Thermal stability and crystal structure of bis(1,2 ethanediol)zinc sulfate

Single crystals of the complex bis(1,2-enthanediol)zinc sulfate have been prepared. The crystal structure was determined by X-ray crystallography. Both 1,2-ethanediol (ethylene glycol) molecules chelate the zinc ion, the four glycolic oxygen atoms and the two oxygen atoms of the sulfate ion forming an octahedron around the zinc. Each sulfate ion is bonded to two zincs, forming an endless polymer chain. A hydrogen-bonding network between the ethylene glycol molecules and the sulfate ions is observed. On heating, the complex melts and decomposes, a polymeric structure of the thermal intermediate product is suggested.     

Ultraviolet spectra of silicate glasses: A review of some experimental evidence

Ultraviolet spectroscopy is a useful experimental tool for the determination of the electronic structure of glasses. This paper discusses the ultraviolet spectra of SiO₂ and high-purity silicate glasses. It considers in turn, absorption intrinsic to the SiO network, the effects of network modifiers, impurity-induced absorption, luminescence and radiation damage, both permanent and transient, in the wavelength region extending from 90 to 350 nm.     

Thermal lens and Z-scan measurements: Thermal and optical properties of laser glasses – A review

In this paper, the application of thermal lens and Z-scan techniques to the study of the thermo-optical and spectroscopic properties of solid-state laser glasses is described. The theoretical basis for quantitative measurements of thermal diffusivity and conductivity, temperature coefficient of the optical path length change, heat efficiency, fluorescence quantum efficiency, losses mechanisms (Auger upconversion and concentration quenching) and the line shape of the nonlinear refractive index are presented and discussed. The electronic contribution to the nonlinearity was investigated using the Z-scan technique in the time-resolved mode. The measurements were performed spectroscopically, allowing the determination of the line shapes of real and imaginary parts of the nonlinear refractive index, n₂, in resonance with laser transitions. The results were interpreted by considering resonant and nonresonant contribution to n₂. The magnitude of electronic and thermal contributions to the refractive index changes in solid-state laser glasses were also compared, and the thermal properties as a function of the temperature in the range of 20 up to 600 K are presented.     

X-ray divergent-beam (Kossel) technique: A review

The development of the X-ray divergent-beam (Kossel) technique over the last 50 years is traced. The fundamentals of this technique and ways to implement it experimentally are considered, and its potential for studying the real structure of crystals is analyzed in detail.     

Piezoelectricity in crystallizing ferroelectric polymers: Poly(vinylidene fluoride) and its copolymers (A review)

The piezoelectricity observed in poly(vinylidene fluoride) (PVDF) and its copolymers involves three components that are associated with the presence of at least two phases (crystalline and amorphous) in the polymer structure. The main contributions to the phenomenon observed are made by the size effect and electrostriction, which are related to each other. These contributions manifest themselves through the mechanism of strain-induced reversible transformations of a number of domains of the anisotropic amorphous phase into the crystalline state under the action of mechanical or electrical fields. With due regard for different packings of chains in the amorphous and crystalline phases, this mechanism accounts for the large Poisson ratios μ₃₁ obtained for textured films of flexible-chain crystallizing polymers. The dependence of the piezoelectric coefficient d ₃₂ on the static stress in textured films is governed by the change in the fraction of the crystalline phase due to strong anisotropy of the elastic constants in the film plane. It is shown that the shear deformations of polymers are characterized by a strong piezoelectric response. The specific features revealed in the piezoelectric effect under bending deformations are described for films with an inhomogeneous distribution of polarization over the cross section. The general regularities of the electrostriction in the polymers and inorganic relaxor ferroelectrics studied are considered.     

Structural chemistry of oxoperoxo complexes of vanadium(V): A review

This paper presents a review of the structural features of monomeric, dimeric, and polymeric oxoperoxo complexes of vanadium(V). The structural manifestations of the trans effect of multiply bonded oxo and peroxo ligands in pseudooctahedral oxo monoperoxo complexes of vanadium(V) are compared. The dependence of the geometric parameters of the structural fragment V(O₂)_n (n = 1, 2) (V-O, O-O bond lengths; OVO angles) on the type of coordination seven-vertex polyhedron (pseudooctahedron, n = 1; pseudotrigonal bipyramid, n = 2) of the metal atom is analyzed. Regular distortions of the coordination polyhedra of vanadium atoms (pseudooctahedron, pseudotrigonal bipyramid, pseudotetragonal pyramid, pseudotetrahedron) are considered.     

