1, 3, 3-tetra-methylguanidinium acetate (10 mol%) as recyclable catalyst under solvent free condition at ambient temperature. No competitive side reactions (isocyanate, urea and N, N-di-Boc) were observed. α-Amino alcohols afforded the N-Boc-derivative without oxazolidinone formation.     

Simultaneous microemulsion liquid chromatographic analysis of fat-soluble vitamins in pharmaceutical formulations: Optimization using genetic algorithm

An environmentally benign and simple method has been proposed for separation and determination of fat-soluble vitamins using isocratic microemulsion liquid chromatography. Optimization of parameters affecting the separation selectivity and efficiency including surfactant concentration, percent of cosurfactant (1-butanol), and percent of organic oily solvent (diethyl ether), temperature and pH were performed simultaneously using genetic algorithm method. A new software package, MLR-GA, was developed for this purpose. The results indicated that 73.6 mM sodium dodecyl sulfate, 13.64% (v/v) 1-butanol, 0.48% (v/v) diethyl ether, column temperature of 32.5 °C and 0.02 M phosphate buffer of pH 6.99 are the best conditions for separation of fat-soluble vitamins. At the optimized conditions, the calibration plots for the vitamins were obtained and detection limits (1.06–3.69 μg mL⁻¹), accuracy (recoveries > 94.3), precision (RSD < 3.96) and linearity (0.01–10 mg mL⁻¹) were estimated. Finally, the amount of vitamins in multivitamin syrup and a sample of fish oil capsule were determined. The results showed a good agreement with those reported by manufactures.     

Quantum corrections to the entropy of Einstein–Maxwell dilaton–axion black holes

We study corrections to the entropy of Einstein–Maxwell dilaton–axion black holes beyond semiclassical approximations. We consider the entropy of the black hole as a state variable and derive these corrections using the exactness criteria of the first law of thermodynamics. We note that from this general frame-work the entropy corrections for “simpler” black holes like Schwarzschild, Reissner–Nordström and anti-de Sitter–Schwarzschild black holes follow easily. This procedure gives us the modified area law as well.     

Synthesis of 5-aryl-1,3-dimethyl-6-(alkyl- or aryl-amino) furo [2,3-d]pyrimidine derivatives by reaction between isocyanides and pyridinecarbaldehydes in the presence of 1,3-dimethylbarbituric acid

5-Aryl-6-(alkyl- or aryl-amino)-1,3-dimethylfuro [2,3-d]pyrimidine derivatives were obtained by in situ reaction alkyl or aryl isocyanides and pyridinecarbaldehyde derivatives in the presence of 1,3-dimethylbarbituric acid in dichloromethane without any prior activation or modifications.     

Wave-function-based characteristics of hybrid mesons

We propose some extensions of the quark potential model to hybrids, fit them to the lattice data and use them for the purpose of calculating the masses, root mean square radii and wave functions at the origin of the conventional and hybrid charmonium mesons. We treat the ground and excited gluonic field between a quark and an antiquark as in the Born-Oppenheimer expansion, and use the shooting method to numerically solve the required Schrödinger equation for the radial wave functions; from these wave functions we calculate the mesonic properties. For masses we also check through a Crank Nichelson discretization. For hybrid charmonium mesons, we consider the exotic quantum number states with J ^PC = 0^+?, 1^?+ and 2^+?. We also compare our results with the experimentally observed masses and theoretically predicted results of the other models. Our results have implications for scalar form factors, energy shifts, magnetic polarizabilities, decay constants, decay widths and differential cross-sections of conventional and hybrid mesons.     

Defect induced ferromagnetism in carbon-doped ZnO thin films

We report on room temperature ferromagnetism in C-doped ZnO thin films prepared by electron beam evaporation. Magnetization, Hall effect, X-ray photoemission spectroscopy (XPS) and X-ray diffraction studies have been conducted to investigate the source and nature of ferromagnetism in C-doped ZnO. The samples were observed to have n-type conduction with the carrier concentration increasing with C doping. XPS does not give any evidence for C substituted at the O site, and is more consistent with the formation of C-O bonds and with the presence of C primarily in the +4 state. It is suggested that the ferromagnetism originates in the development of Zn vacancies that are stabilized due to the incorporation of C in a high valence state (C⁴⁺).