Correlations of Electrical Properties and Molecular Structure Measured by Junctions Incorporating Self Assembled Monolayers

Electron transfer processes through organic molecules have been studied extensively i) in the last 30 years using transient spectroscopy in donor-acceptor supramolecular systems1 ii) in the last decade using an electrochemical approach in self assembled monolayers (SAMs) organized at the electrode interface. 2 We measured electron transfer rate through molecular systems as current flowing between molecules sandwiched between two metal electrodes. Fabrication of metal-molecule-metal junction is a challenging task. We report a series of studies of electron transfer processes carried out in junctions that are based on Hg electrodes (Fig 1), Hg-SAM//SAM-M, where M is a metal surface (Au, Ag, Hg). The junctions are easy to assemble (because the mercury electrode is compliant) and compatible with SAMs incorporating organic groups having a range of structures. We used two different types of junction. 1)Two electrodes junctions are used to measure the current flowing through SAMs of different chemical structure, sandwiched between the electrodes and to correlate electron transfer rate with the chemical structure of molecules (Interfacers 1 and 2 in Fig 1).3,4,5 . When photoactive molecules are incorporate in the SAMs, the current flowing through the junction changes upon irradiation.