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Cell Dimensions (cell + dimension)
Kinds of Cell Dimensions Selected AbstractsGrowth and characterization of strontium tartrate pentahydrate crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2008A. Firdous Abstract Silica gel impregnated with L-tartaric acid and using strontium nitrate as the second reactant leads to the growth of well faceted strontium tartrate pentahydrate single crystals. The morphological developmen and internal cell dimensions are observed to be different from the ones reported in the literature for strontium tartrate trihydrate crystals. The crystals are characterized using XRD, CH analysis, SEM, FTIR spectroscopy and thermoanalytical techniques. The crystals are observed to be thermally stable upto about 105°C but thereafter start decomposing and ejecting water of hydration at various stages, finally reducing to strontium oxide. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rh(I) and Pd(II) complexes of methoxy functionalized heterocyclic carbene: Synthesis and characterizationCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2006M. E. Günay Abstract A new methoxy functionalized 2-(trichloromethyl)-1,3-diarylimidazolidin (6) was synthesized as the precursor for N-heterocyclic carbene complexes of Pd(II) and Rh(I) by the condensation of N,N'-bis(2,4-dimethoxyphenyl)-1,2-diaminoethane with chloral. The structures of all compounds have been elucidated by a combination of multinuclear NMR spectroscopy, elemental analysis and in one instance, by single crystal X-ray diffraction. Compound 8, C27H34N2O4ClRh, crystallizes in the triclinic space group P-1 with cell dimensions a = 9.7642(12)Å, b = 11.1914(11)Å, c = 13.0102(14)Å, , = 104.034(9)°, , = 106.658(9)°, , = 99.658(9)° with Z = 2. The molecular structure of 8 shows the geometry around the Rh metal to be a slightly distorted square planar. The crystal structure shows the formation of centrosymmetric dimers via intermolecular C-H...Cl hydrogen bonds. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and structure of a new one-dimensional cobalt complex with dicyanamide and 4-picolyl choride bridgesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006Hongxia Pei Abstract The synthesis and structure of the 1D cobalt (II) complex, [Co(L)2(dca)2] (1) (dca = dicyanamide, C2N3,, L = 4-picolyl choride) is reported. Complex 1 crystallized in triclinic system, space group P -1, with cell dimensions of a = 7.291(2) Å, b = 7.481(2) Å, c = 9.007(3) Å, , =104.444(4)°, , = 96.971(4)°, , =102.618(4)°, V = 456.1(2) Å3, Z = 1, Dc = 1.624 Mg/m3. In complex 1, Co (II) is 6-coordinated by N atoms of four dca ligands and two L ligands. The centrosymmetric CoN6 chromophore is an axially elongated octahedron that has Co-N distances ranging from 2.122(3) to 2.154(3) Å. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal structure analysis of {[,-N,N,-Bis(salicylidene)-1,3-propanediaminato]nickel(II)}dichloromercury(II)CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2006C. Ar Abstract The title compound, a hetero-dinuclear complex with Ni(II) and Hg(II) ions, forms crystals which belong to the triclinic system, space group P1, with unit cell dimensions a = 8.9620(12), b = 9.2370(11), c = 12.0810(13) Å, , = 92.100(3)° , , = 105.317(5)°, , = 110.502(3)°, V = 894.2(2) Å3. The cell contains two molecules. The Ni,Hg distance is 3.4859(7) Å. The distance Hg...Hga (symmetry code: -x,-y,-z) between the neighbouring molecules is 4.7514(7) Å. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, spectroscopic studies and ab-initio structure determination from X-ray powder diffraction of bis-(N-3-acetophenylsalicylaldiminato)copper(II)CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2005S. Banerjee Abstract The synthesis, spectroscopic studies and crystal structure determination from X-ray powder diffraction have been carried out for bis-(N-3-acetophenylsalicylaldiminato)copper(II). The structure is triclinic, space group P1 with unit cell dimensions a = 11.817(1) Å, b = 12.087(1) Å, c = 9.210(1) Å, , = 102.62(1)°, , = 111.16(1)°, , = 86.15(1)°, V = 1197.0(2)Å3, Z = 2. The structure has been solved by Monte Carlo simulated annealing approach and refined by GSAS package. The final Rp value was 8.68%. The coordination geometry around the copper atom in the complex is intermediate between square-planar and tetrahedral with two salicylaldimine ligands in trans arrangement. Intermolecular C,H,O hydrogen bonds between molecules related by translation generate infinite chains along [010] direction. The molecular chains are linked via additional C,H,O hydrogen bonds to form a three-dimensional supramolecular network. