Crystal Structure of Na9[H3W12O42]·24H2O, a Compound Containing the Protonated Paratungstate B Anion ('Acid Paratungstate'), and Cyclic Voltammetry of Acidified [H2W12O42]10- Solutions

1999 ◽  
Vol 52 (10) ◽  
pp. 955 ◽  
Author(s):  
Annette L. Nolan ◽  
Eric N. Wilkes ◽  
Trevor W. Hambley ◽  
Christine C. Allen ◽  
Robert C. Burns ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cyclic Voltammetry ◽  
Hydrogen Atom ◽  
Internal Cavity ◽  
Molecular Orbital Calculations ◽  
Hydrogen Atoms ◽  
Triclinic Space Group ◽  
Electrochemically Active ◽  
Paratungstate B

Crystallization of a solid at pH 4.0 from an aqueous acidified Rh3+–[WO4]2− solution resulted in the isolation of Na9[H3W12O42]·24H 2 O, which contains the protonated paratungstate B anion and which is likely the species identified previously as ‘acid paratungstate’. The compound is triclinic, space group P1– , a 10.603(2), b 12.134(3), c 14.042(3) Å, α 114.78(1), β 101.84(1), γ 108.34(1)˚, V 1432.9(5) Å3 , Z 1, and the structure was solved to an R1 value of 0.0404 (wR 2 0.1108) for 5997 independent observed reflections. The anion exhibits essentially the same isopolytungstate framework as paratungstate B, [H2W12O42]10− , consisting of two W3O13 and two W3O14 structural subunits linked by shared vertices. Bond valence arguments place two of the hydrogen atoms unequivocally in the internal cavity of the anion, with the remaining hydrogen atom also likely located in this cavity, but disordered over several internal oxygen atoms. The protonation of [H2W12O42 ]10− is shown to lead to species that are electrochemically reducible. Extended-HÜckel molecular orbital calculations confirm that protonation of paratungstate B within the internal cavity leads to a change in composition of the LUMO, now based mainly on electrochemically reducible W3O13 as opposed to (essentially) non-reducible W3O14 structural subunits. This results in species that are considerably more electrochemically active than the unprotonated anion. The role of [H3W12O42]9− as an intermediate in the polymerization of [WO4]2− to give the solution form of ψ-metatungstate, [H7W11O40]7− , which crystallizes as [H4W11O38]6− , is also discussed.

scholarly journals Crystal structure of 4-[(1R,2S,5R)-2-isopropyl-5-methylcyclohexyl] 2-methyl (2S,4S,5R)-1-[(2S,3R,5R)-5-methoxycarbonyl-2-(2-methylphenyl)pyrrolidine-3-carbonyl]-5-(2-methylphenyl)pyrrolidine-2,4-dicarboxylate

2019 ◽  
Vol 75 (5) ◽  
pp. 537-539
Author(s):  
Polina M. Ivantcova ◽  
Mikhail N. Sokolov ◽  
Konstantin V. Kudryavtsev ◽  
Andrei V. Churakov
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Atom ◽  
Title Compound ◽  
Carbonyl Oxygen ◽  
Hydrogen Atoms ◽  
Compound C ◽  
Methylene Groups ◽  
Adjacent Molecule ◽  
Amide Fragment

The title compound, C38H50N2O7, represents a chiral β-proline dipeptide. Corresponding stereogenic centres of constituting pyrrolidine units have opposite absolute configurations. The central amide fragment is planar within 0.1 Å and adopts a Z configuration along the N—CO bond. In the crystal, the hydrogen atoms of the methylene groups form several short intermolecular C—H...O contacts with the carbonyl oxygen atoms of an adjacent molecule. The only active amino hydrogen atom is not involved in hydrogen bonding.

scholarly journals Hydrogen atom disorder in the crystal structure of o-phenylenediacetic acid

