We characterized the single-molecule electronic properties of ladder and non-ladder molecules using the STM-BJ method . In this experiment, a gold tip electrode is repeatedly moved into and out of contact with a gold substrate electrode in solution containing molecules with terminal anchor groups, resulting in the repeated making and breaking of molecular junctions. During each molecular 'pulling' event, the current is measured for a constant applied bias across the molecular junction. The experiment begins as the tip moves away from the bottom (substrate) electrode, resulting in a sharp decrease in molecular conductance typically observed at one unit of quantum conductance (G0, where G0 = 2e 2 /h or 77.5 μS; e, electron charge; h, Planck's constant), which indicates the start of the single-molecule pulling event. Molecular conductance is then measured as junction displacement increases, which corresponds to formation of a single-molecule junction. At junction breakage, the molecular conductance abruptly decreases to the limit of detection of the instrument (~10 -5.5 G0). The STM-BJ instrument is automated, and the experiment is repeated over an ensemble of 10 3 -10 4 molecules. Single-molecule conductance data are then analyzed using 1D and two-dimensional (2D) histograms without data selection (Methods).