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Journal ArticleDOI

Hydrogen bonds, and σ-hole and π-hole bonds – mechanisms protecting doublet and octet electron structures

15 Nov 2017-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 19, Iss: 44, pp 29742-29759
TL;DR: The hydrogen bond interaction and σ-hole and π-hole bonds are steered by the same mechanisms and the increase of the polarization of bonds to this centre seems to be the common effect.
Abstract: The hydrogen bond interaction and σ-hole and π-hole bonds are steered by the same mechanisms. There is electron charge transfer from the Lewis base to the Lewis acid unit, and further, for various interactions the same mechanisms try to protect the former electronic structure of the Lewis acid centre. The increase of the polarization of bonds to this centre seems to be the common effect. In the case of the A-HB hydrogen bond it is the increase of the polarization of the A-H bond connected with the outflow of the electron charge from the H-atom to the A-centre. For other interactions the outflow of electron charge from the Lewis acid centre is also observed. These electron charge shifts try to protect the doublet/octet structure of the acidic centre. The extremely strong interaction is often equivalent to the formation of new covalent bonds or it may lead to chemical reactions. Numerous interactions may be treated as the preliminary stages of chemical reactions: hydrogen bond - proton transfer, dihydrogen bond - molecular hydrogen release, tetrel bond - SN2 reaction, etc.
Citations
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Journal ArticleDOI
TL;DR: A total of 202 halogen-bonded complexes have been studied using a dual-level approach to determine geometries, natural bond order charges, charge transfer, dipole moments, electron and energy density distributions, vibrational frequencies, local stretching force constants, and relative bond strength orders n.
Abstract: A total of 202 halogen-bonded complexes have been studied using a dual-level approach: ωB97XD/aug-cc-pVTZ was used to determine geometries, natural bond order charges, charge transfer, dipole moments, electron and energy density distributions, vibrational frequencies, local stretching force constants, and relative bond strength orders n. The accuracy of these calculations was checked for a subset of complexes at the CCSD(T)/aug-cc-pVTZ level of theory. Apart from this, all binding energies were verified at the CCSD(T) level. A total of 10 different electronic effects have been identified that contribute to halogen bonding and explain the variation in its intrinsic strength. Strong halogen bonds are found for systems with three-center-four-electron (3c-4e) bonding such as chlorine donors in interaction with substituted phosphines. If halogen bonding is supported by hydrogen bonding, genuine 3c-4e bonding can be realized. Perfluorinated diiodobenzenes form relatively strong halogen bonds with alkylamines as...

90 citations

Journal ArticleDOI
TL;DR: In this paper, the features of non-covalent hole interactions of the halogen, chalcogen and pnictogen bond families were discussed by means of molecular orbital theory and the analysis of charge transfer and electrostatic forces.
Abstract: By means of molecular orbital theory and the analysis of charge transfer and electrostatic forces, we discuss the features of non-covalent hole interactions of the halogen, chalcogen and pnictogen bond families. The use of MOs allows us to explain and predict the location of holes, and to design novel interactions such as systems with σ and π holes on the same or opposite sides. In view of the orbital origin of the hole interactions, we suggest that many chalcogen and pnictogen bonds are largely based on π holes and not on the commonly accepted σ holes. In addition, a new type of hole interaction based on δ holes is found on the sextuply bonded dimolybdenum.

65 citations

Journal ArticleDOI
TL;DR: The tetrel bond (TB) recruits an element drawn from the C, Si, Ge, Sn, Pb family as electron acceptor in an interaction with a partner Lewis base as discussed by the authors.
Abstract: The tetrel bond (TB) recruits an element drawn from the C, Si, Ge, Sn, Pb family as electron acceptor in an interaction with a partner Lewis base. The underlying principles that explain this attractive interaction are described in terms of occupied and vacant orbitals, total electron density, and electrostatic potential. These principles facilitate a delineation of the factors that feed into a strong TB. The geometric deformation that occurs within the tetrel-bearing Lewis acid monomer is a particularly important issue, with both primary and secondary effects. As a first-row atom of low polarizability, C is a reluctant participant in TBs, but its preponderance in organic and biochemistry make it extremely important that its potential in this regard be thoroughly understood. The IR and NMR manifestations of tetrel bonding are explored as spectroscopy offers a bridge to experimental examination of this phenomenon. In addition to the most common σ-hole type TBs, discussion is provided of π-hole interactions which are a result of a common alternate covalent bonding pattern of tetrel atoms.

