Paper summary
Intermolecular single-electron transfer on electrically insulating films is a key process in molecular electronics and an important example of a redox reaction. Electron-transfer rates in molecular systems depend on a few fundamental parameters, such as interadsorbate distance, temperature, and, in particular, the Marcus reorganization energy. Here, we investigate redox reactions of single phthalocyanine (NPC) molecules on multilayered NaCl films. Employing the atomic force microscope as an ultralow current meter allows us to measure the differential conductance related to transitions between two charge states in both directions. Our approach provides insight into single-electron intermolecular transport.