Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin

2001 ◽  
Vol 58 (1) ◽  
pp. 125-133 ◽  
Author(s):  
Armand Budzianowski ◽  
Andrzej Katrusiak
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Molecular Conformation ◽  
Lactone Ring ◽  
Structural Transformations ◽  
Unit Cell ◽  
Crystal Symmetry ◽  
Translational Symmetry ◽  
Ring Conformation ◽  
Conformational Disorder

Conformational disorder and inversions of the lactone ring induce structural transformations in the crystals of 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin, C14H18O3. The onset of ordering of the lactone ring at 300 K proceeds continuously, changes the space group from P21/m to P21/c and doubles the unit cell; the abrupt inversion of the lactone rings at 225 K changes the crystal translational symmetry in the (010) plane. The mechanism combining the molecular conformation and dynamics with the crystal structure, its symmetry, and phase transitions is presented.

Über neue monocyclische Acyloxyfluoroborane 2.2.6.6-Tetrafluoro-1.4-dialkyl-1.3.5-trioxa-1.6-diboracyclohexene: Darstellung, Molekül- und Kristallstruktur/ New Monocyclic Acyloxyfluoroboranes 2,2,6,6-Tetrafluoro-1,4-dialkyl-1,3,5-trioxa-2,6-diboracyclohexenes: Synthesis, Molecular and Crystal Structure

1983 ◽  
Vol 38 (5) ◽  
pp. 554-558 ◽  
Author(s):  
Herbert Binder ◽  
Walter Matheis ◽  
Hans-Jörg Deiseroth ◽  
Han Fu-Son
Keyword(s):  
Crystal Structure ◽  
Organic Acid ◽  
Structure Determination ◽  
Unit Cell ◽  
Ring Conformation ◽  
X Ray ◽  
Conformational Isomers ◽  
Ring Group ◽  
Acid Anhydrides

Abstract Acyloxyfluoroboranes Trimeric alkoxydifluoroboranes (F2BOR)3 (2) react with organic acid anhydrides by substitution of a ring group OR forming monocyclic acyloxyfluoroboranes of the type 2,2,6,6-tetrafluoro-l,4-dialkyl-l,3,5-trioxa-2,6-diboracyclohexene (3). The X-ray crystal structure determination of 3a shows two conformational isomers: two planar and two non-planar six-membered rings are present in the unit cell. The ring conformation is influenced by weak intermolecular H — F interactions.

scholarly journals Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin. Erratum

2002 ◽  
Vol 58 (3) ◽  
pp. 565-565
Author(s):  
Armand Budzianowski ◽  
Andrzej Katrusiak
Keyword(s):  
Lactone Ring ◽  
Crystal Symmetry ◽  
Online Version ◽  
Ring Conformation ◽  
Acta Cryst

In the paper by Budzianowski & Katrusiak (2002) Acta Cryst. (2002), B58, 125–133 Figs. 5 and 8 on pages 131 and 132 were transposed while adjusting colour details indicated by the authors in the proof. Revised PDF versions of these pages are available in the online version of this erratum, which is available through Crystallography Journals Online.

scholarly journals Packing polymorphism in the structure oftrans-aqua[N,N′-bis(salicylidene)ethane-1,2-diamine-κ4O,N,N′,O′]chloridomanganese(III) monohydrate

2018 ◽  
Vol 74 (12) ◽  
pp. 1778-1782
Author(s):  
Juan Alberto Reyes Perea ◽  
Sylvain Bernès ◽  
Ma Guadalupe Quintero Téllez
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Unit Cell Parameter ◽  
Molecular Conformation ◽  
Cell Parameter ◽  
Title Complex ◽  
Unit Cell ◽  
Alternative Synthesis ◽  
Space Group ◽  
Structural Database

The crystal structure of the title complex (systematic name:trans-aquachlorido{2,2′[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato-κ4O,N,N′,O′}manganese(III) monohydrate), [Mn(C16H14N2O2)Cl(H2O)]·H2O has been reported previously in the space groupP21/n[Panjaet al.(2003).Polyhedron,22, 1191–1198]. We obtained the same hydrated complex through an alternative synthesis, and crystallized a new polymorph, in the space groupP21. The molecular conformation of the complex is virtually unmodified, but the absence of the glide plane in the new polymorph halves the unit-cell parameterc, affording a non-centrosymmetric crystal structure withZ= 2, while the previously reported crystal is centrosymmetric withZ= 4. Both phases represent a case of packing polymorphism, similar to other dimorphic crystal structures retrieved from the Cambridge Structural Database.

