Electrostatically Driven Co-Pi Aromatic Interactions

A series of N-arylimide molecular balances were developed to study and measure carbonyl-aromatic (CO-pi) interactions. Carbonyl oxygens were observed to form repulsive interactions with unsubstituted arenes and attractive interactions with electron-deficient arenes with multiple electron-withdrawing groups. The repulsive and attractive CO-pi aromatic interactions were well-correlated to electrostatic parameters, which allowed accurate predictions of the interaction energies based on the electrostatic potentials of the carbonyl and arene surfaces. Due to the pronounced electrostatic polarization of the C=O bond, the CO-pi aromatic interaction was stronger than the previously studied oxygen-pi and halogen-pi aromatic interactions.