Study of through-space substituent–π interactions using N-phenylimide molecular balances

Abstract

Substituent–π interactions associated with aromatic stacking interactions were experimentally measured using a small N-phenylimide molecular balance model system. The direct interaction of the substituent (NH₂, CH₃, OH, F, Br, CF₃ and NO₂) with an aromatic ring was measured in the absence of the aromatic stacking interactions in solution. The measured substituent–π energies were found to correlate well with the Hammett σ_m parameter similar to the substituent effects observed in aromatic stacking systems. The persistent electrostatic trends in substituent effects can arise from the direct electrostatic interactions between substituents and opposing π-systems.