Beyond Simple Structure-Function Relationships: The Interplay of Geometry, Electronic Structure, and Molecule/Electrode Coupling in Single-Molecule Junctions

Structure-function relationships constitute an important tool to investigate the fundamental principles of molecular electronics. Most commonly, this involves identifying a potentially important molecular structural element, followed by designing and synthesizing a set of related organic molecules, and finally interpretation of their experimental and/or computational quantum transport properties in the light of this structural element. Though this has been extremely powerful in many instances, we demonstrate here the common need for more nuanced relationships even for relatively simple structures, using both experimental and computational results for a series of stilbene derivatives as a case study. In particular, we show that the presence of multiple competing and subtle structural factors can combine in unexpected ways to control quantum transport in these molecules. Our results clarify the reasons for previous widely varying and often contradictory reports on charge transport in stilbene derivatives and highlight the need for refined multidimensional structure-property relationships in single-molecule electronics.