scholarly journals Classification of So-Called Non-Covalent Interactions Based on VSEPR Model

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4939
Author(s):  
Sławomir J. Grabowski
Keyword(s):  
Lewis Acid ◽  
Halogen Bond ◽  
Lewis Base ◽  
Pnicogen Bond ◽  
Interacting Species ◽  
Base Site ◽  
Non Covalent Interactions ◽  
Tetrel Bonds

The variety of interactions have been analyzed in numerous studies. They are often compared with the hydrogen bond that is crucial in numerous chemical and biological processes. One can mention such interactions as the halogen bond, pnicogen bond, and others that may be classified as σ-hole bonds. However, not only σ-holes may act as Lewis acid centers. Numerous species are characterized by the occurrence of π-holes, which also may play a role of the electron acceptor. The situation is complicated since numerous interactions, such as the pnicogen bond or the chalcogen bond, for example, may be classified as a σ-hole bond or π-hole bond; it ultimately depends on the configuration at the Lewis acid centre. The disadvantage of classifications of interactions is also connected with their names, derived from the names of groups such as halogen and tetrel bonds or from single elements such as hydrogen and carbon bonds. The chaos is aggravated by the properties of elements. For example, a hydrogen atom can act as the Lewis acid or as the Lewis base site if it is positively or negatively charged, respectively. Hence names of the corresponding interactions occur in literature, namely hydrogen bonds and hydride bonds. There are other numerous disadvantages connected with classifications and names of interactions; these are discussed in this study. Several studies show that the majority of interactions are ruled by the same mechanisms related to the electron charge shifts, and that the occurrence of numerous interactions leads to specific changes in geometries of interacting species. These changes follow the rules of the valence-shell electron-pair repulsion model (VSEPR). That is why the simple classification of interactions based on VSEPR is proposed here. This classification is still open since numerous processes and interactions not discussed in this study may be included within it.

scholarly journals π-Hole Tetrel Bonds—Lewis Acid Properties of Metallylenes

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 112
Author(s):  
Sławomir J. Grabowski
Keyword(s):  
Quantum Theory ◽  
Crystal Structures ◽  
Lewis Acid ◽  
Natural Bond Orbital ◽  
Database Search ◽  
Lewis Base ◽  
Atoms In Molecules ◽  
Acid Properties ◽  
Structural Database ◽  
Tetrel Bonds

The MP2/aug-cc-pVTZ calculations were performed on the dihalometallylenes to indicate their Lewis acid and Lewis base sites. The results of the Cambridge Structural Database search show corresponding and related crystal structures where the tetrel center often possesses the configuration of a trigonal bipyramid or octahedron. The calculations were also carried out on dimers of dichlorogermylene and dibromogermylene and on complexes of these germylenes with one and two 1,4-dioxide molecules. The Ge⋯Cl, Ge⋯Br, and Ge⋯O interactions are analyzed. The Ge⋯O interactions in the above mentioned germylene complexes may be classified as the π-hole tetrel bonds. The MP2 calculations are supported by the results of the Quantum Theory of Atoms in Molecules (QTAIM) and the Natural Bond Orbital (NBO) approaches.

scholarly journals Catalytic Activation via π –Backbonding in Halogen Bonds?

2020 ◽  
Author(s):  
Andrew Wang ◽  
Pierre Kennepohl
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Lewis Base ◽  
Computational Studies ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Bases ◽  
Chemical Catalysis ◽  
Catalytic Activation

The role of halogen bonding (XB) in chemical catalysis has largely involved using XB donors as Lewis acid activators to modulate the reactivity of partner Lewis bases. We explore a more uncommon scenario, where a Lewis base modulates reactivity via a spectator halogen bond interaction. Our computational studies reveal that spectator halogen bonds may play an important role in modulating the rate of S<sub>N</sub>2 reactions. Most notably, π acceptors such as PF<sub>3</sub> significantly decrease the barrier to subsitution by decreasing electron density in the very electron rich transition state. Such π-backbonding represents an example of a heretofor unexplored situation in halogen bonding: the combination of both s-donation and π-backdonation in this “non-covalent” interaction.

scholarly journals α-Functionalization of Ketones via a Nitrogen Directed Oxidative Umpolung

2020 ◽  
Author(s):  
Gabriel M. Kiefl ◽  
Tanja Gulder
Keyword(s):  
Organic Chemistry ◽  
Lewis Acid ◽  
Lewis Base ◽  
Structural Space ◽  
Versatile Tool ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Reversing the polarity in molecules is a versatile tool for expanding the boundaries of structural space. Despite a manifold of different umpolung methods available today, overcoming the inherent reactivity still remains a constant challenge in organic chemistry. The oxidative α-functionalization of ketones by external nucleophiles constitute such an example. Herein, we present a hypervalent F-iodane mediated umpolung of pyridyl ketones triggered by Lewis base Lewis acid non-covalent interactions. A wide variety of external nucleophiles are introduced with high regioselectivity applying this substratedirecting concept.<br>

scholarly journals α-Functionalization of Ketones via a Nitrogen Directed Oxidative Umpolung