64 citations

Journal ArticleDOI
TL;DR: Tetrel bonds were weakest for the fully hydrogenated acids and surpassed pnicogen bonds when F had been added to the acid and strengthened the interactions as the number of F atoms rises.
Abstract: Ab initio calculations are employed to assess the relative strengths of various noncovalent bonds. Tetrel, pnicogen, chalcogen, and halogen atoms are represented by third-row atoms Ge, As, Se, and Br, respectively. Each atom was placed in a series of molecular bonding situations, beginning with all H atoms, then progressing to methyl substitutions, and F substituents placed in various locations around the central atom. Each Lewis acid was allowed to engage in a complex with NH3 as a common nucleophile, and the strength and other aspects of the dimer were assessed. In the context of fully hydrogenated acids, the strengths of the various bonds varied in the pattern of chalcogen > halogen > pnicogen ≈ tetrel. Methyl substitution weakened all bonds, but not in a uniform manner, resulting in a greatly weakened halogen bond. Fluorosubstitution strengthened the interactions, increasing its effect as the number of F atoms rises. The effect was strongest when the F atom lay directly opposite the base, resulting in a halogen > chalcogen > pnicogen > tetrel order of bond strength. Replacing third-row atoms by their second-row counterparts weakened the bonds, but not uniformly. Tetrel bonds were weakest for the fully hydrogenated acids and surpassed pnicogen bonds when F had been added to the acid.

60 citations

Journal ArticleDOI
TL;DR: The additional substituents arising from hypervalency present a number of complicating issues for the formation of noncovalent bonds, and hypervalent chalcogen bonding is examined by way of YF4 and YF6 and ZF5 is used to model pnicogen bonding.
Abstract: The additional substituents arising from hypervalency present a number of complicating issues for the formation of noncovalent bonds. The XF5 molecule (X=Cl, Br, I) was allowed to form a halogen bond with NH3 as the base. Hypervalent chalcogen bonding is examined by way of YF4 and YF6 (Y=S, Se, Te), and ZF5 (Z=P, As, Sb) is used to model pnicogen bonding. Pnicogen bonds are particularly strong, with interaction energies approaching 50 kcal mol-1 , and also involve wholesale rearrangement from trigonal bipyramidal in the monomer to square pyramidal in the complex, subject to a large deformation energy. YF4 chalcogen bonding is also strong, and like pnicogen bonding, is enhanced by a heavier central atom. XF5 halogen bond energies are roughly 9 kcal mol-1 , and display a unique sensitivity to the identity of the X atom. The crowded octahedral structure of YF6 permits only very weak interactions. As the F atoms of SeF6 are replaced progressively by H, a chalcogen bond appears in combination with SeH⋅⋅⋅N and NH⋅⋅⋅F H-bonds. The strongest such chalcogen bond appears in SeF3 H3 ⋅⋅⋅NH3 , with a binding energy of 7 kcal mol-1 , wherein the base is located in the H3 face of the Lewis acid. Results are discussed in the context of the way in which the positions and intensities of σ-holes are influenced by the locations of substituents and lone electron pairs.

59 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors.
Abstract: A new direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors. It appears that these new features can give a strong reduction in the error of the interaction energy, and they seem to be particularly suitable for computations in the important region near the minimum energy. It has been generally accepted that this problem is dominated by unresolved difficulties and the relation of the new methods to these apparent difficulties is analysed here.

19,483 citations

Book
01 Jan 1939

14,299 citations

Journal ArticleDOI
TL;DR: This paper presents a meta-modelling procedure called "Continuum Methods within MD and MC Simulations 3072", which automates the very labor-intensive and therefore time-heavy and expensive process of integrating discrete and continuous components into a discrete-time model.
Abstract: 6.2.2. Definition of Effective Properties 3064 6.3. Response Properties to Magnetic Fields 3066 6.3.1. Nuclear Shielding 3066 6.3.2. Indirect Spin−Spin Coupling 3067 6.3.3. EPR Parameters 3068 6.4. Properties of Chiral Systems 3069 6.4.1. Electronic Circular Dichroism (ECD) 3069 6.4.2. Optical Rotation (OR) 3069 6.4.3. VCD and VROA 3070 7. Continuum and Discrete Models 3071 7.1. Continuum Methods within MD and MC Simulations 3072

13,286 citations

Book
01 Jan 1990
TL;DR: In this article, the quantum atom and the topology of the charge desnity of a quantum atom are discussed, as well as the mechanics of an atom in a molecule.
Abstract: List of symbols 1. Atoms in chemistry 2. Atoms and the topology of the charge desnity 3. Molecular structure and its change 4. Mathematical models of structural change 5. The quantum atom 6. The mechanics of an atom in a molecule 7. Chemical models and the Laplacian of the charge density 8. The action principle for a quantunm subsystem Appendix - Tables of data Index

11,853 citations