Disordered sodium alkoxides from powder data: crystal structures of sodium ethoxide, propoxide, butoxide and pentoxide, and some of their solvates
The crystal structures of sodium ethoxide (sodium ethanolate, NaOEt), sodium n-propoxide (sodium n-propanolate, NaOnPr), sodium n-butoxide (sodium n-butanolate, NaOnBu) and sodium n-pentoxide (sodium n-amylate, NaOnAm) were determined from powder X-ray diffraction data. NaOEt crystallizes in space group P421m, with Z = 2, and the other alkoxides crystallize in P4/nmm, with Z = 2. To resolve space-group ambiguities, a B ä rnighausen tree was set up, and Rietveld refinements were performed with different models. In all structures, the Na and O atoms form a quadratic net, with the alkyl groups pointing outwards on both sides...
Source: Acta Crystallographica Section B - January 21, 2021 Category: Chemistry Authors: Beske, M. Cronje, S. Schmidt, M.U. Tapmeyer, L. Tags: sodium alkoxide powder data solvate isopropanol B ä rnighausen tree PXRD research papers Source Type: research
Polymorphism and surface diversity arising from stress-induced transformations – the case of multicomponent forms of carbamazepine
This study considers 15 carbamazepine (CBZ) multicomponent crystal forms, with the aim of identifying the structural and surface features that drive the outcome of thermal stress-induced transformations. Analysis of the crystal structures, and specifically the degree of similarity with the CBZ polymorphs produced by desolvation-like processes, identifies some degree of correlation between structural features. In particular, mutually exclusive supramolecular motifs identified previously within CBZ crystal structures are frequently (but not invariably) preserved, and thereby provide some indication of the anticipated polymor...
Source: Acta Crystallographica Section B - January 16, 2021 Category: Chemistry Authors: Schneider-Rauber, G. Arhangelskis, M. Bond, A.D. Ho, R. Nere, N. Bordawekar, S. Sheikh, A.Y. Jones, W. Tags: crystal engineering stress-induced transformation carbamazepine solvate cocrystal hydrate research papers Source Type: research
HAR, TAAM and BODD refinements of model crystal structures using Cu K α and Mo K α X-ray diffraction data
The Independent Atom Model (IAM) of electron density is used in routine X-ray data analysis. However, this model does not give a quantitative description of the electron-density distribution. A better model that allows for modelling of aspherical charge density deformations is introduced by the Hansen – Coppens variant of the multipole model of electron density. However, the application of this model requires crystals of excellent quality and high-resolution XRD data which are quite often difficult criteria to fulfil. Therefore, Mo K α and Cu K α data of three model compounds (tricyclic imide, xylitol and methylu...
Source: Acta Crystallographica Section B - January 15, 2021 Category: Chemistry Authors: Wanat, M. Malinska, M. Gutmann, M.J. Cooper, R.I. Wozniak, K. Tags: Hirshfeld atom refinement HAR transferable aspherical atom model TAAM charge density aspherical scattering factors BODD research papers Source Type: research
Effect of disordered imidazole substructure on proton dynamics in imidazolium malonic acid salt
The influence of a disorder in cation substructure on proton conductivity of imidazolium malonate (Im-MAL) is studied. Imidazolium in salts with dicarboxylic acids have been found to have a well ordered hydrogen-bond network and only in Im-MAL [Pogorzelec-Glaser et al. (2006). Mater. Sci.-Pol. (2006), 24, 245 – 252] were two types of cation observed: ordered Im-I and disordered Im-II. Im-I is involved in hydrogen bonds with malonic acid molecules, whereas Im-II is disordered between two symmetrically equivalent positions with occupancy of 0.5. NMR studies by Mizuno et al. [Hyperfine Interact. (2015), 230, 95 – 100]...
Source: Acta Crystallographica Section B - January 14, 2021 Category: Chemistry Authors: Ł awniczak, P. Pogorzelec-Glaser, K. Pietraszko, A. Hilczer, B. Tags: imidazolium malonate ordered and disordered cations effect of disordered imidazole substructure on proton conductivity research papers Source Type: research
An investigation of a series of layered Zn-1,4-diazabicyclo[2.2.2]octane metal – organic frameworks: local structure and adsorption properties of mixed-metal centre
The mixed-metal pillar-layered metal – organic frameworks of Zn(bdc)(DABCO)0.5, Zn0.5Cu0.5(bdc)(DABCO)0.5 and Cu(bdc)(DABCO)0.5 (bdc = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane) are investigated for their local structures and gas adsorption properties. According to the obtained electron paramagnetic resonance (EPR) spectra, the distorted structures around Cu2+ are proposed to be tetragonally and orthorhombically elongated [CuO4N] with the well fitted high-order perturbation formulae of the EPR parameters. Due to the doped Cu2+, the adsorption isotherms of industrially relevant gases (CO2, CO, CH4 an...
Source: Acta Crystallographica Section B - January 4, 2021 Category: Chemistry Authors: Ding, C.-C. Chu, X.-H. Zhang, M.-J. Fu, J. Tags: ZnDABCO series doped Cu2 electron paramagnetic resonance (EPR) local structures of mixed ligands adsorption properties research papers Source Type: research
