Stereochemistry of crown ethers, X-ray crystallographic structures, solid phase 13C NMR, and solution conformational equilibria in cis-syn-cis dicyclohexano-15-crown-5 ether and its sodium thiocyanate complex

1992 ◽  
Vol 70 (3) ◽  
pp. 981-991 ◽  
Author(s):  
G W Buchanan ◽  
S. Mathias ◽  
C. Bensimon ◽  
J. P. Charland
Keyword(s):  
Crown Ethers ◽  
Solid Phase ◽  
Sodium Thiocyanate ◽  
Free Energies ◽  
Ring Inversion ◽  
Thiocyanate Complex ◽  
X Ray ◽  
X Ray Crystallography ◽  
Temperature Solution ◽  
In Cis

The structures of the title materials have been determined via X-ray crystallography. In the free crown ether, there is effectively a plane of symmetry that bisects the molecule. In the NaNCS complex, ring inversion of one of the cyclo-hexane moieties has occurred, giving a distorted pentagonal pyramidal coordination geometry about the sodium ion. For the free crown, two conformers, whose free energies differ by ca. 0.5 kJ / mol in solution can be detected via 13C NMR at 168 K. Limiting low-temperature solution spectra are compared to those which have been obtained in the solid phase using the 13C CPMAS technique. Key words: crown ethers, stereochemistry, X-ray, NMR.

Dibenzo-15-crown-5 ether and its sodium thiocyanate complex. X-ray crystallographic and NMR studies in the solid phase and in solution

1991 ◽  
Vol 69 (3) ◽  
pp. 404-414 ◽  
Author(s):  
G. W. Buchanan ◽  
S. Mathias ◽  
Y. Lear ◽  
C. Bensimon
Keyword(s):  
Solid Phase ◽  
Free Ligand ◽  
Resonance Assignments ◽  
Sodium Thiocyanate ◽  
Torsional Angle ◽  
Nmr Studies ◽  
Thiocyanate Complex ◽  
X Ray ◽  
Asymmetric Structures ◽  
Temperature Solution

For the title systems, single crystal X-ray data indicate the presence of totally asymmetric structures. These features are reflected in the multiplicity of resonances in the solid phase 13C NMR spectra. Some of the 13C chemical shift trends are analyzed in terms of torsional angle influences. In solution, resonance assignments have been made with the aid of 2D methods. Stereochemical inferences are drawn from NOESY spectra and 1H–1H couplings. Low temperature solution experiments indicate that conformational interconversions in both the free ligand and the NaNCS complex are rapid on the NMR timescale down to 163 K. Key words: crown ethers, NMR, stereochemistry.

cis-Cyclohexano-9-crown-3 ether. Solid state and low-temperature solution stereochemistry as determined by X-ray crystallography and nuclear magnetic resonance spectroscopy

1993 ◽  
Vol 71 (7) ◽  
pp. 951-959 ◽  
Author(s):  
G.W. Buchanan ◽  
A.B. Driega ◽  
A. Moghimi ◽  
C. Bensimon ◽  
K. Bourque
Keyword(s):  
Low Temperature ◽  
Nmr Spectra ◽  
Solid Phase ◽  
Resonance Spectroscopy ◽  
Ring Inversion ◽  
X Ray ◽  
Common Features ◽  
X Ray Crystallography ◽  
Temperature Solution ◽  
C Nmr

The X-ray crystal structure of the title material has been determined at −130 °C. Low-temperature 1H1H COSY, 13C1H HETCOR, and DEPT 13C NMR spectra have been recorded, which permit unambiguous assignments of all carbon resonances when ring inversion is slow on the NMR timescale. The limiting low-temperature solution phase 13C spectrum has many common features with the solid phase 13C CPMAS spectrum recorded at 300 K. Spectra for the 7,10-tetra-deuterio derivative have also been obtained and substituent influences on 13C shieldings are discussed in detail.

Reformulation from x-ray crystallography of a dinuclear thiocyanate complex of rhenium. The first observation of solely N-bonded, bridging thiocyanate

1979 ◽  
Vol 18 (10) ◽  
pp. 2719-2723 ◽  
Author(s):  
F. Albert Cotton ◽  
Alan Davison ◽  
William H. Ilsley ◽  
Harvey S. Trop
Keyword(s):  
Thiocyanate Complex ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Charting Hydrogen Bond Anisotropy

2019 ◽  
Author(s):  
Diogo Santos-Martins ◽  
Stefano Forli
Keyword(s):  
Hydrogen Bond ◽  
Chemical Biology ◽  
Solid Phase ◽  
Electronic Configuration ◽  
Interaction Energies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Chemical Groups ◽  
High Degree ◽  
Context Free

