π covalency in the halogen bond

Area of Science:

• Chemistry
• Chemical Biology
• Materials Science

Background:

• Halogen bonds are directional intermolecular interactions crucial in chemistry and chemical biology.
• Current models liken halogen bonds to hydrogen bonds, focusing on their σ-symmetric component.
• The potential for π-covalency in halogen bonds remains unexplored in existing theoretical frameworks.

Purpose of the Study:

• To investigate the presence and implications of π-covalency in halogen bonds.
• To re-evaluate the established analogy between halogen bonds and hydrogen bonds.
• To propose a revised model for understanding halogen bonding.

Main Methods:

• Computational analysis of chlorine K-edge X-ray absorption spectra.
• Study of halogen bonds formed between chloride and halogenated triphenylamine-based radical cations.

Main Results:

• Evidence of π-covalency was found in the studied halogen bonds.
• The findings indicate that π-covalency is an operative component of these interactions.
• Computational analysis supported the experimental observations.

Conclusions:

• Halogen bonding exhibits π-covalency, a feature not accounted for in hydrogen bond models.
• Halogen bonds are more accurately described by analogy to metal coordination bonds.
• This revised understanding opens new avenues for utilizing halogen bonds to modulate electronic properties of conjugated systems.