Benzene-1,2-disulfonate dianion: another compound with meshed cogwheel substituents?

1996 ◽  
Vol 52 (3) ◽  
pp. 562-568 ◽  
Author(s):  
N. Nagel ◽  
P. Eller ◽  
H. Bock
Keyword(s):  
Crystal Structures ◽  
Disulfonic Acid ◽  
Conformational Isomerization ◽  
Tetramethylammonium Salts

Crystal structures of the dipotassium and potassium tetramethylammonium salts of benzene-1,2-disulfonic acid have been determined at 200 K and a PM3 enthalpy hypersurface for the substituent rotations of the free benzene-1,2-disulfonate dianion was calculated. The cogging of the two sulfonate groups as well as the possible pathways of conformational isomerization are discussed and compared with already investigated molecules containing adjacent threefold substituents.

Crystal Structures of Two Salts from Piperidine, Naphthalene-1,5-Disulfonic Acid, and 4-Nitrophthalic Acid

2015 ◽  
Vol 46 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Shouwen Jin ◽  
Chao Feng ◽  
Xianhong Wen ◽  
Daqi Wang
Keyword(s):  
Crystal Structures ◽  
Disulfonic Acid

Syntheses, characterization, and crystal structures of the tetramethylammonium salts of the novel weakly coordinating anions [MeCO2{B(C6F5)3}]– and [MeCO2{B(C6F5)3}2]–

2006 ◽  
Vol 84 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Simona Mitu ◽  
Michael C Baird
Keyword(s):  
Crystal Structures ◽  
The Novel ◽  
Carbocationic Polymerization ◽  
Weakly Coordinating Anions ◽  
Weakly Coordinating ◽  
Tetramethylammonium Salts

The novel compounds [Me4N][MeCO2{B(C6F5)3}] and [Me4N][MeCO2{B(C6F5)3}2] are prepared and characterized spectroscopically and crystallographically. The compounds are salts of the unisolable acids MeCO2H·B(C6F5)3 and MeCO2H·2B(C6F5)3, respectively, which are sufficiently strong that they can protonate isobutene and initiate its carbocationic polymerization. The 1:1 adduct contains a conventional, monodentate acetate ion coordinated to the B(C6F5)3, while the 2:1 adduct contains a bridging acetate ligand.Key words: weakly coordinating anions, carbocationic polymerization, isobutene, polyisobutene.

scholarly journals Crystal structures of human soluble adenylyl cyclase reveal mechanisms of catalysis and of its activation through bicarbonate

2014 ◽  
Vol 111 (10) ◽  
pp. 3727-3732 ◽  
Author(s):  
Silke Kleinboelting ◽  
Ana Diaz ◽  
Sebastien Moniot ◽  
Joop van den Heuvel ◽  
Michael Weyand ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Metabolic Regulation ◽  
Disulfonic Acid ◽  
Side Chain ◽  
Adenylyl Cyclases ◽  
Cellular Functions ◽  
Sperm Activation ◽  
Catalytic Domains ◽  
Substrate Analog ◽  
Cation Sites

cAMP is an evolutionary conserved, prototypic second messenger regulating numerous cellular functions. In mammals, cAMP is synthesized by one of 10 homologous adenylyl cyclases (ACs): nine transmembrane enzymes and one soluble AC (sAC). Among these, only sAC is directly activated by bicarbonate (HCO3−); it thereby serves as a cellular sensor for HCO3−, carbon dioxide (CO2), and pH in physiological functions, such as sperm activation, aqueous humor formation, and metabolic regulation. Here, we describe crystal structures of human sAC catalytic domains in the apo state and in complex with substrate analog, products, and regulators. The activator HCO3− binds adjacent to Arg176, which acts as a switch that enables formation of the catalytic cation sites. An anionic inhibitor, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid, inhibits sAC through binding to the active site entrance, which blocks HCO3− activation through steric hindrance and trapping of the Arg176 side chain. Finally, product complexes reveal small, local rearrangements that facilitate catalysis. Our results provide a molecular mechanism for sAC catalysis and cellular HCO3− sensing and a basis for targeting this system with drugs.