<div>Hydrogen bond (HB) is an essential interaction in countless phenomena, and regulates the chemistry of life. HBs are characterized by two main features, strength and directionality, with a high degree of heterogeneity across different chemical groups. These characteristics are dependent on the electronic configuration of the atoms involved in the interaction, which, in turn, is influenced strongly by the molecular environment where they are found. Studies based on the analysis of HB in solid phase, such as X-ray crystallography, suffer from significant biases due to the packing forces. These will tend to better describe strong HBs at the expenses of weak ones, which are either distorted or under represented. Using quantum mechanics (QM), we calculated interaction energies for about a hundred acceptor and donors, in a rigorously defined set of geometries. We performed about 180,000 independent QM calculations, covering all relevant angular components, and mapping strength and directionality in a context free from external biases, with both single-site and cooperative HBs. We show that by quantifying directionality, there is not correlation with strength, and therefore these two components need to be addressed separately. Results demonstrate that there are very strong HB acceptors (e.g.,DMSO) with nearly isotropic interactions, and weak ones (e.g.,thioacetone) with a sharp directional profile. Similarly, groups can have comparable directional propensity, but be very distant in the strength spectrum (e.g., thioacetone and pyridine). These findings have implications for biophysics and molecular recognition, providing new insight for chemical biology, protein engineering, and drug design. The results require rethinking the way directionality is described, with implications for the thermodynamics of HB.</div>

The first naphthodiazaphosphorinane in the solid phase; syntheses, spectroscopic studies and X-ray crystallography of some new 1,3,2-diheterophosphorus compounds

2009 ◽  
Vol 20 (3) ◽  
pp. 481-488 ◽  
Author(s):  
Khodayar Gholivand ◽  
Zahra Shariatinia ◽  
Sheida Ansar ◽  
Seyedeh Mahdieh Mashhadi ◽  
Farzaneh Daeepour
Keyword(s):  
Solid Phase ◽  
Spectroscopic Studies ◽  
X Ray ◽  
X Ray Crystallography

A novel 1:1 benzenesulfonamide: 18-crown-6 complex as uncovered via 13C solid phase NMR spectroscopy and X-ray crystallography

1989 ◽  
Vol 67 (7) ◽  
pp. 1212-1218 ◽  
Author(s):  
G. W. Buchanan ◽  
C. Morat ◽  
J. P. Charland ◽  
C. I. Ratcliffe ◽  
J. A. Ripmeester
Keyword(s):  
Crown Ether ◽  
Correlation Time ◽  
Molecular Motion ◽  
Solid Phase ◽  
Crystallographic Structure ◽  
Temperature Dependent ◽  
X Ray ◽  
X Ray Crystallography ◽  
Anisotropic Motion ◽  
Motional Correlation Time

A 1:1 complex of 18-crown-6 ether and benzenesulfonamide has been prepared, whose melting point is within 4° of the previously reported 1:2 complex. The X-ray crystallographic structure shows pseudo D3d symmetry in the crown ether portion of this complex, in contrast to the 1:2 complex, which exhibits Ci symmetry in the macrocycle. The temperature dependent 13C CPMAS NMR spectra of these complexes have two regions of broadening for the crown ether carbons. At higher temperatures, a dipolar "washout" mechanism is operative, leading to broadening when molecular motion has a correlation time approximately equal to the inverse of the decoupling field. At lower temperatures broadening occurs when the motional correlation time is equal to the inverse of the chemical shift difference. From application of the Arrhenius equation, the activation energy for the molecular motion in solid 18-crown-6 is found to be approximately 10kcal/mol. Evidence for independent anisotropic motion in the benzenesulfonamide moiety of the 1:1 complex is also presented. Keywords: crown ether, molecular motion, solid phase NMR.

Synthesis of cis-p-dioxano-12-crown-4 and X-ray crystallography of the (1:1) complex with lithium thiocyanate

1998 ◽  
Vol 76 (2) ◽  
pp. 142-146
Author(s):  
Alex B Driega ◽  
Gerald W Buchanan ◽  
Corinne Bensimon
Keyword(s):  
Crown Ethers ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Group A ◽  
Lithium Thiocyanate

The synthesis of a novel 12-crown-4 analogue (cis-p-dioxano-12-crown-4 or cis-3,6,9,13,15- pentaoxabicyclo[9.3.1]pentadecane) is described. The (1:1) LiNCS complex crystallizes in the monoclinic Cc space group; a = 8.4973(2) Å, b = 18.0659(4) Å, c = 8.9168(1) Å, and β = 90.713(1)° with Z = 4. The crown adopts C1 symmetry to which the Li+ is coordinated in a rectangular pyramid with an apical -NCS.Key words: crown ethers, structure, complexation.

scholarly journals 2′-Methylseleno-modified oligoribonucleotides for X-ray crystallography synthesized by the ACE RNA solid-phase approach

2007 ◽  
Vol 36 (3) ◽  
pp. 970-983 ◽  
Author(s):  
Barbara Puffer ◽  
Holger Moroder ◽  
Michaela Aigner ◽  
Ronald Micura
Keyword(s):  
Solid Phase ◽  
X Ray ◽  
Phase Approach ◽  
X Ray Crystallography

DielsAlderCyclization of a Dihydropyridine: NMR Spectroscopy, X-Ray Crystallography, and DFT Computations. Bent Aromatic Dimeric Clusters in the Solid Phase

2014 ◽  
Vol 97 (10) ◽  
pp. 1365-1382
Author(s):  
Gideon Fraenkel ◽  
Jinhua Song ◽  
Albert Chow ◽  
Judith C. Gallucci
Keyword(s):  
Nmr Spectroscopy ◽  
Solid Phase ◽  
X Ray ◽  
Dft Computations ◽  
X Ray Crystallography
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