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) 1 he 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) Go have been found for BPY-EY but only one (4 2 0 5) x 10 Go for PPBPY EY The disparity is attributed to stem differences between the molecules at the electrode