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C Direction (c + direction)
Selected AbstractsChemInform Abstract: Solution-Phase Synthesis of Aminooxy Peptoids in the C to N and N to C Directions.CHEMINFORM, Issue 35 2002Injae Shin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Crystal structure, thermal analysis and IR spectrometric investigation of bis (2-amino-6-methyl) pyridinium sulfateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006T. Guerfel Abstract The synthesis method, crystal structure determination, phase transitions studied by thermal analysis and IR spectrometric investigation of 2C6H9N2+.SO42, are reported. The compound crystallizes in the monoclinic space group C2/c (no. 15) with a = 10.5068(4) Å, b = 10.2225(5) Å, c = 14.0422(7) Å, and , = 104.489(3)°. The atomic arrangement can be described by layers built by all the components of the structure and centered by planes z = 1/4 and 3/4. The organic molecules form channels parallel to the c direction with dimensions of 4.163(1)Å and 5.148(4)Å. Thermal analysis shows that the anhydrous compound presents an irreversible weak phase transition. The IR study, based on theoretical analyses and on the literature data allows the interpretation of the IR spectrum. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cation Ordering and Domain Boundaries in Ca[(Mg1/3Ta2/3)1,xTix]O3 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Mao Sen Fu Cation ordering and domain boundaries in perovskite Ca[(Mg1/3Ta2/3)1,xTix]O3 (x=0.1, 0.2, 0.3) microwave dielectric ceramics were investigated by high-resolution transmission electron microscopy (HRTEM) and Rietveld analysis. The variation of ordering structure with Ti substitution was revealed together with the formation mechanism of ordering domains. When x=0.1, the ceramics were composed of 1:2 and 1:1 ordered domains and a disordered matrix. The 1:2 cation ordering could still exist until x=0.2 but the 1:1 ordering disappeared. Neither 1:2 nor 1:1 cation ordering could exist at x=0.3. The space charge model was used to explain the cation ordering change from 1:2 to 1:1 and then to disorder. A comparison between the space charge model and random layer model was also conducted. HRTEM observations showed an antiphase boundary inclined to the (111)c plane with a projected displacement vector in the ,001,c direction and ferroelastic domain boundaries parallel to the ,100,c direction. [source] Precipitation of Carbonated Calcium Phosphate Powders from a Highly Supersaturated Simulated Body Fluid SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Ingo Hofmann Carbonated hydroxy apatite (CHA) powders were prepared by precipitation from a modified simulated body fluid (5 × M-SBF). The ionic concentrations were five times higher than in human blood plasma with the exception of Mg2+ and HCO3, concentrations that were reduced in order to accelerate crystal growth. Spheroaggregates of CHA platelets with molar (Ca+Mg)/P ratios ranging from 1.44 to 1.56 were obtained after precipitation at 50°C. The crystallite size in the c direction was approximately 31 nm and depending on the precipitation time, a CO32, content of 1.8,5.2 wt% was determined. Using this low-temperature precipitation method, CHA powders with a high specific surface area of 83 m2/g and a composition and crystallite size close to those of the mineral phase of human bone were obtained. [source] Single crystal X-ray study of the modulated structure in Ga2XTe3 with the defect zinc-blende structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009S. Kashida Abstract Ga2Te3 crystallizes into the zinc-blende structure, where one third of the cation sites is vacant. Single crystal X-ray diffraction studies on quenched and annealed Ga2Te3 and CuGaTe2 crystals are reported. The obtained diffraction maps show, other than the zinc-blende type main reflections, satellite reflections at q1,1/17[110]c in quenched Ga2Te3 crystals and q2,1/20[210]c in annealed Ga2Te3 crystals, where the subscript c means the cubic sub-lattice. The analysis of the satellite reflections shows that the modulation is two dimensional, and is ascribed to a coupled mode of the amplitude type modulation caused by Ga vacancies and the displacive modulation of surrounding Te atoms, which has the polarization vector along the <001>c direction. The