scholarly journals Redetermined crystal structure of β-DL-methionine at 320 K

2015 ◽  
Vol 71 (6) ◽  
pp. o398-o399 ◽  
Author(s):  
Carl Henrik Görbitz ◽  
Jan Christian Paulsen ◽  
Jon Borgersen
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonding ◽  
Phase Shift ◽  
Hydrogen Bonds ◽  
Torsion Angle ◽  
Side Chain ◽  
Acta Cryst ◽  
Space Group ◽  
Major Conformation

The structure of β-DL-methionine, C5H11NO2S, in the space groupC2/c, is here confirmed to be fully ordered all the way up to the phase transition at approximately 326 K, where displacive sliding of molecular bilayers gives the disorderedP21/cα form [data at 340 K; Görbitz (2014).Acta Cryst.E70, 341–343]. The geometry of hydrogen bonds in LD–LD hydrogen-bonding patterns [Görbitzet al.(2009).Acta Cryst.B65, 393–400] at the hydrophilic core of each molecular bilayer are virtually unperturbed by the phase shift, but the C—C—S—C torsion angle of the side chain changes fromtransat 320 K togauche+ for the major conformation at 340 K.

scholarly journals Crystal structure of 2′-hydroxyacetophenone 4-methylthiosemicarbazide

2015 ◽  
Vol 71 (4) ◽  
pp. o244-o245
Author(s):  
Junita Jamsari ◽  
Nur Fatihah Abas ◽  
Thahira Begum S. A. Ravoof ◽  
Edward R. T. Tiekink
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Torsion Angle ◽  
Organic Molecule ◽  
Side Chain ◽  
Water Molecules ◽  
Ethyl Group

In the organic molecule of the title hydrate, C11H15N3OS·H2O, {systematic name: 3-ethyl-1-{(E)-[1-(2-hydroxyphenyl)ethylidene]amino}thiourea monohydrate}, a dihedral angle of 5.39 (2)° is formed between the hydroxybenzene ring and the non-H atoms comprising the side chain (r.m.s. deviation = 0.0625 Å), with the major deviation from planarity noted for the terminal ethyl group [the C—N—C—C torsion angle = −172.17 (13)°]. The N—H H atoms aresynand an intramolecular hydroxy–imine O—H...N hydrogen bond is noted. In the crystal, the N-bonded H atoms form hydrogen bonds to symmetry-related water molecules, and the latter form donor interactions with the hydroxy O atom and with a hydroxybenzene ring, forming a O—H...π interaction. The hydrogen bonding leads to supramolecular tubes aligned along thebaxis. The tubes are connected into layersviaC—H...O interactions, and these stack along thecaxis with no directional interactions between them.

Structure of ammonium hydrogen succinate above and below the phase transition around 170K

1996 ◽  
Vol 52 (2) ◽  
pp. 323-327 ◽  
Author(s):  
A. Hirano ◽  
Y. Kubozono ◽  
H. Maeda ◽  
H. Ishida ◽  
S. Kashino
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonds ◽  
Order Phase Transition ◽  
Space Group ◽  
X Ray ◽  
Ammonium Hydrogen ◽  
Significant Change ◽  
Short Hydrogen Bonds ◽  
Second Order Phase Transition

For crystals of ammonium hydrogen succinate it is known that the space group is P{\bar 1} with Z = 2 at 293 K and the second-order phase transition occurs around 170 K. X-ray crystal structure analyses above and below 170 K have been carried out in order to study the change in mode of short hydrogen bonds between the hydrogen succinate ions. The space group was determined to be P{\bar 1} at 150 and 190 K by structure analysis. No ordering of the H-atom positions in the short hydrogen bonds occurs by the phase transition. The hydrogen bonds show a decrease in the O...O distances with a decrease in temperature from 290 to 190 K, but no significant change in the geometries between 190 and 150 K. Disorder of the NH4 + ion is not observed at 297, 190 and 150 K. Significant change through the phase transition is found only in the geometry of one of the N—H...O hydrogen bonds between ammonium and hydrogen succinate ions.

scholarly journals A substrate selected by phage display exhibits enhanced side-chain hydrogen bonding to HIV-1 protease

