Wechselwirkungen in Molekülkristallen, 157 [1, 2]. Mischkristallzüchtung und Strukturbestimmungen von Tetra(3,4-dimethylphenyl)-imidodiphosphat-Salzen mit Alkalikation- Verhältnissen K⊕/Rb⊕(1:5) und Rb⊕/Cs⊕(1:1) / Interaction in Molecular Crystals, 157 [1, 2]. Mixed Crystal Growth and Structure Determinations of Tetrakis(3,4-dimethylphenyl)-imidodiphosphate Salts with Alkali Cation Ratios K⊕/Rb⊕ (1:5) and Rb⊕/Cs⊕ (1:1)

2000 ◽  
Vol 55 (9) ◽  
pp. 785-795 ◽  
Author(s):  
Hans Bock ◽  
Erik Heigel
Keyword(s):  
Alkali Cation ◽  
Van Der Waals Interactions ◽  
Crystal Lattices ◽  
X Ray ◽  
Alkali Ions ◽  
Structure Determinations ◽  
Phenyl Rings ◽  
Total Reflexion ◽  
The Individual ◽  
Cation Ratios

Mixed crystals of tetrakis(3,4-dimethylphenyl)imidodiphosphate salts with alkalication ratios K⊕/Rb⊕ (1:5) and Rb⊕/Cs⊕ (1:1), (1:3) as well as (3:1) have been grown by suspending finely ground stoichiometric mixtures of alkali carbonates in toluene solutions of the strongly chelating ligand HN(PO(OR)2)2 - The cation ratios were measured by Total Reflexion X-Ray Fluorescence (TXRF) analysis and the single crystal structures of the polymeric K⊕/Rb⊕ as well as the Rb⊕/Cs⊕ imidodiphosphate salts determined by X-ray structure analysis. The selectivity of the various alkali ions for insertion in the crystal lattices of the individual imidodiphosphate salts has been confirmed by concentration-dependent crystallizations and discussed based on the structural analysis of the differing ligand conformations. The unit cell parameter dependence on the alkali cation radii provided information on van der Waals interactions between adjacent phenyl rings of the imidodiphosphate ligands and suggests the selective alkali cation insertion to be partly due to supramolecular repulsion within the lipophilic phenyl skin during the selfaggregation of the polymeric salt chains

scholarly journals Conformation and supramolecular arrangement of 1,3:2,4-dibenzyli-dene-D-sorbitol in solution and in single crystals

2021 ◽  
Author(s):  
Fernán Berride ◽  
Victor M. Sánchez-Pedregal ◽  
Bruno Dacuña ◽  
Eurico Cabrita ◽  
Armando Navarro-Vázquez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Nmr Spectroscopy ◽  
Van Der Waals Interactions ◽  
Side Chain ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Intermolecular Hydrogen Bonds ◽  
X Ray ◽  
Definitive Evidence ◽  
Phenyl Rings

The X-ray crystal structure of the gelator 1,3:2,4-dibenzylidene-D-sorbitol (DBS) is reported here. DBS is an important gelating molecule known for nearly 130 years, that has eluded crystallization until now. The crystal obtained presents an axial stacking of DBS molecules stabilized by both Van der Waals interactions and intermolecular hydrogen bonds of the side chain hydroxyl groups with either neighboring DBS or water molecules. The crystal structure shows definitive evidence for the frequently assumed “butterfly” type aggregation mode and experimentally proves the equatorial placement of the phenyl rings. The conformation of DBS has been analyzed in the crystal structure and compared with that determined in solution through NMR spectroscopy.

