Investigating Bay-Substituted 6,7-Dihydrodibenzo[][4,7]phenanthroline, a Class of Tunable Hindered Rotors: Synthesis and Molecular Dynamics.

We developed a convenient and flexible synthesis of 6,7-dihydrodibenzo[][4,7]phenanthroline derivatives with bay region substituents via Friedländer condensation. Thanks to the mild reaction conditions, unsymmetrical bay-substituted systems also become accessible. The rigid phenanthroline framework holds various functional groups in the bay region in enough proximity for intramolecular interactions to manifest. Measuring the hindered rotational motions in this system unveils subtle structure-property relationships. Most notably, through rotamer distribution, π-π interactions between polycyclic aromatic hydrocarbons were found to scale with the π-surface coverage areas.