Synthesis,growth conditions,and crystal structures of alkali metal hypophosphites <Emphasis Type="Italic">M</Emphasis>H<Subscript>2</Subscript>PO<Subscript>2</Subscript>

Metal hypophosphites are widely used in various fields. However, their structures have not been adequately studied. The synthesis conditions (the temperature and precursors) were found and crystals of anhydrous Li, K, Rb, Cs, and NH₄ hypophosphites were grown. The structures of these compounds were established by X-ray diffraction analysis. These crystal structures can be described as packings of layers consisting of hypo-phosphite anions coordinated to metal cations. In all these salts, the hypophosphite anions serve as bridges between four cations belonging to the same layer. Each oxygen atom is bound to two cations.     

Crystal structures of 2-(2-methoxyphenyl) perimidine and its hemihydrate

The crystal structures of the title compound and that of its hemihydrate have been determined. The anhydrous compound is roughly planar due to an intramolecular hydrogen bond (IMHB). The orange color can be related to its planarity and to the greater degree of overlapping between the perimidine and the phenyl group than in the hemihydrate. The yellow hemihydrate is not planar and the water molecule joins through O-HN hydrogen bonds two molecules related by a crystallographic twofold axis. In solution the compound behaves like the anhydrous form.     

The Precipitation of Sparingly-soluble Alkaline-earth Metal and Transition Metal Oxyanion Salts from Aqueous Solution at Ambient Temperatures to 100 °C: Anhydrous and Hydrated Precipitate Phases

The anhydrous and hydrated phases of the sparingly-soluble barium, strontium, calcium, magnesium, lead(II), mercury(II), cadmium, zinc, copper(II), nickel(II), cobalt(II), iron(II) and manganese(II) salts of series of inorganic and organic oxyanions, precipitated from aqueous solution at ambient temperatures to 100 °C, have been tabulated and classified. The alkaline-earth and transition metal chromates, molybdates and tungstates are mainly anhydrous. The alkaline-earth and transition metal carbonates, orthophosphates, orthoarsenates, sulphates, selenates, bromates and iodates show mixed character. The precipitated barium, some strontium, lead(II) and mercury(II) salts are anhydrous: many of the other salts are precipitated as hydrates and the hydration numbers generally increase from one-half to three with decrease in the cation radius. All the alkaline-earth and transition metal oxalates (except lead oxalate) are precipitated as hydrates (below 100 °C). The hydration numbers at ambient temperatures generally increase from two to three-four but there is no clear inverse variation with cation radius. These results are explained by Johnson's thermodynamic treatment for the free energies of solution and precipitation (and crystallisation) of ionic salts.     

氧化镍纳米晶体的制备及其过程分析

为了开发一种新型纳米氧化镍催化剂,能有效地应用于生物质气化过程中去除焦油,本文采用均匀沉淀法成功地制备了纳米氧化镍晶体,并利用TGA、FTIR、XRD、BET、YEM等分析手段对前驱体和产品的性能进行了表征.同时,对前驱体的分解过程进行了全面的分析.分析结果表明前驱体是水合碱式碳酸镍,其分子式为NiCO3·Ni(OH)2·nH2O,它能在360℃下完全分解转化为纳米NiO,同时煅烧条件对合成纳米NiO的晶体粒径影响很大.实验证实所得纳米NiO颗粒呈球形,分散性好,纯度较高,属立方晶系结构,平均粒径约为7.5nm,其BET表面积为187.98m2/g,这显示纳米NiO晶体具有作为高效催化材料的应用可行性.     

Polymorphism of sorbitol

The polymorphism of sorbitol was investigated, confirming the existence of four anhydrous crystalline phases plus the hydrate. The crystallised melt (CM), the alpha form, and the gamma form were obtained via a dry route. The CM was confirmed to be a crystalline state with a spherulite morphology. The alpha form was obtained via direct conversion from the CM, in contrast to more complicated routes previously reported, and was found to have a very high crystallinity. Gamma crystals were obtained by seeding the melt at high temperature; however, crystallinity was clearly less than for alpha crystals.     

A comparison of the crystal structures of (dabcoH2)CuCl4 and (dabcoH2)CuCl4⋅H2O

The crystal structures of the anhydrous and monohydrated (dabcoH₂)CuCl₄nH₂O salts (n = 0,1) have been determined and a comparison of their crystal structures has been reported. The anhydrous salt is monoclinic P2₁/c with a = 9.045(2) Å, b = 6.9270(10) Å, c = 18.767(4) Å and = 90.07(3)° with V = 1175.8(4) ų. The hydrated salt is also monoclinic P2₁/c with a = 9.266(2) Å, b = 9.395(2) Å, c = 14.386(3) Å and = 93.32(3)° with V = 1250.3(5) ų. The structures of the two salts are closely related. Both compounds contain isolated distorted (compressed) tetrahedral CuCl₄ ^2– anions, diprotonated dabco cations, and in the case of the hydrated salt, lattice H₂O molecules. In the anhydrous salt, each of the two N–H⁺ groups of the dabcoH₂ ²⁺ dications form bifurcated hydrogen bonds to chloride ions on adjacent CuCl₄ ^2– anions along the c axis, thus forming chains running parallel to the c axis. In the hydrated salt, a water molecule is inserted into one of the pair of bifurcated hydrogen bonds, forming instead N–H O–H CuCl₄ ^2– linkages. The chains thus formed are cross-linked by O–H Cl hydrogen bonds between the chains. Because of this additional hydrogen bonding, the CuCl₄ ^2– anions in the hydrated salt are distorted further from tetrahedral geometry.     

