scholarly journals Relationships between Interaction Energy and Electron Density Properties for Homo Halogen Bonds of the [(A)nY–X···X–Z(B)m] Type (X = Cl, Br, I)

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2733 ◽  
Author(s):  
Maxim L. Kuznetsov
Keyword(s):  
Kinetic Energy ◽  
Interaction Energy ◽  
Electron Density ◽  
Bond Critical Point ◽  
Kinetic Energy Density ◽  
Large Set ◽  
Halogen Bonds ◽  
Absolute Deviation ◽  
The Individual ◽  
Best Estimator

Relationships between interaction energy (Eint) and electron density properties at the X···X bond critical point or the d(X···X) distance were established for the large set of structures [(A)nY–X···X–Z(B)m] bearing the halogen bonds Cl···Cl, Br···Br, and I···I (640 structures in total). The best estimator of Eint is the kinetic energy density (Gb), which reasonably approximates the whole set of the structures as −Eint = 0.128Gb2 − 0.82Gb + 1.66 (R2 = 0.91, mean absolute deviation 0.39 kcal/mol) and demonstrates low dispersion. The potential and kinetic energy densities, electron density, and the d(X···X) distance behave similarly as estimators of Eint for the individual series Cl···Cl, Br···Br, and I···I. A number of the Eint(property) correlations are recommended for the practical application in the express estimates of the strength of the homo-halogen bonds.

scholarly journals Strength of the [Z–I···Hal]− and [Z–Hal···I]− Halogen Bonds: Electron Density Properties and Halogen Bond Length as Estimators of Interaction Energy

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2083
Author(s):  
Maxim L. Kuznetsov
Keyword(s):  
Bond Length ◽  
Interaction Energy ◽  
Electron Density ◽  
Halogen Bond ◽  
Bond Critical Point ◽  
Halogen Bonds ◽  
Curvature Potential ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Bond energy is the main characteristic of chemical bonds in general and of non-covalent interactions in particular. Simple methods of express estimates of the interaction energy, Eint, using relationships between Eint and a property which is easily accessible from experiment is of great importance for the characterization of non-covalent interactions. In this work, practically important relationships between Eint and electron density, its Laplacian, curvature, potential, kinetic, and total energy densities at the bond critical point as well as bond length were derived for the structures of the [Z–I···Hal]– and [Z–Hal···I]– types bearing halogen bonds and involving iodine as interacting atom(s) (totally 412 structures). The mean absolute deviations for the correlations found were 2.06–4.76 kcal/mol.

scholarly journals The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy

2019 ◽  
Vol 75 (9) ◽  
pp. 1190-1201 ◽  
Author(s):  
Ruimin Wang ◽  
Janine George ◽  
Shannon Kimberly Potts ◽  
Marius Kremer ◽  
Richard Dronskowski ◽  
...  
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Halogen Bond ◽  
Bond Distance ◽  
Bond Critical Point ◽  
Halogen Bonds ◽  
Derived Properties ◽  
The Many ◽  
A Minor ◽  
Experimental Electron Density

Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl...Cl contacts vary smoothly as a function of the interaction distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitrogen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow intermediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated interaction. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetrafluorodiiodobenzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

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