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.

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.

Stereochemistry of oxygenated 10-membered rings: X-ray crystal structure, theoretical calculations and 1H and 13C NMR studies of benzo-10-crown-3 ether in solution and in the solid phase

1997 ◽  
Vol 404 (3) ◽  
pp. 307-317 ◽  
Author(s):  
G.W. Buchanan ◽  
M. Gerzain ◽  
C. Bensimon ◽  
R. Ellen ◽  
V.M. Reynolds
Keyword(s):  
Crystal Structure ◽  
13C Nmr ◽  
Solid Phase ◽  
Theoretical Calculations ◽  
Nmr Studies ◽  
1H And 13C Nmr ◽  
X Ray

An example of conformational disorder in solids: X-ray crystallographic and 13C CPMAS NMR studies of dibenzo and dicyclohexano-13-crown-4 ethers and some lithium complexes

1990 ◽  
Vol 68 (1) ◽  
pp. 49-58 ◽  
Author(s):  
G. W. Buchanan ◽  
R. A. Kirby ◽  
J. P. Charland
Keyword(s):  
Crystal Structure ◽  
Crown Ethers ◽  
Nmr Spectra ◽  
Solid Phase ◽  
Nmr Studies ◽  
13C Cpmas Nmr ◽  
Conformational Disorder ◽  
X Ray ◽  
Lithium Complexes ◽  
Cis Isomer

For the cis–anti–cis isomer of dicyclohexano-13-crown-4 ether, disorder has been detected in the crystal structure, with two conformations being present in the ratio of ca. 3:2. Crystal structures for two Li+ complexes of the cis–syn–cis isomer have also been determined. Representative 13C solid phase NMR spectra are presented and discussed for these systems and the related dibenzo substituted compounds. Keywords: crown ethers, solids, NMR, conformation.

Benzo-9-crown-3 ether: X-ray crystal structure, NMR studies in solution and the solid phase, and ab initio calculations of isotropic 13C chemical shifts using LORG with a D95V basis set

1993 ◽  
Vol 71 (12) ◽  
pp. 1983-1989 ◽  
Author(s):  
G.W. Buchanan ◽  
A.B. Driega ◽  
A. Moghimi ◽  
C. Bensimon ◽  
R.A. Kirby ◽  
...  
Keyword(s):  
Ab Initio ◽  
Solid Phase ◽  
Chemical Shifts ◽  
Basis Set ◽  
Length Variation ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
X Ray ◽  
Localized Orbital ◽  
C Nmr

Using the X-ray crystal geometry as input, the 13C NMR chemical shifts of benzo-9-crown-3 ether have been calculated via ab initio methods using a localized orbital local origin (LORG) approach. Reasonable agreement is found between the calculated values for an isolated molecule in the gas phase and those obtained in the 13C CPMAS NMR spectrum. Solid phase 13C spectra of the C7,10-d4 derivative confirm the existence of a 7.9 ppm shift difference between these sites in the solid, whereas in solution they are conformationally averaged to one resonance. The effects of C—H bond length variation on calculated 13C shifts have been explored.

ChemInform Abstract: X-RAY AND NMR STUDIES OF A CYCLOPHOSPHAMIDE-LIKE MOLECULE, CIS-2-OXO-2-DIMETHYLAMINO-3-PHENYL-5-TERT-BUTYL-1,3,2-OXAZAPHOSPHORINANE. TWIST CONFORMATION IN BOTH SOLID PHASE AND IN SOLUTION

1979 ◽  
Vol 10 (26) ◽  
Author(s):  
G. S. BAJWA ◽  
W. G. BENTRUDE ◽  
N. S. PANTALEO ◽  
M. G. NEWTON ◽  
J. H. HARGIS
Keyword(s):  
Solid Phase ◽  
Nmr Studies ◽  
X Ray ◽  
Tert Butyl ◽  
Twist Conformation

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.

X-ray and NMR studies of a cyclophosphamide-like molecule, cis-2-oxo-2-dimethylamino-3-phenyl-5-tert-butyl-1,3,2-oxazaphosphorinane. Twist conformation in both solid phase and in solution

1979 ◽  
Vol 101 (6) ◽  
pp. 1602-1604 ◽  
Author(s):  
Gurdip S. Bajwa ◽  
Wesley G. Bentrude ◽  
N. S. Pantaleo ◽  
M. Gary Newton ◽  
J. Howard Hargis
Keyword(s):  
Solid Phase ◽  
Nmr Studies ◽  
X Ray ◽  
Tert Butyl ◽  
Twist Conformation

Impact of Rutile Fraction on TiO2 Visible-Light Absorption and Visible-Light-Induced Photocatalytic Activity

2018 ◽  
Author(s):  
David Maria Tobaldi ◽  
Luc Lajaunie ◽  
ana caetano ◽  
nejc rozman ◽  
Maria Paula Seabra ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Light Absorption ◽  
Solid Phase ◽  
Diffraction Method ◽  
Band Alignment ◽  
Quantitative Phase Analysis ◽  
Transmission Microscopy ◽  
Visible Light Absorption ◽  
X Ray

