Distribution by Scientific Domains

Kinds of P212121

  • group p212121
  • orthorhombic p212121
  • orthorhombic space group p212121
  • space group p212121

  • Selected Abstracts

    Synthesis, growth and characterization of single crystals of pure and thiourea doped L-glutamic acid hydrochloride

    R. Sathyalakshmi
    Abstract L(+)Glutamic acid hydrochloride [HOOC (CH2)2CH(NH2) COOH·HCl], a monoamino dicarboxylic acid salt of L-Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L-Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV-Vis-NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L-Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X-ray diffraction analysis and it crystallizes in orthorhombic space group P212121. UV-Vis-NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L-Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L-Glutamic acid hydrochloride crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Configuration, conformation and crystal structure of rabdosianin b

    Bao Lin Li
    Abstract Rabdosianin B, 7,20-epoxy-7,-hydroxy-1,,6,,11,,15,-tetraacetoxy- ent -kaur-16-ene, C28H38O10, was the first isolated from Isodon henryi. It consists of three six-membered rings A, B, C and one five-membered ring D. The fused-ring system A, B and C are in chair, boat and chair conformations, respectively, and ring D is in an envelope conformation, on the basis of NMR and X-ray diffraction analysis. The crystal of rabdosianin B is in orthorhombic crystal system with space group P212121, lattice constants: a = 9.969(1) Å, b = 15.400(3) Å, and c = 17.624(3) Å, Z = 4. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Structure, growth and optical properties of Zn0.24Ni0.76(SO4)·7H2O single crystal

    Xinxin Zhuang
    Abstract A new crystalline complex zinc nickel sulfate heptahydrate (ZNSH) has been prepared. The crystal structure was investigated by x-ray single crystal diffraction method and the empirical formula is Zn0.24Ni0.76(SO4)·7H2O. The ZNSH crystal belongs to the orthorhombic space group P212121 with cell parameters a = 6.7742(14) Å, b = 11.748(2) Å, c = 12.009(2) Å. The deep-green ZNSH single crystal with dimension of 30 × 25 × 25 mm3 has been grown by the cooling solution method. The constituent ratio of ZNSH crystal grown from various compounding solutions at temperature range 40-50 °C is approximate invariant. The crystal absorption spectra with theoretical analysis are reported. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Synthesis, Structure and Magnetic Properties of a Tetranuclear Copper(II) Complex on the Basis of a 2-Substituted Glucopyranoside Schiff Base Ligand,

    Anja Burkhardt
    Abstract Condensation of a derivatized 2-aminoglucose fragment with salicylaldehyde affords the new sugar-based Schiff base ligand benzyl 4,6- O -benzylidene-2-deoxy-2-salicylideneamino-,- D -glucopyranoside (H2L). The reaction of the dibasic ligand H2L with [Cu(CH3COO)2]·H2O leads to the formation of the tetranuclear copper(II) complex [{Cu(L)}4] (3) by a self-assembly process. The X-ray structural analysis of complex 3 which crystallizes together with two molecules of chloroform and one molecule of ethanol in the space group P212121 revealed for all copper atoms a NO3 coordination environment with a square-planar geometry. The tetranuclear molecule 3 consists of four chiral building blocks {Cu(L)} with the rare 2,3-coordination of the trans -configured donor atoms of the sugar backbone. The observed coordination mode of the building blocks exemplifies how chitosan-derived polysaccharide ligands can act as a chiral support for transition-metal complexes. The C-3 alcoholate oxygen atoms of the carbohydrate unit is bridging adjacent {Cu(L)} moieties resulting in an eight-membered Cu4O4 ring with a boat-like conformation. Temperature-dependent magnetic measurements of 3 indicate moderate antiferromagnetic interactions between the four copper(II) ions with a coupling constant of J = ,130 cm,1.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Structural Studies of ,-Cyclodextrin and Permethylated ,-Cyclodextrin Inclusion Compounds of Cyclopentadienyl Metal Carbonyl Complexes

