Halogen bonding in mono- and dihydrated halobenzene

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Halogen bonding is a significant non-covalent interaction.
• Understanding halogen bonding in systems with water is crucial for various chemical and biological processes.

Purpose of the Study:

• To investigate the formation and strength of halogen bonds in halobenzene-water systems.
• To compare halogen bonding with hydrogen bonding interactions in these systems.
• To explore the influence of water molecule number on halogen bond formation.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• The M06-2X functional and specific basis sets (6-31+G(d) and aug-cc-pVDZ-PP) were used.
• The counterpoise procedure corrected for basis set superposition error.

Main Results:

• Halogen bonds form in halobenzene-water (XPh-H2O) systems for halogens heavier than chlorine (X > Cl).
• Halogen bond strength increases down the halogen group.
• In XPh-H2O, hydrogen bonds (CH•••Ow and OwHw•••X) are present, and X•••Hw interactions are stronger than X•••Ow halogen bonds for X ≠ At.
• In halobenzene-dihydrate (XPh-(H2O)2) systems, halogen bonds form only for X > Br.
• Water molecules preferentially form dimers, influencing halogen bond formation.

Conclusions:

• Halogen bond formation in halobenzene-water systems is dependent on the halogen's identity and the number of water molecules.
• Competition from hydrogen bonds and the tendency for water dimer formation can prevent halogen bond formation, especially for lighter halogens.
• The strength of halogen bonds increases with atomic number down the halogen group.