Unexpected Charge Effects Strengthen π-Stacking Pancake Bonding.

Area of Science:

• Materials Science
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Phenalenyls (PLYs) are key building blocks in functional materials, known for facilitating electron/hole transport via π-stacking.
• PLYs serve as a model for π-stacking pancake bonding, typically involving two-electron multicenter bonding (2e/mc).

Purpose of the Study:

• To investigate the impact of charge on the binding energies and bonding nature of phenalenyl (PLY) and olympicenyl (OPY) dimers.
• To explore the role of perfluorination in modifying these intermolecular interactions.

Main Methods:

• Computational modeling was used to analyze the electronic structure and binding energies of neutral and charged PLY and OPY dimers.
• The study examined both non-fluorinated and perfluorinated (PF) systems.

Main Results:

• Positively charged PLY and OPY dimers (PLY₂⁺, OPY₂⁺) showed a near-doubling of binding energy compared to neutral dimers.
• Negatively charged perfluorinated dimers (PF-PLY₂^-, PF-OPY₂^-) exhibited strong binding, a reversal of the charge effect seen in non-fluorinated systems.
• Pancake bonding in charged dimers involved single-electron (1e/mc) or three-electron (3e/mc) multicenter bonding, differing from the 2e/mc in neutral dimers.
• A strong preference for large intermolecular overlap and π-bonding over σ-bonding was observed in charged dimers.

Conclusions:

• Charge significantly alters intermolecular interactions and bonding in PLY and OPY systems, leading to enhanced binding energies and novel multicenter bonding types.
• Perfluorination plays a crucial role in reversing charge effects on binding, enabling strong interactions in negatively charged dimers.
• These findings offer insights into designing advanced electronic materials with tunable intermolecular properties.