An alternative method to obtain direct opal photonic crystal structures

We describe the protocol that we have elaborated in order to obtain monosize polystyrene spheres. Starting from these spheres a simple and effective method, based on spin-coating technique, was developed to realize colloidal photonic crystal structures. The process produces compact 3D arrays of polystyrene microspheres (opals) that are organized into crystalline lattices. This process offers the ability to rapidly form 3D photonic crystals using inexpensive instrumentation, which makes it attractive for an array of applications. Process parameters, fabricated structures, and their experimental characterization are presented.     

On some tendencies in modern crystal chemistry

Tendencies in modern crystal chemistry, such as the representation of crystal structures in the form of planar atomic nets of different geometry and the simulation (assembly) of structures from “building blocks” of different complexity, have been briefly analyzed in terms of the original concept of the crystalline state.     

Raman spectroscopic studies of gadolinium trichloride as a function of temperature

Laser Raman spectrometry is being used in our laboratory to identify the crystal structures of lanthanide and actinide compounds. The phonon Raman spectrum of an ionic, crystalline sample is characteristic of the particular crystal structure(s) exhibited by the sample. GdCl₃ exhibits two crystal structures, UCl₃-type hexagonal and PuBr₃-type orthorhombic. In the literature it is proposed that the low-temperature form is the PuBr₃-type orthorhombic. Results of experiments in our laboratory suggest that the low-temperature form is the UCl₃-type hexagonal. Interconversion between these two forms can be accomplished with temperature. In the present work, laser Raman spectrometry was used to monitor crystal structure changes in GdCl₃ as a function of temperature and to determine the temperature at which the orthorhombic-to-hexagonal phase transformation occurs.     

Crystal Chemistry of 1:1 Molecular Complexes of Carbamate Salts Formed by Slow Aerial Carbonation of Amines

Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complex of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another. Index Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complexes of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another.      

Classification of hydrated oxygen compounds of boron

The known structural classifications of borates are based on the analysis of boron-oxygen radicals consisting of B-triangles and B-tetrahedra sharing O atoms to form more complicated structures. Such classifications ignore the possible presence and the role of hydrogen bonds, which may be the only bonds or additional bonds linking the [BO₃]-and [BO₄]-groups. A new detailed classification of hydrated boron compounds taking into account hydrogen bonds between the B-polyhedra is proposed.     

Solid State Structures of Anhydrous 1-Aminoethylidenediphosphonic Acid

Abstract  

The 1-aminoethylidenediphosphonic acid (AEDPH₄) is anhydrous when it is synthesized according to the U.S. Patent 4239695. It crystallizes in water to form hydrous crystal AEDPH₃·H₃O (1). With the help of a simple low-temperature, low-pressure hydrothermal method and template 2,2′-bidpyridyl (2,2′-bipy), single crystals with the same structure of the anhydrous AEDPH₄ (2) is obtained. Compound 2 were characterized by elemental analysis (EA), infrared spectrometry (IR), thermogravimetric analysis (TGA) and X-ray single crystal diffraction. In compounds 2, the AEDPH₄ molecules are linked into 3D supramolecules by various hydrogen bonds.     

Pharmaceutical Salts of Fluoroquinolone Antibacterial Drugs with Acesulfame Sweetener

Novel organic salts of norfloxacin and ciprofloxacin with artificial sweeteners such as saccharin and acesulfame were prepared. The two salts 1 and 2 were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Finally, the crystal structures were solved by single crystal X-ray diffraction data and the structures were analyzed in terms of supramolecular synthons. In norfloxacin acesulfamate 1, two norfloxacin cations and two acesulfame anions form an eight membered cyclic tetramer supramolecular synthon. The salt, ciprofloxacin acesulfamate 2, has a similar structure as salt 1. This study contributes the importance of crystal engineering and supramolecular chemistry to the pharmaceutical applications in terms of interactions and structural correlations in the design of new solid phases.

Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.     

Crystal and molecular structures of <Emphasis Type="Italic">trans</Emphasis>-2-(4′-dimethylaminobenzylideneacetyl)-5,5-dimethylcyclohexane-1,3-dione

The crystal and molecular structures of a cyclic β-triketone, namely, trans-2-(4′-dimethylaminobenzylideneacetyl)-5,5-dimethylcyclohexane-1,3-dione (I), are determined using X-ray diffraction analysis. It is established that the compound in the crystalline state exists in a diketo-enol form stabilized by intramolecular hydrogen bonds. The specific features of the structure and the physicochemical and fluorescence properties of the compound are discussed.     

