Crystal Structure of t‐boc‐O‐benzyl‐L‐tyrosyl‐D‐alanyl‐L‐(O‐benzyl)‐glutamate : monohydrate

The crystal structure of a tripeptide, t‐boc‐O‐benzyl‐L‐tyrosyl‐D‐alanyl‐L‐(O‐benzyl)‐glutamate has been determined by direct methods, and refined by full‐matrix least squares procedures to a final R‐index of 0.060. The peptide conformation corresponds to a reverse turn — Type II , stabilized by a 4 — 1 N‐H...O hydrogen bond, with the amide proton also forming a bifurcated hydrogen bond to an oxygen atom from the C‐terminus of a neighbouring molecule.     

Isolation and characterization of a new polymorph of D‐sorbitol

A new polymorph of D‐sorbitol (named as F form) was discovered in this paper. A reliable isolation method for this new polymorph was developed. Three other known polymorphs of D‐sorbitol were also prepared for comparative purpose. The new F form was analyzed and characterized by using PXRD, DSC, Raman and FTIR spectroscopy. By comparing with current polymorphs' data, it was proved that F form is a new form that was not reported in any literatures. From PXRD data, it was confirmed that the crystallinity of the new form is very high. From DSC data, it was found that the new form is less stable than any known anhydrous forms. It was also found by transformation experiments that the new F form can transform into alpha form in methanol solution through a solution mediated transformation mechanism. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Syntheses and X‐Ray crystal structures of aminated 4,4'‐Bi‐1,2,4‐triazole salts

3‐Amino‐4,4'‐bi‐1,2,4‐triazole hydrochlorate and 3,3'‐diamino‐4,4'‐bi‐1,2,4‐triazole ditosylate were obtained with the reduction of 3,3',5,5'‐tetraazide‐4,4'‐bi‐1,2,4‐triazole (TABT) by (Ph)₃P/H₂O and the followed salt forming reaction with concentrated HCl and aqueous TsOH, respectively. Their structures were characterized with elemental analyses, IR, MS, ¹H and ¹³C NMR spectra. The single crystals were cultivated and determined with X‐ray diffraction, test results reveal that H⁺ combines with electron‐rich N atom in triazole ring to form ionic salts, two N,N‐linked triazoles are almost perpendicular to each other due to lower steric hindrance. The aromatic π…π stacking interactions and hydrogen bonds between molecules are observed. These two novel salts and their derivatives may be applied in coordination chemistry, medicinal chemistry and energetic materials.     

Synthesis and crystallographic characterization of a chiral complex of (R)‐2‐(pyridin‐2‐ylmethylene)amino‐2′‐hydroxy‐1,1′‐binaphthyl(L) with hydrated nickel(II) acetate

A chiral complex of (R)‐2‐((pyridin‐2‐ylmethylene)amino)‐2′‐hydroxy‐1,1′‐binaphthyl ( L ) with hydrated nickel (II) acetate has been synthesized and spectroscopically characterized. The crystal structure of [NiL₂(CH₃OH)(CH₃COO)]CH₃COO·CH₃OH has been determined by single‐crystal X‐ray diffraction. The complex crystallizes in the orthorhombic space group P 2(1) 2(1) 2(1) with cell constants a = 15.1035 (19), b = 17.836 (2), c = 18.730 (2)Å, α = β = γ = 90.00°, Z = 4. The structure was solved by direct methods and refined to R = 0.0346 (wR₂ = 0.0863). The analytical result of the crystal structure indicates that a pair of L ligands chelate to a Ni (II) atom in an asymmetric fashion with one Ni‐N bond being longer than the other, the Ni (II) atom is further coordinated by one methanol molecule and one acetate anion to form a distorted octahedral geometry. In the crystal of the complex, the coordination cation [NiL₂(CH₃OH)(CH₃COO)]⁺, the uncoordinated methanol molecule and uncoordinated acetate anion are further assembled into one‐dimensional chain structure via intermolecular hydrogen bonds along the a‐axis. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bandgap characters in GaAs‐based ternary alloys