2020 ◽  
Vol 19 (1) ◽  
pp. 109-115
Author(s):  
Lenka Krešáková ◽  
Juraj Kuchár ◽  
Juraj Černák
Keyword(s):  
Crystal Structure ◽  
Hydrogen Atom ◽  
Hydrogen Bonds ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Molecular Crystal ◽  
Free Acid ◽  
Bulk Sample ◽  
Hydrogen Atoms ◽  
Carboxylate Groups

H2opda (1) (o-phenylenediacetic acid) was prepared in the form of single crystals. It exhibits molecular crystal structure. The main feature of the supramolecular structure of 1 is formation of hydrogen bonded dimers via a pair of O-H×××O hydrogen bonds. The hydrogen atoms in COOH groups are disordered in 0.67(2):0.33(2) ratio. The conformation of the free acid is characterized by cis arrangement of the carboxylate groups with respect to the plane of the aromatic ring. The powder diffraction pattern of the bulk sample corroborated the phase identity of the commercial material with that of the studied single crystal.

Crystallographic studies on neuroleptics of the benzocycloheptapyridoisoquinoline series. The crystal structure of butaclamol hydrobromide and the absolute configuration and crystal structure of dexclamol hydrobromide

1976 ◽  
Vol 54 (17) ◽  
pp. 2715-2722 ◽  
Author(s):  
P. H. Bird ◽  
F. T. Bruderlein ◽  
L. G. Humber
Keyword(s):  
Crystal Structure ◽  
Hydrogen Atom ◽  
Membered Ring ◽  
Axial Position ◽  
Aromatic Rings ◽  
Hydrogen Atoms ◽  
Space Group ◽  
Cell Dimensions ◽  
R Value ◽  
Hydroxy Groups

The compound butaclamol hydrobromide crystallizes in space group P21/c with cell dimensions; a = 14.38(3), b = 13.31(3), c = 12.07(3) Å, β = 101.64(8)°. The structure was solved by Patterson methods and non-hydrogen atoms have been refined isotropically using a full-matrix least-squares to an R value of 0.17 for 779 observed reflections.The compound dexclamol hydrobromide crystallizes in space group P212121 with a = 8.412(2), b = 24.392(7), c = 10.465(2) Å. Refinement of non-hydrogen atoms using isotropic thermal parameters and rigid aromatic rings converted at R = 0.090 using 1249 observed reflections, for the preferred enantiomorph, and R = 0.099 for the other enantiomorph.Both compounds have their hydroxy groups in the axial position, and both adopt conformations of the seven membered ring such that the C13b hydrogen atom experiences a flagpolebowsprit interaction with a hydrogen atom of C9.

Engineering the internal cavity of neuroglobin demonstrates the role of the haem-sliding mechanism

2014 ◽  
Vol 70 (6) ◽  
pp. 1640-1648 ◽  
Author(s):  
G. Avella ◽  
C. Ardiccioni ◽  
A. Scaglione ◽  
T. Moschetti ◽  
C. Rondinelli ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ligand Binding ◽  
Structural Characterization ◽  
Heterogeneous Group ◽  
Internal Cavity ◽  
Intramolecular Coordination ◽  
Cavity Volume ◽  
Sliding Mechanism ◽  
The Brain

Neuroglobin is a member of the globin family involved in neuroprotection; it is primarily expressed in the brain and retina of vertebrates. Neuroglobin belongs to the heterogeneous group of hexacoordinate globins that have evolved in animals, plants and bacteria, endowed with the capability of reversible intramolecular coordination, allowing the binding of small gaseous ligands (O2, NO and CO). In a unique fashion among haemoproteins, ligand-binding events in neuroglobin are dependent on the sliding of the haem itself within a preformed internal cavity, as revealed by the crystal structure of its CO-bound derivative. Point mutants of the neuroglobin internal cavity have been engineered and their functional and structural characterization shows that hindering the haem displacement leads to a decrease in CO affinity, whereas reducing the cavity volume without interfering with haem sliding has negligible functional effects.

