Single molecule conductance of bipyridyl ethynes: the role of surface binding modes.

We report on the experimental studies of single molecule conductance of 1,2-bi(pyridin-4-yl)ethyne (BPY-EY) and perfluoro-1,2-bi(pyridin-4-yl)ethyne (PFBPY-EY). The conductance measurements of the molecules bridging two Au electrodes have been carried out in toluene solutions using the scanning tunneling microscopy (STM) based break junction technique. Two conductance values of (2.2 ± 0.5) x 10 -4 and (5.0 ± 0.8) x 10 -5 G 0 have been found for BPY-EY but only one, (4.2 ± 0.5) x 10 -5 G 0 , for PFBPY-EY. The disparity is attributed to steric differences between the molecules at the electrode.