    Susana S. Braga
    Abstract [CpM(CO)nCl] complexes with M = Fe (n = 2) and Mo (n = 3) have been immobilised in plain ,-cyclodextrin (,-CD) and permethylated ,-CD (TRIMEB) by methods tailored according to the stabilities and solubilities of the individual components. Four adducts were obtained with a 1:1 host/guest stoichiometry. The compounds were studied by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), 13C{1H} CP/MAS NMR and FTIR spectroscopy. A comparison of the experimental powder XRD data for the TRIMEB/[CpMo(CO)3Cl] inclusion compound with reference patterns revealed that the crystal packing is very similar to that reported previously for a TRIMEB/ethyl laurate inclusion compound. The unit-cell parameters refined to a = 14.731, b = 22.476, c = 27.714 Å (volume = 9176.3 Å3), and the space group was confirmed as P212121. A hypothetical structural model of the inclusion compound was subsequently obtained by global optimisation using simulated annealing. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    On the purity of 2-[ortho -anilinyl]-1,3-benzoxazole derived from 2H -3,1-benzoxazine-2,4(1H)dione (isatoic anhydride) [1,2],

    Karen M. Button
    The Lewis acid catalyzed synthesis and chromatographic purification of isatoic anhydride-derived 2-(2,-anilinyl)-1,3-benzoxazole (2) can result in the co-isolation of 2 and a light pink colored impurity (<5%). This latter species has been identified (NMR, single crystal X-ray diffraction, mp) as 2,-hydroxy-2-aminobenzanilide (3), which represents a predictable intermediate in the formation of 2. Compound 3 crystallizes in an orthorhombic crystal system of space group P212121 with four molecules in the unit cell (, = , = , = 90°; a = 6.715 (2) Å, b = 12.100 (4) Å, c = 13.321 (4) Å; V = 1082.2 (6) Å3). Pure 2 is characterized as a colorless, high-melting solid; unlike the dark colored oil that is isolated if 2 contains traces of 3. J. Heterocyclic Chem., (2010). [source]

    Comparison of the three-dimensional structures of a human Bence-Jones dimer crystallized on Earth and aboard US Space Shuttle Mission STS-95,

    Simon S. Terzyan
    Abstract Crystals of a human (Sea) Bence-Jones dimer were produced in a capillary by vapor diffusion under microgravity conditions in the 9 day US Space Shuttle Mission STS-95. In comparison to ground-based experiments, nucleation was facile and spontaneous in space. Appearance of a very large (8,×,1.6,×,1.0,mm) crystal in a short time period is a strong endorsement for the use of microgravity to produce crystals sufficiently large for neutron diffraction studies. The Sea dimer crystallized in the orthorhombic space group P212121, with a,=,48.9,Å, b,=,85.2,Å, and c,=,114.0,Å. The crystals grown in microgravity exhibited significantly lower mosaicities than those of ground-based crystals and the X-ray diffraction data had a lower overall B factor. Three-dimensional structures determined by X-ray analysis at two temperatures (100 and 293,K) were indistinguishable from those obtained from ground-based crystals. However, both the crystallographic R factor and the free R factor were slightly lower in the models derived from crystals produced in microgravity. The major difference between the two crystal growth systems is a lack of convection and sedimentation in a microgravity environment. This environment resulted in the growth of much larger, higher-quality crystals of the Sea Bence-Jones protein. Structurally, heretofore unrecognized grooves on the external surfaces of the Sea and other immunoglobulin-derived fragments are regular features and may offer supplementary binding regions for super antigens and other elongated ligands in the bloodstream and perivascular tissues. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Structural characterization of anhydrous naloxone- and naltrexone hydrochloride by high resolution laboratory X-ray powder diffraction and thermal analysis

