Lewis-Base Adducts of Lead(II) Compounds. XXI. Revisitations: Synthesis and Structure of the Hydrated 1 : 2 Adduct of Lead(II) Bis(perchlorate) and 2,4,6-Tris(2-pyridyl)-1,3,5-triazine and a Low-Temperature Redetermination of the Structure of Bis(2-aminLewis-Base Adducts of Lead(II) Compounds

2002 ◽  
Vol 55 (10) ◽  
pp. 661 ◽  
Author(s):  
J. M. Harrowfield ◽  
H. Miyamae ◽  
B. W. Skelton ◽  
A. A. Soudi ◽  
A. H. White
Keyword(s):  
Low Temperature ◽  
Structure Determination ◽  
Aqueous Ethanol ◽  
Lewis Base ◽  
Asymmetric Unit ◽  
Nitrate Complex ◽  
X Ray ◽  
Perchlorate Ion ◽  
Crystallographic Symmetry ◽  
Independent Molecules

Lead(II) perchlorate crystallizes from aqueous ethanol with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (trz) as a 1 : 2 trihydrate adduct, [(trz)2Pb(OH2)(O2ClO2)](ClO4)�2H2O, as has been confirmed by a low temperature (ca .153 K) single crystal X-ray structure determination. The lead(II) environment is derivative of that of the previously recorded hydrated (rather than the methanol solvated) nitrate complex, comprising a pair of tridentate trz ligands, and, in place of the pair of bidentate nitrates, a unidentate water and an unsymmetrically bidentate perchlorate ion. A redetermination of the structure of bis(2-aminomethylpyridine)lead(II) bis(perchlorate) has resulted in a non-disordered model, still based upon the [Pb(amp)2(OClO3)2] entity, where amp = 2-aminomethylpyridine, but with eight independent molecules, devoid of any crystallographic symmetry, comprising the asymmetric unit of the structure, which is described in a larger unit cell of lower symmetry.

4,4′-Bithiazoles as Ligands: Crystal and Molecular Structure of bis(O,O′-Nitrato)(2,2′-diphenyl-4,4′-bithiazole)copper(II) (Two Polymorphs)

2003 ◽  
Vol 56 (9) ◽  
pp. 949 ◽  
Author(s):  
S. Ali Asghar Torabi ◽  
Fahimeh Jamali ◽  
George A. Koutsantonis ◽  
Ali Morsali ◽  
Brian W. Skelton ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Low Temperature ◽  
Molecular Complex ◽  
Structure Determination ◽  
Crystal And Molecular Structure ◽  
Plane Angle ◽  
Asymmetric Unit ◽  
X Ray ◽  
Crystallographic Symmetry

A low-temperature single-crystal X-ray structure determination of the 1 : 1 adduct of copper(II) nitrate with 2,2′-diphenyl-4,4′-bithiazole (L) shows it to be a molecular complex with L behaving as a symmetrical N,N′ chelate, and the nitrate groups as unsymmetrical O,O′ chelates: [LCu(O2NO)2]. Two polymorphs, both monoclinic P21/c, have been obtained from acetonitrile (‘α’) and methanol (‘β’), respectively, with one molecule, devoid of crystallographic symmetry, in the asymmetric unit of each structure. The copper environments are distorted planar four-coordinate, cis-N2CuO2 (Cu–N 2.011(1), 1.973(1), Cu–O 1.995(1), 1.962(1) Å), ‘in-plane’ angle sum Σ 369.5°, with longer trans, axial contacts (Cu–O 2.455(1), 2.458(2) Å) for the α-form; respective values are 1.995(5), 1.991(4), 1.997(4), 1.973(3) Å, 360.4°, 2.500(4), and 2.396(4) Å for the β-form.