2020 ◽  
Author(s):  
Gabriel M. Kiefl ◽  
Tanja Gulder
Keyword(s):  
Organic Chemistry ◽  
Lewis Acid ◽  
Lewis Base ◽  
Structural Space ◽  
Versatile Tool ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Reversing the polarity in molecules is a versatile tool for expanding the boundaries of structural space. Despite a manifold of different umpolung methods available today, overcoming the inherent reactivity still remains a constant challenge in organic chemistry. The oxidative α-functionalization of ketones by external nucleophiles constitute such an example. Herein, we present a hypervalent F-iodane mediated umpolung of pyridyl ketones triggered by Lewis base Lewis acid non-covalent interactions. A wide variety of external nucleophiles are introduced with high regioselectivity applying this substratedirecting concept.<br>

Testing the tools for revealing and characterizing the iodine–iodine halogen bond in crystals

2017 ◽  
Vol 73 (2) ◽  
pp. 217-226 ◽  
Author(s):  
Ekaterina Bartashevich ◽  
Irina Yushina ◽  
Kristina Kropotina ◽  
Svetlana Muhitdinova ◽  
Vladimir Tsirelson
Keyword(s):  
Electron Density ◽  
Halogen Bond ◽  
Electron Shell ◽  
Electron Localization Function ◽  
Electron Localization ◽  
Localization Function ◽  
Non Covalent Interactions ◽  
The One ◽  
Covalent Interactions

To understand what tools are really suitable to identify and classify the iodine–iodine non-covalent interactions in solid organic polyiodides, we have examined the anisotropy of the electron density within the iodine atomic basin along and across the iodine–iodine halogen bond using the Laplacian of electron density, one-electron potential and electron localization function produced by Kohn–Sham calculations with periodic boundary conditions. The Laplacian of electron density exhibits the smallest anisotropy and yields a vague picture of the outermost electronic shells. The one-electron potential does not show such a deficiency and reveals that the valence electron shell for the halogen-bond acceptor iodine is always wider than that for the halogen-bond donor iodine along its σ-hole direction. We have concluded that the one-electron potential is the most suitable for classification of the iodine–iodine bonds and interactions in complicated cases, while the electron localization function allows to distinguish the diiodine molecule bonded with the monoiodide anion from the typical triiodide anion.

The dual role of pnicogen as Lewis acid and base and the unexpected interplay between the pnicogen bond and coordination interaction in H3N⋯FH2X⋯MCN (X = P and As; M = Cu, Ag, and Au)

2015 ◽  
Vol 39 (3) ◽  
pp. 2067-2074 ◽  
Author(s):  
Hongying Zhuo ◽  
Qingzhong Li ◽  
Wenzuo Li ◽  
Jianbo Cheng
Keyword(s):  
Lewis Acid ◽  
Binary Systems ◽  
Ternary Systems ◽  
Dual Role ◽  
Coordination Interaction ◽  
Pnicogen Bond ◽  
Acid And Base ◽  
Lewis Acid And Base

Ternary systems H3N⋯FH2X⋯MCN (X = P and As; M = Cu, Ag, and Au) as well as the corresponding pnicogen-bonded and coordination-bonded binary systems have been studied.

scholarly journals Catalytic Activation via π –Backbonding in Halogen Bonds?

2020 ◽  
Author(s):  
Andrew Wang ◽  
Pierre Kennepohl
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Lewis Base ◽  
Computational Studies ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Bases ◽  
Chemical Catalysis ◽  
Catalytic Activation

The role of halogen bonding (XB) in chemical catalysis has largely involved using XB donors as Lewis acid activators to modulate the reactivity of partner Lewis bases. We explore a more uncommon scenario, where a Lewis base modulates reactivity via a spectator halogen bond interaction. Our computational studies reveal that spectator halogen bonds may play an important role in modulating the rate of S<sub>N</sub>2 reactions. Most notably, π acceptors such as PF<sub>3</sub> significantly decrease the barrier to subsitution by decreasing electron density in the very electron rich transition state. Such π-backbonding represents an example of a heretofor unexplored situation in halogen bonding: the combination of both s-donation and π-backdonation in this “non-covalent” interaction.

Raiders Activity on the Market for Corporate Control as a Product of Coercive Entrepreneurship Evolution

2007 ◽  
pp. 80-92
Author(s):  
A. Kireev
Keyword(s):  
Corporate Control ◽  
Role Of Government ◽  
Market For Corporate Control ◽  
Basic Characteristics

The paper studies the problem of raiders activity on the market for corporate control. This activity is considered as a product of coercive entrepreneurship evolution. Their similarities and sharp distinctions are shown. The article presents the classification of raiders activity, discribes its basic characteristics and tendencies, defines the role of government in the process of its transformation.

ASPECTS IN BUILDING A COMPANY WEB-SITE AND ITS ROLE FOR THE DEVELOPMENT OF BUSINESS

2018 ◽  
pp. 117-124
Author(s):  
Petar Halachev ◽  
Victoria Radeva ◽  
Albena Nikiforova ◽  
Miglena Veneva
Keyword(s):  
Life Cycle ◽  
Web Site ◽  
The Internet ◽  
A Company ◽  
The Web ◽  
Design Construction ◽  
Made In ◽  
Site Types

This report is dedicated to the role of the web site as an important tool for presenting business on the Internet. Classification of site types has been made in terms of their application in the business and the types of structures in their construction. The Models of the Life Cycle for designing business websites are analyzed and are outlined their strengths and weaknesses. The stages in the design, construction, commissioning, and maintenance of a business website are distinguished and the activities and requirements of each stage are specified.

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