nature of the atomic modulations is discussed and the origin of the modulation is ascribed to Jahn-Teller type distortions around Ga vacancies. The experiments done on CuGaTe2 crystals indicate that the cation disorder compound sphalerite type CuGaTe2 contain the same modulated structure as Ga2Te3 crystals, but the cation ordered compound chalcopyrite type CuGaTe2 does not show the modulation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Supramolecular aggregation in 4,4,-bipyridin-1,1,-ium dichloride, 4,4,-bipyridin-1,1,-ium dinitrate and 4,4,-bipyridin-1-ium bromideACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2003Peter Abeta Iyere 4,4,-Bipyridin-1,1,-ium dichloride [C10H10Cl2N2 (I)] and 4,4,-bipyridin-1,1,-ium dinitrate [C10H10N4O6 (II)] have been prepared and the crystal structures determined at 90.0,(2),K. Molecules of (I) are linked by two chlorine-bridged, three-centered N,H,Cl hydrogen bonds into chains along the b axis. The chains are coupled by weak C,H,Cl interactions into a molecular ladder along the c direction. In (II) each nitrate is coordinated to four bipyridinium ions through the interplay of the N,H,O and C,H,O contacts, resulting in a three-dimensional zigzag sheet on the ab plane. The sheets stack along the c axis. In 4,4,-bipyridin-1-ium bromide monohydrate [C10H9N2+·Br,·H2O (III)] the bipyridinium ions are linked by three-center N,H,N, hydrogen bonds in a head-to-tail fashion to form chains along the b axis. The chains are linked by C,H,Br and C,H,OH2 into a three-dimensional framework. [source] Powder X-ray studies of meso -hexamethyl propylene amine oxime (meso -HMPAO) in two different phasesACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Mahmoud Al-Ktaifani Two different forms of meso -3,3,-[2,2-dimethylpropane-1,3-diylbis(azanediyl)]dibutan-2-one dioxime, commonly called meso -hexamethyl propylene amine oxime (HMPAO), C13H28N4O2, designated , and ,, were isolated by fractional crystallization and their crystal structures were determined by powder X-ray diffraction using the direct-space method with the parallel tempering algorithm. The , form was first crystallized from acetonitrile solution, while the , form was obtained by recrystallization of the , phase from diethyl ether. The , form crystallizes in the triclinic system (space group P), with one molecule in the asymmetric unit, while the crystal of the , form is monoclinic (space group P21/n), with one molecule in the asymmetric unit. In both phases, the molecules have similar conformations and RS/EE geometric isomerism. The crystal packing of the two phases is dominated by intermolecular hydrogen-bonding interactions between the two O,H oxime groups of an individual molecule and the amine N atoms of two different adjacent molecules, which lead to segregation of extended poly(meso -HMPAO) one-dimensional chains along the c direction. The structures of the two phases are primarily different due to the different orientations of the molecules in the chains. [source] Bis[4-(dimethylamino)pyridine-,N1]silver(I) nitrate dihydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2009Al-shima'a A. Massoud The title compound, [Ag(C7H10N2)2]NO3·2H2O or [Ag(dmap)2]NO3·2H2O, where dmap is 4-(dimethylamino)pyridine, has a distorted linear coordination geometry around the AgI ion. A novel pattern of water,nitrate hydrogen-bonded anionic strands is formed in the c direction, with the cationic [Ag(dmap)2]+ monomers trapped between them. The AgI ion and the nitrate group atoms, as well as the water molecules (including the H atoms), are on a crystallographic mirror plane (Wyckoff position 4a). The influence of bulky methyl substituents in position 4 of the 4-(dimethylamino)pyridine ligand on packing is discussed. The absolute structure was determined unequivocally. [source] Polymorphism and solvolysis of 2-cyano-3-[4-(N,N -diethylamino)phenyl]prop-2-enethioamideACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2004Vladimir N. Nesterov Two new polymorph forms, (Ia) and (Ib), of the title compound, C14H17N3S, and its solvate with acetonitrile, C14H17N3S·0.25C2H3N, (Ic), have been investigated. Crystals of the two polymorphs were grown from different solvents, viz. ethanol and N,N -dimethylformamide, respectively. The polymorphs have different orientations of the thioamide group relative to the