    Kunihisa Sugimoto
    Abstract The crystal structures of the analgesic compounds anhydrous naloxone and naltrexone hydrochloride were determined ab initio from high resolution laboratory X-ray powder diffraction data. Both compounds crystallize in the orthorhombic space group P212121 with lattice parameters of a,=,14.6588(10) Å, b,=,17.4363(9) Å, c,=,7.96200(22) Å, and V,=,2035.06(23) Å3 for naloxone hydrochloride and a,=,15.4560(5) Å, b,=,14.9809(4) Å, c,=,7.84121(18) Å, and V,=,1815.58(11) Å3 for naltrexone hydrochloride. The crystal structure of anhydrous naloxone hydrochloride forms one-dimensional chains through hydrogen bonds. In the crystal structure of anhydrous naltrexone hydrochloride, two-dimensional sheets are formed by hydrogen bonds. The dehydration processes of naloxone hydrochloride dehydrate and naltrexone hydrochloride tetrahydrate was analyzed by DTA, DSC, TG, and MG. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3316,3323, 2007 [source]

    Solid state characterization of mometasone furoate anhydrous and monohydrate forms

    Xiaoming (Sean) Chen
    Abstract Mometasone furoate is a potent glucocorticoid anti-inflammatory agent. Its anhydrous Form 1 and monohydrate form were characterized by X-ray crystallography, X-ray powder diffraction at ambient and elevated temperature, thermal analysis, FT-IR, and dynamic moisture adsorption. In Form 1, mometasone furoate molecules pack tightly with molecules interlocked in a space group of P212121. The monohydrate form crystallizes in space group P1. The unit cell of the monohydrate contains one water molecule and one mometasone furoate molecule. The water molecules form channels along the a axis and mometasone furoate molecules pack in layers in the same direction. Dehydration was observed between 60 and 100°C by thermogravimetric analysis with a heating rate of 10°C/min. It corresponds to a broad endotherm over the same temperature range in the differential scanning calorimetry with the same heating rate. Variable temperature X-ray powder diffraction reveals that a new anhydrous form (Form 2) was fully produced above 90°C. This crystalline form was converted to Form 1 after being heated above 150°C; and was totally converted to the monohydrate after 1 day at 23°C, 45% RH. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2496-2509, 2005 [source]

    Structural phase transition in [NH3(CH2)5NH3]BiCl5: thermal and vibrational studies

    H. Jeghnou
    Abstract An x-ray diffraction study carried out on the pentylenediammonium pentachlorobismuthate (III) compound [NH3(CH2)5NH3]BiCl5 indicated that it is orthorhombic with a P212121(Z = 4) space group. Differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were also made, which showed that this compound undergoes a unique phase transition at high temperatures. The infrared and Raman spectra recorded at room temperature were interpreted on the basis of data published in the literature. The Raman bands observed below 300 cm,1 are very characteristic of the anions, which are made of isolated (BiCl52, )n units composed of BiCl63, octahedra. Raman spectra recorded at various temperatures confirmed the contribution to the phase-transition mechanism of both the anion and cation motions. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Chiral Crystal Structure of Racemic Binaphthyl Poly(ether ketone) Macrocycles

    Xing Wang
    Abstract Summary: The crystal structure of rigid, hollow, racemic binaphthyl poly(ether ketone) macrocycles has been elucidated by single crystal X-ray analysis. Multitudinal interactions were identified within the chiral space group P212121. The structural analysis revealed that this macrocyclic compound contains an elliptic chiral cavity with a size of 9.80,×,5.18 Å, which is similar to that of cyclodextrins. The knowledge about the interaction sites and the structure of the binaphthyl-based macrocycle provides a unique opportunity to understand its molecular or chiral recognition properties. Space-filling representation of the single (R)-macrocycle. [source]

    Crystal structure of a dimeric form of streptococcal pyrogenic exotoxin A (SpeA1)