The synthesis and X-ray crystal structures of rare earth(III) perfluoroadipate complexes — Novel coordination polymers

2009 ◽  
Vol 87 (1) ◽  
pp. 121-133 ◽  
Author(s):  
Glen B Deacon ◽  
Winfried Elgersma ◽  
Rita Harika ◽  
Peter C Junk ◽  
Brian W Skelton ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Mixed Ligand Complex ◽  
Disulfonic Acid ◽  
Inorganic Polymers ◽  
Two Dimensional ◽  
Ligand Complex ◽  
X Ray ◽  
Carboxylate Oxygen ◽  
Water Ligands ◽  
Oxygen Atoms

A representative series of polymeric hydrated lanthanoid perfluoroadipates [Ln2(pfad)3(H2O)n]·mH2O (Ln = La, Ce, Nd, Gd, Yb) has been prepared from the reaction of perfluoroadipic acid with either the appropriate lanthanoid oxide or Ce2(CO3)3 in water. X-ray crystal structures showed [Ln2(pfad)3(H2O)10]·4H2O (La, Nd) to be two-dimensional inorganic polymers, which contain nine-coordinate Ln atoms to which are attached five water molecules and four carboxylate oxygen atoms. Two pfad ligands bridge two Ln atoms through one carboxylate group, the other being free, whilst one pfad ligand bridges four Ln atoms in a µ4-(η1,η1/η1,η1) manner. In two-dimensional polymeric [Yb2(pfad)2(H2O)8](pfad)·6H2O, each eight-coordinate ytterbium atom has four water ligands and four carboxylate oxygen donor atoms. The two carboxylate ligands bind in a µ4-(η1,η1/η1,η1) manner, and there is one pfad counter-ion per two ytterbium atoms. These structures show features quite different from those of many lanthanoid adipate complexes [Ln2(ad)3(H2O)n]·mH2O, but there is no F-Ln coordination. From the reaction of [Nd2(pfad)3(H2O)10]·4H2O with benzene-1,2-disulfonic acid (H2bds), the mixed ligand complex [Nd2(bds)2(pfad)(H2O)8] was isolated. This is a one-dimensional polymer featuring Nd2(bds)2 units linked together by µ-η2,η2 pfad ligands. Each Nd atom is nine-coordinate with three sulfonate oxygen donors, two carboxylate oxygen atoms, and four water ligands, and the bds ligands bind in the new µ-η2(O,O′),η1(O′′) manner for Ln complexes. Surprisingly, [Na2pfad] was isolated unhydrated from water, the six-coordinate Na atoms being coordinated by four carboxylate oxygen atoms and two (C)-F atoms in an octahedral array. The ligands are duodecadentate, each –CF2CO2 unit binding to five different sodium ions through four oxygen and one α-F atom with the second α-F atom bound to a sodium ion in a OC(O)CF-Na chelate ring.Key words: rare earths, lanthanoid, X-ray crystal structures, adipates, carboxylates.

Pollutant Identification by Selected Area Electron Diffraction

1974 ◽  
Vol 32 ◽  
pp. 532-533
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson ◽  
C. W. Walker
Keyword(s):  
Thermal Treatment ◽  
Electron Diffraction ◽  
Sample Preparation ◽  
Crystal Structures ◽  
Water Samples ◽  
Environmental Samples ◽  
Short Review ◽  
Selected Area Electron Diffraction ◽  
Multiple Component

Selected area electron diffraction (SAD) has been used successfully to determine crystal structures, identify traces of minerals in rocks, and characterize the phases formed during thermal treatment of micron-sized particles. There is an increased interest in the method because it has the potential capability of identifying micron-sized pollutants in air and water samples. This paper is a short review of the theory behind SAD and a discussion of the sample preparation employed for the analysis of multiple component environmental samples.

The Imaging of Crystal Structures and Crystal Defects

1978 ◽  
Vol 36 (3) ◽  
pp. 207-217
Author(s):  
J.M. Cowley
Keyword(s):  
Electron Microscope ◽  
Crystal Structures ◽  
Phase Contrast ◽  
Crystal Defects ◽  
Atom Density ◽  
Lack Of Information ◽  
Spatial Frequencies

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

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