Structure and Action of Molecular Tracks and Motors

1998 ◽  
Vol 4 (S2) ◽  
pp. 456-457
Author(s):  
R.A. Milligan
Keyword(s):  
Conformational Changes ◽  
Molecular Motors ◽  
Three Dimensional ◽  
X Ray ◽  
Myosin I ◽  
Structure Determinations ◽  
Moderate Resolution ◽  
Mechanochemical Cycle ◽  
The Individual ◽  
Muscle Myosin

Molecular motors belonging to the myosin and kinesin superfamilies utilize ATP to move along their respective F-actin and microtubule tracks. The track-motor complexes have not been amenable to crystallization, so x-ray crystallographic investigations have focused on structure determinations of the individual proteins. Although providing detailed descriptions of the structure of each protein, this approach cannot reveal the geometry of interaction of the proteins nor the conformational changes which occur during the mechanochemical cycle. To obtain this information, we use cryoelectron microscopy and image analysis to calculate three dimensional maps of the track-motor complexes at moderate resolution (15-30A) and combine these data with the high resolution x-ray structures to provide near-atomic models of the working assemblies.We have so far built models of the rigor (nucleotide-free) and ADP actomyosin complexes. In smooth muscle myosin II (a collaboration with H.L. Sweeney, U. Perm.) and brush border myosin I (BBMI), the motor domain of the myosin head is similar in both biochemical states.

New aspects of the nitration of some imidazo[1,2-a]pyridines. CNDO/2 calculations from X-ray structures

1982 ◽  
Vol 35 (9) ◽  
pp. 1761 ◽  
Author(s):  
JC Teulade ◽  
R Escale ◽  
JC Rossi ◽  
JP Chapat ◽  
G Grassy ◽  
...  
Keyword(s):  
Experimental Results ◽  
X Ray ◽  
Structure Determinations ◽  
The Individual ◽  
System 1

The reactivity of the imidazo[l,2-a]pyridine system (1) was investigated, CNDO/2 calculations based on X-ray structure determinations of 5-ethoxyimidazo[l,2-a]pyridine (2), ethyl 8-methylimidazo-[1,2-a]pyridine-2-carboxylate (5) and ethyl 6-methyl-3-nitroimidazo[l,2-a]pyridine-2-carboxylate (10c) are compared with experimental results of the nitration of variously substituted imidazo[l,2-a]- pyridines, and are found compatible with the individual reactivities.

scholarly journals The nature and properties of aluminosilicate framework structures

1934 ◽  
Vol 145 (854) ◽  
pp. 80-103 ◽  
Keyword(s):  
Water Molecules ◽  
Chemical Formula ◽  
Framework Structure ◽  
Experimental Proof ◽  
X Ray ◽  
Structure Determinations ◽  
The Individual ◽  
Related Compounds ◽  
Ray Methods ◽  
Oxygen Atoms

In recent years it has been shown by X-ray methods that the structures of a large number of crystals are based on frameworks of linked tetrahedral groups of oxygen atoms. The individual tetrahedra contain silicon or aluminium atoms, and other atoms (such as sodium or potassium) and water molecules or molecular groups (such as CO 3 and SO 4 ) are located in the interstices of the oxygen atom arrangement. Some of the structure determinations are incomplete and lack direct experimental proof, but in others it has been possible to discover the details of the atomic arrangement. The present writer has been associated with several of these detailed investigations, and in this paper presents some general conclusions which may be drawn from an examination of the available data. Experimental details and evidence for the correctness of individual structures have been published elsewhere. For the purpose of the present paper a framework structure is defined as one in which every tetrahedron SiO 4 or AlO 4 shares all its corners with other tetrahedra, thus accounting for all the silicon aluminium and oxygen atoms in the structure; such a crystal has a chemical formula in which the ratio (Si + Al) to O is 1 to 2. Framework structures include the forms of silica, the felspars, the zeolites, the ultramarines, nepheline and kaliophilite, and related compounds which will be mentioned later; also danburite if boron may be supposed to take the place of aluminium in our definition, and probably leucite.

