Abstract
Tetrel bonds are noncovalent interactions formed by tetrel atoms (as σ-hole carriers) with a Lewis base. Here, we present a computational and molecular orbital study on the effect of the geometry of the substituents around the tetrel atom on the σ-hole and on the binding strengths. We show that changing the angles between substituents can dramatically increase bond strength. In addition, our findings suggest that the established Sn > Ge > Si order of binding strength can be changed in sufficiently distorted molecules due to the enhancement of the charge transfer component, making silicon the strongest tetrel donor.
Highlights
Hole interactions [1] are a relatively newly coined term that unites all noncovalent interactions in which a region of positive electrostatic potential on one atom, the hole, interacts with an electron donor
These can be based on σ, π, or δ holes depending on their type of covalent orbital origin [2]. σ-holes are formed at approximately 180◦ to a σ covalent bond, with the magnitude of the positive electrostatic potential depending on the electronegativity of the neighboring atoms
A weak σ-hole 2 of 7 may be formed at the extension of the T-H bonds, but the σ-hole corresponding to the T-F
Summary
Hole interactions [1] are a relatively newly coined term that unites all noncovalent interactions in which a region of positive electrostatic potential on one atom, the hole, interacts with an electron donor These can be based on σ, π, or δ holes depending on their type of covalent orbital origin [2]. We focus on the effect that the angles around the atom have on the binding strengths of tetrel bonds We analyze this by examining the effect on the electrostatic hole and on the frontier orbitals in order to explain the dramatic changes in complexation energies. The effect of the angles between covalent bonds on interaction strength was computationally explained by showing that smaller rings cause the σ-hole to be more exposed, increasing its electrostatic potential [12].
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