A theoretical exploration of unexpected amine···π interactions

Area of Science:

• Computational chemistry
• Molecular interactions
• Quantum chemistry

Background:

• Non-covalent interactions are fundamental to molecular recognition and material properties.
• Amine lone pair···π interactions are typically considered repulsive, challenging conventional understanding.

Purpose of the Study:

• To computationally investigate and characterize counterintuitive attractive interactions between amine lone pairs and π systems.
• To elucidate the underlying electronic and energetic factors governing these interactions.

Main Methods:

• High-level ab initio calculations using MP2 and CCSD(T) methods.
• Symmetry-adapted perturbation theory (SAPT) for interaction energy decomposition.
• Atoms in Molecules (AIM) analysis for electronic structure insights.

Main Results:

• Confirmation of attractive amine lone pair···π interactions when the lone pair is oriented towards the π system.
• SAPT analysis indicates significant contributions from dispersion forces to the observed attraction.
• AIM analysis provides insights into the electronic redistribution driving the interaction.

Conclusions:

• Amine lone pair···π interactions can be attractive under specific geometric arrangements.
• Dispersion forces are critical for stabilizing these counterintuitive interactions.
• Understanding these interactions is vital for designing novel molecular systems and materials.