The hexachloroferrate(III) anion stabilized in hydrogen bonded packing arrangements. A comparison of the X-ray crystal structures and low temperature magnetism of tetrakis (methylammonium) hexachloroferrate (III) chloride (I) and tetrakis (hexamethylenediammonium) hexachloroferrate (III) tetrachloroferrate (III) tetrachloride (II)

1996 ◽  
Vol 247 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Bruce D. James ◽  
Margarita Bakalova ◽  
John Liesegang ◽  
William M. Reiff ◽  
David C.R. Hockless ◽  
...  
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
X Ray ◽  
Hydrogen Bonded

The Through-Bond Interaction of a Sulfur Lone Pair with Oxygenated Substituents in the Thiacyclohexane Framework

2005 ◽  
Vol 58 (7) ◽  
pp. 531
Author(s):  
Laura Andrau ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
Bond Distance ◽  
Lone Pair ◽  
X Ray ◽  
Ester Derivative ◽  
Bond Interaction ◽  
Derivatives Of ◽  
Electron Demand

Low-temperature X-ray crystal structures were determined on a range of derivatives of 4-thiacyclohexanol 5a of varying electron demand with a view to finding evidence for a through-bond interaction between the sulfur lone pair and the oxygenated substituent. In contrast to earlier suggestions, plots of C–OR bond distance versus pKa (ROH) showed that any interaction between the sulfur and the OR group is unlikely to be of a through-bond origin. Furthermore, unimolecular solvolysis rate measurements on the nosylate ester derivative 5g showed that the sulfur actually retards the reaction slightly in comparison with the corresponding sulfur-free analogue 6.

Synthesis and X-ray crystal structures of dinuclear hydrogen-bonded cadmium and lead 2-aminoethanethiolates

Polyhedron ◽  
2005 ◽  
Vol 24 (8) ◽  
pp. 865-871 ◽  
Author(s):  
Mohan S. Bharara ◽  
Chong H. Kim ◽  
Sean Parkin ◽  
David A. Atwood
Keyword(s):  
Crystal Structures ◽  
X Ray ◽  
Cadmium And Lead ◽  
Hydrogen Bonded

Metal Phenoxyalkanoic Acid Interactions. XXV. The Crystal Structures of (2-Formyl-6-Methoxyphenoxy)Acetic Acid and Its Zinc(II) Complex and the Lithium, Zinc(II) and Cadmium(II) Complexes of (2-Chlorophenoxy)Acetic Acid

1987 ◽  
Vol 40 (7) ◽  
pp. 1147 ◽  
Author(s):  
EJ Oreilly ◽  
G Smith ◽  
CHL Kennard ◽  
TCW Mak
Keyword(s):  
Acetic Acid ◽  
Crystal Structures ◽  
Free Acid ◽  
Rotational Symmetry ◽  
Carboxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Third ◽  
Planar Complex ◽  
Hydrogen Bonded

The crystal structures of (2-formyl-6-methoxyphenoxy)acetic acid (1), diaquabis [(2-formyl-6-methoxyphenoxy) acetato ]zinc(11) (2), tetraaquabis [(2-chlorophenoxy) acetato ]zinc(11) (3), triaquabis [(2-chlorophenoxy) acetato ]cadmium(11) dihydrate (4) and lithium (2-chloro- phenoxy )acetate 1.5 hydrate (5) have been determined by X-ray diffraction. The acid (1) forms centrosymmetric hydrogen-bonded cyclic dimers [O…0, 2.677(6) �] which are non-planar. Complex (2) is six-coordinate with two waters [Zn- Ow , 1.997(2) �] and four oxygens from two asymmetric bidentate carboxyl groups [Zn-O, 2.073, 2.381(2) �] completing a skew trapezoidal bipyramidal stereochemistry. Complex (5) is also six-coordinate but is octahedral, with two trans-related unidentate carboxyl oxygens [mean Zn-O, 2.134(9) �] and four waters [mean Zn-O, 2.081(9) �]. The seven-coordinate complex (4) has crystallographic twofold rotational symmetry relating two :symmetric bidentate acid ligands [ Cd -O, 2.26, 2 48(:) �] and two waters [ Cd -O, 2.34(2) �] while the third water lies on this axis [ Cd -O, 2.27(2) �]. In contrast to the monomers (2)-(4), complex (5) is polymeric with tetrahedral lithium coordinated to one water and three carboxylate oxygens [mean Li-0, 1.95(1) �]. The essential conformation of the free acid is retained in complexes (2), (3) and (4) but in (5), it is considerably changed.

