Conformational analysis of selected [2.2]heterophanes: A comparison of stereochemical switching via computational chemistry

Conformational switching of selected [2.2]heterophanes was investigated by computational chemistry. Analyses were carried out by various methods, including Conformational Search in HyperChem, and forced conformational transformations with Energy Profile in Spartan. Stable  anti  and  syn  conformers arising from flipping of aromatic rings within the molecules were observed. The activation energies of the ring flipping process, as well as dipole moments and directions, were obtained by molecular mechanics. The present work shows that simple computational techniques can be employed to screen certain compounds as potential candidates for molecular machinery. Thus, heterophanes demonstrated reversible shifts between two or more configurations which are energetically stable and have different electronic properties, constituting a basic requirement for possible applications as molecular switches.