π-Hole aerogen bonding interactions

2015 ◽  
Vol 17 (38) ◽  
pp. 24748-24753 ◽  
Author(s):  
Antonio Bauzá ◽  
Antonio Frontera
Keyword(s):  
Ab Initio ◽  
Computational Tools ◽  
X Ray ◽  
Square Planar ◽  
High Level

High level ab initio calculations combined with the analysis of available X-ray structures demonstrate the importance of π-hole aerogen bonding interactions in Xe(iv) compounds. The ability of square planar XeF4 and Xe(OMe)4 compounds to interact with electron rich molecules is rationalized using several computational tools.

Radiological safety and assessment of the performance of X-ray systems in veterinary facilities

2020 ◽  
Author(s):  
S. Economides ◽  
C.J. Hourdakis ◽  
C. Pafilis ◽  
G. Simantirakis ◽  
P. Tritakis ◽  
...  
Keyword(s):  
Decision Making ◽  
Radiation Protection ◽  
Atomic Energy Commission ◽  
Atomic Energy ◽  
Regulatory Control ◽  
Continuous Training ◽  
X Ray ◽  
The Public ◽  
Radiological Safety ◽  
High Level

This paper concerns an analysis regarding the performance of X-ray equipment as well as the radiological safety in veterinary facilities. Data were collected from 380 X-ray veterinary facilities countrywide during the on-site regulatory inspections carried out by the Greek Atomic Energy Commission. The analysis of the results shows that the majority of the veterinary radiographic systems perform within the acceptable limits; moreover, the design and shielding of X-ray rooms as well as the applied procedures ensure a high level of radiological safety for the practitioners, operators and the members of the public. An issue that requires specific attention in the optimization process for the proper implementation of veterinary radiology practices in terms of radiological safety is the continuous training of the personnel. The above findings and the regulatory experience gained were valuable decision-making elements regarding the type of the regulatory control of veterinary radiology practices in the new radiation protection framework.

Der Einfluß der Inaktivitätsosteoporose auf die szintigraphische Darstellung knöcherner Verletzungen im Bereich des Handgelenks

1989 ◽  
Vol 28 (04) ◽  
pp. 124-128 ◽  
Author(s):  
J. Spitz ◽  
N. Clemenz ◽  
K. Tittel ◽  
H. Weigand
Keyword(s):  
Bone Scintigraphy ◽  
Plaster Cast ◽  
Scaphoid Bone ◽  
X Ray ◽  
The Third ◽  
High Level ◽  
Clinical Conditions ◽  
Rate Of Accumulation

In addition to its established oncological indications the sensitivity of bone scintigraphy is of steadily increasing significance in traumatology. Inactivity- induced osteoporosis plays a major role during the immobilization period in the plaster cast. In the region of the joints remodelling intensity may reach such a high level that the non-injured bone shows a higher rate of accumulation than the fracture. This process already begins between the third and fourth week of immobilization. The highest uptake is found after fracture of the scaphoid bone at the end of twelve weeks of immobilization. Control scintigraphies at intervals of several days are indicated to differentiate between various clinical conditions (pseudoarthrosis, activated osteoarthrosis, algodystrophy in case of doubtful x-ray results).

Interaction of ditertiary phosphines with phenyl- and 1-naphthyldithiocarbamatonickel(II)

1985 ◽  
Vol 50 (6) ◽  
pp. 1383-1390
Author(s):  
Aref A. M. Aly ◽  
Ahmed A. Mohamed ◽  
Mahmoud A. Mousa ◽  
Mohamed El-Shabasy
Keyword(s):  
Thermal Analysis ◽  
Powder Diffraction ◽  
Spin Structure ◽  
Magnetic Measurements ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
X Ray ◽  
Square Planar

The synthesis of the following mixed ligand complexes is reported: [Ni(phdtc)2(dpm)2], [Ni(phdtc)2(dpe)2], [Ni(phdtc)2(dpp)3], [Ni(1-naphdtc)2(dpm)2], [Ni(1-naphdtc)2], and [Ni(1-naphdtc)2(dpp)2], where phdtc = PhNHCSS-, 1-naphdtc = 1-NaPhNHCSS-, dpm = Ph2PCH2PPh2, dpe = Ph2P(CH2)2PPh2, and dpp = Ph2P(CH2)3PPh2. The complexes are characterised by microanalysis, IR and UV-Vis spectra, magnetic measurements, conductivity, X-ray powder diffraction, and thermal analysis. All the mixed ligand complexes are diamagnetic, and thus a square-planar or square-pyramidal (low-spin) structure was proposed for the present complexes.

