Cation-cation and anion-anion complexes stabilized by halogen bonds.

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Chemical Physics

Background:

• Halogen bonds are crucial non-covalent interactions.
• Understanding interactions between like-charged molecules is challenging.
• Theoretical studies are essential for characterizing unstable chemical systems.

Purpose of the Study:

• To investigate stable minima and transition states of halogen bonds between like-charged molecules.
• To analyze the thermodynamic and kinetic stability of these complexes.
• To elucidate the nature of interactions using advanced computational methods.

Main Methods:

• Theoretical calculations were employed to explore stable minima and dissociation transition states.
• Symmetry-Adapted Perturbation Theory (SAPT) was used to analyze interaction nature.
• Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) theories were applied for detailed analysis.

Main Results:

• Complexes are thermodynamically unstable but kinetically stable in the gas phase.
• Corrected binding energy profiles resemble those of neutral systems after removing charge-charge repulsion.
• Favorable electrostatic interactions exist in minima but diminish at transition states.

Conclusions:

• Halogen bonds can stabilize like-charged molecular complexes kinetically, despite thermodynamic instability.
• Computational methods like SAPT, NBO, and AIM provide insights into these complex interactions.
• The findings contribute to understanding non-covalent interactions in charged systems.