2018 ◽  
Vol 74 (7) ◽  
pp. 690-694 ◽  
Author(s):  
Ian W. Windsor ◽  
Ronald T. Raines
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Molecular Recognition ◽  
Hydrogen Bonds ◽  
Phage Display ◽  
Directed Evolution ◽  
Side Chain ◽  
Endogenous Substrates ◽  
Hiv 1 ◽  
Additional Hydrogen

Crystal structures of inactive variants of HIV-1 protease bound to peptides have revealed how the enzyme recognizes its endogenous substrates. The best of the known substrates is, however, a nonnatural substrate that was identified by directed evolution. The crystal structure of the complex between this substrate and the D25N variant of the protease is reported at a resolution of 1.1 Å. The structure has several unprecedented features, especially the formation of additional hydrogen bonds between the enzyme and the substrate. This work expands the understanding of molecular recognition by HIV-1 protease and informs the design of new substrates and inhibitors.

scholarly journals Crystal structure of pentakis(ethylenediamine-κ2N,N′)lanthanum(III) trichloride–ethylenediamine–dichloromethane (1/1/1)

2014 ◽  
Vol 70 (11) ◽  
pp. 424-426 ◽  
Author(s):  
Hope T. Sartain ◽  
Richard J. Staples ◽  
Shannon M. Biros
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Electron Density ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
Bypass Procedure ◽  
Hydrogen Bonding Network ◽  
Additional Hydrogen

We report here the crystal structure of a ten-coordinate lanthanum(III) metal coordinated by five bidentate ethylenediamine ligands, [La(C2H8N2)5]Cl3·C2H8N2·CH2Cl2. One free ethylenediamine molecule and three Cl−anions are also located in the asymmetric unit. The overall structure is held together by an extensive hydrogen-bonding network between the Cl−anions and the NH groups on the metal-bound ethylenediamine ligands. The free ethylenediamine molecule is held in an ordered position by additional hydrogen bonds involving both the chlorides and –NH groups on the metal-bound ligands. One highly disordered molecule of dichloromethane is located on an inversion center; however, all attempts to model this disorder were unsuccessful. The electron density in this space was removed using the BYPASS procedure [van der Sluis & Spek (1990).Acta Cryst.A46, 194–201].

scholarly journals Crystal structure of 8-hydroxyquinoline: a new monoclinic polymorph

2014 ◽  
Vol 70 (9) ◽  
pp. o924-o925 ◽  
Author(s):  
Raúl Castañeda ◽  
Sofia A. Antal ◽  
Sergiu Draguta ◽  
Tatiana V. Timofeeva ◽  
Victor N. Khrustalev
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Three Dimensional ◽  
Solvent Mixture ◽  
Acta Cryst ◽  
Space Group ◽  
Compound C ◽  
Centrosymmetric Dimers

In an attempt to grow 8-hydroxyquinoline–acetaminophen co-crystals from equimolar amounts of conformers in a chloroform–ethanol solvent mixture at room temperature, the title compound, C9H7NO, was obtained. The molecule is planar, with the hydroxy H atom forming an intramolecular O—H...N hydrogen bond. In the crystal, molecules form centrosymmetric dimersviatwo O—H...N hydrogen bonds. Thus, the hydroxy H atoms are involved in bifurcated O—H...N hydrogen bonds, leading to the formation of a central planar four-membered N2H2ring. The dimers are bound by intermolecular π–π stacking [the shortest C...C distance is 3.2997 (17) Å] and C—H...π interactions into a three-dimensional framework. The crystal grown represents a new monoclinic polymorph in the space groupP21/n. The molecular structure of the present monoclinic polymorph is very similar to that of the orthorhombic polymorph (space groupFdd2) studied previously [Roychowdhuryet al.(1978).Acta Cryst.B34, 1047–1048; Banerjee & Saha (1986).Acta Cryst.C42, 1408–1411]. The structures of the two polymorphs are distinguished by the different geometries of the hydrogen-bonded dimers, which in the crystal of the orthorhombic polymorph possess twofold axis symmetry, with the central N2H2ring adopting a butterfly conformation.

