The stereochemistry of nitrate esters. II. Symmetric stretching frequencies of the nitrato group in nitrate esters of l,4;3,6-di-anhydrohexitols (4,8-dihydroxy-cis-2,6-dioxabicyclo[3.3.0]octanes)

1967 ◽  
Vol 45 (19) ◽  
pp. 2191-2194 ◽  
Author(s):  
L. D. Hayward ◽  
D. J. Livingstone ◽  
M. Jackson ◽  
Valerie M. Csizmadia
Keyword(s):  
Infrared Spectra ◽  
Benzene Solution ◽  
Intramolecular Interaction ◽  
Molecular Conformations ◽  
X Ray ◽  
Nitrate Esters ◽  
X Ray Crystallography ◽  
Structure Configuration ◽  
Configuration And Conformation

In the infrared spectra of mono- and di-nitrate esters of the l,4;3,6-dianhydrides of d-mannitol, d-glucitol, and l-iditol in benzene solution (0.04 M in nitrato groups), the frequencies of the va(NO2) and v(ON) bands (singlets) were 1 645 ± 3 and 843 ± 3 cm−1, respectively, whereas the vs(NO2) band occurred at frequencies characteristic of either an endo (1 282 ± 1 cm−1) or an exo (1 274 ± 1 cm−1) configuration of the nitrato group; the ratios of the band areas were 1.5:1.0:1.0, respectively.The stereospecific frequency of the vs(NO2) band was attributed to non-bonded intramolecular interaction between the nitrato group and vicinal oxy groups on the basis of the spectra run in a series of solvents and the molecular conformations determined by X-ray crystallography. This new stereochemical probe permitted the assignment of the structure, configuration, and conformation in a series of nitrate esters.

Crystal and molecular structure of cis,anti,cis-N,N′-dibenzoyl-3,12-diazatricyclo[6.4.0.02,7]dodecan-6,12-dione and cis,anti,cis-N,N′-dibenzoyl-3,9-diazatricyclo[6.4.0.02,7]dodecan-6,9-dione. Photodimers of N-benzoylcyclohex-2-ene-4-one

1981 ◽  
Vol 59 (22) ◽  
pp. 3136-3140 ◽  
Author(s):  
T. Stanley Cameron ◽  
Ruth E. Cordes ◽  
B. Mario Pinto ◽  
Walter A. Szarek
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Benzene Solution ◽  
X Ray ◽  
X Ray Crystallography

The products of photodimerization of N-benzoylazacyclohex-2-ene-4-one (1) have been investigated by X-ray crystallography. Irradiation of a benzene solution of compound 1 leads to a mixture of head-to-head and head-to-tail, cis,anti,cis adducts, namely, cis,anti,cis-N,N′-dibenzoyl-3,12-diazatricyclo[6.4.0.02,7]dodecan-6,12-dione and cis,anti,cis-N,N′-dibenzoyl-3,9-diazatricyclo[6.4.0.02,7]dodecan-6,9-dione, compounds 2 and 3 respectively.

scholarly journals Solid-state structure of cyclic dipeptides: an X-ray and computational study of cis- and trans-diketopiperazines of N-methyl-phenylalanine with the thia-pipecolic acids and thia-prolines

2017 ◽  
Vol 73 (6) ◽  
pp. 1179-1193 ◽  
Author(s):  
Milos Budesinsky ◽  
Ivana Cisarova ◽  
Frans Borremans ◽  
Jose C. Martins ◽  
Ewald Pauwels
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Amide Bond ◽  
Functional Theory ◽  
Torsion Angles ◽  
Molecular Conformations ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cis And Trans

Ten new crystal structures of cis and trans bicyclic diketopiperazines (DKPs) of thia-pipecolic acid (with sulfur in the β, γ or δ position) or thia-proline (with sulfur in the β or γ position) and N-methyl phenylalanine [(NMe)Phe]: cyclo[(β-S)Pip-(NMe)Phe], cyclo[(γ-S)Pip-(NMe)Phe], cyclo[(δ-S)Pip-(NMe)Phe], cyclo[(β-S)Pro-(NMe)Phe] and cyclo[(γ-S)Pro-(NMe)Phe] were determined with X-ray crystallography. Density functional theory calculations of these molecules in the gas phase succeed in reproducing the observed molecular conformations in the crystal remarkably well. This illustrates the weak to moderate impact of intermolecular packing forces in the absence of classical N—H...O hydrogen bonds. The effect of sulfur on the geometry of the DKP ring and details of amide bond non-planarity are discussed. Molecular flexibility of the DKP ring, as estimated from the calculated deformation energies of its endocyclic ring torsion angles, is not in general the decisive factor for the occurrence of multiple symmetry independent molecules in the unit cell (Z′ > 1), though in some cases a correlation is observed.