Synthesis and Structure of a Clathrated Two-Dimensional Metal-Organic Framework: [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2·H2O (L = Bis(1-pyrazinylethylidene)hydrazine)

2008 ◽  
Vol 73 (1) ◽  
pp. 24-31
Author(s):  
Dayu Wu ◽  
Genhua Wu ◽  
Wei Huang ◽  
Zhuqing Wang
Keyword(s):  
Metal Organic Framework ◽  
Channel Structure ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Square Planar ◽  
Metal Organic ◽  
Aqueous Meoh ◽  
Organic Framework

The compound [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2 was obtained by the reaction of Cd(ClO4)2, bis(1-pyrazinylethylidene)hydrazine (L) and 4,4'-bipyridine in aqueous MeOH. Single-crystal X-ray diffraction has revealed its two-dimensional metal-organic framework. The 2-D layers superpose on each other, giving a channel structure. The square planar grids consist of two pairs of shared edges with Cd(II) ion and a 4,4'-bipyridine molecule each vertex and side, respectively. The square cavity has a dimension of 11.817 × 11.781 Å. Two guest molecules of bis(1-pyrazinylethylidene)hydrazine are clathrated in every hydrophobic host cavity, being further stabilized by π-π stacking and hydrogen bonding. The results suggest that the hydrazine molecules present in the network serve as structure-directing templates in the formation of crystal structures.

Configurational Assignment and Conformational Study of Methylglyoxal Bisdimethylhydrazones Derived from the 2-Ethoxypropenal Precursor

2006 ◽  
Vol 59 (3) ◽  
pp. 211 ◽  
Author(s):  
Leonid B. Krivdin ◽  
Lyudmila I. Larina ◽  
Kirill A. Chernyshev ◽  
Natalia A. Keiko
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Experimental Measurements ◽  
Conformational Study ◽  
Lone Pairs ◽  
Configurational Assignment ◽  
Out Of Plane ◽  
High Level

A configurational assignment of the isomeric methylglyoxal bisdimethylhydrazones derived from the 2-ethoxypropenal precursor has been performed based on experimental measurements and high-level ab initio calculations of 1J(C,C) and 1J(C,H) couplings. The results reveal the marked stereochemical dependence upon the orientation of the lone pairs of both nitrogen atoms in different isomers. Methylglyoxal bisdimethylhydrazone is shown to exist in a mixture of the EE and ZE isomers (ca. 75:25), both of which adopt predominant s-trans conformations with minor (up to 8°) out-of-plane deviations.

scholarly journals The Degree of Oxidation of Graphene Oxide

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 560
Author(s):  
Alexandra Carvalho ◽  
Mariana C. F. Costa ◽  
Valeria S. Marangoni ◽  
Pei Rou Ng ◽  
Thi Le Hang Nguyen ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Ab Initio ◽  
State Of The Art ◽  
High Accuracy ◽  
Precise Determination ◽  
Photoemission Spectroscopy ◽  
Pristine Graphene ◽  
X Ray ◽  
Degree Of Oxidation

We show that the degree of oxidation of graphene oxide (GO) can be obtained by using a combination of state-of-the-art ab initio computational modeling and X-ray photoemission spectroscopy (XPS). We show that the shift of the XPS C1s peak relative to pristine graphene, ΔEC1s, can be described with high accuracy by ΔEC1s=A(cO−cl)2+E0, where c0 is the oxygen concentration, A=52.3 eV, cl=0.122, and E0=1.22 eV. Our results demonstrate a precise determination of the oxygen content of GO samples.

scholarly journals The influence of exocyclic lone pairs on the bonding and geometry of type A mesoionic rings

2021 ◽  
Author(s):  
Christopher Antony Ramsden ◽  
Wojciech Piotr Oziminski
Keyword(s):  
Ab Initio ◽  
Type A ◽  
Nbo Analysis ◽  
Ring Systems ◽  
X Ray ◽  
X Ray Crystallography ◽  
Bond Model ◽  
Lone Pairs ◽  
Mp2 Calculations ◽  
Good Agreement

AbstractBased on structures determined by X-ray crystallography, ab initio MP2 calculations on type A mesoionic rings give geometries in good agreement with observed values. A study of four mesoionic ring systems, each with exocyclic oxygen, nitrogen or carbon groups, shows that the presence and configuration of exocyclic lone pairs significantly influences the geometry and configurational preference. Using a localised bond model and NBO analysis, these effects are rationalised in terms of an anomeric interaction of lone pairs with the antibonding orbitals of adjacent σ bonds. In agreement with experiment, similar effects are calculated for pyran-2-imines.

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