Time filter

Source Type

Gorelik T.E.,Johannes Gutenberg University Mainz | Van De Streek J.,Avant garde Materials Simulation | Kilbinger A.F.M.,University of Fribourg | Brunklaus G.,Max Planck Institute for Polymer Research | And 2 more authors.
Acta Crystallographica Section B: Structural Science

Ab-initio crystal structure analysis of organic materials from electron diffraction data is presented. The data were collected using the automated electron diffraction tomography (ADT) technique. The structure solution and refinement route is first validated on the basis of the known crystal structure of tri-p-benzamide. The same procedure is then applied to solve the previously unknown crystal structure of tetra-p-benzamide. In the crystal structure of tetra-p-benzamide, an unusual hydrogen-bonding scheme is realised; the hydrogen-bonding scheme is, however, in perfect agreement with solid-state NMR data. © 2012 International Union of Crystallography Printed in Singapore-all rights reserved. Source

Schmidt M.U.,Goethe University Frankfurt | Bruning J.,Goethe University Frankfurt | Glinnemann J.,Goethe University Frankfurt | Hutzler M.W.,Goethe University Frankfurt | And 7 more authors.
Angewandte Chemie - International Edition

Stabilizing the unstable: In textbooks barbituric acid is always drawn in its keto tautomeric form, which is indeed preferred in solution and in most polymorphic phases. However, phase IV, obtained by grinding, consists of molecules in the enol form, as shown by neutron powder diffraction. This phase is found to be the most stable one at room temperature; the "unstable" enol tautomer is stabilized by a higher number of hydrogen bonds. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Minguez Espallargas G.,University of Sheffield | Minguez Espallargas G.,University of Valencia | Van De Streek J.,Avant garde Materials Simulation | Fernandes P.,University of Strathclyde | And 5 more authors.
Angewandte Chemie - International Edition

Hydrogen bonding leads the way: Reaction of nonporous crystalline coordination compound 1 with HCl gas results in conversion into the crystalline salt 2 (see picture) following chemisorption and insertion of HCl into Cu - N bonds. Powder diffraction studies show that [CuBr2Cl 2]2- ions formed in 2 are reoriented to maximize the strength of hydrogen bonds and halogen bonds by preferentially involving Cl rather than Br ligands as acceptor sites. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Minguez Espallargas G.,University of Sheffield | Minguez Espallargas G.,University of Valencia | Florence A.J.,University of Strathclyde | Van De Streek J.,Avant garde Materials Simulation | Brammer L.,University of Sheffield

Reaction of green crystalline solid trans-[CuBr2(3-Brpy) 2] 1 (3-Brpy = 3-bromopyridine) with HBr (aq) vapour yields brown crystalline salt (3-BrpyH)2[CuBr4] 2 with quantitative conversion. Notably 2 adopts a different crystal structure to the three mutually isostructural compounds (3-XpyH)2[CuCl4] (X = Cl, Br) and (3-BrpyH)2[CuBr2Cl2] which result from reaction with HCl. Crystalline product 2 has been characterised by X-ray powder diffraction and its conversion back to 1 at 370-400 K has been followed in situ by synchrotron X-ray powder diffraction. Crystalline 1 and 2 are further notable for the presence of intermolecular C-Br⋯Br-Cu halogen bonds and (only in the case of 2) N-H⋯Br-Cu hydrogen bonds. © 2011 The Royal Society of Chemistry. Source

Tobbens D.M.,University of Innsbruck | Tobbens D.M.,Helmholtz Center Berlin | Glinneman J.,Goethe University Frankfurt | Chierotti M.R.,University of Turin | And 2 more authors.

The crystal structure of the high-temperature phase (HT-form or form III) of barbituric acid has been solved from X-ray powder diffraction data. It was found to be monoclinic, space group C2/c, a = 8.5302(3) Å, b = 6.8167(3) Å, c = 9.3304(4) Å, β = 89.865(2)°, volume = 542.54(4) Å 3 at T = 236(1) °C. The crystal structure is closely related to the also monoclinic structure of form II. A combined Rietveld refinement of X-ray and neutron powder diffraction data revealed fine details of the disorder aspects of the structure. 1H variable temperature and 13C MAS solid-state NMR confirmed those and proved the dynamic nature of the rotational disorder of the molecules. Energy optimizations of ordered subgroup structures with dispersion-corrected DFT gave insights into the underlying reason for the disorder. The reorientation of the unique 2-fold symmetry axis at the II → HT phase transition derives from both the anisotropy of the hydrogen bonds and the resulting anisotropy of the thermal rotational disorder. The unusual thermal expansion behavior of form II also finds its explanation in the incipient disorder. © The Royal Society of Chemistry 2012. Source

Discover hidden collaborations