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Highly efficient capture and enumeration of low abundance prostate cancer cells using prostate-specific membrane antigen aptamers immobilized to a polymeric microfluidic deviceELECTROPHORESIS, Issue 18 2009Udara Dharmasiri Abstract Prostate tumor cells over-express a prostate-specific membrane antigen (PSMA) that can be used as a marker to select these cells from highly heterogeneous clinical samples, even when found in low abundance. Antibodies and aptamers have been developed that specifically bind to PSMA. In this study, anti-PSMA aptamers were immobilized onto the surface of a capture bed poised within a PMMA, microchip, which was fabricated into a high-throughput micro-sampling unit (HTMSU) used for the selective isolation of rare circulating prostate tumor cells resident in a peripheral blood matrix. The HTMSU capture bed consisted of 51 ultra-high-aspect ratio parallel curvilinear channels with a width similar to the prostate cancer cell dimensions. The surface density of the PSMA-specific aptamers on an ultraviolet-modified PMMA microfluidic capture bed surface was determined to be 8.4×1012,molecules/cm2. Using a linear velocity for optimal cell capture in the aptamer-tethered HTMSU (2.5,mm/s), a recovery of 90% of LNCaP cells (prostate cancer cell line; used as a model in this example) was found. Due to the low abundance of these cells, the input volume required was 1,mL and this could be processed in ,29,min using an optimized linear flow rate of 2.5,mm/s. Captured cells were subsequently released intact from the affinity surface using 0.25%,w/w trypsin followed by counting individual cells using a contact conductivity sensor integrated into the HTMSU that provided high detection and sampling efficiency (,100%) and did not require staining of the cells for enumeration. [source] Engineering of a monomeric and low-glycosylated form of human butyrylcholinesteraseFEBS JOURNAL, Issue 2 2002Expression, characterization, crystallization, purification Human butyrylcholinesterase (BChE; EC 3.1.1.8) is of particular interest because it hydrolyzes or scavenges a wide range of toxic compounds including cocaine, organophosphorus pesticides and nerve agents. The relative contribution of each N-linked glycan for the solubility, the stability and the secretion of the enzyme was investigated. A recombinant monomeric BChE lacking four out of nine N-glycosylation sites and the C-terminal oligomerization domain was stably expressed as a monomer in CHO cells. The purified recombinant BChE showed catalytic properties similar to those of the native enzyme. Tetragonal crystals suitable for X-ray crystallography studies were obtained; they were improved by recrystallization and found to diffract to 2.0 Å resolution using synchrotron radiation. The crystals belong to the tetragonal space group I422 with unit cell dimensions a = b = 154.7 Å, c = 124.9 Å, giving a Vm of 2.73 Å3 per Da (estimated 60% solvent) for a single molecule of recombinant BChE in the asymmetric unit. The crystal structure of butyrylcholinesterase will help elucidate unsolved issues concerning cholinesterase mechanisms in general. [source] Molecular Auxetic Behavior of Epitaxial Co-Ferrite Spinel Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Matjaz Valant Abstract In functional oxide materials so-called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of ,0.85. A hinge-like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano-devices. [source] Analysis and comparison of morphological reconstructions of hippocampal field CA1 pyramidal cellsHIPPOCAMPUS, Issue 3 2005José Ambros-Ingerson Abstract Morphological reconstructions have become a routine and valuable tool for neuroscientists. The accuracy of reconstructions is a matter of considerable interest given that they are widely used in computational studies of neural function. Despite their wide usage, comparisons of reconstructions obtained using various methodologies are lacking. We reviewed reconstructions of hippocampal CA1 pyramidal cells from five published studies and found marked differences in some of the most basic measurements. For four of the five studies means of total cell length clustered in the 11,479,13,417-,m range. The remaining study had a significantly larger value for this index at 16,992 ± 5,788 ,m. Surface area means varied more than 4-fold from 16,074 to 67,102 ,m2. Volume means varied more than 8-fold from 3,828 to 30,384 ,m3. Simulated passive input resistance means varied from 38.0 to 172.1 M,, reflecting the variability in cell dimensions. Estimates of the electrotonic length varied from 1.26 to 1.56. In two reconstructions used in previously published studies, simulated