The Importance of Lone Pair Electron Delocalization in thecis–transIsomers of 1,2-Dibromoethenes

2005 ◽  
Vol 34 (8) ◽  
pp. 1190-1191 ◽  
Author(s):  
Takashi Yamamoto ◽  
Daisuke Kaneno ◽  
Shuji Tomoda
Keyword(s):  
Lone Pair ◽  
Electron Delocalization ◽  
Lone Pair Electron

Anomalous stabilizing and destabilizing effects in some cyclic π-electron systems

1993 ◽  
Vol 71 (8) ◽  
pp. 1123-1127 ◽  
Author(s):  
Peter Politzer ◽  
M. Edward Grice ◽  
Jane S. Murray ◽  
Jorge M. Seminario
Keyword(s):  
Ab Initio ◽  
Lone Pair ◽  
Electrostatic Potentials ◽  
Electron Delocalization ◽  
Isodesmic Reaction ◽  
Computational Studies ◽  
Electron Systems ◽  
Molecular Electrostatic Potentials ◽  
Lone Pairs

Ab initio computational studies have been carried out for three molecules that are commonly classed as antiaromatic: cyclobutadiene (1), 1,3-diazacyclobutadiene (7), and 1,4-dihydropyrazine (6). Their dinitro and diamino derivatives were also investigated. Stabilizing or destabilizing energetic effects were quantified by means of the isodesmic reaction procedure at the MP2/6-31G*//HF/3-21G level, and calculated molecular electrostatic potentials (HF/STO-5G//HF/3-21G) were used as a probe of electron delocalization. Our results do not show extensive delocalization in the π systems of any one of the three parent molecules. The destabilization found for 1 and 7 is attributed primarily to strain and to repulsion between the localized π electrons in the C=C and C=N bonds, respectively. However, 6 is significantly stabilized, presumably due to limited delocalization of the nitrogen lone pairs. NH2 groups are highly stabilizing, apparently because of lone pair delocalization. NO2 is neither uniformly stabilizing nor destabilizing.

Lone-Pair-Electron-Driven Ionic Displacements in a Ferroelectric Metal–Organic Hybrid

2016 ◽  
Vol 55 (20) ◽  
pp. 10337-10342 ◽  
Author(s):  
Wen-Ping Zhao ◽  
Chao Shi ◽  
Alessandro Stroppa ◽  
Domenico Di Sante ◽  
Fanica Cimpoesu ◽  
...  
Keyword(s):  
Lone Pair ◽  
Organic Hybrid ◽  
Lone Pair Electron ◽  
Metal Organic

scholarly journals Theoretical Study of Sigmatropic Rearrangement of Cycloprop-2-en-1-ol and its Fluorine Derivatives: Pericyclic or Pseudopericyclic Character from NICS and LLPE

2019 ◽  
Vol 31 (3) ◽  
pp. 597-601
Author(s):  
A. Sangeetha ◽  
A. Thaminum Ansari ◽  
Jebakumar Jeevanandam ◽  
S. Jayaprakash
Keyword(s):  
Oxygen Atom ◽  
Gas Phase ◽  
Energy Barrier ◽  
Fluorine Atom ◽  
Theoretical Study ◽  
Lone Pair ◽  
Sigmatropic Rearrangement ◽  
Nucleus Independent Chemical Shift ◽  
Lone Pair Electron ◽  
Rearrangement Reaction

Sigmatropic rearrangement reaction of cycloprop-2-en-1-ol and its fluorine derivatives has been studied theoretically in gas phase and its energy barrier has been calculated. Nucleus-independent chemical shift (NICS) shows sigmatropic rearrangement of cycloprop-2-en-1-ol is pericyclic in nature whereas fluorine derivatives show pseudopericyclic and pericyclic nature. Substitution of fluorine atom at ring is found to increase the energy barrier for –OH migration, while substitution at oxygen atom reduces the barrier. To know the involvement of lone pair of electrons during the reaction, lone pair electron present on oxygen atom is locked by hydrogen bonding. CR-CCSD(T)/6-311+G** levels are used to study the reactions more accurately.

Preparation and properties of sulfur-containing tetraazaporphyrin iron supported on anion-exchange resin

2005 ◽  
Vol 09 (08) ◽  
pp. 537-543 ◽  
Author(s):  
Yuping Lei ◽  
Jie Sun ◽  
Changjun Yang ◽  
Kejian Deng ◽  
Duoyuan Wang
Keyword(s):  
Molecular Oxygen ◽  
Exchange Resin ◽  
Anion Exchange Resin ◽  
Active Oxygen Species ◽  
Oxidative Degradation ◽  
Lone Pair ◽  
Nitrobenzoic Acid ◽  
Lone Pair Electron ◽  
The Stability ◽  
Sulfur Containing

An anion-resin carrying the catalyst iron(II) tetra(1,4-dithin)porphyrazine, ( Fe (II) Pz ( dtn )4/resin), may effectively interact with the lone-pair electron of the sulfur in the Fe (II) Pz ( dtn )4 to keep the absorption for the catalyst molecule, which can efficiently activate molecular oxygen coordinated with iron(II) on the axial orientation of Fe (II) Pz ( dtn )4 through electron transfer in a heterogeneous process. On the other hand, the hydrophilic property of the resin also facilitates adsorption of the anion-substrates in the aqueous solution onto the unoccupied resin surface to increase the substrate concentration around the Fe (II) Pz ( dtn )4 and the contact probability between the substrate with activated molecular oxygen to promote the oxidative degradation of these adsorbed substrates. The stability and repeatability of the Fe (II) Pz ( dtn )4/resin were determined by some control experiments. The results indicate that Fe (II) Pz ( dtn )4 was stable enough in the presence of active oxygen species under irradiation of visible light and could degrade recalcitrant organic pollutants such as rhodamine B and p-nitrobenzoic acid. It can be reused at least 5 cycling runs without losing activity.