The existence and origins of the bowing character in the bandgap variation of GaAs‐based ternary alloys are theoretically investigated based on two different computational methods. Within the framework of the virtual crystal approximation (VCA), both the empirical sp³s * tight‐binding (TB) method with, and without, the inclusion of the spin‐orbit coupling effects, and the first‐principle full‐potential linear augmented plane wave (FP‐LAPW) technique are applied on both the common‐cation GaSb_xAs_1‐x and the common‐anion Ga_1‐xIn_xAs alloys. These methods are used to calculate the bandgap energy, the partial and total densities of states and the constituent charge ionicity versus the composition x. The results show that the bowing behavior exists in the case of common‐cation alloys (GaSb_xAs_1‐x) as a manifestation of a competition between the anion atoms (As and Sb) in trapping the made‐available‐cationic charges. The bowing parameter is found to be proportional to the electronegativity characters of the competing anions (χanion). Consistent with this in the case of common‐anion alloys (Ga_1‐xIn_xAs), as due to the lack of anion competition, the bowing is just absent and the variation of bandgap energy is found to be rather linear. The excellent agreement between our theoretical results and recent photoluminescence data has corroborated our claim. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of the new radical cation salt (<Emphasis Type="Italic">DOET</Emphasis>)<Subscript>4</Subscript>[Fe(CN)<Subscript>5</Subscript>NO]<Subscript>1.25</Subscript>(C<Subscript>6</Subscript>H<Subscript>5</Subscript>Cl)<Subscript>0.75</Subscript>

A new radical cation salt based on 4,5-(1,4-dioxanediyl-2,3-dithio)-4′,5′-ethylenedithiotetrathiafulvalene (DOET) with the photochromic anion [Fe(CN)₅NO]^2?, namely, (DOET)₄[Fe(CN)₅ NO]_1.25(C₆H₅Cl)_0.75, is synthesized. Single crystals of this salt are studied using X-ray diffraction [a = 10.398(2) Å, b = 11.168(2) Å, c = 18.499(4) Å, α = 103.14(3)°, β = 92.80(3)°, γ = 106.02(3)°, V = 1996.3(7) ų, space group \(P\bar 1\), and Z = 1]. In the structure, radical cation layers alternate with anion layers along the c axis. The centrosymmetric dimers are formed by DOET radical cations in the donor layer with packing of the β type. Like the vast majority of DOET-based salts, the new salt possesses semiconductor properties.     

Nitrogen‐doped zirconia single crystals

The aim of this work is the preparation of nitrogen‐doped single crystals of cation‐stabilized zirconia. Thin plates of these crystals were nitrided in a graphite heated resistance furnace with nitrogen as reaction gas. Several dwell times and reaction temperatures were tested and their effect on the amount of incorporated nitrogen is investigated. During nitridation at high temperatures a rock salt‐type ‘ZrN’ layer grows on the surface, leading to the destruction of the crystal. In contrast to the fluorite‐type bulk material, which can be described as a fast anion conductor, the surface layer shows electronic conductivity. For possible applications of the bulk material (solid electrolyte) the formation of the surface layer must be avoided. Therefore, the interface between surface epilayer and bulk material was investigated in detail by electron microscopy methods. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Re‐Investigation of the Structure of 7Bi2O3 · 2WO3 by Single‐Crystal X‐ray Diffraction

The structure of the oxygen‐deficient compound 7Bi₂O₃ · 2WO₃, a fluorite‐derivative phase considered a candidate for electronic applications because of its high ionic conductivity, is investigated by singlecrystal X‐Ray diffraction employing Ag‐Kα radiation (λ = 0.5608 Å) to minimize the effect of the absorption by the heavy metals. The space‐group type is I4₁, the acentric subgroup of I4₁/a that was previously suggested from powder‐diffraction data and precession‐camera photographs. Lattice parameters are a = 12.513(2), c = 11.231(4) (Z = 2.5). The sample is twinned by syngonic merohedry, class I, with volume ratio of the individuals 0.58/0.42. The ordering of W partly confirms previous models, with one W fully occupying one of the sites on special position. However, the remaining W goes in a site on general position, which shares with Bi, resulting thus more diluted in the structure. The oxygen vacancies are partly ordered in three of the ten anion sites.     