    PROTEIN SCIENCE, Issue 9 2004
    Matthew D. Baker
    Abstract Streptococcal pyrogenic exotoxin A (SpeA1) is a bacterial superantigen associated with scarlet fever and streptococcal toxic shock syndrome (STSS). SpeA1 is found in both monomeric and dimeric forms, and previous work suggested that the dimer results from an intermolecular disulfide bond between the cysteines at positions 90 of each monomer. Here, we present the crystal structure of the dimeric form of SpeA1. The toxin crystallizes in the orthorhombic space group P212121, with two dimers in the crystallographic asymmetric unit. The final structure has a crystallographic R-factor of 21.52% for 7248 protein atoms, 136 water molecules, and 4 zinc atoms (one zinc atom per molecule). The implications of SpeA1 dimer on MHC class II and T-cell receptor recognition are discussed. [source]

    Alternative type I and I, turn conformations in the ,8/,9 ,-hairpin of human acidic fibroblast growth factor

    PROTEIN SCIENCE, Issue 3 2002
    Jaewon Kim
    Abstract Human acidic fibroblast growth factor (FGF-1) has a ,-trefoil structure, one of the fundamental protein superfolds. The X-ray crystal structures of wild-type and various mutant forms of FGF-1 have been solved in five different space groups: C2, C2221, P21 (four molecules/asu), P21 (three molecules/asu), and P212121. These structures reveal two characteristically different conformations for the ,8/,9 ,-hairpin comprising residue positions 90,94. This region in the wild-type FGF-1 structure (P21, four molecules/asu), a his-tagged His93,Gly mutant (P21, three molecules/asu) and a his-tagged Asn106,Gly mutant (P212121) adopts a 3:5 ,-hairpin known as a type I (1,4) G1 ,-bulge (containing a type I turn). However, a his-tagged form of wild-type FGF-1 (C2221) and a his-tagged Leu44,Phe mutant (C2) adopt a 3:3 ,-hairpin (containing a type I, turn) for this same region. A feature that distinguishes these two types of ,-hairpin structures is the number and location of side chain positions with eclipsed C, and main-chain carbonyl oxygen groups (, , +60°). The effects of glycine mutations upon stability, at positions within the hairpin, have been used to identify the most likely structure in solution. Type I, turns in the structural data bank are quite rare, and a survey of these turns reveals that a large percentage exhibit crystal contacts within 3.0 Å. This suggests that many of the type I, turns in X-ray structures may be adopted due to crystal packing effects. [source]

    Structural polymorphism of pyrazinium hydrogen sulfate: extending chemistry of the pyrazinium salts with small anions

    Armand Budzianowski
    Two polymorphs (,, ,) of pyrazinium hydrogen sulfate (pyzH+HSO, abbreviated as PHS) with distinctly different hydrogen-bond types and topologies but close electronic energies have been synthesized and characterized for the first time. The ,-polymorph (P212121) forms distinct blocks in which the pyzH+ and HSO ions are interconnected through a network of NH...O and OH...O hydrogen bonds. The ,-form () consists of infinite chains of alternating pyzH+ and HSO ions connected by NH...O and OH...N hydrogen bonds. Density functional theory (DFT) calculations indicate the possible existence of a hypothetical polar P1 form of the ,-polymorph with an unusually high dipole moment. [source]

    Structures of strontium diformate and strontium fumarate.

    A synchrotron powder diffraction study
    The crystal structures of strontium diformate in space groups P212121 (, form, 295,K), P41212 (, form, 334 and 540,K) and I41/amd (, form, 605,K), and strontium fumarate in space groups Fddd (, form, 105,K) and I41/amd (, form, 293,K) have been determined from synchrotron X-ray powder diffraction data. Except for the ,-strontium diformate, all the structures are based on a diamond-like Sr-ion arrangement, as in strontium acetylene dicarboxylate. The formate ions are disordered in the , phase owing to steric hindrance. The fumarate ions are disordered over four (,) or two (,) symmetry-equivalent orientations. ,-Strontium fumarate crystallizes with a unique 90° carboxylate dihedral angle, and is stable up to 773,K. [source]

    On the polymorphism of benzocaine; a low-temperature structural phase transition for form (II)

    Eric J. Chan
    A low-temperature structural phase transition has been observed for form (II) of benzocaine (BZC). Lowering the temperature doubles the b -axis repeat and changes the space group from P212121 to P1121 with , now 99.37 °. The structure is twinned, the twin rule corresponding to a 21 screw rotation parallel to a. The phase transition is associated with a sequential displacement parallel to a of zigzag bi-layers of ribbons perpendicular to b*. No similar phase transition was observed for form (I) and this was attributed to the different packing symmetries of the two room-temperature polymorphic forms. [source]

    Single-crystal diffuse scattering studies on polymorphs of molecular crystals.


