Electrochemical control of quantum interference in anthraquinone-based molecular switches

TL;DR

This study uses first-principles calculations to demonstrate how electrochemical control can modulate quantum interference effects in anthraquinone-based molecular switches, significantly affecting their conductance states.

Contribution

It introduces a minimal tight-binding model linking molecular orbital symmetries to quantum interference, providing insight into electrochemical switching mechanisms.

Findings

Robust conductance on/off ratios due to quantum interference

Destructive interference present in anthraquinone but absent in hydroquinone

Tight-binding model explains interference based on orbital symmetries

Abstract

Using first-principles calculations we analyze the electronic transport properties of a recently proposed anthraquinone based electrochemical switch. Robust conductance on/off ratios of several orders of magnitude are observed due to destructive quantum interference present in the anthraquinone, but absent in the hydroquinone molecular bridge. A simple explanation of the interference effect is achieved by transforming the frontier molecular orbitals into localized molecular orbitals thereby obtaining a minimal tight-binding model describing the transport in the relevant energy range in terms of hopping via the localized orbitals. The topology of the tight-binding model, which is dictated by the symmetries of the molecular orbitals, determines the amount of quantum interference.