The properties of substituted 3D-aromatic neutral carboranes: the potential for σ-hole bonding

Abstract

The calculated properties of substituted carboranes such as dipole moment, polarisability, the magnitude of the σ-hole and the desolvation free energy are compared with these properties in comparable aromatic and cyclic aliphatic organic compounds. Dispersion and charge transfer energies are similar. However, the predicted strength of the halogen bonds with the same electron donor (based on the magnitude of the σ-hole) is larger for neutral C-vertex halogen-substituted carboranes than for their organic counterparts. Furthermore, the desolvation penalties of substituted carboranes are smaller than those of the corresponding organic compounds, which should further strengthen the halogen bonds of the former in the solvent. It is predicted that substituted carboranes have the potential to form stronger halogen bonds than comparable aromatic hydrocarbons, which will be even more pronounced in the medium. This theoretical study thus lays ground for the rational engineering of halogen bonding in inorganic crystals as well as in biomolecular complexes.

Competition between Halogen, Hydrogen and Dihydrogen Bonding in Brominated Carboranes

“…Recently, we studied the properties of halogenated carboranes using quantum mechanics (QM) methods. These calculations showed that halogenated carboranes had large and highly positive σ‐holes when an X atom was covalently attached to the C‐vertex of a neutral carborane molecule …”

Chalcogen Bonding in Protein−Ligand Complexes: PDB Survey and Quantum Mechanical Calculations

“…The strength of σ‐hole bonding can be inferred from the σ‐hole magnitude (V S,max ), which is defined as the most positive value of the ESP surface . The more positive the V S,max value, the stronger the X‐bond ,. The V S,max value depends on various characteristics of moieties appended to the X‐containing molecule, such as polarisability, electronegativity and electron‐withdrawing capability .…”

“…The more positive the V S,max value, the stronger the X‐bond ,. The V S,max value depends on various characteristics of moieties appended to the X‐containing molecule, such as polarisability, electronegativity and electron‐withdrawing capability . The properties of a σ‐hole (such as the V S,max value) can thus be modulated by substituting certain moieties on the molecule of interest.…”

It Is Important to Compute Intramolecular Hydrogen Bonding in Drug Design?

“…Therefore, in YBs, as well as in other non-covalent interactions, the importance of the electrostatic interaction term is uppermost [426,437]. Several works have been carried out regarding the tunability of the mentioned σ -holes in different types of interactions, including halogen, chalcogen, and pnicogen [438,439,440,441]. In particular, the effect on the σ -hole upon substitution on aromatic rings has been previously studied [438,442,443,444].…”