Dimethyl-, Disilyl- and Digermylsulfide: Different Intermolecular Contacts in the Solid State

2004 ◽  
Vol 59 (6) ◽  
pp. 635-638 ◽  
Author(s):  
Norbert W. Mitzel ◽  
Udo Losehand
Keyword(s):  
Solid State ◽  
Low Temperature ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermolecular Contacts

The compounds (H3C)2S, (H3Si)2S and (H3Ge)2S have been crystallised in situ on a diffractometer and their crystal structures determined by low-temperature X-ray diffraction. The molecules are present as monomers in the crystals. The aggregation of the molecules through secondary intermolecular contacts in the crystal is different: (H3C)2S is weakly associated into dimers by S···S contacts, whereas (H3Si)2S and (H3Ge)2S form Si···S and Ge···S contacts in an ice-analogous aggregation motif. Important geometry parameters are (H3C)2S: C-S 1.794(av) Å , C-S-C 99.2(1)°; (H3Si)2S: Si- S 2.143(1) Å , Si-S-Si 98.4°; (H3Ge)2S Ge-S 2.223(2) and 2.230(2) Å , Ge-S-Ge 98.2(1)◦.

Thermal expansion of β-succinic acid and α-adipic acid in relation to their crystal structures

1965 ◽  
Vol 285 (1402) ◽  
pp. 370-381 ◽  
Keyword(s):  
Thermal Expansion ◽  
Succinic Acid ◽  
Crystal Structures ◽  
Adipic Acid ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Molecular Packing ◽  
X Ray ◽  
Angular Vibration ◽  
Hydrogen Bonded

The thermal expansion quadrics of β -succinic acid and α -adipic acid have been determined by X-ray Weissenberg method. In adipic acid, X-ray measurements have been made between —100 and +100°C and in succinic acid between —150 and +130°C. In these monoclinic crystals, the minimum expansion corresponds to the c axis, which coincides with the direction of the hydrogen-bonded molecular columns. In other directions along which van der Waals forces prevail, thermal expansion is greater, being maximum perpendicular to the (100) planes, the direction of the obtuse bisectrix of the molecular packing angle. The thermal expansion is quantitatively explained by assuming an increase in the angular vibration of the molecules.

Crystal structures of the flavonoid Oroxylin A and the regioisomers Negletein and Wogonin

2020 ◽  
Vol 76 (5) ◽  
pp. 490-499
Author(s):  
Ruel Valerio Robles De Grano ◽  
Elena V. Vashchenko ◽  
Madiha Nisar ◽  
Herman H.-Y. Sung ◽  
Valerii V. Vashchenko ◽  
...  
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
Pharmaceutical Formulation ◽  
Oroxylin A ◽  
X Ray ◽  
First Time

The flavonoid Oroxylin A (6-methoxychrysin or 5,7-dihydroxy-6-methoxy-2-phenyl-4H-chromen-4-one, C16H12O5) and its regioisomers are of increasing interest for a variety of bioactive functions and their pharmaceutical formulation is of importance. Previous difficulties in the separation and misidentification of Oroxylin A from its regioisomers Wogonin (8-methoxychrysin or 5,7-dihydroxy-8-methoxy-2-phenyl-4H-chromen-4-one) and Negletein (5,6-dihydroxy-7-methoxyflavone or 5,6-dihydroxy-7-methoxy-2-phenyl-4H-chromen-4-one) render its full structural and powder X-ray characterization highly desirable. The low-temperature (100 K) crystal structures of Oroxylin A, Negletein and Wogonin sesquihydrate are reported for the first time. Wogonin crystallizes in two related but distinct hydrated forms. These have very similar powder diffractograms, indicating that such issues need to be addressed for its pharmaceutical formulation.

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