A novel four-coordinate zinc(II) complex of the di-N-hydroxypropylated tetraaza macrocycle

The compound [Zn(L²)Cl]ClO₄·H₂O (1) (L² = 2,13,-bis(3-hydroxypropyl)-5,16-di-methyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) has been synthesized and structurally characterized. 1 crystallizes in the monoclinic system, space group P2₁/c with a = 8.932(2), b = 16.189(2), c = 22.492(4) Å = 95.34(2)° V = 3238.3(11) ų; and Z = 4. The zinc atom is placed in a highly distorted tetrahedral environment bonding with three nitrogen atoms of the macrocycle and one chlorine atom.     

Specific structural features of copper(II) complexonates with nitrilotriacetate anions: A review

The specific structural features of copper(II) complexes with nitrilotriacetate anions (H_n Nta, n = 0?2) are considered with due regard for the original results and data available in the literature. The structural features and the degree of distortion of copper coordination polyhedra (such as a (4 + 1) elongated square pyramid, a trigonal bipyramid, a (4 + 2) symmetric elongated tetragonal bipyramid, and a (4 + 1 + 1) asymmetric elongated tetragonal bipyramid) are discussed. Criteria for identification of five-vertex copper(II) polyhedra of the general formula Cu(H_n Nta)X (n = 0?2; X = Cl, Br, N, O) are proposed for the cases of a distorted square pyramid, a distorted trigonal bipyramid, and a polyhedron intermediate between them. The modes of coordination of H_n Nta ^{3 ? n} ligands with a mctal arc described in terms of crystal chemical formulas.     

A novel metal‐organic coordination complex crystal: tri‐allylthiourea zinc chloride (ATZC)

A new metal‐organic coordination nonlinear optical crystal, tri‐allylthiourea zinc chloride (ZnCl₂(AT)₃, where AT is CH₂=CHCH₂NHCSNH₂, abbreviated as ATZC), is reported. It was synthesized in water and recrystallized in ethanol. For the crystal structure, optical and thermal characterization were determined by elemental analyses, X‐ray diffraction, infrared spectroscopy, differential scanning calorimeter, thermogravimetric analysis, and powder SHG efficiency meansurement. It belongs to the trigonal system, space group R3, with a = 11.0498(4) Å, c = 16.0416(11) Å, z = 3 and V = 1696.24(15) ų. It exhibits powder SHG efficiency the same order as Urea crystal. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A novel two-dimensional zinc(II) complex of a di-N-carboxymethylated tetraaza macrocycle linked by hydrogen-bonds

The complex [ZnL]·10H₂O (L = 2,13-bis(2-carboxymethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) has been synthesized and structurally characterized. It crystallizes in the monoclinic system, space group P2₁/c with a = 10.159(1), b = 10.066(3), c = 17.268(2) Å, = 102.92(1)°, V = 1721.0(5) ų, and Z = 2. The crystal structure reveals an axially elongated octahedral geometry with bonds from the zinc(II) ion to the secondary and tertiary amines of the macrocycle and two oxygen atoms of the pendant carboxymethyl groups. The molecules of the zinc(II) complex are connected into a two-dimensional chain via hydrogen bonds.     

Crystallographic studies of dihalogeno-tetramethylethylenediamine complexes of zinc,cadmium and mercury. I: crystal and molecular structure of dichloro-(N,N,N′,N′-tetramethylethylenediamine)zinc(II)

The crystal structure of dichloro-(N,N,N,N-tetramethylethylenediamine)zinc(II), C₆H₁₆Cl₂N₂Zn, has been determined from 1684 reflexions measured on a Siemens four-circle diffractometer (A.E.D.) using the /2-scan technique and CuK radiation. The crystals are monoclinic, space groupP2₁/c,a = 7·716(3),b = 13·335(9),c =11·545(5) Å, = 105·59(6) ° andZ = 4. The structure was solved by Fourier methods, and refined by full-matrix least squares to a finalR (conventional) of 6·7 %. Anisotropic thermal parameters were evaluated for the non-hydrogen atoms, but the hydrogen atoms were assigned the equivalent isotropic thermal parameters of the carbon atoms to which they were bonded. The geometry around the zinc atom is distorted tetrahedral, with the Zn-Cl and Zn-N average bond lengths of 2·207(4) and 2·08(1) Å respectively.     

