Spectroscopic and Thermal Study of Mixed Ligand Complexes of Cobalt (II) with β-Diketones and Pyrazinamide.

Abstract

The synthesis of mixed ligand of cobalt (II) with β-diketones (β-dik) (acetylacetone and hexafluoroacetylacetone) and pyrazinamide is proposed. The compounds were investigated by IR- and diffuse reflectance spectroscopies, differential thermal analysis. It is shown that Co (II) β-diketonates (acetylacetone, hexafluoroacetylacetone) mixed ligand complexes with pyrazinamide have a structure corresponding to a distorted octahedron, having D_4h symmetry. The complexes are bonded through hydrogen bonds via water molecules.     

Synthesis and Structural Study of the Cu2ZnSn1 – xSixSe4 System

Crystallography Reports - The quaternary semiconductor compounds Cu2ZnSnSe4, Cu2ZnSiSe4, and Cu2ZnSn1 – xSixSe4 solid solutions on their basis have been synthesized from the...     

Crystal Structure and Third-Order Nonlinear Optical Properties Study of Tetraphenylporphyrin and Its Nickle Complex at Wavelength 532 nm and 1064 nm

Tetraphenylporphyrin (TPP) and its nickel(II) (NiTPP) complex have been synthesized, their crystal structures have been determined by means of X-ray single crystal diffraction. The TPP possesses good planarity in the porphyrin core, while in the complex the planarity disappeared. The central nickel(II) ion coordinates with four nitrogen atoms, which constructed a distorted square environment. Their third-order nonlinear optical properties have been studied using Z-scan technique at wavelength 532 nm and 1064 nm in picosecond (ps) domain. At 532 nm nonlinear absorption were observed, TPP shows two-photon absorption (TPA) combined with saturable absorption (SA), while NiTPP shows SA. At 1064 nm nonlinear refraction were observed, the molecular second hyperpolarizability γ of the NiTPP was about 1.4 times larger than that of the TPP.     

Inclusion Compounds of Plant Growth Regulators in Cyclodextrins. Part VI. Study of the Inclusion Compound of MCPA in β-Cyclodextrin by X-Ray Crystallography

Abstract  

The structure of the 4-chloro-2-methylphenoxyacetic acid (MCPA) inclusion compound in β-Cyclodextrin (β-CD) has been investigated by X-ray crystallography. The inclusion complex crystallizes in the P2₁ space group with unit cell dimensions a = 15.860(2) ?, b = 24.275 (5) ?, c = 19.334(6) ? and β = 108.80(3)°. Its asymmetric unit contains two β-CD molecules which host two disordered MCPA guest molecules (2:2 host:guest stoichiometry) occupying overall five sites. It also contains 16.13 water molecules distributed over 36 sites. One water molecule is entrapped inside the dimeric cavity, forming a hydrogen bond with the chlorine atom of a guest. The two complexes of the asymmetric unit are located alongside and they form head-to-head dimers with the symmetry related complexes by the 2-fold screw axis (b-axis). The dimers form channels developed along the a-axis.     

Structural and magnetic properties of ZnO and Zn1−xMnxO nanocrystals

Chemical precipitation of metal-ions from aqueous solution has been successfully used to produce Zn_1?xMn_xO nanocrystals, in the form of nano-powder. X-ray diffraction (XRD) measurements reveal that the as-prepared samples are single-phase materials and their lattice constant changes with the variation of Mn-concentration, which indicates the incorporation of Mn²⁺ into the hosting ZnO. These findings are corroborated by the observation of the well defined six hyperfine lines of Mn²⁺ ion in the electron paramagnetic resonance (EPR) spectra of the samples with a low Mn-concentration, and of a broad EPR line, which manifests the onset of Mn–Mn exchange interaction, in the samples with an elevated value of x.     

Structural Investigations of RNA–Protein Complexes in Post-Ribosomal Era

Crystallography Reports - Structural studies of RNA–protein complexes are important for understanding many molecular mechanisms occurring in cells (e.g., regulation of protein synthesis and...     

Structural regularities of helicoidally-like biopolymers in the framework of algebraic topology: II. α-Helix and DNA structures

The developed apparatus of the “structural application” of algebraic geometry and topology makes it possible to determine topologically stable helicoidally-like packings of polyhedra (clusters). A packing found is limited by a minimal surface with zero instability index; this surface is set by the Weierstrass representation and corresponds to the bifurcation point. The symmetries of the packings under consideration are determined by four-dimensional polyhedra (polytopes) from a closed sequence, which begins with diamondlike polytope {240}. One example of these packings is a packing of tetrahedra, which arises as a result of the multiplication of a peculiar starting aggregation of tetrahedra by a fractional 40/11 axis with an angle of helical rotation of 99°. The arrangement of atoms in particular positions of this starting aggregation allows one to obtain a model of the α-helix. This apparatus makes it possible to determine a priori the symmetry parameters of DNA double helices.     