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXI. The 1 : 1 Adducts of the Copper(I) Halides (Cl, Br, I) With Bis(2-diphenylphosphinoethyl)phenylphosphine, 'triphos'

1991 ◽  
Vol 44 (7) ◽  
pp. 919 ◽  
Author(s):  
RD Hart ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Structure Determination ◽  
Copper Atom ◽  
Phosphorus Atom ◽  
Lewis Base ◽  
The Other ◽  
Asymmetric Unit ◽  
X Ray

The 1 : 1 adducts between the copper(I) halides, CuX , X = Cl , Br, I, and the title ligand, 'triphos', Ph2P(CH2)2P(Ph)(CH2)2PPh2, have been synthesized and characterized by single-crystal X-ray structure determination. The three complexes are isomorphous : monoclinic P21/c, a ≈ 14.5, b ≈ 20.5, c ≈ 24.5 Ǻ, β ≈ 118.5°; the asymmetric unit of each structure is the binuclear [Cu2X2( triphos )2] unit (with one acetonitrile solvate). Residuals were 0.047, 0.049 and 0.065 for 6006, 4832 and 5108 'observed', independent reflections respectively. About each copper atom, the four-coordinate environment comprises a terminal halogen [Cu- Cl,Br,I , 2.305(3), 2.311(2); 2.441(2), 2.443(2); 2.614(2), 2.614(2)Ǻ], two phosphorus atoms (central and distal) from the same ligand , and one distal phosphorus atom from the other ligand.

Constituents of Millingtonia hortensis: Isolation and Crystal Structure of trans-1-(2'-Hydroxyethyl)cyclohexane-1,4-diol

1989 ◽  
Vol 42 (8) ◽  
pp. 1397 ◽  
Author(s):  
K Naowsaran ◽  
BW Skelton ◽  
U Tooptakong ◽  
P Tuntiwachwuttikul ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Determination ◽  
Chair Conformation ◽  
Cyclohexane Ring ◽  
Asymmetric Unit ◽  
X Ray ◽  
Independent Molecules

The isolation of trans-1-(2'-hydroxyethyl)cyclohexane-1,4-diol from the flowers of Millingtonia hortensis and its characterization, including a single-crystal X-ray structure determination at 295 K, is described. Crystals are triclinic, P1, a 12.348(5), b 11 .390(5), c 6.575(3) � , α 112.16(3), β 90.79(4), γ°, Z 4. R was 0.045 for 1475 independent 'observed', diffractometer reflections. In the two independent molecules of the asymmetric unit, the cyclohexane ring is in the usual 'chair' conformation with the ring hydroxy substituents occupying axial positions. The hydroxyethyl groups, however, adopt different orientations in the two molecules.

Sur la structure cristalline des dimethyl-1,1 germa-1 (et sila-1) cycloundécanediols-6,7

1975 ◽  
Vol 53 (23) ◽  
pp. 3596-3598 ◽  
Author(s):  
François Brisse ◽  
Aviva Battat ◽  
Jean-Claude Richer ◽  
Pierre Mazerolles ◽  
Alfreda Faucher
Keyword(s):  
Asymmetric Unit ◽  
Space Group ◽  
X Ray ◽  
Independent Molecules

1,1-Dimethyl-1-germa (and-1-sila) -6,7-cycloundecanediol (C12H26O2Ge and C12H26O2Si) are isostructural as established by their X-ray powder patterns. The dimensions of the triclinic cells are as follows: for the silicon derivative, a = 10.53, b = 12.45, and c = 12.43 Å, α = 81.5°, β = 67.0°, and γ = 76.3°; for the germanium derivative, a = 10.56, b = 12.50, and c = 12.58 Å, α = 82.1°, β = 67.8°, and γ = 76.1°. If the space group is [Formula: see text] there will be two independent molecules in each asymmetric unit.

scholarly journals Structures of mono-unsaturated triacylglycerols. IV. The highest melting β′-2 polymorphs of trans-mono-unsaturated triacylglycerols and related saturated TAGs and their polymorphic stability

2008 ◽  
Vol 64 (2) ◽  
pp. 249-259 ◽  
Author(s):  
Jan B. van Mechelen ◽  
Rene Peschar ◽  
Henk Schenk
Keyword(s):  
Powder Diffraction Data ◽  
Asymmetric Unit ◽  
Double Chain ◽  
Molecular Conformations ◽  
X Ray ◽  
Acyl Chains ◽  
Independent Molecules ◽  
The Difference ◽  
Polymorphic Stability ◽  
Prime 2