CN substituent, with s-cis and s-trans geometry of the C=C,C=S diene fragment, respectively. Compound (Ic) contains two independent molecules, A and B, with s-cis geometry, and the solvate molecule lies on a twofold axis. The core of each molecule is slightly non-planar; the dihedral angles between the conjugated C=C,CN linkage and the phenyl ring, and between this linkage and the thioamide group are 13.4,(2) and 12.0,(2)° in (Ia), 14.0,(2) and 18.2,(2)° in (Ib), 2.3,(3) and 12.7,(4)° in molecule A of (Ic), and 23.2,(3) and 8.1,(4)° in molecule B of (Ic). As a result of strong conjugation between donor and acceptor parts, the substituted phenyl rings have noticeable quinoid character. In (Ib), there exists a very strong intramolecular steric interaction (H,H = 1.95,Å) between the bridging and thioamide parts of the molecule, which makes such a form less stable. In the crystal structure of (Ia), intermolecular N,H,N and N,H,S hydrogen bonds link molecules into infinite tapes along the [10] direction. In (Ib), such intermolecular hydrogen bonds link molecules into infinite (101) planes. In (Ic), intermolecular N,H,N hydrogen bonds link molecules A and B into dimers, which are connected via N,H,S hydrogen bonds and form infinite chains along the c direction. [source] Displaced ,,, stacking and hydrogen bonds in 3-bromo- N -(2-hydroxy-1,1-dimethylethyl)benzamideACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2004Yao-Wen Wu The molecules of the title compound, C11H14BrNO2, are assembled into a two-dimensional network by a combination of hydrogen bonds and stacking interactions. The phenyl rings are stacked along the c direction by displaced ,,, interactions, forming a lipophilic layer. The aliphatic amide residues are interconnected along [100] by O,H,O, N,H,O and C,H,O hydrogen bonds, forming hydrophilic layers. [source] The effect of molecular planarity on crystal non-centrosymmetry in benzylidene,aniline derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2002De-Chun Zhang In the title compound, N -(2-methoxyphenyl)-4-nitrobenzylideneamine, C14H12N2O3, the two phenyl rings make a dihedral angle of 48.0,(2)° and the nitro group is at an angle of 6.5,(1)° with respect to its attached phenyl ring. In the crystal structure, molecules are related as centrosymmetric pairs through ,,, interactions and are further connected through strong C,H,O hydrogen bonds [C,O 3.4259,(17),Å and C,H,O 167°], forming molecular stacks along [100]. These stacks associate further through longer C,H,O interactions, forming two-dimensional networks. In the c direction, there are only weak van der Waals interactions. The relationship between the molecular planarity and its centrosymmetry is also briefly described. [source] 3,6-Bis(dimethylamino)-10-propylacridinium iodideACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2001Raffaella Puliti In the title compound, C20H26N3+·I,, the acridinium moiety shows mirror symmetry about the central C,N vector. The fused tricyclic system is only approximately planar and the geometry is affected by the presence of both dimethylamino groups and the propyl substitution at the central N atom. The propyl chain adopts an extended trans conformation and the plane through the chain C atoms is perpendicular to the mean plane through the rings. The I, ion is involved in short-range hydrogen-bonding interactions with two centrosymmetrically related cations via three activated acridinium C atoms. Stacks of acridinium cations propagate through the crystal along the c direction. The ring overlap is partial, but the dimethylamino groups also participate in the stacking. [source] A new rubidium beryllium borate, RbBe4(BO3)3ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2006Xiao-Hong Wen Single crystals of a new rubdidium beryllium borate, RbBe4(BO3)3, have been obtained by spontaneous nucleation from a high-temperature melt. This new orthorhombic (Pnma) structure type contains [Be2BO4], rings, made of two BeO4 tetrahedra and one BO3 triangle, which constitute the basic structural units. The m plane runs through the B and one of the O atoms and intersects the ring. These rings form chains in the a direction, which are connected in the b and c directions to form zeolite-type cages in which the Rb+ cations are located, at sites of m symmetry. [source] | |||||||||||||