Importance of the nitrogen lone electron pair orientation in stereospecific opiates

1974 ◽  
Vol 17 (8) ◽  
pp. 907-908 ◽  
Author(s):  
B. Belleau ◽  
T. Conway ◽  
F. R. Ahmed ◽  
A. D. Hardy
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Nitrogen Lone Electron Pair

14N Nuclear Quadrupole Coupling Constants of Acetamide and α-Fluoroacetamide

1993 ◽  
Vol 48 (7) ◽  
pp. 787-792 ◽  
Author(s):  
N. Heineking ◽  
H. Dreizler
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Coupling Constants ◽  
Rotational Spectra ◽  
Quadrupole Coupling ◽  
Full Coupling ◽  
Nuclear Quadrupole ◽  
First Time ◽  
Hyperfine Structures ◽  
Nitrogen Lone Electron Pair

Abstract The 14N nuclear quadrupole hyperfine structures in the rotational spectra of acetamide, CH3CONH2 , and α-fluoroacetamide, FCH2CONH2 , have been resolved. From the observed patterns, the quadrupole coupling constants have been determined with high precision. The results provide evidence of considerable derealization of the nitrogen lone electron pair. For acetamide, the full coupling tensor has been determined from a combined analysis of the ground and first excited state of the methyl group internal rotation. The spectrum of α-fluoroacetamide-[15N] has been obtained for the first time, and a refined structure is proposed.

Synthesis, Electronic Structure and Anti-Cancer Activity of the Phenyl Substituted Pyrazolo[1,5-a][1,3,5]triazines

2021 ◽  
Vol 25 ◽  
Author(s):  
Evgenia S. Veligina ◽  
Nataliya V. Obernikhina ◽  
Stepan G. Pilyo ◽  
Oleksiy D. Kachkovsky ◽  
Volodymyr S. Brovarets
Keyword(s):  
Electronic Transition ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Anti Cancer ◽  
Protein Molecules ◽  
Biological Affinity ◽  
Cancer Types ◽  
Derivatives Of ◽  
Cancer Activity

: Background: Synthesis of a series of 2-(dichloromethyl)pyrazolo[1,5- a][1,3,5]triazines was carried out and evaluated in vitro for their anticancer activity against a panel of 60 cell lines derived from nine cancer types. The joint quantum-chemical and experimental study of the influence of the extended πconjugated phenyl substituents on the electron structure of the pyrazolo[1,5-a][1,3,5]triazines as Pharmacophores were performed. It is shown that the decrease in the barriers to the rotation of phenyl substituents in compounds 1-7 possibly leads to an increase in the anti-cancer activity, which is in agreement with the change in the parameter biological affinity ϕ0. Analysis of the S0 → S1 electronic transitions (π→π*) of the pyrazolo[1,5-a][1,3,5]triazines shows that an increase in their intensity correlates with anti-cancer activity. Thus, the introduction of phenyl substituents increases the likelihood of investigated pyrazolo[1,5-a][1,3,5]triazines interacting with protein molecules (Biomolecule) by the π stacking mechanism. In both methyl and phenyl derivatives of pyrazolo[1,5-a][1,3,5]triazines, the second electronic transition includes the n-MO (the level of the lone electron pair in two-coordinated nitrogen atoms). The highest intensity of the η→π* electronic transition is observed in pyrazolo[1,5-a][1,3,5]triazine with pyridine residue, which does not exhibit anti-cancer activity, but exhibits antiviral activity [13]. It can be assumed that the possibility of the formation of [Pharmacophore-Biomolecule] complex by hydrogen bonding ([H-B]) mechanism with protein molecules increases.

scholarly journals Crystal structures of the dioxane hemisolvates ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide]

2017 ◽  
Vol 73 (10) ◽  
pp. 1409-1413 ◽  
Author(s):  
Robert Rosin ◽  
Wilhelm Seichter ◽  
Monika Mazik
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Three Dimensional ◽  
Supramolecular Network ◽  
Halogen Bonds ◽  
Host Interactions ◽  
Compound Ii ◽  
Noncovalent Bonding

The syntheses and crystal structures ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide dioxane hemisolvate, C11H10BrN3O·0.5C4H8O2, (I), and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide] dioxane hemisolvate, 2C11H9Br2N3O·0.5C4H8O2, (II), are described. The molecules adopt a conformation with the N—H hydrogen pointing towards the lone electron pair of the adjacent naphthyridine N atom. The crystals of (I) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—Br...π halogen bonds. The crystals of compound (II) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—H...π contacts and C—Br...π halogen bonds. The structure of the substituent attached in the 7-position of the naphthyridine skeleton has a fundamental influence on the pattern of intermolecular noncovalent bonding. While the Br atom of (I) participates in weak C—Br...Oguestand C—Br...π contacts, the Br atoms of compound (II) are involved in host–host interactionsviaC—Br...O=C, C—Br...N and C—Br...π bonding.

scholarly journals Synthesis, Crystal Structure and Vibrational Properties of bis (N-benzylmethylammonium) Pentachlorobismuthate (III)

2012 ◽  
Vol 8 (2) ◽  
pp. 1566-1580 ◽  
Author(s):  
Hiba Khili ◽  
Najla Chaari ◽  
Mohamed Fliyou ◽  
Slaheddine Chaabouni
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Crystal Packing ◽  
Three Dimensional ◽  
Average Density ◽  
Infrared And Raman Spectra ◽  
Organic Layers ◽  
Dimensional Network ◽  
Anionic Layer ◽  
Inorganic Layers