Specific features of the structure of tungsten(VI) mononuclear six-coordinate oxohalide complexes: A review

The specific features revealed in the structure of the mononuclear octahedral oxohalide complexes of tungsten(VI) have been considered. The structural features of tungsten(VI) monooxo and dioxo complexes, as well as pseudodioxo compounds (tungsten(VI) monoxo complexes containing an additional multiply bonded ligand (=Y) of another type), have been analyzed.     

Growth reactions and mechanisms in chemical beam epitaxy (CBE)

The rapidly increasing interest in chemical beam epitaxy (CBE) and related ultra-high vacuum (UHV)-based epitaxial growth techniques has arisen primarily as a result of their expected technological advantages compared to either the conventional molecular beam epitaxy (MBE) or metalorganic vapour phase epitaxy (MOVPE) processes. The CBE-related techniques do, however, provide the additional important advantage, compared to MOVPE, that the UHV environmental allows in-vacuo analytical techniques to be used to provide in-situ characterization regarding the composition and crystallography of the growing layers, and also vital information regarding the growth mechanisms involved. The present paper reviews the current understanding relating to III–V CBE reaction mechanisms, and highlights specific topics which require further investigation.     

A comparative study of novel chalcone derivative by X-ray and quantum chemical calculations (Ab-initio and DFT): Experimental and theoretical approach

A novel bio-organic molecule, 3-(3-chloro-4-methoxy-phenyl)-1-(4,5-dimethoxy-2-methyl phenyl) prop-2-en-1-one (I), has been synthesized and characterized by FTIR, ¹H, and ¹³C NMR. To understand the role of solvents, UV-vis absorption, and fluorescence study has been carried out using different solvents. The single-crystal X-ray diffraction technique has been studied to confirm the three dimensional structure of the compound and the hydrogen bond interactions involved in the stability of the structure. The ab-initio and density functional theory (DFT) are used to optimize the molecular structure. The calculated results show that the predicted geometry can well reproduce structural parameters. In addition, frontier molecular orbitals and Mullikan charge distributions are carried out by using RHF and B3LYP methods. The synthesized compound has been screened for its antimicrobial and antifungal activities against different panel of organisms.     

A novel metal‐organic coordination complex crystal: tris allylthiourea zinc bromide (ATZB) as a nonlinear optical material

A new second order nonlinear optical coordination complex crystal tris allylthiourea zinc bromide was synthesized and grown from ethanol for the first time. Elemental analyses, X‐ray powder diffraction and infrared spectroscopy confirmed the formation of the new material. The thermal characterization was determined by the differential thermal analysis and thermogravimetric analysis. The transmission spectrum of the crystal shows a wide transparent UV‐Vis‐NIR band. The powder SHG efficiency is higher than that of urea crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,dielectric and photoconducting studies of tetrathiourea mercury(II) tetrathiocyanato zinc(II) NLO single crystals

A highly efficient nonlinear optical single crystals of tetrathiourea mercury (II) tetrathiocyanato zinc(II), Hg(N₂H₄CS )₄Zn(SCN)₄, (TMTZ) were conveniently grown from mixture solvent of ethanol–water by slow evaporation technique. The grown crystals exhibited needle-shaped morphology. The cell parameters of TMTZ single crystals were determined by single-crystal X-ray diffraction. The grown crystals were subjected to optical characterization by FT-IR, FT-Raman and UV–Vis–NIR techniques. The dielectric study of TMTZ showed low dielectric loss in the high-frequency region. The photoconductivity studies confirm that the TMTZ crystal has negative photoconducting nature.