Syntheses and crystal structures of two new coordination polymers constructed from 2‐bromo‐1,4‐benzenedicarboxylate

To explore the possibility of obtaining the metal‐organic frameworks (MOFs) bearing the 2‐bromo‐1,4‐benzenedicarboxylate ligand, one new Mn(II) and one Co(II) coordination polymers, [Mn(HL)₂(bipy)₂·2H₂O]·bipy ( 1 ) and [Co(L)(bpe)] ( 2 ) (bipy=4,4′‐bipyridine; bpe=1,2‐bis(4‐pyridyl)ethene) were synthesized and characterized by elemental analysis and X‐ray diffraction analysis. Compounds 1 exhibits one‐dimensional coordination chains, which are further connected to form two dimensional supramolecular networks through hydrogen bonding interactions. Compound 2 presents a two‐fold interpenetrating two‐dimensional layer structure. The 2‐bromo‐1,4‐benzenedicarboxylate anion exhibits different coordination modes in the two complexes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature‐concentration oscillations of crystal‐solution phase equilibria in the presence of trace impurities of surface‐active agents

Using the examples of aqueous salt solutions NaNO₃, KNO₃, RbNO₃, K₂SO₄, NaBr·2H₂O, KBr, and NH₄NO₃, it was experimentally proven that the new phenomena, i.e. temperature‐concentration oscillations of crystal‐solution phase equilibria detected previously in the range of 15–45 °C remain in the presence of trace impurities (10^‐4–10^‐3 wt. %) of ion‐active organic matters. The signs of breaks transformation into pair oscillations of “maximum‐minimum” type are established for the K₂SO₄, NaBr, KBr solutions. The efficiency of influence of trace impurities on phase equilibria sharply rises in the areas of the temperature‐concentration oscillations (the saturation temperature ranges up to 10 K). The impurity efficiency is promoted by the presence of the amides in its content (as compared with the sulphates) and an increase in length of the hydrocarbon radical. The phenomenon is absent in case of an addition of ion‐inactive compounds. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solvothermal synthesis of flower‐like lanthanum tartrate and lanthanum oxide microspheres in ethanol‐water mixed system

Monodispersed lanthanum tartrate microspheres with flower‐like shape were synthesized by a mild solvothermal method using ethanol‐water mixed system as the solvent. Lanthanum oxide with reserved spherical shape was subsequently fabricated by a following calcination process. X‐ray diffraction analyses (XRD), X‐ray spectroscopy (EDS), scanning electron microscopy (SEM), thermogravimetry‐differential thermal analysis (TG‐DTA) were employed to characterize the composition, structure, and morphology of the products. The lanthanum tartrate microspheres were aggregated by nanosheets as petals. Size of the aggregation and thickness of the petal vary with the vol.% of ethanol. As the vol.% of ethanol increases the degree of aggregation and the thickness of the petal decrease, and other properties such as the size distribution, dispersion are also modulated. These alterations can be interpreted by the changing dielectric constant of mixed solvent. Such lanthanum tartrate can be applied to fabricate micro‐sphereshaped lanthanum oxide after calcination. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of Spiro[2‐benzoyl‐cyclohexyl‐4,5‐diphenylpyrrolidine‐3,3'‐chroman‐4‐one]

3‐Phenyl‐chroman‐4‐one is the basic unit of isoflavonoids which are found in the plants of the sub‐family papilionoidae of Leguminosae. They are known to possess antifungal and antibacterial properties. Crystal data of the title compound : Monoclinic, space group P2₁/c, a = 14.021(3), b = 18.682(4), c = 11.362(2) Å, β = 95.75(3)°, R = 0.066. The two phenyl rings directly attached to the pyrrolidine ring are nearly perpendicular to it. The dihydropyrone moiety adopts a half‐chair conformation while the cyclohexane ring attached to the pyrrolidine ring adopts a chair conformation. The best plane passing through the chroman‐4‐one moiety makes a dihedral angle of 82.2(3)° with the pyrrolidine ring. The molecule is stabilized by one intra‐ and two intermolecular C‐H...O hydrogen bonds.     