    The drug benzocaine (ethyl 4-aminobenzoate), commonly used as a local anaesthetic, is a bimorphic solid at room temperature. Form (I) is monoclinic P21/c, while the metastable form (II) is orthorhombic P212121. Three-dimensional diffuse X-ray scattering data have been collected for the two forms on the 11-ID-B beamline at the Advanced Photon Source (APS). Both forms show strong and highly structured diffuse scattering. The data have been interpreted and analysed using Monte Carlo (MC) modelling on the basis that the scattering is purely thermal in origin and indicates the presence of highly correlated molecular motions. In both forms (I) and (II) broad diffuse streaks are observed in the 0kl section which indicate strong longitudinal displacement correlations between molecules in the ,031, directions, extending over distances of up to 50,Å. Streaks extending between Bragg peaks in the hk0 section normal to [100] correspond to correlated motions of chains of molecules extending along a that are linked by N,H...O=C hydrogen bonds and which occur together as coplanar ribbon pairs. The main difference between the two forms is in the dynamical behaviour of the ribbon pairs and in particular how they are able to slide relative to each other. While for form (I) a model involving harmonic springs is able to describe the motion satisfactorily, as simple excursions away from the average structure, there is evidence in form (II) of anharmonic effects that are precursors of a phase transition to a new low-temperature phase, form (III), that was subsequently found. [source]

    High-pressure neutron diffraction study of l -serine-I and l -serine-II, and the structure of l -serine-III at 8.1,GPa

    Stephen A. Moggach
    The hydrostatic compression of l -serine- d7 has been studied to 8.1,GPa by neutron powder diffraction. Over the course of this pressure range the compound undergoes two phase transitions, the first between 4.6 and 5.2,GPa, yielding l -serine-II, and the second between 7.3 and 8.1,GPa, yielding l -serine-III. All three polymorphs are orthorhombic, P212121, and feature chains of serine molecules connected via head-to-tail ND,O hydrogen bonds formed between ammonium and carboxylate groups. The chains are linked into a ribbon by a second set of ND,O hydrogen bonds. The hydroxyl moieties are distributed along the outer edges of the ribbon and in phase I they connect the ribbons into a layer by chains of OD,OD hydrogen bonds. The layers are connected together by a third set of ND,O hydrogen bonds, forming rings with substantial voids at their centres. In the transition from phase I to II these voids begin to close up, but at the cost of breaking the OD,OD chains. The OD,OD hydrogen bonds are replaced by shorter OD,O hydrogen bonds to carboxylate groups. At 7.3,GPa the O,O distance in the OD,O hydrogen bonds measures only 2.516,(17),Å, which is short, and we propose that the phase transition to phase III that occurs between 7.3 and 8.1,GPa relieves the strain that has built up in this region of the structure. The hydroxyl D atom now bifurcates between the OD,O contact that had been present in phase II and a new OD,O contact formed to a carboxylate in another layer. Hirshfeld surface fingerprint plots show that D,D interactions become more numerous, while hydrogen bonds actually begin to lengthen in the transition from phase II to III. [source]

