"Anti-electrostatic" Halogen Bonding between Ions of Like Charge

Area of Science:

• Chemistry
• Crystallography
• Supramolecular Chemistry

Background:

• Halogen bonding is typically viewed as an electrostatic interaction between Lewis acidic halogens and Lewis bases.
• Interactions between like-charged ions, such as anionic halogen bond donors and halides, appear counter-intuitive under this model.

Purpose of the Study:

• To provide an overview of complexes exhibiting "anti-electrostatic" halogen bonding.
• To compare theoretical findings with experimental evidence for these interactions.
• To contrast these with other counter-intuitive adducts and explore underlying mechanisms.

Main Methods:

• Review of theoretical studies on halogen bonding.
• Analysis of crystal structure databases.
• Examination of experimental data from crystalline and solution-phase studies.

Main Results:

• Theoretical studies support the existence of "anti-electrostatic" halogen bonding.
• Experimental evidence, including crystal structures and solution observations, confirms these interactions.
• Comparison with hydrogen bonding reveals similarities in counter-intuitive adduct formation.

Conclusions:

• "Anti-electrostatic" halogen bonding is a valid phenomenon, supported by both theoretical and experimental data.
• These interactions challenge purely electrostatic explanations, highlighting the role of other factors like charge-transfer and polarization.
• The study expands the understanding of non-covalent interactions beyond traditional models.