A new insight into π-π stacking involving remarkable orbital interactions

Area of Science:

• Chemistry
• Materials Science
• Chemical Physics

Background:

• Pi-pi stacking is crucial in various scientific fields, including materials science, chemical synthesis, and drug design.
• Despite extensive research, a unified description of the factors influencing pi-pi stacking and its weak bonding remains elusive.

Purpose of the Study:

• To propose a unified model for pi-pi stacking interactions.
• To elucidate the interplay of forces governing pi-pi stacking at different molecular distances.

Main Methods:

• Density functional theory (DFT) calculations with dispersion correction were employed.
• The study focused on the benzene sandwich dimer and related systems (benzene-phenol, toluene, benzonitrile).

Main Results:

• Intermolecular orbital interactions were analyzed, revealing significant hybridization contributing to interaction energy.
• A model was developed describing the balance between dispersion, Pauli repulsion, electrostatic, and orbital interactions.
• At equilibrium, these forces collectively contribute to the formation of weak intermolecular bonds.

Conclusions:

• The proposed unified model provides a comprehensive understanding of pi-pi stacking.
• Intermolecular orbital interactions play a significant role in pi-pi stacking, previously underestimated.
• The findings advance the understanding of non-covalent interactions in chemical and material systems.