Crystallographic and Spectroscopic Evidence of O-Bonding in 3d-MetaI Dicyanomethanidonitrite Complexes

2001 ◽  
Vol 56 (1) ◽  
pp. 100-104 ◽  
Author(s):  
M. Hvastijová ◽  
J. Kohout ◽  
J. W. Buchler ◽  
H. W. Katzenmeier ◽  
J. Kožíšek ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Infrared Spectra ◽  
Spectroscopic Evidence ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pyridine Complexes ◽  
Pyridine Complex ◽  
Pyridine Nitrogen ◽  
Oxygen Atoms

Abstract The coordination of the dicyanomethanidonitrite group through the nitroso oxygen atom in the tetrakis(pyridine) complexes [M{ONC(CN)2}2(py)4], M = Ni, Co, Cu, and in the bis(pyridine) complex [Cu{ONC(CN)2}2(py)2] was proved by X-ray crystallography of the Ni11 complex and re-evaluated infrared spectra. The Ni11 and Co11 complexes exhibit almost octahedral structures composed of four pyridine nitrogen atoms and two oxygen atoms of dicyanomethanidonitrite ions. Both copper(II) complexes display a considerable axial distortion of the pseudooctahedral arrangement. In the bis(pyridine) Cu11 complex the ONC(CN)2 groups are involved in the bridging function by use of the oxygen and nitrile nitrogen atoms.

Dicyanomethylene Compounds as Cyanation Reagents

2002 ◽  
Vol 57 (4) ◽  
pp. 460-470 ◽  
Author(s):  
Dietrich Döpp ◽  
Sabine Jüschke ◽  
Gerald Henkel
Keyword(s):  
Carbon Atom ◽  
Single Crystal ◽  
Benzene Solution ◽  
Acetonitrile Solution ◽  
X Ray ◽  
X Ray Crystallography ◽  
Hydride Abstraction

Ethenetetracarbonitrile (2, in benzene solution) and 1,3-dioxoindan-2-ylidene propanedinitrile (4, in ethanol or acetonitrile solution) act on N-aryl-2,3-dihydro-1H-benz[d,e]isoquinolines 6a-d and N-aryl-6,7-dihydro-5H-dibenz[c,e]azepines 11a-d via hydride abstraction followed by addition of cyanide to the iminium carbon atom forming the corresponding 1- and 5-carbonitriles 9a-d and 13a-d, respectively, in moderate to medium yields.Additionally , the known 1,3-dihydroxy-2H-inden-2-ylidenepropanedinitrile 15 and a novel dispirocyclopropane (17) are formed from 4 in the reaction with 6 in acetonitrile and ethanol, respectively. The structures of 17 and 6-(4-methylphenyl)-6,7-dihydro-5H-dibenz[c,e]azepine-5-carbonitrile have been unambiguously confirmed by single-crystal X-ray crystallography.

Preparation and Characterization of Two New Luminescent Material

2011 ◽  
Vol 322 ◽  
pp. 365-368
Author(s):  
Zhi Xiang Ji
Keyword(s):  
Infrared Spectra ◽  
Elemental Analysis ◽  
Luminescent Properties ◽  
Ethanol Solution ◽  
Luminescent Materials ◽  
Luminescent Material ◽  
X Ray ◽  
X Ray Crystallography ◽  
Blue Region

Two new luminescent materials were prepared by the reaction of Eu (III) and Tb (III) ions with N’-(2-acetyl-3-methylpyrazine)-4-toluene-sulfonylhydrazide in ethanol solution, respectively. The composition of the luminescent materials was confirmed by elemental analysis, infrared spectra and X-ray crystallography. The luminescent properties of two new luminescent materials were investigated in solid. The results show that two new luminescent materials have strong characteristic luminescence in red and blue region, respectively.

Complexes of the crown thioether ligand 2,5,8-trithia[9]-o-benzenophane, (TT[9]OB). Synthesis and molecular structure of [Cu(NCS)(TT[9]OB)]

1991 ◽  
Vol 69 (7) ◽  
pp. 1141-1145 ◽  
Author(s):  
Stephen J. Loeb ◽  
George K. H. Shimizu
Keyword(s):  
Metal Centre ◽  
Neutral Complex ◽  
Orthorhombic Space Group ◽  
Acetonitrile Molecule ◽  
Molecular Conformations ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Thiocyanate Ligand ◽  
Distorted Tetrahedral Coordination

The macrocyclic thioether ligand 2,5,8-trithia[9]-o-benzenophane (TT[9]OB) reacts with [Cu(CH3CN)4][ClO4] to yield the Cu(I) complex [Cu(CH3CN)(TT[9]OB)][ClO4]. The coordinated acetonitrile molecule is displaced by the ambidentate, thiocyanate (NCS)− ion to form the neutral complex [Cu(NCS)(TT[9]OB)] which was characterized by infrared spectroscopy, 1H NMR spectroscopy, and X-ray crystallography. The title complex crystallized in the orthorhombic space group Pbca with a = 14.447(3) Å, b = 15.034(4) Å, c = 14.851(4) Å, V = 3232.2(14) Å3, and Z = 8. The structure refined to R = 5.15% and Rw = 5.92% for 1149 reflections with Fo2 > 3σ(Fo2). The Cu(I) ion has a distorted tetrahedral coordination sphere with TT[9]OB occupying three sites while the fourth site is occupied by the thiocyanate ligand which is N-bound to the metal centre. A comparison is made of the molecular conformations of free TT[9]OB and that found for complexed TT[9]OB in [Cu(NCS)(TT[9]OB)] and [Cu(Ph2PMe)(TT[9]OB)][ClO4]. Key words: thioether, macrocyclic metal complex.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

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