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Special Issue "σ and π Holes: A New Class of Non-Covalent Interactions"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Inorganic Chemistry".

Deadline for manuscript submissions: closed (30 April 2019)

Special Issue Editor

Guest Editor
Dr. Antonio Caballero

Departamento de Química Orgánica, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain
E-Mail
Interests: Halogen Bonding; Hydrogen Bonding; Anion-π; Supramolecular Chemistry; Anion Recognition; Cation Recognition; Supramolecular Polymers; Self Assembly

Special Issue Information

Dear Colleagues,

For many years, the research field of the non-covalent interactions has been largely dominated by electrostatic interactions and especially hydrogen bonding interactions. Recently, the study of new non-covalent interactions, based on the existence of the denominated sigma or pi hole, has grown enormously from a theoretical and experimental point of view. Without any doubt, halogen bonding interactions have become in the most promising interactions and numerous examples have been reported. Motivated by the relevance of the results obtained for halogen atoms, many researchers have focused their research on the study of other groups: aerogen, chalcogen, pnicogen, tetrel and icosagen atoms.

This Special Issue aims to highlight the role of this brand new form of noncovalent interaction that has recently appeared in several research fields, including catalysis, crystal engineering, molecular recognition, materials science, as well as theoretical aspects.

Dr. Antonio Caballero
Guest Editor

Manuscript Submission Information

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Keywords

  • Halogen bonding
  • Aerogen bonding
  • Chalcogen bonding
  • Pnicogen bonding
  • Tetrel bonding
  • Icosagen bonding
  • Hydrogen bonding

Published Papers (3 papers)

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Research

Open AccessArticle
Dual Geometry Schemes in Tetrel Bonds: Complexes between TF4 (T = Si, Ge, Sn) and Pyridine Derivatives
Molecules 2019, 24(2), 376; https://doi.org/10.3390/molecules24020376
Received: 5 January 2019 / Revised: 18 January 2019 / Accepted: 18 January 2019 / Published: 21 January 2019
Cited by 3 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
When an N-base approaches the tetrel atom of TF4 (T = Si, Ge, Sn) the latter molecule deforms from a tetrahedral structure in the monomer to a trigonal bipyramid. The base can situate itself at either an axial or equatorial position, leading [...] Read more.
When an N-base approaches the tetrel atom of TF4 (T = Si, Ge, Sn) the latter molecule deforms from a tetrahedral structure in the monomer to a trigonal bipyramid. The base can situate itself at either an axial or equatorial position, leading to two different equilibrium geometries. The interaction energies are considerably larger for the equatorial structures, up around 50 kcal/mol, which also have a shorter R(T··N) separation. On the other hand, the energy needed to deform the tetrahedral monomer into the equatorial structure is much higher than the equivalent deformation energy in the axial dimer. When these two opposite trends are combined, it is the axial geometry which is somewhat more stable than the equatorial, yielding binding energies in the 8–34 kcal/mol range. There is a clear trend of increasing interaction energy as the tetrel atom grows larger: Si < Ge < Sn, a pattern which is accentuated for the binding energies. Full article
(This article belongs to the Special Issue σ and π Holes: A New Class of Non-Covalent Interactions)
Figures

Graphical abstract

Open AccessArticle
Differential Binding of Tetrel-Bonding Bipodal Receptors to Monatomic and Polyatomic Anions
Molecules 2019, 24(2), 227; https://doi.org/10.3390/molecules24020227
Received: 26 December 2018 / Revised: 5 January 2019 / Accepted: 5 January 2019 / Published: 9 January 2019
Cited by 3 | PDF Full-text (3526 KB) | HTML Full-text | XML Full-text
Abstract
Previous work has demonstrated that a bidentate receptor containing a pair of Sn atoms can engage in very strong interactions with halide ions via tetrel bonds. The question that is addressed here concerns the possibility that a receptor of this type might be [...] Read more.
Previous work has demonstrated that a bidentate receptor containing a pair of Sn atoms can engage in very strong interactions with halide ions via tetrel bonds. The question that is addressed here concerns the possibility that a receptor of this type might be designed that would preferentially bind a polyatomic over a monatomic anion since the former might better span the distance between the two Sn atoms. The binding of Cl was thus compared to that of HCOO, HSO4, and H2PO4 with a wide variety of bidentate receptors. A pair of SnFH2 groups, as strong tetrel-binding agents, were first added to a phenyl ring in ortho, meta, and para arrangements. These same groups were also added in 1,3 and 1,4 positions of an aliphatic cyclohexyl ring. The tetrel-bonding groups were placed at the termini of (-C≡C-)n (n = 1,2) extending arms so as to further separate the two Sn atoms. Finally, the Sn atoms were incorporated directly into an eight-membered ring, rather than as appendages. The ordering of the binding energetics follows the HCO2 > Cl > H2PO4 > HSO4 general pattern, with some variations in selected systems. The tetrel bonding is strong enough that in most cases, it engenders internal deformations within the receptors that allow them to engage in bidentate bonding, even for the monatomic chloride, which mutes any effects of a long Sn···Sn distance within the receptor. Full article
(This article belongs to the Special Issue σ and π Holes: A New Class of Non-Covalent Interactions)
Figures

Graphical abstract

Open AccessArticle
Tetrel Bond between 6-OTX3-Fulvene and NH3: Substituents and Aromaticity
Received: 3 December 2018 / Revised: 16 December 2018 / Accepted: 17 December 2018 / Published: 20 December 2018
PDF Full-text (1714 KB) | HTML Full-text | XML Full-text
Abstract
Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the –OCH3 group at the exocyclic carbon of [...] Read more.
Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the –OCH3 group at the exocyclic carbon of fulvene can form a moderate carbon bond with NH3 with an interaction energy of about −10 kJ/mol. The –OSiH3 group engages in a stronger tetrel bond than does the –OGeH3 group, while a reverse result is found for both –OSiF3 and –OGeF3 groups. The abnormal order in the former is mainly due to the stronger orbital interaction in the –OSiH3 complex, which has a larger deformation energy. The cyano groups adjoined to the fulvene ring not only cause a change in the interaction type, from vdW interactions in the unsubstituted system of –OCF3 to carbon bonding, but also greatly strengthen tetrel bonding. The formation of tetrel bonding has an enhancing effect on the aromaticity of the fulvene ring. Full article
(This article belongs to the Special Issue σ and π Holes: A New Class of Non-Covalent Interactions)
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