Single-molecule conductance of a chemically modified, {\pi}-extended tetrathiafulvalene and its charge-transfer complex with F4TCNQ

TL;DR

This study investigates the electrical conductance of a chemically modified, π-extended tetrathiafulvalene molecule and its charge-transfer complex, revealing measurable conductance only in the complex, supported by experimental and theoretical analysis.

Contribution

First single-molecule conductance measurements of a charge-transfer complex, demonstrating conductance differences between neutral and complexed forms using break junction techniques.

Findings

Conductance observed only in the charge-transfer complex.

Neutral molecule's conductance likely below measurement sensitivity.

Experimental results supported by theoretical calculations.

Abstract

We describe the synthesis and single molecule electrical transport properties of a molecular wire containing a ${\pi}$-extended tetrathiafulvalene (exTTF) group and its charge-transfer complex with F4TCNQ. We form single molecule junctions using the in-situ break junction technique using a home-built scanning tunneling microscope with a range of conductance between 10 G$_{0}$ down to 10$^{-7}$ G$_{0}$. Within this range we do not observe a clear conductance signature of the neutral parent molecule, suggesting either that its conductance is too low or that it does not form stable junctions. Conversely, we do find a clear conductance signature in the experiments carried out on the charge-transfer complex. Due to the fact we expected this species to have a higher conductance than the neutral molecule, we believe this supports the idea that the conductance of the neutral molecule is very low, below our measurement sensitivity. This is further supported by our theoretical calculations. To the best of our knowledge, these are the first reported single molecule conductance measurements on a molecular charge-transfer species.