Interplay between halogen bonds and π-π stacking interactions: CSD search and theoretical study

Area of Science:

• Crystallography
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Halogen bonds and π-π stacking are crucial noncovalent interactions in crystal engineering.
• Their coexistence and interplay in crystal packing are frequently observed in databases like the Cambridge Structural Database (CSD).

Purpose of the Study:

• To investigate the mutual influence between halogen bonds and π-π stacking interactions.
• To analyze the energetic effects when these two interactions coexist in molecular complexes.
• To provide experimental validation for the combined effects of these interactions.

Main Methods:

• Ab initio calculations at the MP2 level of theory were employed.
• Analysis of structural, energetic, and charge transfer properties.
• Quantum Theory of Atoms in Molecules (QTAIM) was utilized for interaction characterization.

Main Results:

• Distinct energetic effects arise from the coexistence of halogen bonds and π-π stacking.
• These effects are rationalized by the directionality of charge transfer between the interacting systems.
• QTAIM analysis confirmed the strengthening or weakening of interactions based on electron density variations.

Conclusions:

• The interplay between halogen bonds and π-π stacking significantly impacts crystal structures.
• Understanding these combined interactions is key for predicting and designing crystal packing.
• Experimental evidence from the CSD supports the computational findings on the synergistic effects of these noncovalent interactions.