Solvent effect on halogen bonding: the case of the I⋯O interaction

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Supramolecular Chemistry

Background:

• Halogen bonding is a crucial non-covalent interaction.
• Understanding solvent effects is vital for predicting molecular complex behavior.
• Iodobenzene derivatives and formaldehyde serve as model systems for I⋯O halogen bonds.

Purpose of the Study:

• To investigate the influence of solvent polarity on I⋯O halogen bonding.
• To evaluate the performance of various Density Functional Theory (DFT) functionals in modeling these interactions.
• To compare computational results with experimental observations.

Main Methods:

• Systematic variation of substituents on iodobenzene derivatives.
• High-level computational calculations using MP2 and DFT methods.
• Employing the aug-cc-pVDZ basis set and iodine pseudopotential.
• Utilizing the conductor-like polarizable continuum model (CPCM) for solvent simulations (diethylether, water) and in vacuo comparisons.

Main Results:

• Halogen bond distances decreased with increasing solvent polarity (in vacuo < diethylether < water).
• Interaction energies decreased in absolute value with increasing solvent polarity, indicating a destabilizing solvent effect.
• Most tested DFT functionals, except B3LYP, adequately described halogen bonding compared to MP2.
• M06-HF excelled in predicting interaction energies in vacuo, while PBE performed best in solution.
• M06-2X provided superior reproduction of halogen bond geometrical parameters.

Conclusions:

• Solvent polarity significantly impacts I⋯O halogen bond strength and geometry.
• DFT methods, particularly M06-HF and PBE, are reliable for studying solvent effects on halogen bonding.
• The choice of functional is critical for accurately modeling halogen bond characteristics in different environments.