Classical Electrostatics Remains the Driving Force for Interanion Hydrogen and Halogen Bonding

Area of Science:

• Chemical Physics
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Anion-anion interactions, including interanion hydrogen bonding (IAHB) and interanion halogen bonding (IAXB), present counterintuitive binding phenomena.
• The stability of these complexes challenges conventional electrostatic paradigms due to overall Coulombic repulsion.

Purpose of the Study:

• To investigate the fundamental mechanisms governing interanion hydrogen bonding (IAHB) and halogen bonding (IAXB).
• To elucidate the role of electrostatic interactions in the stability of metastable anion adducts.

Main Methods:

• Employed the energy decomposition approach based on the block-localized wavefunction method (BLW-ED).
• Utilized multipole expansion in the AMOEBA polarizable force field with state-specified atomic multipoles.

Main Results:

• Identified a nonmonotonic electrostatic interaction in interanion complexes, featuring a Coulombic barrier, unlike monotonic repulsion in conventional bonding.
• Demonstrated that other energy components exhibit monotonic behavior, similar to conventional hydrogen/halogen bonding.
• Validated the nonmonotonic electrostatic behavior using the AMOEBA force field, confirming interpretability via classical electrostatics.

Conclusions:

• Interanion hydrogen bonding (IAHB) and halogen bonding (IAXB) stability arises from a balance between local attractive forces and global Coulombic repulsion.
• There is no fundamental conceptual difference between conventional and interanion hydrogen/halogen bonding.
• The findings support a concise model of stability influenced by cooperativity between attractive and repulsive forces, observed in modified molecular capsules.