Electrostatically Driven CO-π Aromatic Interactions.

A series of N-arylimide molecular balances were developed to study and measure carbonyl-aromatic (CO-π) 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-π 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-π aromatic interaction was stronger than the previously studied oxygen-π and halogen-π aromatic interactions.

Measurement of Solvent OH-π Interactions Using a Molecular Balance.

A molecular torsion balance was designed to study and measure OH-π interactions between protic solvents and aromatic surfaces. These specific solvent-solute interactions were measured via their influence on the folded-unfolded equilibrium of an N-arylimide rotor. Protic solvents displayed systematically weaker solvophobic interactions than aprotic solvents with similar solvent cohesion parameters. This was attributed to the formation of OH-π interactions between the protic solvents and the exposed aromatic surfaces in the unfolded conformer that offset the stronger solvophobic effects for protic solvents.

Solvent-induced reversible solid-state colour change of an intramolecular charge-transfer complex.

A dynamic intramolecular charge-transfer (CT) complex was designed that displayed reversible colour changes in the solid-state when treated with different organic solvents. The origins of the dichromatism were shown to be due to solvent-inclusion, which induced changes in the relative orientations of the donor pyrene and acceptor naphthalenediimide units.