Halogen bonds and σ-holes

2017 ◽  
Vol 203 ◽  
pp. 9-27 ◽  
Author(s):  
Timothy Clark
Keyword(s):  
Special Reference ◽  
Intermolecular Interactions ◽  
Measurable Quantity ◽  
Coulomb Interactions ◽  
Halogen Bonds ◽  
Bonding Theory ◽  
Weak Intermolecular Interactions ◽  
Different Levels ◽  
Physical Principles

The models behind simple bonding theory and the origins of some components often proposed to be involved in weak intermolecular bonds are described with special reference to σ-hole bonding, of which halogen bonds are a subset. A protocol for the analysis of weak intermolecular interactions is proposed on the basis of sound physical principles. This protocol uses three different levels of interaction; “permanent” Coulomb interactions between unperturbed monomers, relaxed Coulomb interactions and dispersion. Of the three, only dispersion is not a real, measurable quantity. It is, however, included in order to describe interactions that cannot be treated entirely by the first two levels.

Structural Investigation of Weak Intermolecular Interactions (Hydrogen and Halogen Bonds) in Fluorine-Substituted Benzimidazoles

2014 ◽  
Vol 14 (7) ◽  
pp. 3499-3509 ◽  
Author(s):  
Marta Pérez-Torralba ◽  
M. Ángeles García ◽  
Concepción López ◽  
M. Carmen Torralba ◽  
M. Rosario Torres ◽  
...  
Keyword(s):  
Intermolecular Interactions ◽  
Structural Investigation ◽  
Halogen Bonds ◽  
Weak Intermolecular Interactions

scholarly journals Convenient Access to Functionalized Non-Symmetrical Atropisomeric 4,4′-Bipyridines

Compounds ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 58-74
Author(s):  
Emmanuel Aubert ◽  
Emmanuel Wenger ◽  
Paola Peluso ◽  
Victor Mamane
Keyword(s):  
Solid State ◽  
Intermolecular Interactions ◽  
Medicinal Chemistry ◽  
Crystal Packing ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Halogen Bonds ◽  
Cross Coupling Reactions ◽  
Cyano Groups ◽  
Post Functionalization

Non-symmetrical chiral 4,4′-bipyridines have recently found interest in organocatalysis and medicinal chemistry. In this regard, the development of efficient methods for their synthesis is highly desirable. Herein, a series of non-symmetrical atropisomeric polyhalogenated 4,4′-bipyridines were prepared and further functionalized by using cross-coupling reactions. The desymmetrization step is based on the N-oxidation of one of the two pyridine rings of the 4,4′-bipyridine skeleton. The main advantage of this methodology is the possible post-functionalization of the pyridine N-oxide, allowing selective introduction of chlorine, bromine or cyano groups in 2- and 2′-postions of the chiral atropisomeric 4,4′-bipyridines. The crystal packing in the solid state of some newly prepared derivatives was analyzed and revealed the importance of halogen bonds in intermolecular interactions.

On the influence of weak intermolecular interactions on the molecular crystal density of 1,3,5-triazine trinitroalkyl derivatives

2021 ◽  
Vol 57 (3) ◽  
pp. 266-273
Author(s):  
Kyrill Yu. Suponitsky ◽  
Aleksei A. Anisimov ◽  
Ivan V. Ananyev ◽  
Alexander A. Lashakov ◽  
Svetlana V. Osintseva ◽  
...  
Keyword(s):  
Intermolecular Interactions ◽  
Molecular Crystal ◽  
Weak Intermolecular Interactions ◽  
Crystal Density

Studies of the Biting-habits of African Mosquitos. An Appraisal of Methods employed, with special Reference to the twenty-four-hour Catch

1954 ◽  
Vol 45 (1) ◽  
pp. 199-242 ◽  
Author(s):  
A. J. Haddow
Keyword(s):  
Vertical Distribution ◽  
Special Reference ◽  
Geometric Mean ◽  
Seasonal Abundance ◽  
Central Tendency ◽  
Valuable Method ◽  
Different Seasons ◽  
Working Out ◽  
Different Levels ◽  
Biting Behaviour

It is felt that the 24-hour catch presents a valuable method of studying the biting-behaviour of mosquitos in the field, and further that conclusions concerning seasonal abundance, vertical distribution and times of biting-activity must be based on catches of this type if serious errors of interpretation are to be avoided.The time-divisions of the catch should not exceed one hour, and even shorter intervals may be desirable. Timing should be related to the actual times of sunrise and sunset. Where possible, a series of consecutive catches should be carried out, and a shift system must be carefully considered in relation to the particular series projected.Usually the results from different levels above ground should be treated separately in working out biting-cycles, and this may also apply to results from different seasons or different localities. Further, while in some instances the summation of long series of catches seems permissible, in others it is not, and in these detailed analysis of the figures may be necessary before consistent behaviour-patterns become apparent.In cases where a measure of the central tendency is to be employed, the geometric mean as modified by C. B. Williams appears to be the most suitable.

scholarly journals Synthesis, Structure and Chiral Inclusion Crystallisation of Tetrakis(4-Ethynylphenyl)Ethylene Derivatives

2002 ◽  
Vol 2002 (5) ◽  
pp. 209-212 ◽  
Author(s):  
Koichi Tanaka ◽  
Takaichi Hiratsuka ◽  
Yuko Kojima ◽  
Yasuko T. Osano
Keyword(s):  
Intermolecular Interactions ◽  
Guest Molecules ◽  
Host Molecules ◽  
Weak Intermolecular Interactions

Achiral host molecules, tetrakis(4-ethynylphenyl)ethylene 3 and tetrakis(4-bromoethynylphenyl)ethylene 4, formed chiral host–guest inclusion crystals with achiral guest molecules via weak intermolecular interactions.

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