    Ezetimibe anhydrate, determined from laboratory powder diffraction data

    Jürgen Brüning
    Ezetimibe {systematic name: (3R,4S)-1-(4-fluorophenyl)-3-[(3S)-3-(4-fluorophenyl)-3-hydroxypropyl]-4-(4-hydroxyphenyl)azetidin-2-one}, C24H21F2NO3, is used to lower cholesterol levels by inhibiting cholesterol resorption in the human intestine. The crystal structure of ezetimibe anhydrate was solved from laboratory powder diffraction data by means of real-space methods using the program DASH [David et al. (2006). J. Appl. Cryst.39, 910,915]. Subsequent Rietveld refinement with TOPAS Academic [Coelho (2007). TOPAS Academic User Manual. Version 4.1. Coelho Software, Brisbane, Australia] led to a final Rwp value of 8.19% at 1.75,Å resolution. The compound crystallizes in the space group P212121 with one molecule in the asymmetric unit. The molecules are closely packed and two intermolecular hydrogen bonds form an extended hydrogen-bond architecture. [source]

    (E)- N2 -{4-[(E)-2-(4-Chlorobenzoyl)ethenyl]-3-methyl-1-phenyl-1H -pyrazol-5-yl}- N1,N1 -dimethylformamidine: polarized molecules within sheets of ,-stacked hydrogen-bonded chains

    Jairo Quiroga
    The molecules of the title compound, C22H21ClN4O, are conformationally chiral, and in the space group P212121 each crystal contains only one conformational enantiomer. The intramolecular dimensions provide evidence for polarization of the electronic structure. Molecules are linked by a single C,H...,(arene) hydrogen bond into chains, which are themselves weakly linked into sheets by an aromatic ,,, stacking interaction. [source]

    2-Methoxy-3-methyl-6-oxo-4-(2,3,4-tri- O -acetyl-,- d -xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde 0.065-hydrate and 2-methylsulfanyl-6-oxo-4-(2,3,4-tri- O -acetyl-,- d -xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde: hydrogen-bonded structures in one or three dimensions

    Justo Cobo
    The organic components of 2-methoxy-3-methyl-6-oxo-4-(2,3,4-tri- O -acetyl-,- d -xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde 0.065-hydrate, C18H23N3O10·0.065H2O, (I), which crystallizes with Z, = 2 in the space group P212121, are linked into a three-dimensional framework structure by a combination of four C,H...O hydrogen bonds. In 2-methylsulfanyl-6-oxo-4-(2,3,4-tri- O -acetyl-,- d -xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde, C17H21N3O9S, (II), where the pyrimidine fragment is disordered with two different conformations for the methylsulfanyl substituent, molecules are linked into chains of rings by a combination of N,H...O and C,H...O hydrogen bonds. [source]

    Concomitant polymorphism and conformational isomerism in 4-acetylresorcinol

    Peter G. Jones
    Two polymorphs of the title compound [systematic name: 1-(2,4-dihydroxyphenyl)ethanone], C8H8O3, were investigated. The known structure [designated (I-M); P21/c, Z = 4; previously investigated at room temperature by Robert, Moore, Eichhorn & Rillema (2007). Acta Cryst. E63, o4252] was redetermined at low temperature, and a new form [(I-O); P212121, Z = 12] was discovered in the same sample. In both forms, the molecules are planar (apart from the methyl H atoms) and they contain intramolecular O,H...O=C hydrogen bonds. In polymorph (I-M), molecules are linked into chains by a single intermolecular O,H...O hydrogen bond, and the chains are linked into sheets by two C,H...O hydrogen bonds. Three O,H...O hydrogen bonds link the molecules of polymorph (I-O) into chains and neighbouring chains are connected by one C,H...O interaction to form an offset layer structure. Two weak methyl C,H...O interactions link the layers. [source]

