Spiro-Conjugated Molecular Junctions: Between Jahn–Teller Distortion and Destructive Quantum Interference

Abstract

The quest for molecular structures exhibiting strong quantum interference effects in the transport setting has long been on the forefront of chemical research. We establish theoretically that the unusual geometry of spiro-conjugated systems gives rise to complete destructive interference in the resonant-transport regime. This results in a current blockade of the type not present in meta-connected benzene or similar molecular structures. We further show that these systems can undergo a transport-driven Jahn-Teller distortion, which can lift the aforementioned destructive-interference effects. The overall transport characteristics are determined by the interplay between the two phenomena. Spiro-conjugated systems may therefore serve as a novel platform for investigations of quantum interference and vibronic effects in the charge-transport setting. The potential to control quantum interference in these systems can also turn them into attractive components in designing functional molecular circuits.

Beyond Marcus theory and the Landauer-Büttiker approach in molecular junctions: A unified framework

“…This constitutes an important limitation of our approach, since the above assumption is not necessarily always valid as it has been observed experimentally 66 , and discussed theoretically. 23,25,48,74,75…”

Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

“…This is in close analogy to similar systems where such cases of destructive quantum interference has been described in detail. 45,117,[119][120][121] Though we only assess one pair of frontier orbitals for each molecule here, other pairs of helical p-orbitals also become degenerate at 90°, in accordance with the Coulson-Rushbrooke orbital pairing theorem. 39,[114][115] We conclude from this analysis, that even though helical p-orbitals only have pseudo p-symmetry given the nodal planes follow a helix, the same theoretical analysis of destructive quantum interference applies as in the general case for psystems.…”

Helical orbitals and circular currents in linear carbon wires

“…As we shall demonstrate, this is a consequence of destructive quantum interference. [48][49][50] Splitting helical orbitals with substituents Any pair of substituents that preserves the helicogenic C 2 symmetry of the molecule can be used to reduce the symmetry and obtain helical molecular orbitals. However, simple substituents have little effect on the energetic splitting of the helical orbitals.…”