Straightforward access to chiral diol bidentate ligands: their efficient enantioselective induction in the addition of diethylzinc to aromatic aldehydes

Enantiopure C₂‐symmetric diol bidentate ligands have been synthesized in a straightforward manner through a three‐step reaction with good yields. The synthesized C₂‐symmetric diol bidentate ligands were used in the addition of diethylzinc to various aromatic aldehydes, a general catalytic benchmark reaction, in order to assess their enantioselective induction properties. The enantioselective addition of diethylzinc to 1‐naphthaldehyde and 3‐chlorobenzaldehyde was achieved with an enantiomeric excess (ee) of up to 98%. All synthesized ligands were also evaluated in the addition of diethyzinc to aromatic aldehydes including an extra metal such as Ti(IV) (up to 99% ee). Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of surfactant on electrokinetic properties of polyindole/TiO2-conducting nanocomposites in aqueous and nonaqueous media

In this study, polyindole (PIN)/TiO₂ nanocomposites were synthesized with and without the presence of sodium dodecylsulfate, anionic surfactant, with two different PIN contents. The synthesized materials were subjected to various characterizations namely: particle size, apparent density, conductivity, dielectric constants, magnetic susceptibility, elemental analysis, Fourier transform infrared spectroscopy spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Characterization results revealed the successful preparations of PIN/TiO₂ hybrid nanocomposites. Electrokinetic properties of all the materials were determined by zeta (ζ)-potential measurements in aqueous and nonqueous media. Effects of pH, temperature, presence of various electrolytes, and surfactants on electrokinetic properties of the materials were examined.     

PP-waves in the generalized Einstein theories

We present pp-waven solution to the generalized Einstein-Maxwell field theory introduced by Horndeski and to Mansouri-Chang theory of gravitation.     

The first metal complex of p-nitrobenzoxasulfamate. Synthesis, spectral and structural characterization of triaquabis(p-nitrobenzoxasulfamato)copper(II) monohydrate

The local structure of molten LaCl₃ was investigated by X-ray absorption fine structure of the La K-edge. The nearest La³⁺-Cl⁻ distance and coordination number were 2.89±0.01 Å and 7.4±0.5 from the curve fitting of the first peak in the Fourier transform magnitude |FT|. The coordination number larger than 6 suggests that the local structure of molten LaCl₃ is not a simple octahedral coordination (LaCl₆)³⁻, but 7-fold (LaCl₇)⁴⁻ and/or 8-fold (LaCl₈)⁵⁻ complexes. The first La³⁺-La³⁺ distance, of which correlation was observed as a weak second peak in the |FT|, was evaluated to be 4.9 Å. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl₃ in which the edge-sharing connection of the 6-fold (YCl₆)³⁻ mainly exists.     

Synthesis of R-(-)-2-ethyl-N-benzyl (benzo-monoaza-15-crown-5) and the Crystal Structure of Its Sodium Perchlorate Complex

A new complex of a chiral monoaza-crown ether, [R-(-)-2-ethyl-N-benzyl-4,7,10,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene...NaClO₄], has been prepared and studied by x-ray diffraction. The compound crystallizes in space group P2₁ with cell dimensions a = 8.721(1), b = 16.318(2), c = 8.905(1) Å, = 100.80(1)°. The sodium cation is heptacoordinated and located significantly out of the best plane of the macrocycle ring. The donor atoms of the macrocycle are in the half-chair arrangement.     

Synthesis of chiral crown ethers and complexation with chiral protonated amine compounds: X-ray crystal and nuclear magnetic resonance studies of perchlorate salt of chiral benzo-monoaza-15-crown-5 and chiral monoaza-15-crown-5

The X-ray crystal structure of IX, perchlorate salt of R-(?-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-H?O hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(?)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification.     

New copper(II), manganese(III), nickel(II) and zinc(II) complexes with a chiral quadridentate Schiff base

A chiral Schiff base ligand (H₂L) was obtained by condensing 2-hydroxynaphthalene-1-carbaldehyde with substituted (1R,2R)-(–)-diaminocyclohexane. Chiral Schiff base complexes [CuL], [NiL], [ZnL] and [MnLOH] have been synthesized and characterized by elemental analyses, _M, i.r., u.v.–vis. and ¹H-n.m.r. and magnetic measurements.     

EPR study of gamma-irradiated 2-Bromo-4′-methoxyacetophenone single crystals

The gamma-irradiated single crystals of 2-Bromo-4′-methoxyaceto-phenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA.     

Biological activities,phenolic profiles and essential oil components of Tanacetum cilicicum (BOISS.) GRIERSON

Tanacetum species are consumed as tea in Turkey. We comparatively evaluated the phytochemical potentials and antioxidant activities of the essential oil and methanolic extracts of Tanacetum cilicicum. The chemical constitutes of T. cilicicum essential oil and antioxidant activity of this species was analysed by gas chromatography–mass spectrometry (GC–MS) method. Bicyclo (3,1,1) hept-2-en-4-ol (21.92%), camphor (15.56%) and 1,8-cineole (13.45%) which are oxygenated monoterpenes were found as the major constituents. Phenolic acids and flavonoids were quantificated by HPLC–UV. Catechin was found as the main component. The essential oils and methanolic extracts were evaluated by antioxidant activities. The leaves exhibited significant metal chelation activity with a value of 20.75 ± 4.63 μg/mL.     

Stereoelectronic effects on molecular geometries and state-energy splittings of ligated monocopper dioxygen complexes

The relative energies of side-on versus end-on binding of molecular oxygen to a supported Cu(I) species, and the singlet versus triplet nature of the ground electronic state, are sensitive to the nature of the supporting ligands and, in particular, depend upon their geometric arrangement relative to the O2 binding site. Highly correlated ab initio and density functional theory electronic structure calculations demonstrate that optimal overlap (and oxidative charge transfer) occurs for the side-on geometry, and this is promoted by ligands that raise the energy, thereby enhancing resonance, of the filled Cu dxz orbital that hybridizes with the in-plane pi* orbital of O2. Conversely, ligands that raise the energy of the filled Cu dz2 orbital foster a preference for end-on binding as this is the only mode that permits good overlap with the in-plane O2 pi*. Because the overlap of Cu dz2 with O2 pi* is reduced as compared to the overlap of Cu dxz with the same O2 orbital, the resonance is also reduced, leading to generally more stable triplet states relative to singlets in the end-on geometry as compared to the side-on geometry, where singlet ground states become more easily accessible once ligands are stronger donors. Biradical Cu(II)-O2 superoxide character in the electronic structure of the supported complexes leads to significant challenges for accurate quantum chemical calculations that are best addressed by exploiting the spin-purified M06L local density functional, single-reference completely renormalized coupled-cluster theory, or multireference second-order perturbation theory, all of which provide predictions that are qualitatively and quantitatively consistent with one another.