<div>Titanium dioxide is by far the most utilised semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile−anatase mixture would improve its visible-light absorption.</div><div>In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2. </div><div>The structural characterisation was done via advanced X-ray diffraction method, namely the Rietveld-RIR method, to attain a full quantitative phase analysis of the specimens. The microstructure was also investigated via an advanced X-ray method, the whole powder pattern modelling. These methods were validated combining advanced aberration-corrected scanning transmission microscopy and high-resolution electron energy-loss spectroscopy. The photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range.</div><div>Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light?</div><div>We tried to give a reply to that question.</div><div>Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-induced catalytic activity (i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects). That is: not photocatalysis <i>sensu-strictu</i>.</div><div>On the other hand, the gas-solid phase results showed that a higher amount of the rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for an actual photocatalytic oxidation of isopropanol.</div>

New Copper Compounds with Antiplatelet Aggregation Activity

2019 ◽  
Vol 15 (8) ◽  
pp. 850-862
Author(s):  
Mirthala Flores-García ◽  
Juan Manuel Fernández-G. ◽  
Cristina Busqueta-Griera ◽  
Elizabeth Gómez ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Schiff Base ◽  
Solid State ◽  
Thrombotic Event ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
Schiff Base Ligands ◽  
X Ray ◽  
Antiplatelet Aggregation ◽  
Aggregation Activity ◽  
L1 And L2

Background: Ischemic heart disease, cerebrovascular accident, and venous thromboembolism have the presence of a thrombotic event in common and represent the most common causes of death within the population. Objective: Since Schiff base copper(II) complexes are able to interact with polyphosphates (PolyP), a procoagulant and potentially prothrombotic platelet agent, we investigated the antiplatelet aggregating properties of two novel tridentate Schiff base ligands and their corresponding copper( II) complexes. Methods: The Schiff base ligands (L1) and (L2), as well as their corresponding copper(II) complexes (C1) and (C2), were synthesized and characterized by chemical analysis, X-ray diffraction, mass spectrometry, and UV-Visible, IR and far IR spectroscopy. In addition, EPR studies were carried out for (C1) and (C2), while (L1) and (L2) were further analyzed by 1H and 13C NMR. Tests for antiplatelet aggregation activities of all of the four compounds were conducted. Results: X-ray diffraction studies show that (L1) and (L2) exist in the enol-imine tautomeric form with a strong intramolecular hydrogen bond. NMR studies show that both ligands are found as enol-imine tautomers in CDCl3 solution. In the solid state, the geometry around the copper(II) ion in both (C1) and (C2) is square planar. EPR spectra suggest that the geometry of the complexes is similar to that observed in the solid state by X-ray crystallography. Compound (C2) exhibited the strongest antiplatelet aggregation activity. Conclusion: Schiff base copper(II) complexes, which are attracting increasing interest, could represent a new approach to treat thrombosis by blocking the activity of PolyP with a potential anticoagulant activity and, most importantly, demonstrating no adverse bleeding events.

Solution multinuclear (31P,111Cd,77Se) magnetic resonance studies of cadmium complexes of heterocyclic aromatic thiones and the structure of [tetrakis(2(1H)-pyridinethione)cadmium] nitrate, [Cd(C5H5NS)4](NO3)2

2000 ◽  
Vol 78 (5) ◽  
pp. 590-597 ◽  
Author(s):  
Umarani Rajalingam ◽  
Philip AW Dean ◽  
Hilary A Jenkins
Keyword(s):  
Cadmium Nitrate ◽  
Cadmium Complexes ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stoichiometric Reaction ◽  
Complex Salts ◽  
Reduced Temperature ◽  
Aromatic Heterocyclic ◽  
Phosphine Chalcogenides

The complex salts CdL4(O3SCF3)2 (L = 2(1H)-pyridinethione (Py2SH), 4(1H)-pyridinethione (Py4SH), or 2(1H)-quinolinethione (Q2SH)) have been synthesized by the stoichiometric reaction of Cd(O3SCF3)2 and the appropriate thione. Both ambient-temperature 13C and reduced-temperature 111Cd NMR of CdL4(O3SCF3)2 in solution are consistent with L being bound through sulfur. Reduced-temperature NMR (31P, 77Se, 111Cd, as appropriate) of mixtures of CdL4(O3SCF3)2 and Cd(EPCy3)4(O3SCF3)2 (E = Se, Cy = c-C6H11) and of Cd(EPCy3)4(O3SCF3)2 (E = S, Se) and L in solution provides evidence for various [CdLn(EPCy3)4-n]2+. Similarly, reduced-temperature metal NMR of [CdL4]2+ and [CdL'4]2+ (L, L' = Py2SH, Py4SH, Q2SH; L not equal L') in solution shows the formation of [CdLnL'4-n]2+. Thus it has been demonstrated that at reduced temperature [CdL4]2+ is intact in solution and exchange of L is slow on the timescale of the metal chemical shift differences. From the NMR studies of Cd(EPCy3)4(O3SCF3)2 (E = S, Se):L mixtures, the binding preferences are found to be L > EPCy3 in solution. Similarly, from the reduced temperature metal NMR spectra of mixtures where L and L' compete for Cd(II) in solution, the binding preferences are Py4SH > Py2SH > Q2SH. The structure of Cd(Py2SH)4(NO3)2 (4) has been determined by single crystal X-ray analysis. Colorless crystals of 4 are tetragonal, I4(1)/acd with 8 molecules per unit cell of dimensions a = 18.660(3), c = 15.215(3) Å. The structure is comprised of recognizable NO3- anions and [Cd(Py2SH)4]2+ cations. In the cations, which have S4 symmetry, the ligands are S-bound. A network of NH···O hydrogen bonds links the cations and anions.Key words: aromatic heterocyclic thiones, cadmium complexes, phosphine chalcogenides, 111Cd, 31P, 77Se NMR, X-ray crystallography.

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