Application of D‐optimal experimental design in nano‐sized ZSM‐5 synthesis for obtaining higher crystallinity

D‐optimal experimental design with three levels of SiO₂/Al₂O₃, template/SiO₂, H₂O/SiO₂, SiO₂/Na₂O and TPABr/TPAOH ratio parameters was used to optimize the experimental parameters by the analysis of variance (ANOVA). The effects of above mentioned ratios in the initial synthetic mixture on the crystallinity of the ZSM‐5 zeolite were studied. The synthesized samples were characterized by XRD, FE‐SEM, and TEM analysis. Fischer test results showed that SiO₂/Al₂O₃ and H₂O/SiO₂ molar ratios are the most and least effective parameters, respectively, in the range studied. The most important two‐way interaction variable was that of template/SiO₂ and Na₂O/SiO₂ molar ratios. The optimum composition of the gel compound to achieve relative maximum crystallinity is SiO₂/Al₂O₃ = 99.96, template/SiO₂ = 0.16, H₂O/SiO₂ = 34.68, Na₂O/SiO₂ = 0.02 and TPABr/TPAOH = 1.44.     

FT‐IR spectroscopic and thermal studies on pure and impurity added calcium tartrate tetrahydrate crystals

Pure and impurity (strontium) added calcium tartrate tetrahydrate single crystals were grown by the gel method. The FT‐IR spectra of these crystals were recorded in the wavenumber range 400–4000 cm^–1. The thermograms of the grown crystals were recorded in the temperature range 50–900 °C. FT‐IR spectra reveals the presence of water molecules, O‐H bond, C‐O and carbonyl C=O bonds. The thermograms show that these crystals are thermally unstable and decompose into its oxide through many stages. DTA curve of the pure crystal shows three endothermic and one exothermic peaks. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gas‐phase synthesis of Fe‐Bi metastable and dumbbell particles

Fe‐Bi nanoparticles were prepared in the gas‐phase by DC magnetron sputtering and in‐fight annealing. The morphological, structural and compositional properties were investigated by High‐resolution transmission electron microscopy, energy dispersive X‐ray spectroscopy and scanning transmission electron microscopy. High‐resolution microscopy studies show that primary particles produced without in‐flight annealing are spherical with a diameter of about 50 nm. Particles sintered at 773 K acquire a dumbbell structure with Fe‐FeO and Bi sections.     

Synthesis and structure of 2D‐ and 3D‐ inorganic‐organic coordination polymers: based on Ag‐hmt subunit

Two new inorganic‐organic complexes, namely, [Ag₂(hmt)₂]Cr₂O₇·H₂O ( 1 ) and [Ag(hmt)(tar)_0.5]·H₂O ( 2 ), (hmt = hexamethylenetetramine, Tar = tartarate,), have been synthesized in H₂O/CH₃CN solvent at room temperature. Both molecules have the common [Ag₃hmt₃]³⁺ layers. Compound 1 is a two‐dimensional structure, and Complex 2 shows three‐dimensional topology. In complex 2 , the tartarate molecules are connected with adjacent layers to form parallelogram pores of 18.55×7.44 Å, which are occupied by two water molecules. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

KDP single crystal growth via three‐dimensional motion growth method

A novel system for rapid crystal growth, namely three‐dimensional motion growth method (“3D MGM”) was proposed. Using this system, a potassium dihydrogen phosphate (KDP) seed was grown to a single crystal with a final size of 50×55×85 mm³. The KDP crystal was characterized by Raman spectroscopy, UV‐vis‐NIR spectroscopy, extinction ratio, laser damage threshold, and etching studies. Raman spectrum shows KDP crystal grown by “3D MGM” maintains good crystallinity as that grown by rotating‐crystal method (“RCM”). The “3D MGM” grown KDP crystal has much better transmittance, higher extinction ratio, higher damage threshold and less dislocation density, compared to “RCM” grown crystal.     