Hydratisierte Cyanoelpasolithe: Die Kristallstrukturen von (NMe4)2Li(H2O)2[Cr(CN)6] und (NMe4)2Na(H2O)[M(CN)6] (M = Cr, Co) / Hydrated Cyano Elpasolites: The Crystal Structures of (NMe4)2Li(H2O)2[Cr(CN)6] and (NMe4)2Na(H2O)[M(CN)6] (M = Cr, Co)

2000 ◽  
Vol 55 (6) ◽  
pp. 487-494 ◽  
Author(s):  
Martin Schwarten ◽  
Michael Witzei ◽  
Dietrich Babel
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
X Ray ◽  
Alkali Ions ◽  
Structural Details ◽  
Structure Determinations

The results of single crystal X-ray structure determinations are reported for monoclinic (NMe4)2Li(H2O)2[Cr(CN)6] (a = 1736.7(2), = 888.0(1), c = 1659.3(1) p m ,β = 119.33(1)°; C2/c, Z = 4) and orthorhombic (NMe4),Na(H2O)[Cr(CN)6] (a = 960.0(2), b = 885.0(2), c = 1269.8(3) pm; Pnmm, Z = 2) and (NMe4)2Na(H2O)[Co(CN)6] (a = 1854.5(4), b = 853.5(1), c = 1328.7(3) pm; Pnma, Z = 4), the latter exhibiting a superstructure of the NaCr compound. The average distances within the hexacyano groups are Cr-C: 207.8 resp. 208.3 pm and Co-C: 189.5 pm. The alkali ions are incorporated into the elpasolite-like arrangement of the bigger ions as di- or monohydrated species [Li(H2O)2]+ and [Na(H2O)]+ resp., becoming tetrahedrally coordinated [LiO2N2] and [NaON3] within the lattice and fixed by hydrogen bridges O-H...N as well. Some structural details and relations are discussed.

Abinitiostructure determination ofm-toluidine by powder X-ray diffraction

2004 ◽  
Vol 37 (3) ◽  
pp. 464-471 ◽  
Author(s):  
Mwaffak Rukiah ◽  
Jacques Lefebvre ◽  
Marc Descamps ◽  
Stephanie Hemon ◽  
Alexander Dzyabchenko
Keyword(s):  
Hydrogen Bonds ◽  
Metastable Phase ◽  
Lattice Energy ◽  
Real Space ◽  
Rigid Bodies ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Phenyl Rings

The powder X-ray diffraction pattern of the crystalline phase ofm-toluidine has been recorded with a sensitive curved detector (CPS120) at 150 K. The structure has been solved by real-space methods (simulated annealing) followed by Rietveld refinements with phenyl rings as rigid bodies and with soft constraints on bond lengths for peripheral atoms. The cell is monoclinic with space groupP21/candZ= 8. Equivalent molecules form chains alongc. The crystalline cohesion is achieved by N—H...N hydrogen bonds between neighbouring chains of non-equivalent molecules and by van der Waals interactions of neighbouring chains of equivalent molecules. The hydrogen-bonding network has been confirmed by lattice-energy minimization. Anisotropic strain effects of the cell have been calculated. The directions of the minimal strains correspond to the directions of the hydrogen bonds. An explanation of the difficulty to crystallize the metastable phase is given.

Neue Pentaphosphaferrocene

2009 ◽  
Vol 64 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Fabian Dielmann ◽  
Roger Merkle ◽  
Sebastian Heinl ◽  
Manfred Scheer
Keyword(s):  
Crystal Lattice ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cyclopentadienyl Ligand ◽  
Π Stacking ◽  
Diffraction Structure ◽  
Structure Determinations ◽  
Phenyl Rings ◽  
Derivatives Of

By cothermolysis of [CpRFe(CO)2]2 [CpR = η5-C5(CH2Ph)5 (Cpbn) (1) and η5-C5Me4C2H4SMe (CpS) (2)] with P4 phosphorus two novel pentaphosphaferrocenes of the formula [CpRFe(η5-P5)] [CpR = CpS (3), Cpbn (4)] have been synthesised and comprehensively characterised. These two products represent the first derivatives of this class of compounds with a functionalised as well as a sterically bulky adjacent cyclopentadienyl ligand. The pentabenzylcyclopentadienyl derivative 4 as well as both of the starting materials [CpRFe(CO)2]2 1 and 2 have been additionally characterised by X-ray diffraction structure determinations. The pentaphosphaferrocene 4 represents in the crystal lattice highly aggregated units via intra- and intermolecular π-stacking interactions of the phenyl rings of the Cpbn ligand.

