Visualizing And Comparing Quantum Interference In The π-system And σ-system Of Organic Molecules

Quantum interference effects in conjugated molecules have been well explored, with benzene frequently invoked as a pedagogical example. These interference effects have been understood through a quantum interference map in which the electronic transmission is separated into interfering and non-interfering terms, with a focus on the π-orbitals for conjugated molecules. Recently, saturated molecules have also been reported to exhibit destructive quantum interference effects, however the very different σ-orbital character in these molecules means that it is not clear how orbital contributions manifest. Herein, we demonstrate that the quantum interference effects in conjugated molecules are quite different from those observed saturated molecules, as demonstrated by the quantum interference map. While destructive interference in the π-system arises from interference terms between paired occupied and virtual orbitals, this is not the case in saturated systems. Instead, destructive interference is evident when contributions from a larger number of non-paired orbitals cancel leading to the more subtle and varied manifestations of destructive interference in saturated systems.