The crystal structure of eugaAl

1992 ◽  
Vol 50 (2) ◽  
pp. 1452-1453
Author(s):  
H. Brigitte Krause ◽  
Yonglin Qian
Keyword(s):  
Crystal Structure ◽  
Electron Microscope ◽  
Zone Axis ◽  
Unit Cell ◽  
Polycrystalline Specimen ◽  
Lattice Constants

A polycrystalline specimen of nominal formula EuGaAl with unknown crystal structure was investigated by various electron microscope techniques; EDS-, SED-, and CBED data were taken on a Philips 400 electron microscope operated at 100kV, HREM data on a Hitachi 9000 microscope operated at 300kV. The EDS data confirmed the composition for the bulk of the material but, in addition, revealed particles with other fractions of the elements. Only the EuGaAl particles were further investigated. The unit cell was determined to be orthorhombic with a ratio: a/b=0.969(2) , a/c=0.234(2) and b/c=0.234(2). The lattice constants are a=4.54(5)Ȧ, b=4.68Ȧ and c=19.97(20)Ȧ. Based on systematic extinctions for hkl reflections with h+l=2n+l, the unit cell was found to be b-centered. CBED patterns of the [001], [100], and [010] zone axes are shown in Fig. 1. The zone axis patterns are in agreement with the above stated data except for diffused (2m+l,2n+l,0)- reflections, not compatible with the above stated systematic absences. But these occurred only occasionally in conjunction with a complicated noncommensurate superlattice pattern.

scholarly journals Crystal Structures of New Ivermectin Pseudopolymorphs

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 172
Author(s):  
Kirill Shubin ◽  
Agris Bērziņš ◽  
Sergey Belyakov
Keyword(s):  
Crystal Structure ◽  
Molecular Conformation ◽  
Methyl Tert Butyl Ether ◽  
Minor Role ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
Structure Space

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like γ-valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P212121). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role; the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis.

scholarly journals Crystal Structure Refinements of Four Monazite Samples from Different Localities

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1028 ◽  
Author(s):  
M. Mashrur Zaman ◽  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Large Unit Cell ◽  
A Site

This study investigates the crystal chemistry of monazite (APO4, where A = Lanthanides = Ln, as well as Y, Th, U, Ca, and Pb) based on four samples from different localities using single-crystal X-ray diffraction and electron-probe microanalysis. The crystal structure of all four samples are well refined, as indicated by their refinement statistics. Relatively large unit-cell parameters (a = 6.7640(5), b = 6.9850(4), c = 6.4500(3) Å, β = 103.584(2)°, and V = 296.22(3) Å3) are obtained for a detrital monazite-Ce from Cox’s Bazar, Bangladesh. Sm-rich monazite from Gunnison County, Colorado, USA, has smaller unit-cell parameters (a = 6.7010(4), b = 6.9080(4), c = 6.4300(4) Å, β = 103.817(3)°, and V = 289.04(3) Å3). The a, b, and c unit-cell parameters vary linearly with the unit-cell volume, V. The change in the a parameter is large (0.2 Å) and is related to the type of cations occupying the A site. The average <A-O> distances vary linearly with V, whereas the average <P-O> distances are nearly constant because the PO4 group is a rigid tetrahedron.

LaMg11 with a giant unit cell synthesized by hydrogen metallurgy: Crystal structure and hydrogenation behavior

2010 ◽  
Vol 58 (7) ◽  
pp. 2510-2519 ◽  
Author(s):  
Roman V. Denys ◽  
Andrey A. Poletaev ◽  
Jan Ketil Solberg ◽  
Boris P. Tarasov ◽  
Volodymyr A. Yartys
Keyword(s):  
Crystal Structure ◽  
Unit Cell

The crystal chemistry of the uranyl carbonate mineral grimselite, (K, Na)3Na[(UO2)(CO3)3](H2O), from Jáchymov, Czech Republic

2012 ◽  
Vol 76 (3) ◽  
pp. 443-453 ◽  
Author(s):  
J. Plášil ◽  
K. Fejfarová ◽  
R. Skála ◽  
R. Škoda ◽  
N. Meisser ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Czech Republic ◽  
Structure Refinement ◽  
Unit Cell ◽  
Carbonate Mineral ◽  
X Ray Diffraction ◽  
The Czech Republic ◽  
Cell Parameters ◽  
Uranyl Carbonate ◽  
Diffraction Peaks

AbstractTwo crystals of the uranyl carbonate mineral grimselite, ideally K3Na[(UO2)(CO3)3](H2O), from Jáchymov in the Czech Republic were studied by single-crystal X-ray diffraction and electron-probe microanalysis. One crystal has considerably more Na than the ideal chemical composition due to substitution of Na into KO8 polyhedra; the composition of the other crystal is nearer to ideal, and similar to synthetic grimselite. The presence of Na atoms in KO8 polyhedra, which are located in channels in the crystal structure, reduces their volume, and as a result the unit-cell volume also decreases. Structure refinement shows that the formula for the sample with the anomalously high Na content is (K2.43Na0.57)Σ3.00Na[(UO2)(CO3)3](H2O). The unit-cell parameters, refined in space group P2c, are a = 9.2507(1), c = 8.1788(1) Å, V = 606.14(3) Å3 and Z = 2. The crystal structure was refined to R1 = 0.0082 and wR1 = 0.0185 with a GOF = 1.33, based on 626 observed diffraction peaks [Iobs>3σ(I)].

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