scholarly journals Crystals at a Carrefour on the Way through the Phase Space: A Middle Path

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1583
Author(s):  
Yury V. Torubaev ◽  
Ivan V. Skabitsky
Keyword(s):  
Phase Space ◽  
Crystal Packing ◽  
Close Packing ◽  
Supramolecular Synthon ◽  
Crystal Forms ◽  
Existing Structures ◽  
Unique Model ◽  
Polymorphic Forms ◽  
Independent Molecules ◽  
The Way

Multiple supramolecular functionalities of cyclic α-alkoxy tellurium-trihalides (including Te---O, Te---X (X = Br, I) and Te---π(C=C) supramolecular synthons) afford rich crystal packing possibilities, which consequently results in polymorphism or Z’ > 1 crystal structures. Example of three crystal forms of cyclohexyl-ethoxy-tellurium-trihalides, one of which combines the packing of two others, affords a unique model to observe the supramolecular synthon evolution at the early stages of crystallization, when crystals on the way find themself at a carrefour between the evolutionally close routes, but fail to choose between two energetically close packing patterns, so taking the “middle path”, which incorporates both of them (and results in two crystallographically independent molecules). In general, this allows a better understanding of the existing structures, and an instrument to search for the new polymorphic forms.

New polymorphs of an old drug: conformational and synthon polymorphism of 5-nitrofurazone

2016 ◽  
Vol 72 (2) ◽  
pp. 263-273 ◽  
Author(s):  
Dorota Pogoda ◽  
Jan Janczak ◽  
Veneta Videnova-Adrabinska
Keyword(s):  
Hydrogen Bond ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Molecular Organization ◽  
Hydrogen Bond Donor ◽  
Scanning Calorimetry ◽  
Geometrical Isomers ◽  
Crystal Forms ◽  
Donor And Acceptor ◽  
Polymorphic Forms

Two new polymorphic forms of 5-nitrofurazone (5-nitro-2-furaldehyde semicarbazone) have been synthesized and structurally characterized by single-crystal and powder X-ray diffraction methods, vibrational spectroscopy (FT–IR and temperature Raman), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Hirshfeld surface analysis. The compound crystallizes in three different polymorphic formsP21/a(polymorph α),P21(polymorph β) andP21/c(polymorph γ), the crystal structures of two of which (polymorphs β and γ) represent new structure determinations. The solid-state molecular organization in the three crystal forms is analyzed and discussed in terms of molecular conformation, crystal packing and hydrogen-bonded networks. All three crystals are formed fromtransgeometrical isomers, but the molecular conformation of the α-polymorph issyn–anti–anti–anti, while that of β- and γ-polymorphs issyn–anti–syn–syn. As a consequence of this the hydrogen-bond donor and acceptor sites of the molecules are oriented differently, which in turn results in different hydrogen-bond connectivity and packing patterns.

Polymorphic forms of lupane triterpenoid betulonic aldehyde (betulonal)

2014 ◽  
Vol 70 (9) ◽  
pp. 847-851
Author(s):  
Elwira Chrobak ◽  
Ewa Michalik ◽  
Joachim Kusz ◽  
Maria Nowak ◽  
Stanisław Boryczka
Keyword(s):  
Dimethyl Sulfoxide ◽  
Crystal Packing ◽  
Van Der Waals ◽  
Aldehyde Group ◽  
Geometric Parameters ◽  
Van Der Waals Interactions ◽  
Asymmetric Unit ◽  
Cyclopentane Ring ◽  
Polymorphic Forms ◽  
Independent Molecules

The lupane triterpenoid betulonic aldehyde [also known as betulonal; systematic name: lup-20(29)-en-28-al-3-one, C30H46O2] is a product of betulin oxidation. Crystals were obtained from hexane [form (I)] and dimethyl sulfoxide [form (II)] solutions. Forms (I) and (II) are both orthorhombic. The molecular geometric parameters in the two forms are similar, but the structures are different with respect to the crystal packing. Polymorph (I) contains two independent molecules in the asymmetric unit, while polymorph (II) contains only one molecule, which has a disordered aldehyde group [the disorder ratio is 0.769 (4):0.231 (4)]. In each molecule, the six-membered rings have chair conformations, whereas the cyclopentane ring in each molecule adopts an envelope conformation. All the rings in the lupane nucleus aretrans-fused. The extended structures of both polymorphs are stabilized by weak intermolecular C—H...O and van der Waals interactions. Weak intramolecular C—H...O interactions are also observed.