An accurate determination of the structure of ammonium oxamate

1963 ◽  
Vol 275 (1363) ◽  
pp. 469-491 ◽  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Atom ◽  
Accurate Determination ◽  
Three Dimensional ◽  
Ammonium Ion ◽  
Intensity Data ◽  
Single Bond ◽  
Hydrogen Atoms ◽  
Librational Motion

The crystal structure of ammonium oxamate (CONH 2 .COONH 4 ) has been studied using Cu Ka X-radiation, by means of a three-circle diffractometer incorporating a xenon-filled proportional counter. Accurate three-dimensional intensity data were collected and a least-squares refinement was carried out. The positions of the hydrogen atoms were obtained and refined. A peak of electron density, about half as high as a hydrogen atom, was observed at the centre of the C—C bond and a correction applied for it increased the length of the bond by 0.003 Å. The bond lengths were corrected for librational motion, and the values obtained are C—C =1.564 ±0.002 Å; C—N = 1.324± 0.002 Å; C—O (amidic) = 1.248± 0.002 A; C— O (carboxylate) = 1.257 + 0.003 Å and 1.256 ± 0.003 Å. The oxamate ion is found to be planar, and the ammonium ion tetrahedral. The length of the C—C bond is greater than any theoretical value yet suggested for the length of a single bond between trigonally hybridized carbons atoms.

scholarly journals Planarversusnon-planar: The important role of weak C—H...O hydrogen bonds in the crystal structure of 5-methylsalicylaldehyde

2017 ◽  
Vol 73 (2) ◽  
pp. 155-158 ◽  
Author(s):  
Ulrich Baisch ◽  
Marie Christine Scicluna ◽  
Christian Näther ◽  
Liana Vella-Zarb
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Aromatic Ring ◽  
Structural Changes ◽  
Intermolecular Hydrogen Bonding ◽  
Hydrogen Atoms ◽  
Methyl Carbon ◽  
Distorted Geometry

The crystal structure of 5-methylsalicylaldehyde (5-MSA; systematic name 2-hydroxy-5-methylbenzaldehyde), C8H8O2, was discovered to be a textbook example of the drastic structural changes caused by just a few weak C—H...O interactions due to the additional methylation of the aromatic ring compared to salicylaldehydeSA. This weak intermolecular hydrogen bonding is observed between aromatic or methyl carbon donor atoms and hydroxyl or aldehyde acceptor oxygen atoms withd(D...A) = 3.4801 (18) and 3.499 (11) Å. The molecule shows a distorted geometry of the aromatic ring with elongated bonds in the vicinity of substituted aldehyde and hydroxyl carbon atoms. The methyl hydrogen atoms are disordered over two sets of sites with occupancies of 0.69 (2) and 0.31 (2).

ChemInform Abstract: Crystal Structure of Na9 [H3W12O42]×24H2O, a Compound Containing the Protonated Paratungstate B Anion (′Acid Paratungstate′), and Cyclic Voltammetry of Acidified [H2W12O42]10- Solutions.

ChemInform ◽  
2010 ◽  
Vol 31 (12) ◽  
pp. no-no
Author(s):  
Annette L. Nolan ◽  
Christine C. Allen ◽  
Robert C. Burns ◽  
Geoffrey A. Lawrance ◽  
Eric N. Wilkes ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cyclic Voltammetry ◽  
Paratungstate B

scholarly journals Synthesis, Crystal Structure, Density Functional Theory (DFT) Calculations and Molecular Orbital Calculations of 4-Bromoanilinium Perchlorate Single Crystal

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1070
Author(s):  
Mir Waqas Alam ◽  
Mohd Farhan ◽  
Basma Souayeh ◽  
Muhammad Aamir ◽  
Muhammad Shuaib Khan
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Aromatic Ring ◽  
Molecular Orbital ◽  
Density Functional ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Chemical Calculation ◽  
Hydrogen Atoms ◽  
Hydrogen Bond Interactions