    A new polymorph of triphenylmethylamine: the effect of hydrogen bonding

    Victor N. Khrustalev
    Crystallization of the hexane reaction mixture after treatment of LiGe(OCH2CH2NMe2)3 with Ph3CN3 gives rise to a new triclinic (space group P) polymorph of triphenylmethylamine, C19H17N, (I), containing dimers formed by N,H...N hydrogen bonds, whereas the structure of the known orthorhombic (space group P212121) polymorph of this compound, (II), consists of isolated molecules. While the dimers in (I) lie across crystallographic inversion centres, the molecules are not truly related by them. The centrosymmetric structure is due to the statistical disordering of the amino H atoms participating in the N,H...N hydrogen-bonding interactions, and thus the inversion centre is superpositional. The conformations and geometric parameters of the molecules in (I) and (II) are very similar. It was found that the polarity of the solvent does not affect the capability of triphenylmethylamine to crystallize in the different polymorphic modifications. The orthorhombic polymorph, (II), is more thermodynamically stable under normal conditions than the triclinic polymorph, (I). The experimental data indicate the absence of a phase transition in the temperature interval 120,293,K. The densities of (I) (1.235,Mg,m,3) and (II) (1.231,Mg,m,3) at 120,K are practically equal. It would seem that either the kinetic factors or the effects of the other products of the reaction facilitating the hydrogen-bonded dimerization of triphenylmethylamine molecules are the determining factor for the isolation of the triclinic polymorph (I) of triphenylmethylamine. [source]

    Salts of maleic and fumaric acids with oxine: the role of isomeric acids in hydrogen-bonding patterns

    S. Franklin
    Both maleic and fumaric acid readily form adducts or complexes with other organic molecules. The 1:1 adduct formed by quinolin-8-ol (oxine) with maleic and fumaric acid are salts, namely 8-hydroxyquinolinium hydrogen maleate, C9H8NO+·C4H3O4,, (I), and 8-hydroxyquinolinium hydrogen fumarate, C9H8NO+·C4H3O4,, (II). The cations and anions of both salts are linked by ionic N+,H...O, hydrogen bonds. The maleate salt crystallizes in the space group P212121, while the fumarate salt crystallizes in P. The maleic and fumaric acids in their complex forms exist as semimaleate and semifumarate ions (mono-ionized state), respectively. Classical N,H...O and O,H...O hydrogen bonds, together with short C,H...O contacts, generate an extensive hydrogen-bonding network. The crystal structures of the maleate and fumarate salts of oxine have been elucidated to study the importance of noncovalent interactions in the aggregation and interaction patterns of biological molecules. The structures of the salts of the Z and E isomers of butenedioic acid (maleic and fumaric acid, respectively) with quinolin-8-ol are compared. [source]

    Two new non-centrosymmetric lithium salts of glycine: bis(glycine) lithium chromate monohydrate and bis(glycine) lithium molybdate

    Michel Fleck
    In bis­(glycine) lithium chromate monohydrate {systematic name: poly[aquadi-,-glycinato-,-tetra­oxochromato(VI)-dilithium(I)]}, [CrLi2(C2H5NO2)2O4(H2O)]n, (I) (space group P212121), and bis­(glycine) lithium molybdate {systematic name: poly[di-,-glycinato-,-tetra­oxomolybdato(VI)-dilithium(I)]}, [Li2Mo(C2H5NO2)2O4]n, (II) (space group P21), all atoms are located on general positions. The crystal structure of (I) is characterized by infinite chains of corner-sharing [LiO4] tetra­hedra, which are connected by glycine mol­ecules to form layers. [CrO4] tetra­hedra are attached to the [LiO4] tetra­hedra. Compound (II) contains dimers of [LiO4] tetra­hedra which are connected by [MoO4] tetra­hedra to form chains, which are in turn connected by glycine mol­ecules to form double layers. [source]

    trans -(dl -Isoleucinato- N,O)[tris(2-aminoethyl)amine-,4N]cobalt(III) diperchlorate

    Jiwen Cai
    The racemic title compound, trans -[N,N -bis(2-amino­ethyl)-1,2-ethanediamine-,4N]­(dl -isoleucinato- N,O)­cobalt(III) di­per­chlor­ate, [Co(C6H18N4)(C6H12NO2)](ClO4)2, crystallizes in the enantiomorphous space group P212121 with Z = 12 (Z, = 3). Each of the three cations in the asymmetric unit represents a different chirality of the isoleucine ligand; two of them are R (or d) and the third is the S (or l) enantiomer. The mixture crystallizes in a so-called unbalanced crystallization, in which the cations adopt a chiral array of composition RRS or SSR, depending on the crystal selected for data collection. [source]


