Crystal Structure of the Hydrated Strontium Salt of Methotrexate:  Two Independent Molecules with Different Conformations§

2001 ◽  
Vol 44 (2) ◽  
pp. 269-273 ◽  
Author(s):  
Donald Mastropaolo ◽  
Arthur Camerman ◽  
Norman Camerman
Keyword(s):  
Crystal Structure ◽  
Strontium Salt ◽  
Independent Molecules

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.

scholarly journals Theoretical Study of the Structures of 4-(2,3,5,6-Tetrafluoropyridyl)Diphenylphosphine Oxide and Tris(Pentafluorophenyl)Phosphine Oxide: Why Does the Crystal Structure of (Tetrafluoropyridyl)Diphenylphosphine Oxide Have Two Different P=O Bond Lengths?

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2778
Author(s):  
Joseph R. Lane ◽  
Graham C. Saunders
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Phosphine Oxide ◽  
Density Functional ◽  
Lone Pair ◽  
Diphenylphosphine Oxide ◽  
Functional Theory ◽  
Weak Hydrogen Bonding ◽  
Independent Molecules ◽  
The Difference

The crystal structure of 4-(2,3,5,6-tetrafluoropyridyl)diphenylphosphine oxide (1) contains two independent molecules in the asymmetric unit. Although the molecules are virtually identical in all other aspects, the P=O bond distances differ by ca. 0.02 Å. In contrast, although tris(pentafluorophenyl)phosphine oxide (2) has a similar crystal structure, the P=O bond distances of the two independent molecules are identical. To investigate the reason for the difference, a density functional theory study was undertaken. Both structures comprise chains of molecules. The attraction between molecules of 1, which comprises lone pair–π, weak hydrogen bonding and C–H∙∙∙arene interactions, has energies of 70 and 71 kJ mol−1. The attraction between molecules of 2 comprises two lone pair–π interactions, and has energies of 99 and 100 kJ mol−1. There is weak hydrogen bonding between molecules of adjacent chains involving the oxygen atom of 1. For one molecule, this interaction is with a symmetry independent molecule, whereas for the other, it also occurs with a symmetry related molecule. This provides a reason for the difference in P=O distance. This interaction is not possible for 2, and so there is no difference between the P=O distances of 2.

3-n-Butyl-2-methoxy-1-benzothieno[3,2-d]pyrimidin-4(3H)-one

2006 ◽  
Vol 62 (4) ◽  
pp. o1319-o1320 ◽  
Author(s):  
Min-Hui Cao ◽  
Sheng-Zhen Xu ◽  
Yang-Gen Hu
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Benzene Ring ◽  
Title Compound ◽  
Thiophene Ring ◽  
Stacking Interactions ◽  
Asymmetric Unit ◽  
Compound C ◽  
Π Stacking ◽  
Independent Molecules

The title compound, C15H16N2O2S, contains a five-membered thiophene ring fused to a benzene ring and a substituted pyrimidinone ring. All three rings in each of the independent molecules of the asymmetric unit lie in approximately the same plane. The crystal structure is stabilized by intermolecular C—H...O hydrogen bonding and π–π stacking interactions.

scholarly journals Dielectric properties of the system: 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4᾽-methylaniline

2021 ◽  
Vol 16 (2) ◽  
pp. 138-147
Author(s):  
S. A. Syrbu ◽  
M. S. Fedorov ◽  
E. A. Lapykina ◽  
V. V. Novikov
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Anisotropy ◽  
Specific Electrical Conductivity ◽  
Conductivity Anisotropy ◽  
Independent Molecules ◽  
System Properties ◽  
The Individual