Problems with the preparation of anhydrous single crystal sulphates. I. M2+SO4 (M = Fe,Co, Ni)

The article deals with the problems retarded to preparing the single crystals of anhydrous sulphates of the iron-metal group. The article provides a comprehensive review on up to date recent knowledge on the chemical and physical properties of these sulphates and, in addition, it describes some methods of preparing their anhydrous form. Also inform about the experiments of single crystal growth. It exhibits the facility of the solution of this problem, that is still under investigation.     

Synthesis,characterization and thermal analysis of ursolic acid solid forms

This study performed a solid‐state characterization of ursolic acid (UA) crystalline forms, a poorly water‐soluble triterpene with anticancer activity. Two new polymorphs (form I, II), two new solvates (propanol and isopropanol solvates), and a known ethanol solvate were determined and elucidated using a combination of multi‐techniques, including X‐ray single crystal and powder diffraction, Fourier transform infrared spectroscopy (FT‐IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A colorless single crystal of UA was grown from a propanol solution, and its crystalline structure was determined through X‐ray single crystal diffraction. It was determined that the propanol solvate was crystallized in the orthorhombic space group P2₁2₁2₁ with unit‐cell parameters a = 7.17200 (8) Å, b = 12.24100 (16) Å, c = 33.8950 (4) Å and Z = 4. The ethanol solvate and propanol solvate were isomorphous crystals. The results of the thermal analysis demonstrate that form I is a meta‐stable form, while form II is a stable form that is monotropically related.     

Dinuclear Complexes and a One-dimensional Chain Involving Difunctional Ligands Containing the Acetylacetonate Functionality

Abstract Systems containing two acetylacetonate (acac) ligands separated by an aromatic spacer (1–3) react with Cu(II) in the presence of bidentate nitrogen ligands to form crystalline, capped, dinuclear (zero-dimensional) structures (6–8). Noncovalent interactions between stacked aromatic ligands on adjacent molecules in 7 and 8 produce one-dimensional chains in the crystal. Molecules 1–3 fail to produce crystalline, one-dimensional chains with covalent metal-organic bonding on reaction with Cu(II) alone. System 5, which contains a single acac ligand and a pyridyl nitrogen, forms a crystalline, one-dimensional chain on reaction with Cu(II) in the presence of a bidentate nitrogen ligand (9). The covalent bonding ribbon of the chain passes from acac to Cu(II) to the pyridyl nitrogen and back to acac. The phenanthroline ligands in 9 provide noncovalent bonding with adjacent chains in the crystal to produce a two-dimensional layered structure. Graphical abstract Dinuclear Complexes and a One-dimensional Chain Involving Difunctional Ligands Containing the Acetylacetonate Functionality Joseph B. Lambert and Zhongqiang Liu Two acetylacetonate ligands separated by an aromatic spacer react with Cu(II) in the presence of bidentate nitrogen ligands to form crystalline, capped, dinuclear (zero-dimensional) structures, whereas acetylacetonate linked to pyridine forms a crystalline, one-dimensional chain on reaction with Cu(II) with phenanthroline ligands on adjacent chains noncovalently bonded to form a two-dimensional layered structure in the crystal. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mott‐hopping processes in neodymium oxide thin films prepared on Si(100) substrates

Thin Nd oxide films were prepared on Si (P) substrates to form MOS structure. The oxide films were annealed at different conditions and their crystal structures were determined by X‐ray diffraction (XRD). The dc electrical transport properties of the devices with amorphous and crystalline Nd oxide were investigated. The current‐temperature J(T) characteristics suggest that the carrier transport through the insulator follows Mott's variable‐range hopping (VRH) mechanism and its results were compared with the results obtained from X‐ray diffraction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structures of tetracyanoethylene and its tricyanovinyl derivatives with intramolecular charge transfer: A review

The results of X-ray structure investigations of crystalline compounds with a tricyanovinyl group (individual substances, molecular complexes, and ionic salts) and related compounds are generalized. The most interesting geometric and conformational characteristics of the molecules and ions are discussed. Consideration is given to the crystal chemical features of the compounds involved. The structural formulas of 73 compounds and the reliability factors (R factors) of crystal structure determination are given in the tables.     

Problems with the Preparation of Anhydrous Single Crystal Sulphates II

The article deals with the problem of preparing single crystals of anhydrous sulphates of amphoteric metals lead and tin. It gives a comprehensive review on up to date recent knowledge on the chemical and physical properties of these sulphates and, in addition, it describes some methods of preparing their pure anhydrous form. It also informs about the experiments of single crystal growth. It draws attention to several possibilities of the solution of this problem, which is still not satisfactorily solved.