The β_1^{\prime}-2 crystal structures of a series of mixed-chain saturated and trans-mono-unsaturated triacylglycerols containing palmitoyl, stearoyl and elaidoyl acyl chains have been solved from high-resolution powder diffraction data, from synchrotron as well as laboratory X-ray sources. The structures crystallized in the space group I2 with two independent molecules forming a dimer in the asymmetric unit, and packed in double-chain length layers. Unlike the corresponding β-2 structures the solved β_1^{\prime}-2 structures have different molecular conformations for the symmetric and the asymmetric mixed triacylglycerols, both with the sn-2 chain in a leg position of the chair-shaped conformation. A transformation to the β-2 structure with the sn-2 chain in the back position is complicated and unlikely to take place in the solid state. A novel β′-2 polymorph of PSS has been crystallized and its structure has been solved. The melting point (239 K) of this so-called β_0^{\prime}-2 polymorph is 2 K above that of the β_1^{\prime}-2 polymorph and almost equal to that of the β-2 polymorph of PSS. The difference in packing of the β_0^{\prime}-2 versus β_1^{\prime}-2 structure explains the slow β_1^{\prime}-2 to β_0^{\prime}-2 phase transition. The transition is strikingly similar to the β2-3 to β1-3 transition in cis-mono-unsaturated triacylglycerols.

Crystal Structures of Seven Terephthaldiamide Derivatives

2002 ◽  
Vol 57 (8) ◽  
pp. 914-921 ◽  
Author(s):  
P. G. Jones ◽  
J. Ossowski ◽  
P. Kus
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Layer Structure ◽  
Inversion Symmetry ◽  
Asymmetric Unit ◽  
X Ray ◽  
Layer Structures ◽  
Structure Determinations ◽  
Independent Molecules

N,N′-Dibutyl-terephthaldiamide (1), N,N′-dihexyl-terephthaldiamide (2), N,N′-di(tert-butyl)- terephthaldiamide (3), N,N,N′,N′-tetrabutyl-terephthaldiamide (4), 1,1′-terephthaloylbis- pyrrolidine (5), 1,1′-terephthaloyl-bis-piperidine (6), and 4,4′-terephthaloyl-bis-morpholine (7) have been synthesised and physicochemically characterised. The X-ray structure determinations reveal imposed inversion symmetry for compounds 1-6; compound 3 has two independent molecules with inversion symmetry in the asymmetric unit. Compounds 1-3 form classical hydrogen bonds of the type N-H···O=C, leading to a ribbon-like arrangement of molecules (1 and 2) or a layer structure (3). Compound 3 also displays a very short C-H···O interaction, a type of hydrogen bond that is also observed in compounds 4-7, which lack classical donors; thereby compounds 4-6 form layer structures and 7 a complex threedimensional network.

Kristallstrukturen der selenid- bzw. sulfidverbrückten Gold(I)verbindungen [Se(AuPPh3)+3]PF6- und [S(AuPPh3)2] · CH2Cl2/Crystal Structures of the Selenide- and Sulphide-Bridged Gold(I) Complexes [Se(AuPPh3)3]+PF6- and [S(AuPPh3)2] · CH2Cl2

1982 ◽  
Vol 37 (8) ◽  
pp. 944-949 ◽  
Author(s):  
Cornelia Lensch ◽  
Peter G. Jones ◽  
George M. Sheldrick
Keyword(s):  
Crystal Structures ◽  
Structure Determination ◽  
Asymmetric Unit ◽  
Light Atom ◽  
X Ray ◽  
Ray Methods

Abstract The Compound [S(AUPPh3)2] · CH2Cl2 was prepared from Ph3PAuCl and H2S in CH2Cl2 and characterised by X-ray structure determination [P21/c, a = 1851.6(4), b = 2225.1(6), c = 880.3(2) pm, β = 96.32(1)°, Z = 4, R = 0.053]. A constrained refinement of the light atom positions was necessary because of pseudosymmetry. Ph3PAuPF6 reacts with Se(Sn)(CH3)3)2 to give [Se(AuPPh3)3]+PF6- which was also characterised by X-ray methods [P1̄, a = 1539.5(6), b = 1800.5(7), c = 2289.5(9) pm, α = 89.35(3), β = 72.44(3), γ = 69.75(3)°, Z = 4, R = 0.061]. There are two formula units in the asymmetric unit. Both structures show short Au···Au contacts (ca. 300-340 pm).

