Dual Noncovalent Bonding to Planar Tetracoordinated Oxygen

Area of Science:

• Computational chemistry
• Inorganic chemistry
• Materials science

Background:

• The OTr4 molecule features an oxygen atom at the center of a square with four triel (Tr) atoms.
• Halogen atoms (X) from FX or MeX can bind to the oxygen, forming T-shaped complexes.

Purpose of the Study:

• To investigate the nature and strength of interactions in OTr4 complexes with halogen-containing molecules.
• To elucidate the components of the binding interactions and factors influencing their strength.

Main Methods:

• Quantum chemical calculations were employed to analyze the electronic structure and bonding characteristics.
• Interaction energies were calculated to quantify the strength of the observed bonds.

Main Results:

• Two distinct bonding components were identified: a classical halogen bond and a triel bond.
• Charge transfer occurs between oxygen's pz orbital and the halogen's antibonding orbital (halogen bond).
• Charge transfer also occurs from halogen lone pairs to the triel atoms' empty lone pair orbitals (triel bond).

Conclusions:

• Both halogen and triel bonds are present in all studied dyads.
• The relative strength of these bonds depends on the specific halogen molecule (FX vs. MeX) and the identity of the triel atom.
• Fluorine-containing molecules (FX) form substantially stronger bonds with OTr4 complexes compared to methyl-containing molecules (MeX).