somatic excitatory postsynaptic potentials (EPSPs) varied 2,4-fold in amplitude, time to peak and half-width, for synaptic inputs at similar locations. Substantial jitter on the z -axis was identified as one likely source of the discrepancy in total cell length, while substantial differences in diameter measurements across studies, and sometimes within the same study, accounted for the variability in surface area and volume. While some part of the observed variability is surely due to the diversity of CA1 pyramidal cells, our analysis suggests that a substantial portion stemmed from methodological inconsistencies and from technological limitations. Suggestions are made for improving the quality and usefulness of morphological reconstructions. We conclude that reconstructions across studies have substantial variability in measures that are very relevant to neuronal function. Consequently, modelers are advised to use more than just one reconstructed cell in their simulations of neural function. © 2004 Wiley-Liss, Inc. [source] Defining and optimizing algorithms for neighbouring particle identification in SPH fluid simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2008G. Viccione Abstract Lagrangian particle methods such as smoothed particle hydrodynamics (SPH) are very demanding in terms of computing time for large domains. Since the numerical integration of the governing equations is only carried out for each particle on a restricted number of neighbouring ones located inside a cut-off radius rc, a substantial part of the computational burden depends on the actual search procedure; it is therefore vital that efficient methods are adopted for such a search. The cut-off radius is indeed much lower than the typical domain's size; hence, the number of neighbouring particles is only a little fraction of the total number. Straightforward determination of which particles are inside the interaction range requires the computation of all pair-wise distances, a procedure whose computational time would be unpractical or totally impossible for large problems. Two main strategies have been developed in the past in order to reduce the unnecessary computation of distances: the first based on dynamically storing each particle's neighbourhood list (Verlet list) and the second based on a framework of fixed cells. The paper presents the results of a numerical sensitivity study on the efficiency of the two procedures as a function of such parameters as the Verlet size and the cell dimensions. An insight is given into the relative computational burden; a discussion of the relative merits of the different approaches is also given and some suggestions are provided on the computational and data structure of the neighbourhood search part of SPH codes. Copyright © 2008 John Wiley & Sons, Ltd. [source] A molecular mechanics force field for biologically important sterolsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2005Zoe Cournia Abstract A parameterization has been performed of the biologically important sterols cholesterol, ergosterol, and lanosterol for the CHARMM27 all-atom molecular mechanics force field. An automated parameterization method was used that involves fitting the potential to vibrational frequencies and eigenvectors derived from quantum-chemical calculations. The partial charges were derived by fitting point charges to quantum-chemically calculated electrostatic potentials. To model the dynamics of the hydroxyl groups of the sterols correctly, the parameter set was refined to reproduce the energy barrier for the rotation of the hydroxyl group around the carbon connected to the hydroxyl of each sterol. The frequency-matching plots show good agreement between the CHARMM and quantum chemical normal modes. The parameters are tested in a molecular dynamics simulation of the cholesterol crystal structure. The experimental geometry and cell dimensions are well reproduced. The force field derived here is also useful for simulating other sterols such as the phytosterols sigmasterol, and campesterol, and a variety of steroids. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1383,1399, 2005 [source] Complexes of Co(II) and Zn(II) with ofloxacin.JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2002Crystal structure of [Co(oflo)2(MeOH)2]·4MeOH Abstract Ofloxacin (oflo) is able to interact with Co(II) and Zn(II) salts to form complexes with the general formula [M(oflo)2],·,4H2O, (M,=,Co, Zn). Bonding takes place through one of the oxygen atoms of the carboxylate group (acting as a monodentate) and the oxygen atom of the ketonic group. The IR bands of the carboxylic and ketonic group at 1713 and 1622 cm,1, respectively, shift to 1615 and 1575 cm,1 in the complexes. After dissolution in methanol, complex [Co(oflo)2],·,4H2O crystallizes as [Co(oflo)2(MeOH)2],·,4MeOH, where Co(II) ion is in an octahedral environment of oxygen atoms. This compound crystallizes in the triclinic system, spatial group P-1, with unit cell dimensions a,=,9.3670(12), b,=,11.4135(17), c,=,11.851(2) Å y ,,=,71.999(14), ,,=,73.698(12), ,,=,83.528(14)°. Magnetic properties (effective magnetic moment 5.02 BM) and visible spectrum (bands at 490, 510, and 1152 nm) are characteristic of such an octahedral geometry. 