Spontaneous deformation of protocatechuic acid monohydrate crystals: crystallographic aspects

1983 ◽  
Vol 387 (1793) ◽  
pp. 311-330 ◽  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Protocatechuic Acid ◽  
Crystal Structure Analysis ◽  
Stable Phase ◽  
Space Group ◽  
Molecular Arrangement ◽  
Two Phases

Remarkable aspects of the crystallization of 3,4-dihydroxybenzoic acid (protocatechuic acid, PCA) from water as described by R. W. Wood ( Proc. R. Soc. Lond . A 197,283-294 (1949)) are confirmed. This compound crystallizes as the monohydrate in four different polymorphic phases: three are triclinic (oblique needles, needles and rhombs) and belong to one subgroup, while the fourth, monoclinic, phase constitutes a separate subgroup. It is probable that the triclinic rhombs are the stable phase at 25° C, with the other phases monotropically related to it. Crystal data for the triclinic needles are a = 9.926(9), b = 9.532(9), c = 8.131(8)Å, α = 100.8(1), β = 90.7(1), γ = 102.4(1)°, Z = 4, space group P1 - ; and for th e triclinic rhombs a = 12.693(9), b = 8.011(6), c = 8.121(6) Å, α = 72.2(1), β = 108.5(1), γ = 103.2(1)°, Z = 4, space group P1 - . Both crystals can be described in terms of a unit cell containing eight formula units, with dimensions a ≈ 12.7, b ≈ 9.5, c ≈ 13.0 Å, α ≈ 88, β ≈ 101, γ ≈ 107°; the space group for the triclinic needles is B1 - and for the triclinic rhombs A1 - . Crystal structure analyses (four-circle diffractometer, MoKα) of these two phases (triclinic needles, 1287 reflexions used in the final refinement cycle, R F = 11.1%; triclinic rhombs, 1761 reflexions, R F = 6.9%) show that both contain essentially similar layer pairs of PCA and H 2 O molecules, with hydrogen bonding both within each layer and, apparently, between them; however, the stacking of the layer pairs in the two phases differs. The crystals of the oblique needles are so small and unstable to stress that crystal structure analysis was not possible. The crystal structure of the monoclinic needles ( a = 12.32(1), b = 3.64(1), c = 17.60(2) Å, β = 107.7(2)°, Z = 4, space group P2 1 / n was determined (CuK α , 787 reflexions, R F = 6.8%); the overall molecular arrangement differs from that in the triclinic phases in an absence of PCA•H 2 O layers although there are distinct resemblances between the hydrogen bonding schemes. The phase transition ‘oblique needles → triclinic needles’ is ‘single crystal to single crystal’ and is a topotaxic transition. The phase transition ‘triclinic needles → triclinic rhombs’ is ‘single crystal to oriented polycrystal’ and is described as partially topotaxic, there being preservation of layer arrangement but not of complete three-dimensional orientation.

scholarly journals A variable-temperature study of a phase transition in barbituric acid dihydrate

2005 ◽  
Vol 61 (4) ◽  
pp. 464-472 ◽  
Author(s):  
Gary S. Nichol ◽  
William Clegg
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Barbituric Acid ◽  
Crystal Packing ◽  
Variable Temperature ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group

The crystal structure of barbituric acid dihydrate (C4H4N2O3·2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH2 H atoms) lying on the mirror plane [Al-Karaghouli et al. (1977). Acta Cryst. B33, 1655–1660; Jeffrey et al. (1961). Acta Cryst. 14, 881–887]. The present study has found that at low temperatures, below 200 K, the crystal structure is no longer orthorhombic but is non-merohedrally twinned monoclinic, space group P21/n. This phase is stable down to 100 K. Above 220 K the crystal structure is orthorhombic, and between 200 and 220 K the structure undergoes a phase change, with the monoclinic-to-orthorhombic phase transition itself taking place at around 216–217 K. The size of the β angle in the monoclinic structure is temperature dependent; at 100 K β is around 94° and it decreases in magnitude towards 90° as the temperature increases. Although the hydrogen-bonding motifs are the same for both crystal systems, there are significant differences in the crystal packing, in particular the out-of-plane displacement of the two water molecules and the sp 3-hybridized C atom of barbituric acid.