Objectives. Our aim was to study the dielectric properties of the 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4’-methylaniline system and reveal how different concentrations of N-(4-n-butyloxybenzylidene)-4’-methylaniline additives affect the dielectric properties of 4-n-pentyloxybenzoic acid.Methods. System properties were investigated using polarization thermomicroscopy and dielcometry.Results. We found that dielectric anisotropy changes its sign from positive to negative at the transition temperature of the high-temperature nematic subphase to the low-temperature one. The anisotropy of the dielectric constant of N-4-n-butoxybenzylidene-4’-methylaniline has a positive value and increases as to the system approaches the crystalline phase. The crystal structure of the 4-n-pentyloxybenzoic acid contains dimers formed by two independent molecules due to a pair of hydrogen bonds. The crystal structure of N-(4-n-butoxybenzylidene)-4’-methylaniline contains associates formed by orientational interactions of two independent molecules. 4-n-Pentyloxybenzoic acid dimers (270 nm) and associates of N-4-n-butoxybenzylidene-4’- methylaniline (250 nm) proved to have approximately the identical length. Considering the close length values of the structural units of both compounds and the dielectric anisotropy sign, we assume that the N-4-n-butoxybenzylidene-4’-methylaniline associates are incorporated into the supramolecular structure of the 4-n-pentyloxybenzoic acid. The specific electrical conductivity of the compounds under study lies between 10−7 and 10−12 S∙cm−1. The relationship between the specific electrical conductivity anisotropy and the system composition in the nematic phase at the identical reduced temperature, obtained between 100 and 1000 Hz is symbatic. However, the electrical conductivity anisotropy values of the system obtained at 1000 Hz are lower compared to those obtained at 100 Hz. At N-(4-n-butoxybenzylidene)-4’-methylaniline concentrations between 30 and 60 mol %, the electrical conductivity anisotropy values are higher than those of the individual component.Conclusions. A change in the sign of the dielectric constant anisotropy of the 4-n-pentyloxybenzoic acid during nematic subphase transitions was established. We showed that the system has the highest dielectric constant anisotropy value when components have an equal number of moles. Highest electrical conductivity anisotropy values are observed when the concentration of the N-4-n-butoxybenzylidene-4᾽-methylaniline system lies between 30 and 60 mol %. 

Pyridin-Addukte von Cyclothiazeno-Vanadiumdichlorid Die Kristallstruktur von [VCl2(N3S2)(C5H5N)] / Pyridine Adducts of Cyclo-thiazeno Vanadium Dichloride The Crystal Structure of [VCl2(N3S2)(C5H5N)]

1985 ◽  
Vol 40 (12) ◽  
pp. 1631-1637 ◽  
Author(s):  
Ruth Christophersen ◽  
Paul Klingelhöfer ◽  
Ulrich Müller ◽  
Kurt Dehnicke
Keyword(s):  
Crystal Structure ◽  
Ir Spectra ◽  
Chlorine Atom ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
Trigonal Bipyramidal ◽  
Independent Molecules

Abstract The pyridine complexes of cyclo-thiazeno vanadium dichloride, [VCl2(N3S2)py] and [VCl2(N3S2)(py)2] were synthesized by reactions of polymeric VCl2(N3S2) with varying amounts of pyridine in CH2Cl2. The compounds were characterized by their IR spectra as well as by their 51V NM R spectra. The crystal structure of [VCl2(N3S2)(C5H5N)] was determined by means of X-ray diffraction (1582 independent observed reflexions, R = 0.031). Crystal data: orthorhombic, space group Pnma, a = 1372, b - 2261, c - 1068 pm, Z = 12. In the lattice there are two monomeric, crystallographically independent molecules [VCl2(N3S2)(C5H5N)], which differ only slightly. The vanadium atoms have a trigonal bipyramidal coordination with the N atom of the pyridine molecule and one chlorine atom in apical positions, and with one chlorine atom and the N atoms of the cyclo-thiazeno ligand in equatorial positions. The VN bond lengths of the planar VN3S2 ring of 174 pm correspond to double bonds

scholarly journals Crystal structure of 3-amino-5,5-dimethyl-2-[(E)-2-nitroethenyl]cyclohex-2-en-1-one

2014 ◽  
Vol 70 (11) ◽  
pp. 379-381
Author(s):  
Brigita Vigante ◽  
Dmitrijs Stepanovs ◽  
Andrejs Pelss ◽  
Anatoly Mishnev
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Asymmetric Unit ◽  
Envelope Conformation ◽  
Compound C ◽  
The Mean ◽  
Independent Molecules