On the Origin of the Red Color of Aqueous-Solutions of 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone (ddq). Crystal Structure of the Ammonium Salt of 2-Cyano-5,6-Dichloro-3-Hydroxy-1,4-Benzoquinone

1987 ◽  
Vol 40 (3) ◽  
pp. 625 ◽  
Author(s):  
HD Becker ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Aqueous Solutions ◽  
Single Crystal ◽  
Ammonium Salt ◽  
Structure Determination ◽  
Aqueous Ethanol ◽  
X Ray ◽  
Red Color ◽  
Hydrolysis Of

Hydrolysis of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in aqueous ethanol gives the deep-red coloured ammonium salt of a monocyano-dichloro-monohydroxy-benzoquinone which crystallizes in the tetragonal space group I41 /a, a 20.832(5), c 8.618(2) �, Z 16. Single-crystal X-ray structure determination (R 0.036 for 1185 'observed' reflections) show the presence of ammonium cations forming hydrogen bonds in the lattice alternatingly with the tautomeric anion of 2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone and 3-cyano-5,6-dichloro-4-hydroxy-1,2-benzoquinone.

scholarly journals Diosgenone: a secondP21polymorph

2012 ◽  
Vol 68 (8) ◽  
pp. o2358-o2358 ◽  
Author(s):  
María-Guadalupe Hernández Linares ◽  
Gabriel Guerrero-Luna ◽  
Sylvain Bernès ◽  
Marcos Flores-Alamo ◽  
María A. Fernández-Herrera
Keyword(s):  
Relative Orientation ◽  
Asymmetric Unit ◽  
Space Group ◽  
X Ray ◽  
Therapeutic Alternative ◽  
Structure Report ◽  
Independent Molecules

Diosgenone [(20S,22R,25R)-spirost-4-en-3-one, C27H40O3] has been proposed as a new therapeutic alternative for the treatment of malaria. The first X-ray structure report for diosgenone was by Piroet al.[(2002).Z. Naturforsch. Teil C,57, 947–950] in the space groupP21(Z′ = 2). We now report a new polymorph in the same space group, with two molecules in the asymmetric unit. Both molecules have similar conformations, characterized by a skewed envelopeAring, which contains the C=C bond conjugated with the ketone functionality at C3. The dimorphism results from a modification of the relative orientation of the molecules in the asymmetric unit: two independent molecules were arranged antiparallel in the Piro report, while they are parallel in the present determination.

3(5),4-Dimethyl- and 3,4,5-trimethylpyrazole at 200 K. X-ray crystallography and quantum-chemical analysis

1999 ◽  
Vol 55 (3) ◽  
pp. 441-447 ◽  
Author(s):  
Lourdes Infantes ◽  
Concepción Foces-Foces ◽  
Jose Elguero
Keyword(s):  
Quantum Chemical ◽  
Molecular Structures ◽  
Asymmetric Unit ◽  
Quantum Chemical Analysis ◽  
X Ray ◽  
X Ray Crystallography ◽  
Crystal And Molecular Structures ◽  
Unit Form ◽  
Proton Disorder ◽  
Independent Molecules

The crystal and molecular structures of 3(5),4-dimethylpyrazole, C5H8N2, (I), and of 3,4,5-trimethylpyrazole, C6H10N2, (II), have been determined at 200 K. In (I) the 4,5-dimethylpyrazole tautomer is present in the solid state and the six independent molecules in the asymmetric unit form trimers via NH...N hydrogen bonds related by a pseudo centre of symmetry. The asymmetric unit of (II) contains one and a half molecules: these exhibit NH proton disorder and are hydrogen bonded to each other via their respective NH groups to form chains. Ab initio calculations at HF and B3LYP/6-31G** levels indicate that the 3,4-dimethylpyrazole tautomer is more stable than the 4,5-dimethylpyrazole tautomer by only approximately 0.5  kcal  mol−1 (1 kcal mol−1 = 4.184 kJ mol−1).

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