scholarly journals Crystal structure and halogen–hydrogen bonding of a Delépine reaction intermediate

2021 ◽  
Vol 77 (1) ◽  
pp. 1-4
Author(s):  
David Z. T. Mulrooney ◽  
Helge Müller-Bunz ◽  
Tony D. Keene
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Surface Analysis ◽  
Van Der Waals ◽  
Hirshfeld Surface ◽  
Van Der Waals Interactions ◽  
Hirshfeld Surface Analysis ◽  
Space Group ◽  
Molecular Salt

The reaction of 1,5-dibromopentane with urotropine results in crystals of the title molecular salt, 5-bromourotropinium bromide [systematic name: 1-(5-bromopentyl)-3,5,7-triaza-1-azoniatricyclo[3.3.1.13,7]decane bromide], C11H22BrN4 +·Br− (1), crystallizing in space group P21/n. The packing in compound 1 is directed mainly by H...H van der Waals interactions and C—H...Br hydrogen bonds, as revealed by Hirshfeld surface analysis. Comparison with literature examples of alkylurotropinium halides shows that the interactions in 1 are consistent with those in other bromides and simple chloride and iodide species.

scholarly journals Crystal structure of (E)-N′-(4-chlorobenzylidene)-4-methylbenzenesulfonohydrazide: a hexagonal polymorph

2014 ◽  
Vol 70 (12) ◽  
pp. o1250-o1251 ◽  
Author(s):  
J. Balaji ◽  
J. John Francis Xavier ◽  
S. Prabu ◽  
P. Srinivasan
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Acta Cryst ◽  
Triclinic Space Group ◽  
Space Group ◽  
Compound C ◽  
Benzene Rings ◽  
Title Molecule

The title compound, C14H13ClN2O2S, crystallized in the enantiomorphic defining hexagonal space groupP61[Flack parameter = −0.02 (7)]. The partially hydrated form of the same compound, crystallizing in the triclinic space groupP-1, has been reported previously [Kiaet al.(2009b).Acta Cryst.E65, o1119], as has the crystal structure of the bromo derivative, also crystallizing in the space groupP-1 [Kiaet al.(2009a).Acta Cryst.E65, o821]. The title molecule is non-planar with the planes of the benzene rings being inclined to one another by 76.62 (13)°, and has anEconformation about the C=N bond. In the crystal, molecules are linkedviaN—H...O hydrogen bonds forming 61helical chains running along [001]. The chains are linkedviaC—H...O hydrogen bonds, C—H...π interactions and short Cl...O [3.015 (3) Å] interactions, forming a three-dimensional structure.

TheN1-(2′-deoxyribofuranoside) of 3-iodo-5-nitroindole: a universal nucleoside forming nitro–iodo interactions

2009 ◽  
Vol 65 (3) ◽  
pp. o100-o102 ◽  
Author(s):  
Simone Budow ◽  
Peter Leonard ◽  
Henning Eickmeier ◽  
Hans Reuter ◽  
Frank Seela
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Nitro Group ◽  
Hydroxy Group ◽  
Torsion Angle ◽  
Title Compound ◽  
Stacking Interactions ◽  
Sugar Moiety ◽  
Determining Factors

The title compound [systematic name: 1-(2-deoxy-β-D-erythro-pentofuranosyl)-3-iodo-5-nitro-1H-indole], C13H13IN2O5, exhibits anantiglycosylic bond conformation with a χ torsion angle of −114.9 (3)°. The furanose moiety shows a twisted C2′-endosugar pucker (S-type), withP= 141.3° and τm = 40.3°. The orientation of the exocyclic C4′—C5′ bond is +ap(gauche,trans), with a γ torsion angle of 177.4 (2)°. The extended crystal structure is stabilized by hydrogen bonding and I...O contacts, as well as by stacking interactions. The O atoms of the nitro group act as acceptors, forming bifurcated hydrogen bonds within theacplane. Additionally, the iodo substituent forms an interplanar contact with an O atom of the nitro group, and another contact with the O atom of the 5′-hydroxy group of the sugar moiety within theacplane is observed. These contacts can be considered as the structure-determining factors for the molecular packing in the crystal structure.

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