Intramolecular π-stacking in isostructural conformational probes depends strongly on charge separation, a proton NMR study

Our solution state conformational methods used previously to study a dicationic molecular template for intramolecular aromatic association were applied to a neutral hydrocarbon analogue to probe the effect of charge on conformation. Conformational analysis of the hydrocarbon revealed modest solvent dependence in largely unfolded molecules. Conformations found in the solid state were unfolded also corroborating the findings of the solution-state study. This study also adds solid-state evidence for three competing solution-state conformers previously predicted by calculations. In the absence of charge, the molecular template does not favor intramolecular association of aromatic substituents. These results agree with the chemical literature and previous reports of neutral hydrocarbon intramolecular association in the solution state.