The non-covalent interactions have an extensive impact on the physical, chemical and biological activity of materials. A new anilinium derivative, 4-bromoanilinium perchlorate (4BAP), has been synthesized, and its structure was determined by single-crystal X-ray diffraction analysis. The quantum chemical calculation tools are implemented to explore the electronic and structural properties of 4BAP. The lattice parameters of the crystal structure are a = 5.0752 (8), b = 7.0540 (11), c = 13.5360 (2) Å, α = 91.073 (5)°, β = 90.991 (5)° and γ = 105.052 (5)°, with 2 molecules per unit cell (Z = 2). In the crystal structure of 4BAP, N-H⋯O hydrogen bond interactions dominate. Along the b-axis, the molecules strongly interact through N1-H3⋯O4 hydrogen bonds, and the hydrogen bonding links the molecules into extended chains running along the b-axis. The more delocalized electrons around the aromatic ring may influence the nonlinear activity of the materials. NBO results suggested more electron delocalization around the aromatic ring, which suggests that the title molecule could be used for nonlinear optical applications. The feasible reactivity tendency was determined from the frontier molecular orbital (FMO) analysis. The H...H interactions account for 9.8% of the surface area, and the crystal structure can accommodate a higher fraction of hydrogen atoms. The calculated values of dipole moment, polarizability and first-order hyperpolarizability are 13.5028 D, 20.504 × 10−24 esu and 2.1218 × 10−30 esu, respectively.

scholarly journals Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

2018 ◽  
Vol 14 ◽  
pp. 838-848 ◽  
Author(s):  
Elias Christoforides ◽  
Andreas Papaioannou ◽  
Kostas Bethanis
Keyword(s):  
Crystal Structure ◽  
Inclusion Complex ◽  
Mammalian Cells ◽  
Inclusion Compound ◽  
Physicochemical Characterization ◽  
Md Simulations ◽  
Cholesterol Removal ◽  
Triclinic Space Group

The role of beta-cyclodextrin (β-CD) in cholesterol removal primarily from mammalian cells and secondly from dairy products has been studied thoroughly in recent years. Although the physicochemical characterization of the inclusion compound of cholesterol in β-CD has been achieved by various methods, no crystal structure has been determined so far. We report here the crystal structure of the inclusion compound of cholesterol in β-CD. The inclusion complex crystallizes in the triclinic space group P1 forming head-to-head dimers which are stacked along the c-axis. One well-defined cholesterol molecule ‘axially’ encapsulated inside the β-CD dimer and 22 water molecules that stabilize the complexes in the crystalline state comprise the asymmetric unit of the structure. The dimers are arranged in an intermediate (IM) channel packing mode in the crystal. Moreover, MD simulations, at 300 and 340 K, based on the crystallographically determined coordinates of the complex show that the formed cholesterol/β-CD inclusion compound remains very stable in aqueous solution at both temperatures.

scholarly journals The role of a cholesta-8,14-dien-3β-ol system in cholesterol biosynthesis

1969 ◽  
Vol 111 (5) ◽  
pp. 757-761 ◽  
Author(s):  
M. Akhtar ◽  
I. A. Watkinson ◽  
A. D. Rahimtula ◽  
D. C. Wilton ◽  
K. A. Munday
Keyword(s):  
Hydrogen Atom ◽  
Cholesterol Biosynthesis ◽  
Tritiated Water ◽  
Mevalonic Acid ◽  
Hydrogen Atoms ◽  
Steroid Biosynthesis ◽  
Methyl Group

The biosynthesis of cholesterol from squalene and tritiated water is described. Degradation of the cholesterol indicated that C-15 may be involved in cholesterol biosynthesis. In accordance with this view it is shown that in the conversion of [2RS−3H2]mevalonic acid into cholesterol one of the hydrogen atoms at C-15 is removed. A mechanism for the removal of the 14α-methyl group in steroid biosynthesis that involves the labilization of a C-15 hydrogen atom is outlined. In accordance with the requirement of this scheme it is shown that 4,4′-dimethyl-cholesta-8,14-dien-3β-ol is converted into cholesterol.

Sign in / Sign up

Export Citation Format

Share Document