Magnetic properties and crystal structure of β-Ta

Polycrystalline samples of β-Ta with Frank-Kasper σ-phase structure prepared by electrolysis are studied. The atomic parameters are determined by the Rietveld method. The magnetic susceptibility is measured in the temperature range 4.2 < T < 273 K and the dependence of the magnetization on the magnetic field strength is measured at 4.2 and 77 K. The analysis of interatomic distances and the results of magnetic measurements indicate that clusters with a localized excess charge exist in β-Ta. The data obtained in this study suggest structural changes in β-Ta at T < 77 K.     

Structural Study of Polymorphism in [La(Gly)3·2H2O](ClO4)3

Journal of Chemical Crystallography - The crystal structures of [La(Gly)3·2H2O](ClO4)3 were determined by X-ray diffraction analysis at temperatures 100&nbsp;K and 300&nbsp;K: space...     

The Peculiarities of the Optical Absorption of Monocrystalline Fluorene and Its Heteroanalogues in the Energy Range Between 3.5 eV and 8.5 eV

Electronic absorption spectra of carbazole, dibenzofuran and fluorene were obtained in all three crystallographic directions (energy range 3.5-8.5eV). All electronic transitions with transition dipoles at oblique angles to a and b crystallographic axes can be traced to parental molecular states.

Crystal transitions with parallel transition dipoles can be traced to parental molecular states for thin (0.1-0.2μ) crystals, slow crystallized from melt under uniaxial pressure. For sublimation flakes and crystals fast crystallized from melt, these transitions cannot be traced to parental molecular states since their spectra have continuous, essentially uniform intensity distribution except for such transition at the onset of absorption.     

Study of the Reactivity of Ni Nanotubes in Media with Different рН

Nickel nanotubes have been synthesized by electrochemical deposition, and their reactivity in aggressive media has been investigated. Kinetic curves of the variation in the atomic ratio between Ni and O in the nanotube crystal structure as a function of the medium acidity are built.     

Production and Study of Silver Nanoparticles by 532 nm Laser Pulse Ablation in NaCl Solution

In this experimental research, silver nanoparticles are produced in NaCl solution by the laser ablation method. Our aim was to investigate the effect of the amount of NaCl in the ablation medium on the characteristics of nanoparticles. A 7 ns pulsed Neodymium YAG laser (Nd:YAG) at 5 J/cm2 fluence and 532 nm wavelength was employed to produce Ag nanoparticles in distilled water with four different concentrations of NaCl. The optical properties, size distribution, and agglomeration of nanoparticles were investigated by several diagnostics. The UV–Visible absorption spectra of the Ag nanoparticles exhibit absorptions in the UV region because of surface plasmon resonance. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the size distribution and morphology of nanoparticles. Dynamic light scattering (DLS) was employed to measure the hydrodynamic size of nanoparticles in suspensions. With X-ray diffraction (XRD) pattern, the lattice structure of nanoparticles was studied. Fourier transform infrared (FTIR), photoluminescence (PL) spectra were obtained to observe the molecular structure and atomic energy levels of particles.     

Structural mechanism of α → γ-transformation in Fe-32%Ni alloy

An intermediate 9R paramagnetic phase in the form of large extended plates has been found for the first time in metastable Fe-32%Ni alloy. This phase is formed during slow heating at a rate of 0.3°C/min in the middle of the temperature range of α → γ transformation. The structure of the new 9R phase has been established using electron diffraction.     

Study of hyperfine interactions in Fe–Co nanocomposite films by Mössbauer spectroscopy and NMR

Nanogranular magnetic films were produced by the specially designed UHV plasma-jet system with DC hollow-cathode discharge. We investigated the properties of these ferromagnetic FeCo-AlN films. The samples were studied by nuclear magnetic resonance, Mössbauer spectroscopy, and transmission electron microscopy. The films are composed of nanoparticles of cubic FeCo, 2–10 nm in size, embedded in amorphous matrix containing Al, N and O. The Mössbauer spectra indicate that the orientation of local magnetic moments on the surface is random for the sample with 1:1 Fe/Co ratio, while the magnetization lays in the plane of the layer for samples with Fe/Co smaller than 1 (0.91–0.95).     

Structural Features and Mutual Influence of the Layers in PZT–LNO–SiOx–Si and PZT–LNO–Si Compositions

Crystallography Reports - The phase composition and specific features of the microstructures of layers in the Pb(Zr0.52Ti0.48)O3–LaNiO3–Si and...