The [C8H12N]2 BiCl5 compound crystallised in the triclinic system with space group  P-1  with a = 9,833(4),                     b = 10,044(7), c = 12,225(7) Å, a= 78.82(4), β = 75,42(4), g= 76.89°(5)  and Z = 2. The average density value, ρx = 1.518 g.cm-3  is in agreement with the calculated one, ρx = 1.494 g.cm-3. The atomic arrangement can be described as an alternation of organic and inorganic layers. The anionic layer is built up of octahedral [Bi2Cl10]-4. The organic layers are arranged in sandwich between the anionic ones. The crystal packing is governed by means of the ionic N–H---Cl hydrogen bonds, forming a three dimensional network. The nature of the distortion of the inorganic polyhedra has been studied and can be attributed to the stereo activity of the Bi(III) lone electron pair. The infrared and Raman spectra was recorded in the 4000–400 cm-1 frequency region.

Darstellung und Kristallstruktur von Tl4TiS4, TI4SnS4 und Tl4TiSe4 / Preparation and Crystal Structure of Tl4TiS4, TI4SnS4 and Tl4TiSe4

1984 ◽  
Vol 39 (6) ◽  
pp. 705-712 ◽  
Author(s):  
Kurt O. Klepp ◽  
Günther Eulenberger
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Monoclinic System ◽  
The Mean ◽  
Similar Description ◽  
Oriented Parallel ◽  
Stereochemical Activity

AbstractThe isostructural compounds Tl4TiS4, Tl4SnS4 and Tl4TiSe4 crystallize in the monoclinic system, space group P21/c with a = 8.328, b = 8.191, c = 15.248 Å, β = 104.53°; a = 8.395, b = 8.280, c = 15.398 A, ft = 103.69°, and a = 8.517, b = 8.389, c = 15.672 Å, β = 103.50°, respectively. There are four formula units in the unit cell. The crystal structures were determined and refined from single crystal diffractometer data. They are characterized by isolated tetrahedral thioanions which are connected with each other by Tl+ ions. The mean bond lengths are Ti-S = 2.26 Å, Sn-S = 2.40 Å and Ti -Se = 2.38 Å. The Tl atoms are surrounded by six and seven chalcogen atoms, respectively, in an irregular and polar arrangement, thus indicating stereochemical activity of the lone electron pair of the Tl+ ions. Tl-S distances vary from 2.93 to 3.98 Å, Tl-Se distances from 3.03 to 3.96 Å. The Tl atoms have nearest Tl neighbours at distances ranging from 3.46 to 3.65 Å. The crystal structure can be described as built from pseudotetragonal slabs oriented parallel to (001) which contain the cations and the tetrahedral anions. It is shown that a similar description is valid also for the crystal structures of Tl4GeS4 [1] and Na4SnS4 [2, 3].

Studies on bond and atomic valences. I. correlation between bond valence and bond angles in SbIII chalcogen compounds: the influence of lone-electron pairs

1996 ◽  
Vol 52 (1) ◽  
pp. 7-15 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Statistical Analysis ◽  
Valence State ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Continuous Change ◽  
Oxidation Number ◽  
Electron Pairs ◽  
Atomic Valence ◽  
Bond Valence Parameter

In the present bond-valence concept the bond-valence parameter ro is treated as constant for a given pair of atoms, and it is assumed that the bond valence sij is a function of the corresponding bond length Dij , and that the atomic valence is an integer equal to the formal oxidation number for Vi derived from stoichiometry. However, from a statistical analysis of 76 [SbIIIS n ] and 14 [SbIIISe n ] polyhedra in experimentally determined structures, it is shown that for SbIII—X bonds (X = S, Se), ro is correlated with {\bar \alpha} i , the average of the X—Sb—X angles between the three shortest Sb—X bonds. This is interpreted as a consequence of a progressive retraction of the 5s lone-electron pair from the SbIII nucleus, which can be considered as continuous change of the actual atomic valence act Vi of Sb from +3 towards +5. A procedure is derived to calculate an effective atomic valence eff Vi of SbIII from the geometry, {\bar \alpha} i and Dij , of the [SbIII Xn ] polyhedra, which approximates act Vi and is a better description of the actual valence state of SbIII than the formal valence for Vi . Calculated eff V SbIII are found to vary between +2.88 and +3.80 v.u. for [SbIIIS n ] and between +2.98 and +3.88 v.u. for [SbIIISe n ] polyhedra. It is suggested that a corresponding modification of the present bond-valence concept is also required for other cations with lone-electron pairs.

scholarly journals Lone-pair effect on carrier capture in Cu2ZnSnS4solar cells

2019 ◽  
Vol 7 (6) ◽  
pp. 2686-2693 ◽  
Author(s):  
Sunghyun Kim ◽  
Ji-Sang Park ◽  
Samantha N. Hood ◽  
Aron Walsh
Keyword(s):  
Solar Cells ◽  
Fast Electron ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Electron Hole ◽  
Carrier Capture ◽  
Hole Recombination

Fast electron–hole recombination in kesterite solar cells is linked to the chemistry of the Sn lone electron pair.

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