Elemental mass loss in silicate minerals during x-ray analysis

1990 ◽  
Vol 48 (4) ◽  
pp. 804-805
Author(s):  
P.E. Champness ◽  
R.W. Devenish
Keyword(s):  
Mass Loss ◽  
Current Density ◽  
Damage Mechanism ◽  
Beam Current ◽  
Single Chain ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Alkali Ions ◽  
Structural Order ◽  
Sheet Silicate

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

scholarly journals Resolving Entangled JH-H-Coupling Patterns for Steroidal Structure Determinations by NMR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2643
Author(s):  
Danni Wu ◽  
Kathleen Joyce Carillo ◽  
Jiun-Jie Shie ◽  
Steve S.-F. Yu ◽  
Der-Lii M. Tzou
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr Spectroscopy ◽  
Chemical Shifts ◽  
Atomic Level ◽  
Molecular Structures ◽  
Naturally Occurring ◽  
Structure Determinations ◽  
Ligand Interactions ◽  
Synthetic Steroids ◽  
The Individual

For decades, high-resolution 1H NMR spectroscopy has been routinely utilized to analyze both naturally occurring steroid hormones and synthetic steroids, which play important roles in regulating physiological functions in humans. Because the 1H signals are inevitably superimposed and entangled with various JH–H splitting patterns, such that the individual 1H chemical shift and associated JH–H coupling identities are hardly resolved. Given this, applications of thess information for elucidating steroidal molecular structures and steroid/ligand interactions at the atomic level were largely restricted. To overcome, we devoted to unraveling the entangled JH–H splitting patterns of two similar steroidal compounds having fully unsaturated protons, i.e., androstanolone and epiandrosterone (denoted as 1 and 2, respectively), in which only hydroxyl and ketone substituents attached to C3 and C17 were interchanged. Here we demonstrated that the JH–H values deduced from 1 and 2 are universal and applicable to other steroids, such as testosterone, 3β, 21-dihydroxygregna-5-en-20-one, prednisolone, and estradiol. On the other hand, the 1H chemical shifts may deviate substantially from sample to sample. In this communication, we propose a simple but novel scheme for resolving the complicate JH–H splitting patterns and 1H chemical shifts, aiming for steroidal structure determinations.

scholarly journals Crystal structure of pimecrolimus Form B, C43H68ClNO11

2021 ◽  
Vol 36 (1) ◽  
pp. 35-42
Author(s):  
Shivang Bhaskar ◽  
Joseph T. Golab ◽  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Density Functional ◽  
Van Der Waals Interactions ◽  
Powder Diffraction File ◽  
X Ray ◽  
Weak Intermolecular Interactions ◽  
Significant Difference ◽  
Atomic Coordinates ◽  
Solid State Conformation

The crystal structure of pimecrolimus Form B has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Pimecrolimus crystallizes in the space group P21 (#4) with a = 15.28864(7), b = 13.31111(4), c = 10.95529(5) Å, β = 96.1542(3)°, V = 2216.649(9) Å3, and Z = 2. Although there are an intramolecular six-ring hydrogen bond and some larger chain and ring patterns, the crystal structure is dominated by van der Waals interactions. There is a significant difference between the conformation of the Rietveld-refined and the DFT-optimized structures in one portion of the macrocyclic ring. Although weak, intermolecular interactions are apparently important in determining the solid-state conformation. The powder pattern is included in the Powder Diffraction File™ (PDF®) as entry 00-066-1619. This study provides the atomic coordinates to be added to the PDF entry.

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