The asymmetric unit of the title compound, C10H14N2O3, contains two independent molecules with similar conformations. In the both molecules, the cyclohexene rings adopt the same envelope conformation with the flap C atoms lying 0.658 (3) and 0.668 (3) Å from the mean planes formed by the remaining atoms. In the crystal, adjacent molecules are connectedviaN—H...O hydrogen bonds and weak C—H...O interactions, forming supramolecular layers parallel to (-101).

scholarly journals Crystal structure of {2,2′-[ethylenebis(nitrilomethanylylidene)]diphenolato-κ4O,N,N′,O′}oxidovanadium(IV) methanol monosolvate

2014 ◽  
Vol 70 (11) ◽  
pp. m380-m381
Author(s):  
Rachel E. Hsuan ◽  
Jemma E. Hughes ◽  
Thomas H. Miller ◽  
Nabila Shaikh ◽  
Phoebe H. M. Cunningham ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Basal Plane ◽  
Solvent Molecule ◽  
Vanadium Atom ◽  
Asymmetric Unit ◽  
Extended Structure ◽  
Independent Molecules ◽  
Ethylenediamine Ligand

Two independent molecules of the title solvated complex, [V(C16H14N2O2)O]·CH3OH, also known as [N,N′-bis(salicylidene)ethylenediamine]oxidovanadium(IV) or vanadyl salen, crystallize in the asymmetric unit. Each disordered methanol solvent molecule [occupancy ratios 0.678 (4):0.322 (4) and 0.750 (5):0.250 (5)] is linked to a [N,N′-bis(salicylidene)ethylenediamine]oxidovanadium(IV) molecule by an O—H...O hydrogen bond and to others by C—H...O hydrogen bonds. The resulting extended structure consists of a bilayer of molecules parallel to theabplane. Despite the fact that solvates are common in complexes derived from substituted analogues of theN,N′-bis(salicylidene)ethylenediamine ligand, the title solvate is the first one of [N,N′-bis(salicylidene)ethylenediamine]oxidovanadium(IV) to be structurally characterized. The two vanadyl species have very similar internal geometries, which are best characterized as distorted square-based pyramidal with the vanadium atom displaced from the N2O2basal plane by 0.5966 (9) Å in the direction of the doubly-bonded oxide ligand.

3-Ethylpentan-3-ol

2006 ◽  
Vol 62 (5) ◽  
pp. o2064-o2065 ◽  
Author(s):  
Andrew D. Bond
Keyword(s):  
Crystal Structure ◽  
Crystal Growth ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Asymmetric Unit ◽  
Compound C ◽  
Independent Molecules

The crystal structure of the title compound, C7H16O, has been determined at 150 (2) K following in situ crystal growth from the liquid. The structure contains four independent molecules in the asymmetric unit, forming a fourfold cyclic arrangement via O—H...O hydrogen bonds.

scholarly journals 6-(Hex-5-enyloxy)naphthalene-2-carboxylic acid

2014 ◽  
Vol 70 (6) ◽  
pp. o696-o697
Author(s):  
Md. Lutfor Rahman ◽  
H. T. Srinivasa ◽  
Mashitah Mohd. Yusoff ◽  
Huey Chong Kwong ◽  
Ching Kheng Quah
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Ring System ◽  
Dihedral Angles ◽  
Carbonyl Groups ◽  
Asymmetric Unit ◽  
Compound C ◽  
Independent Molecules

The asymmetric unit of the title compound, C17H18O3, comprises three independent molecules with similar geometries. In each molecule, the carbonyl group is twisted away from the napthalene ring system, making dihedral angles of 1.0 (2), 1.05 (19)° and 1.5 (2)°. The butene group in all three molecules are disordered over two sets of sites, with a refined occupancy ratio of 0.664 (6):0.336 (6). In the crystal, molecules are oriented with respect to their carbonyl groups, forming head-to-head dimersviaO—H...O hydrogen bonds. Adjacent dimers are further interconnected by C—H...O hydrogen bonds into chains along thea-axis direction. The crystal structure is further stabilized by weak C—H...π interactions.

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