    Silvia Russi
    The title compound, [Fe(C8H11ClO2)(CO)3], has been synthesized, isolated and characterized by single-crystal X-ray diffraction. The mol­ecule crystallizes in the orthorhombic space group P212121. The metal,ligand arrangement is typical of (1,3-diene)­tri­carbonyl­iron complexes. [source]

    Ammonium N -acetyl- l -threoninate and methyl­ammonium N -acetyl- l -threoninate

    Raffaella Puliti
    Ammonium N -acetyl- l -threoninate, NH4+·C6H10NO4,, and methyl­ammonium N -acetyl- l -threoninate, CH6N+·­C6H10NO4,, crystallize in the orthorhombic P212121 and monoclinic P21 space groups, respectively. The two crystals present the same packing features consisting of infinite ribbons of screw-related N -acetyl- l -threoninate anions linked together through pairs of hydrogen bonds. The cations interconnect neighbouring ribbons of anions involving all the nitrogen-H atoms in three-dimensional networks of hydrogen bonds. The hydrogen-bond patterns include asymmetric `three-centred' systems. In both structures, the Thr side chain is in the favoured (g,g+) conformation. [source]

    Atomic resolution studies of haloalkane dehalogenases DhaA04, DhaA14 and DhaA15 with engineered access tunnels

    A. Stsiapanava
    The haloalkane dehalogenase DhaA from Rhodococcus rhodochrous NCIMB 13064 is a bacterial enzyme that shows catalytic activity for the hydrolytic degradation of the highly toxic industrial pollutant 1,2,3-trichloropropane (TCP). Mutagenesis focused on the access tunnels of DhaA produced protein variants with significantly improved activity towards TCP. Three mutants of DhaA named DhaA04 (C176Y), DhaA14 (I135F) and DhaA15 (C176Y + I135F) were constructed in order to study the functional relevance of the tunnels connecting the buried active site of the protein with the surrounding solvent. All three protein variants were crystallized using the sitting-drop vapour-diffusion technique. The crystals of DhaA04 belonged to the orthorhombic space group P212121, while the crystals of DhaA14 and DhaA15 had triclinic symmetry in space group P1. The crystal structures of DhaA04, DhaA14 and DhaA15 with ligands present in the active site were solved and refined using diffraction data to 1.23, 0.95 and 1.22,Å, resolution, respectively. Structural comparisons of the wild type and the three mutants suggest that the tunnels play a key role in the processes of ligand exchange between the buried active site and the surrounding solvent. [source]

    Pseudo-merohedral twinning and noncrystallographic symmetry in orthorhombic crystals of SIVmac239 Nef core domain bound to different-length TCR, fragments

    Walter M. Kim
    HIV/SIV Nef mediates many cellular processes through interactions with various cytoplasmic and membrane-associated host proteins, including the signalling , subunit of the T-cell receptor (TCR,). Here, the crystallization strategy, methods and refinement procedures used to solve the structures of the core domain of the SIVmac239 isolate of Nef (Nefcore) in complex with two different TCR, fragments are described. The structure of SIVmac239 Nefcore bound to the longer TCR, polypeptide (Leu51,Asp93) was determined to 3.7,Å resolution (Rwork = 28.7%) in the tetragonal space group P43212. The structure of SIVmac239 Nefcore in complex with the shorter TCR, polypeptide (Ala63,Arg80) was determined to 2.05,Å resolution (Rwork = 17.0%), but only after the detection of nearly perfect pseudo-merohedral crystal twinning and proper assignment of the orthorhombic space group P212121. The reduction in crystal space-group symmetry induced by the truncated TCR, polypeptide appears to be caused by the rearrangement of crystal-contact hydrogen-bonding networks and the substitution of crystallographic symmetry operations by similar noncrystallographic symmetry (NCS) operations. The combination of NCS rotations that were nearly parallel to the twin operation (k, h, ,l) and a and b unit-cell parameters that were nearly identical predisposed the P212121 crystal form to pseudo-merohedral twinning. [source]