scholarly journals Two polymorphic forms of the oxathiin systemic fungicide active carboxine

2018 ◽  
Vol 74 (12) ◽  
pp. 1741-1745
Author(s):  
Christopher S. Frampton ◽  
Eleanor S. Frampton ◽  
Paul A. Thomson
Keyword(s):  
Title Compound ◽  
Crystal Packing ◽  
Systemic Fungicide ◽  
Monoclinic Space Group ◽  
Triclinic Space Group ◽  
Crystal Forms ◽  
Space Group ◽  
Compound C ◽  
Polymorphic Forms ◽  
Hydrogen Bonded

Two polymorphic crystal forms of the title compound, C12H13NO2S (systematic name: 6-methyl-N-phenyl-2,3-dihydro-1,4-oxathiine-5-carboxamide), were isolated from a truncated, (12 solvent), polymorph screen on pure lyophillized material. Crystals of form 1 were obtained from all solvents included in the screen with the exception of methanol. As isolated from acetonitrile the crystals are triclinic, space group P\overline{1} with Z′ = 2. Crystals of form 2, which were isolated from methanol only are monoclinic, space group I2/a with Z′ = 1. The crystal packing in both structures is dominated by the formation of infinite –NH...O hydrogen-bonded chains through the carboxamide core.

The low-resolution 3D-structure of porin, a channel-forming protein in E. coliouter membranes

1983 ◽  
Vol 41 ◽  
pp. 440-441
Author(s):  
A. Engel ◽  
D.L. Dorset ◽  
A. Massalski ◽  
J.P. Rosenbusch
Keyword(s):  
Crystal Packing ◽  
3D Structure ◽  
Gram Negative Bacteria ◽  
Protein Ratio ◽  
Crystal Forms ◽  
Large Molecules ◽  
Functional Studies ◽  
Voltage Dependent ◽  
Planar Membranes ◽  
Hexagonal Arrays

Porins represent a group of channel forming proteins that facilitate diffusion of small solutes across the outer membrane of Gram-negative bacteria, while excluding large molecules (>650 Da). Planar membranes reconstituted from purified matrix porin (OmpF protein) trimers and phospholipids have allowed quantitative functional studies of the voltage-dependent channels and revealed concerted activation of triplets. Under the same reconstitution conditions but using high protein concentrations porin aggregated to 2D lattices suitable for electron microscopy and image processing. Depending on the lipid-to- protein ratio three different crystal packing arrangements were observed: a large (a = 93 Å) and a small (a = 79 Å) hexagonal and a rectangular (a = 79 Å b = 139 Å) form with p3 symmetry for the hexagonal arrays. In all crystal forms distinct stain filled triplet indentations could be seen and were found to be morphologically identical within a resolution of (22 Å). It is tempting to correlate stain triplets with triple channels, but the proof of this hypothesis requires an analysis of the structure in 3 dimensions.

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

1,1′-Biadamantane-3,3′-diol: a two-dimensional network supported by a `hexameric alcohol cluster' supramolecular synthon

2013 ◽  
Vol 69 (2) ◽  
pp. 175-178 ◽  
Author(s):  
Konstantin V. Domasevitch
Keyword(s):  
Title Compound ◽  
Chair Conformation ◽  
The Other ◽  
Two Dimensional ◽  
Supramolecular Synthon ◽  
Hexagonal Packing ◽  
Compound C ◽  
Dimensional Network ◽  
Grid Topology ◽  
Independent Molecules

