Two-state conductance in single Zn porphyrin molecular junctions

Conductance measurements were taken by forming single molecule junctions between a scanning tunneling microscope tip and a gold substrate. We observed the existence of a two-state conductance in porphyrin molecules ligating a zinc atom. Peaks in the conductance histograms showed molecules changed from a high conductance state to a low conductance state. This effect was not observed for porphyrin molecules without a ligating atom. We discuss how this phenomenon may be attributed to conformational changes in the molecule. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3452353]