1H- and 13C-NMR spectra of the Zn(II) complex indicate only small structural changes in ofloxacin upon coordination to the metallic site. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2416,2423, 2002 [source] Biomedical applications of 10B and 11B NMRNMR IN BIOMEDICINE, Issue 2 2005Peter Bendel Abstract This review focuses mainly on the detection and investigation of molecules used for boron neutron capture therapy (BNCT) by 10B and 11B NMR. In this binary radiation treatment, boron-containing molecules (also called ,BNCT agents') enriched in the 10B isotope, are targeted to the tumor, and irradiated with thermal or epithermal neutrons. Capture of these neutrons by 10B nuclei generates cell-damaging radiation, confined to single cell dimensions. NMR research efforts have primarily been applied in two directions: first, to investigate the metabolism and pharmaco-kinetics of BNCT agents in-vivo, and second, to use localized NMR spectroscopy and/or MRI for non-invasive mapping of the administered molecules in treated animals or patients. While the first goal can be pursued using 11B NMR for natural-abundance samples (80% 11B / 20% 10B), molecules used in the actual treatment are >,95% enriched in 10B, and must therefore be detected by 10B NMR. Both 10B (spin 3) and 11B (spin 3/2) are quadrupolar nuclei, and their typical relaxation times, in common BNCT agents in biological environments, are rather short. This poses some technical challenges, particularly for MRI, which will be reviewed, along with possible solutions. The first attempts at 11B NMR and MRI detection of BNCT agents in biological tissue were conducted over a decade ago. Since then, results from 11B MRI in laboratory animals and in humans have been reported, and 11B NMR spectroscopy provided interesting and unique information about the metabolism of some BNCT agents in cultured cells. 10B NMR was applied either ,indirectly' (in double-resonance experiments involving coupled protons), but also by direct 10B MRI in mice. However, no results involving the NMR detection of 10B-enriched compounds in treated patients have been reported yet. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatial arrangement of molecules in homomolecular Z' = 2 structuresACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2006Elna Pidcock The Box Model of crystal packing describes unit cells in terms of a limited number of arrangements of molecular building blocks. An analysis of Z,, 1 structures has shown that cell dimensions are related to molecular dimensions in a systematic way and that the spatial arrangement of molecules in crystal structures is very similar, irrespective of Z or space group. In this paper it is shown that the spatial arrangement of molecules in Z, = 2 structures are, within the context of the Box Model, very similar to that found for Z,, 1 structures. The absence of crystallographic symmetry does not appear to affect correlations between molecular dimensions and cell dimensions, or between the packing patterns and the positions of molecules in the unit cell, established from the analysis of Z,, 1 structures. The preference shown by Z, = 2 structures for low surface-area packing patterns and the observation that strong energetic interactions are most often found between the large faces of the independent molecules reaffirms the importance of molecular shape in crystal packing. [source] How precise are measurements of unit-cell dimensions from single crystals?ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2000Frank H. Herbstein The results of single-site and many-site measurements of cell dimensions from single crystals are compared for Bond and four-circle diffractometers using samples of corundum (essentially pure rhombohedral ,-Al2O3, aluminum oxide) of high diffraction quality, where the effects of small changes in temperature and composition (Cr2O3, chromium oxide, in solid solution) can be taken into account. Similar comparisons are made for four-circle diffractometer measurements on ruby (,-Al2O3, with 0.46 wt % Cr in solid solution). The precisions are some parts in 105. There is partial support for the Taylor,Kennard [Acta Cryst. (1986), B42, 112,120] dictum that standard uncertainties (s.u.s) of cell parameters from routine four-circle diffractometer measurements are less than those for many-site measurements by factors of 5 for cell lengths and 2.5 for cell angles. For organic crystals, independent repetitions of adequate quality for comparison and analysis of routine four-circle diffractometer measurements are available only for ,-oxalic acid dihydrate and anthracene. The experimental standard uncertainties given for these two crystals agree reasonably well with the sample s.u.s at room temperature, but appreciably less well at ,100,K, again giving partial support to the Taylor,Kennard dictum. The relation between specimen characteristics and attainable precision is emphasized; the precisions for routine measurements on good quality organic crystals are some parts in 104. Area-detector measurements of cell dimensions have also been appraised; currently published s.u.s from such measurements appear to be highly unreliable, and this is supported by a recent analysis of the operation of such diffractometers [Paciorek et al. (1999). Acta Cryst. A55, 543,557]. Formulation of a standard protocol for such measurements is badly needed. The dangers inherent in high degrees of replication are illustrated by recounting Kapteyn's Parable of the Chinese Emperor. Attention is drawn to the fact that there has been little improvement in claimed precisions over the past 40,60 years. [source] Eight 7-benzyl-3- tert -butyl-1-phenylpyrazolo[3,4- d]oxazines, encompassing structures containing no intermolecular hydrogen bonds, and hydrogen-bonded structures in one, two or three dimensionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Juan C. Castillo 7-Benzyl-3- tert -butyl-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C22H25N3O, (I), and 3- tert -butyl-7-(4-methylbenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H27N3O, (II), are isomorphous in the space group P21, and molecules are linked into chains by C,H...O hydrogen bonds. In each of 3- tert -butyl-7-(4-methoxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H27N3O2, (III), which has cell dimensions rather similar to those of (I) and (II), also in P21, and 3- tert -butyl-1-phenyl-7-[4-(trifluoromethyl)benzyl]-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H24F3N3O, (IV), there are no direction-specific interactions between the molecules. In 3- tert -butyl-7-(4-nitrobenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C22H24N4O3, (V), a combination of C,H...O and C,H...N hydrogen bonds links the molecules into complex sheets. There are no direction-specific interactions between the molecules of 3- tert -butyl-7-(2,3-dimethoxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C24H29N3O3, (VI), but a three-dimensional framework is formed in 3- tert -butyl-7-(3,4-methylenedioxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H25N3O3, (VII), by a combination of C,H...O, C,H...N and C,H...,(arene) hydrogen bonds, while a combination of C,H...O and C,H...,(arene) hydrogen bonds links the molecules of 3- tert -butyl-1-phenyl-7-(3,4,5-trimethoxybenzyl)-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C25H31N3O4, (VIII), into complex sheets. In each compound, the oxazine ring adopts a half-chair conformation, while the orientations of the pendent phenyl and tert -butyl substituents relative to the pyrazolo[3,4- d]oxazine unit are all very similar. [source] 5-(4,5-Ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalen-2-one (EDTO,TTP) and 5-[4,5-(ethene-1,2-diyldithio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalen-2-one (VDTO,TTP)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Hong-Feng Chen The title sulfur-rich organic molecular crystals, namely EDTO,TTP (C9H4OS8) and VDTO,TTP (C9H2OS8), are characterized by conjugated C,S bonds and S...S intermolecular short contacts. The planar EDTO,TTP molecules are parallel packed and exhibit strong intermolecular interactions, including side-by-side transverse S...S contacts, face-to-face longitudinal ,,, interactions and C,H...O hydrogen bonding. On cooling the EDTO,TTP crystal from 220 to 120,K, the cell dimensions and the intermolecular distances (such as S...S contacts and especially ,,, spacings) become shorter, while the intramolecular bonds become longer. The curved VDTO,TTP molecules are packed in such a way as to make the crystal fully depolarized. The intermolecular interactions of the VDTO,TTP crystal are relatively weak, because of the weak ,,, interactions and the lack of hydrogen bonding. [source] 4-Hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine and its 7-fluoro and 7-chloro analogues are isomorphous but not strictly isostructuralACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Lina M. Acosta 4-Hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C12H15NO, (I), and its 7-fluoro and 7-chloro analogues, namely 7-fluoro-4-hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C12H14FNO, (II), and 7-chloro-4-hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C12H14ClNO, (III), are isomorphous, but with variations in the unit-cell dimensions which preclude in compound (III) one of the weaker intermolecular interactions found in compounds (I) and (II). Thus the compounds are not strictly isostructural in terms of the structurally significant intermolecular interactions, although the corresponding atomic coordinates are very similar. The azepine rings adopt chair conformations. The molecules are linked by a combination of N,H...O and O,H...N hydrogen bonds into chains of edge-fused R33(10) rings, which in compounds (I) and (II) are further linked into sheets by a single C,H...,(arene) hydrogen bond. The significance of this study lies in its observation of isomorphism in compounds (I),(III), and its observation of a sufficient variation in one of the cell dimensions effectively to alter the range of significant hydrogen bonds present in the crystal structures. [source] Three hexafluoridoiridates(IV), Ca[IrF6]·2H2O, Sr[IrF6]·2H2O and Ba[IrF6]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2007Anton I. Smolentsev The structures of the hexafluoridoiridates(IV) of calcium, Ca[IrF6]·2H2O [calcium hexafluoridoiridate(IV) dihydrate], strontium, Sr[IrF6]·2H2O [strontium hexafluoridoiridate(IV) dihydrate], and barium, Ba[IrF6] [barium hexafluoridoiridate(IV)], have been determined by single-crystal X-ray analysis. The first two compounds are isomorphous. Their metal cations are eight-coordinated in a distorted square-antiprismatic coordination environment, and their anions are represented by an almost ideal octahedron. These two structures can be described as frameworks in which all atoms occupy general positions. Sr[RhF6] and Ba[RhF6] have a different space group (, from powder diffraction data) but similar cell dimensions. The structures are very close to that of Ba[IrF6]. The cation is in a cuboctahedral coordination. The metal atoms are located on special positions of symmetry, while the F atoms are in general positions. [source] A new polymorph of tetraphenyldiboroxaneACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2007Linda Kaufmann A new polymorph of tetraphenyldiboroxane [or oxybis(diphenylborane)], C24H20B2O, (Ia), has been found. It is monoclinic, like the already known form, (Ib), and can be refined in the same space group, namely P21/c, or in the equivalent setting P21/n. The molecular conformations of the two polymorphs differ in the rotations of two of the phenyl rings about the B,C bonds, leading to markedly different packing patterns and cell dimensions. [source] Comparison of GFL,GFR, complexes: further evidence relating GFL bend angle to RET signallingACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Vimal Parkash Glial cell line-derived neurotrophic factor (GDNF) activates the receptor tyrosine kinase RET by binding to the GDNF-family receptor ,1 (GFR,1) and forming the GDNF2,GFR,12,RET2 heterohexamer complex. A previous crystal structure of the GDNF2,GFR,12 complex (PDB code 2v5e) suggested that differences in signalling in GDNF-family ligand (GFL) complexes might arise from differences in the bend angle between the two monomers in the GFL homodimer. Here, a 2.35,Å resolution structure of the GDNF2,GFR,12 complex crystallized with new cell dimensions is reported. The structure was refined to a final R factor of 22.5% (Rfree = 28%). The structures of both biological tetrameric complexes in the asymmetric unit are very similar to 2v5e and different from the artemin,GFR,3 structure, even though there is a small change in the structure of the GDNF. By comparison of all known GDNF and artemin structures, it is concluded that GDNF is more bent and more flexible than artemin and that this may be related to RET signalling. Comparisons also suggest that the differences between artemin and GDNF arise from the increased curvature of the artemin `fingers', which both increases the buried surface area in the monomer,monomer interface and changes the intermonomer bend angle. From sequence comparison, it is suggested that neuturin (the second GFL) adopts an artemin-like conformation, while persephin has a different conformation to the other three. [source] Synthesis, Crystal Structure and Characterization of Two Rare Earth Substituted Keggin-Type GermanotungstatesCHINESE JOURNAL OF CHEMISTRY, Issue 7 2008Jing-Ping WANG Abstract Two germanotungstates