Crystal and Molecular Structure of Bis{2,6‐bis(hydroxymethyl)pyridine‐O,O,N}{μ‐bis(2‐hydroxymethylpyridyl)methanolate‐O,N}dicopper(II)di(propionate). First example of non‐coordinate propionate anoins

Bis{2,6‐bis (hydroxymethyl) pyridine‐O,O,N} {μ‐bis(2‐hydroxymethylpyridyl) methanolate‐O,N} dicopper(II) di(propionate) (CCDC 143763) has been prepared and studied by single‐crystal X‐ray diffraction methods at 293(2) K. The crystal structure consists of dimeric complex cation, [Cu₂(μ‐bhmp)₂(bhmpH)₂]⁺² and propionate anions (bhmp ‐ 2,6‐bis(hydroxymethyl) pyridine; bhmpH ‐ 2‐(6‐hydroxymethylpyridyl) methanolate ) and propionate anions. The complex cation contains two neutral and two monodeprotonated bhmp molecules, each coordinate to one Cu(II) atom in a tridentate chelating manner, via two O atoms and N atom. The monodeprotonated bmph molecules are also tridentate coordinate via N atom and only one O atom, which serve as bridge between two CuO₄N₂ moieties. The propionate anions are “ fixed” to the complex by the hydrogen bonds.     

Structural studies of crystalline oligosaccharides VI: Crystal structure and conformation of benzyl‐4,6‐O‐benzylidene‐3‐O‐benzoyl‐β‐D‐galactoside

Monsaccharides are the building blocks of polysaccharides and hence are the simplest sugar molecules to study the conformation and molecular structures of sugars. Benzyl‐4,6‐O‐benzylidene‐3‐O‐benzoyl‐β‐D‐galactoside is a key intermediate in the synthesis of polysaccharides. Crystal structural investigation of the title compound was undertaken to establish their chemical structure as well as to study their solid state conformation. Crystals of the title compound, obtained from water/methanol, are orthorhombic, space group P2₁2₁2₁, with cell dimensions a=11.290 (4), b=9.941 (1), c= 21.442(2)Å, V= 2406ų, Z=4, D_obs= 1.42 gm/cm³, D_calc=1.423 g/cm³, 2886 reflections were collected on a CAD‐4 diffractometer. The structure was solved by direct methods and refined to a final reliability index of 4.7%. The galactoside sugar has the chair conformation with C2' and C5' deviating from the mean plane of the other atoms of the sugar. The 4,6‐O‐benzylidene ring also has a chair conformation with the benzoyl group proximal to O6'. The crystal structure is stabilized by O‐H…O hydrogen bonds involving O2' as donor and three C‐H…O hydrogen bond interactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrolyte effects on amorphous and supercooled sugar systems

The purpose of the present work was to analyze the modification of sugar thermal transitions in the presence of salts. Solid systems consisted of freeze-dried solutions of trehalose or sucrose, with or without salts (potassium and magnesium chlorides, acetates or citrates at 5:1 sugar:salt molar ratio). The freeze-dried systems were humidified at water activities 0.22 and 0.43 at 25 °C and then incubated at 70 °C. The presence of electrolytes affected the kinetics of several relaxation phenomena in sugar systems. Trehalose and sucrose crystallization was delayed in systems containing salts and this effect was dependent on water–cation interactions and on the size of the anion, being citrate the most inhibiting anion. The delaying effect of ions on sugar crystallization correlated with the degree of changes observed in the asymmetry of the sugar melting peak, and with the magnitude of enthalpy relaxations. Salts decreased peak and onset temperatures of trehalose melting crystals and increased the difference between these temperatures compared to the system without salt. Systems containing potassium citrate and MgCl₂ showed the highest Δc_p, relaxation enthalpies in the amorphous state and crystallization delay, and reflected higher anomalies in trehalose melting behavior.