Molecular dynamics simulations of N-methylacetamide (NMA) in water by the ABEEM/MM model

2009 ◽  
Vol 87 (12) ◽  
pp. 1738-1746 ◽  
Author(s):  
Ping Qian ◽  
Li-Nan Lu ◽  
Zhong-Zhi Yang
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Potential Model ◽  
Lone Pair ◽  
Static Properties ◽  
Range Interaction ◽  
Hydrogen Bond Interaction ◽  
Lone Pair Electron ◽  
Dynamics Simulations

The N-methylacetamide (NMA) is a very interesting kind of compound and often serves as a model of the peptide bond. The interaction between NMA and water provides a convenient prototype for the solvation of peptides in aqueous solutions. We have carried out molecular dynamics (MD) simulations of a NMA molecule in water under 1 atm and 298 K. The simulations make use of the newly developed NMA–water fluctuating charge ABEEM/MM potential model ( Yang, Z. Z.; Qian, P. J. Chem. Phys. 2006, 125, 064311 ), which is based on the combination of the atom-bond electronegativity equalization method (ABEEM) and molecular mechanics (MM). This model has been successfully applied to NMA–water gas clusters, NMA(H2O)n (n = 1–6), and accurately reproduced many static properties. For the NMA–water ABEEM/MM potential model, two characters must be emphasized in the simulations. Firstly, the model allows the charges in system to fluctuate, responding to the ambient environment. Secondly, for two major types of intermolecular hydrogen bonds, which are the hydrogen bond forming between the lone-pair electron on amide oxygen and the water hydrogen, and the one forming between the lone-pair electron on water oxygen and the amide hydrogen, we take special treatments in describing the electrostatic interaction by the use of the parameters klpO=,H and klpO–,HN–, respectively, which explicitly describe the short-range interaction of hydrogen bonds in the hydrogen bond interaction region. All sorts of properties have been studied in detail, such as, radial distribution function, energy distribution, ABEEM charge distribution and dipole moment, and so on. These simulation results show that the ABEEM/MM-based NMA–water potential model appears to be robust, giving the solution properties in excellent agreement with other dynamics simulations on similar systems.

X-ray excited ultralong room-temperature phosphorescence for organic afterglow scintillators

2020 ◽  
Vol 56 (88) ◽  
pp. 13559-13562
Author(s):  
Lele Tang ◽  
Jie Zan ◽  
Hao Peng ◽  
Xi Yan ◽  
Ye Tao ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Room Temperature ◽  
Lone Pair ◽  
Room Temperature Phosphorescence ◽  
X Ray ◽  
Lone Pair Electron

An X-ray excited organic afterglow scintillator is realized by embedding lone-pair electron involved n–π* transitions and charge transfer characters into H-aggregations.

PYRAMIDALITY AND AROMATICITY IN POLYPHOSPHAPHOSPHOLES

2008 ◽  
Vol 07 (06) ◽  
pp. 1203-1214 ◽  
Author(s):  
WEI-QI LI ◽  
LI-LI LIU ◽  
JI-KANG FENG ◽  
ZI-ZHONG LIU ◽  
AI-MIN REN ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Phosphorus Atom ◽  
Lone Pair ◽  
Ring Strain ◽  
Aromatic Molecules ◽  
Lone Pair Electron

Ab initio calculations show that, for the P n( CH )4-n PH with n = 0 - 4, the fully optimized structures have decreasing pyramidality at the tri-coordinated phosphorus atom with n. The interaction between the tri-coordinated phosphorus [Formula: see text] and the carbons–phosphorus π-system [Formula: see text] with different n, the differences of the structure, electron properties and energy among the phospholes indicate that the ring strain and the delocalization of the lone pair electron of tri-coordinated phosphorus should be responsible for this phenomena. Various aromatic criteria such as geometry, magnetism, and energy show that these molecules are aromatic, and their aromaticities increase with the number of phosphorus atoms in the nonplanar pentagons. The electron circulation in the aromatic molecules can promote the delocalization of the lone pair. In contrast to the B3LYP prediction, we draw some similar conclusions, but the planarity and aromaticity of molecules increase largely at the MP2 lever due to the consideration of electron correlation.

Charge density study of hydrogen [(2,4-diaminopyrimidin-1-io)methyl]phosphonate monohydrate

2002 ◽  
Vol 58 (3) ◽  
pp. 519-529 ◽  
Author(s):  
Miroslav Slouf ◽  
Antonin Holy ◽  
Václav Petříček ◽  
Ivana Cisarova
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Charge Density ◽  
Electron Density ◽  
Lone Pair ◽  
X Ray Diffraction ◽  
Area Detector ◽  
Density Maps ◽  
Lone Pair Electron ◽  
Deformation Electron Density

The crystal structure and charge density of hydrogen (2,4-diaminopyrimidin-1-io)methyl]phosphonate monohydrate, C5H9N4O3P·H2O, have been determined by means of single-crystal X-ray diffraction. Diffraction data were collected at 105 K with Mo Kα radiation to a resolution of sin θ/λ = 1.08 Å−1. A four-circle diffractometer equipped with a CCD area detector was used to collect 50 161 reflections over 3 d. 6082 unique reflections with I > 3σ(I) were used in the multipole model to map the deformation electron density and gave the final statistical factors R(F) = 0.0329, wR(F) = 0.0235 and g.o.f. = 1.37. Structure determination revealed that two O atoms in the crystal structure of the title compound act as hydrogen-bond acceptors for more than one hydrogen bond. Examination of deformation electron density maps showed preferential polarization of the lone-pair electron density of the two O atoms into the shortest hydrogen bonds.

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