based on the dysprosium cations and monovacant Keggin anions [GeW11O39]8,, [(CH3)4N]1.5H3.5[Dy(H2O)2(GeW11O39)]·1.5H2O (1) and [Cu(Hen)(en)]2[Cu(H2O)3]0.5{[Cu(H2en)(Hen)]-[Cu(H2O)3]0.5[Dy(GeW11O39)2]}·1.25H2O (2), have been synthesized and characterized by elemental analysis, inductively coupled plasma (ICP) analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. Crystal data for 1: monoclinic, space group C2/c with cell dimensions of a=2.8201(5) nm, b=2.2885(3) nm, c=2.4033(4) nm, ,=123.875(2)°, V=12.878(4) nm3, Z=8, µ=21.239 mm,1; and for 2: monoclinic, space group P21/n with cell dimensions of a=2.12808(5) nm, b=1.63834(4) nm, c=3.18074(4) nm, ,=93.760(2)°, V=11.0658(5) nm3, Z=4, µ=24.803 mm,1. The Dy3+/[GeW11O39]8, ratio of compound 1 is 1:1, and it displays an interesting one dimensional chainlike arrangement. And the Dy3+/[GeW11O39]8, ratio of compound 2 is 1:2 , and it shows a typical dimeric structure. [source] Synthesis and Structural Characterization of 1,4-Di(2-methoxyphenyl)-2,5-piperazinedioneCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007Shu-Sheng Zhang Abstract A new derivative of 2,5-piperazinedione, 1,4-di(2-methoxyphenyl)-2,5-piperazinedione (I), was synthesized by the cyclocondensation reaction of N -2-methoxyphenyl chloroacetamide, and its structure was characterized by elemental analysis, IR, 1H NMR and single crystal X-ray diffraction method. The crystal belongs to monoclinic system, space group P21/c with unit cell dimensions a=0.56934(10) nm, b=1.3880(2) nm, c=1.00329(17) nm, ,=90.376(3)°, V=0.7928(2) nm3, Z=2, Dc=1.367 g·cm,3, ,=0.98 cm,1, R and wR being 0.0606 and 0.1564 respectively for 1549 unique reflections with 1247 observed reflections [I>2,(I)]. The molecule has a crystallographically imposed symmetry center. The three rings in the molecule are each coplanar with their attached groups, excluding methyl H atoms and the H atoms attached to the piperazinedione ring, while the whole molecule is not planar, with dihedral angles of 74.7(1)° between the piperazinedione and each of the two aromatic rings. The crystal structure is stabilized by van der Waals and dipole-dipole forces. [source] Synthesis and characterization of diorganotin compounds {[R2Sn(ON=CHC6H5)]2O}2 and crystal structure of {[(CsH5CH2)2Sn(ON=CHC6H5)]2O}2CHINESE JOURNAL OF CHEMISTRY, Issue 10 2004Han-Dong Yin Abstract Diorganotin compounds ([R2Sn(ON=CHC6H5)]2O)2 [R=C6H5CH2 (1), 2-FC6H4CH2 (2), 4-FC6H4CH2 (3), 2-ClC6H4CH2 (4), 4-ClC6H4CH2 (5)] were synthesized by the reaction of R2SnO with HON=CHC6H5 in 1:1 molar ratio in refluxing anhydrous benzene or toluene. They were characterized by elemental analysis, IR, 1H NMR and 119Sn NMR spectroscopy. And two sets of 119Sn chemical shifts were observed in the 119Sn NMR spectra of these compounds, indicating the presence of two types of environment around the tin atoms. The crystal structure of compound 1 was determined by X-ray single crystal diffraction analysis. The results showed that the crystal of compound 1 belongs to a monoclinic system with space group P21/c and unit cell dimensions: ,=1.0718(9) nm, b=1.9666(17) nm, c=2.0480(17) nm, ,=96.4371(14)°, Dc=1.450 g/cm3, Z=2, F(000)=1888, V=4.290(6) nm3, ,=1.206 mm,1, R1=0.0405, wR2=0.0786. The compound 1 belongs to centrosymmetric dimer structure mode with a four-membered central endo-cyclic Sn2O2 unit in which the bridging oxygen atoms are hi-coordinated. Each bridging oxygen atom also connects with an em-cyclic tin atom. The endo - and exo -cyclic tin atoms are both five-coordinated, and have coordination geometry of distorted trigonal bipyramid. [source] Synthesis and Electronic Structures and Linear Optics of Solid State Compound SrB2O4CHINESE JOURNAL OF CHEMISTRY, Issue 7 2001Hao Zhang Abstract The cluster (SrB2O4)2 existing in crystalline states is employed to model the electronic structure and linear optical properties of solid state compound SrB2O4. This compound is synthesized by high temperature solution reaction, and it crystallizes in the orthorhombic space group Pbcn with cell dimensions a = 1.1995(3), b = 0.4337(1), c = 0.6575(1) nm, V = 0.34202 nm3, and Z = 4, , = 15.14 cm,1, Dcaled = 3.36 g/cm3. The dynamic refractive indices are obtained in terms of INDO/SCI following combination with the Sum-Over-States method. A width of the calculated gap is 4.424 eV between the valence band and conduction band, and the calculated average refractive index is 1.980 at a wavelength of 1.065 ,m. The charge transfers from O2- anion orbitals to Sr2+cation orbitals make the significant contributions to linear polarizability in terms of analyses of atomic state density contributing to the valence and conduction bands. [source] | |||||||||||||