Three-state molecular potentiometer based on a non-symmetrically positioned in-backbone linker

We report on the synthesis and single-molecule conductance of a para-oligo(phenylene)ethynylene (p-OPE) derivative with three well-defined conductance states. Employing theoretical models and comparing to reference compounds we show that this effect is due to the presence of the internal non-symmetrically placed pyrimidine ring, acting as an in-backbone anchor group. This is the first example in which the non-symmetric positioning of an internal binding site opens up two new conduction channels, giving rise, in a simple way, to a system that displays three conduction pathways which differ distinctively in both conductance and length.