Comparison between Tetrel Bonded Complexes Stabilized by σ and π Hole Interactions.

Area of Science:

• Chemical Physics
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Tetrel bonds are non-covalent interactions involving tetrel elements (Si, Ge, Sn).
• These bonds can form through σ-holes (tetravalent) or π-holes (trivalent).
• Understanding factors influencing tetrel bond strength is crucial for molecular design.

Purpose of the Study:

• To compare the strength of σ-hole tetrel bonds in tetravalent molecules with π-hole tetrel bonds in trivalent molecules.
• To investigate the effect of fluorine substitution on tetrel bond strength.
• To evaluate the predictive power of molecular electrostatic potential for interaction energies.

Main Methods:

• Computational modeling of tetrel bonds using molecules like TH₄, TH₃F, TH₂F₂, TH₂=CH₂, THF=CH₂, and TF₂=CH₂ (T = Si, Ge, Sn).
• Complexation with ammonia (NH₃) as a Lewis base to form dimers.
• Analysis of binding energies, electrostatic potentials, and geometric distortions.

Main Results:

• π-hole tetrel bonded complexes exhibit significantly stronger binding than σ-hole tetrel bonded complexes, despite similar hole intensities.
• Progressive replacement of hydrogen with fluorine in the Lewis acid increases tetrel bond strength for both σ and π types.
• Molecular electrostatic potential maxima are not reliable indicators of interaction or Coulombic energy.
• Dimer formation causes significant geometric distortion of the Lewis acid, enhancing σ and π holes.

Conclusions:

• π-hole interactions are more effective in forming strong tetrel bonds compared to σ-hole interactions.
• Fluorine substitution is a viable strategy to enhance tetrel bond strength.
• Geometric distortions play a key role in modulating tetrel bond characteristics.