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

Substituent- 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- energies were found to correlate well with the Hammett sigma(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 -systems.