In the title compound, C20H30O2, one of the two crystallographically independent molecules lies across a centre of inversion and the other resides in a general position (Z′ = 1.5). The supramolecular structure exists as an unusual two-dimensional network incorporating centrosymmetric hexameric hydrogen-bonded alcohol (OH)6clusters [O...O = 2.6637 (12)–2.6993 (12) Å] as the net nodes. The hexamers adopt a chair conformation [O...O...O = 106.55 (4)–115.81 (4)°] and are connected into a network with a square-grid topology (44) by a combination of single and double 1,1′-biadamantanediyl links. The bulky aliphatic groups appear to require specific hexagonal packing and so generate distinct noncovalent hydrophobic layers, which are essential for the stabilization of the hexameric alcohol array rather than the formation of the more commonly encountered tetramer-based arrays.

Topochemically controlled solid-state methyl rearrangement in thiocyanurates

2001 ◽  
Vol 57 (3) ◽  
pp. 428-434 ◽  
Author(s):  
Mark Greenberg ◽  
Vitaly Shteiman ◽  
Menahem Kaftory
Keyword(s):  
Solid State ◽  
Driving Force ◽  
Mirror Plane ◽  
Energy Calculation ◽  
Asymmetric Unit ◽  
Methyl Transfer ◽  
Plate Shape ◽  
Polymorphic Forms ◽  
Independent Molecules ◽  
The Difference

4,6-Dimethoxy-3-methyl-1,3,5-triazine-2(3H)-thione crystallizes in two polymorphic forms, needles and plates. In the needle-shaped crystals (9a) the molecules occupy the crystallographic mirror plane, thus the layers are stacked along the b axis. The molecules of the other polymorph [plate-shape crystals, (9b)] are packed in a herringbone packing mode. Upon heating, (9b) undergoes a phase transition to form (9a). At 378 K the needles undergo O → S topochemically controlled methyl transfer in the solid state to produce 1-methyl-4-methoxy-6-methylthio-1,3,5-triazine-2(1H)-one in 75% yield. The enthalpy of the rearrangement is estimated to be −39.1 kJ mol−1. 1-Methyl-6-methoxy-4-methylthio-1,3,5-triazine-2(1H)-thione crystallizes in space group P21 with two crystallographically independent molecules in the asymmetric unit. Compound (9b) undergoes O → S methyl transfer in the solid state at 373 K. The rearrangement is topochemically assisted and the product, 1-methyl-2,4-bismethylthio-1,3,5-triazine-6(1H)-one, is obtained in quantitative yield. The enthalpy of the rearrangement is estimated to be −58.8 kJ mol−1. The crystal structures of the compounds as well as their DSC thermographs are described and discussed. Energy calculation by ab initio methods shows that the driving force for the reactions is the difference between the molecular energies of the pre-rearranged compounds and their products, 54.2 and 59.3 kJ mol−1 in the two cases, respectively.

Molecular Origins of Polymorphism in Cocoa Butter

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Saeed M. Ghazani ◽  
Alejandro G. Marangoni
Keyword(s):  
Cocoa Butter ◽  
Ternary Phase ◽  
Annual Review ◽  
Food Science ◽  
Publication Date ◽  
Polymorphic Transformations ◽  
Crystal Forms ◽  
Polymorphic Forms ◽  
Phase Behaviors ◽  
Metastable Forms

Cocoa butter displays complex crystallization behavior and six crystal polymorphic forms. Although the crystal structure of cocoa butter has been studied extensively, the molecular interactions between cocoa butter triacylglycerols in relation to polymorphic transformations from metastable forms (forms III and IV) to stable crystal forms (forms V and VI) remain largely unknown. In this review, the triclinic polymorphism and melting profiles of the major triacylglycerols in cocoa butter—POP, POS, and SOS—are reviewed, and their binary and ternary phase behaviors in metastable (pseudoβ′) and stable (β2) crystal forms are discussed. We also attempt to clarify how the transformation of cocoa butter from form IV to V, as a critical step in the tempering of chocolate, is controlled by POS interactions with both POP and SOS. Moreover, we show how the crystal forms V and VI of cocoa butter are templated by crystal forms β3 and β1 of POS, respectively. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 12 is March 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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