Comparison of Bifurcated Halogen with Hydrogen Bonds

Area of Science:

• Chemical bonding
• Supramolecular chemistry
• Computational chemistry

Background:

• Halogen bonds are non-covalent interactions involving a halogen atom acting as a Lewis acid.
• Bifurcated interactions, where a single atom interacts with multiple partners, are common in hydrogen bonding but less explored in halogen bonding.
• Understanding these interactions is crucial for designing molecular assemblies and materials.

Purpose of the Study:

• To investigate the energetic stability of bifurcated halogen bonds.
• To compare bifurcated halogen bonds with bifurcated hydrogen bonds.
• To identify factors influencing the formation and stability of these interactions.

Main Methods:

• Computational modeling was used to construct and analyze bifurcated halogen bond systems.
• Systems included FBr and FI as Lewis acids with NH3 and NCH as bases.
• Analogous hydrogen bond systems with FH as the acid were also studied for comparison.

Main Results:

• Bifurcated halogen bonds are generally energetically less favorable than single linear halogen bonds.
• The energetic penalty is greater when two bases interact with one acid compared to two acids interacting with one base.
• FH, unlike FBr and FI, shows a greater propensity for bifurcated hydrogen bonding with two bases.

Conclusions:

• The stability of bifurcated halogen bonds is influenced by the energetic cost of accommodating multiple interactions.
• The shape of the molecular electrostatic potential and the anisotropy of interacting orbitals play a key role.
• FH's unique electronic properties facilitate bifurcated hydrogen bonding more effectively than FBr and FI in bifurcated halogen bonding.