A Three State NDI Switch: Integration of Pendant Redox Unit for Conductance Tuning

TL;DR

This study demonstrates a three-state conductance switch in NDI single-molecule junctions controlled by electrochemical redox states, with significant conductance differences confirmed by DFT calculations, advancing molecular electronics.

Contribution

It introduces a novel three-state conductance switching mechanism in NDI molecules via pendent redox units, combining experimental STM techniques with DFT modeling.

Findings

Conductance varies over an order of magnitude between redox states.

Redox control enables stable three-state conductance switching.

DFT confirms electrochemical effects on charge transport.

Abstract

We studied charge transport phenomena through a core substituted naphthalenediimide (NDI) single-molecule junctions using the electrochemical STM-based break junction technique in combination with DFT calculations. The conductance switch among three well-defined states is acquired by electrochemically controlling the redox state of the pendent diimide unit of the molecule in ionic liquid, and the conductance difference is more than one order of magnitude between di-anion states and neutral state. The potential dependent charge transport characteristics of the NDI molecules are confirmed by DFT calculations accounting for electrochemical double-layer effects on the conductance of the NDI junctions. This work suggests that the integration of redox unit in the pendent position with strong coupling to molecular backbone can significantly tune the charge transport of the single-molecule device by controlling different redox states.