•Heiko B. Weber, Michelle Di Leo, Joachim Reichert, Marcel Mayor und Mark Elbing
Forschungszentrum Karlsruhe, Institut für Nanotechnologie, Postfach 3640, D-76021 Karlsruhe

It has been demonstrated recently that the break-junction technique can be used to establish single-molecule conductance measurements with conjugated molecules [1]. Here, we focus on a class of molecules, where the conjugated part is divided into several sections. Hence, the electronic conduction process corresponds to subsequent tunneling along a series of conjugated sites (benzene rings). The conductance measurements show qualitative differences of the IVs for the four molecules which are attributed to different topology: while the molecules with 1,3, and 4 rings enclose conjugated islands and show Coulomb-blockade-like IVs, the molecule with 2 benzene units has a single barrier in its center and shows no blockade region.