| Abstract
| - The identification of strategies to assemble nanostructured films with engineered properties on solid supportscan lead to the development of innovative functional materials. In particular, the self-assembly of electroactivemultilayers from simple molecular building blocks on metallic electrodes can offer the opportunity to regulatethe exchange of electrons between the underlying substrate and solution species. In this context, we designedan experimental protocol to prepare electroactive films from bipyridinium bisthiols. Specifically, we foundthat a compound incorporating two bipyridinium dications at its core and terminal thiol groups self-assemblesinto remarkably stable multilayers on polycrystalline gold. The surface coverage of the resulting films can beregulated by adjusting the exposure time of the gold substrate to the bipyridinium solution. Control experimentswith appropriate model compounds demonstrate that both bipyridinium dications as well as both thiol groupsmust be present in the molecular skeleton to encourage multilayer growth. The resulting films transport electronsefficiently from the electrode surface to the film/solution interface. Indeed, they mediate the reduction ofRu(NH3)63+ in the electrolyte solution but prevent the back oxidation of the resulting Ru(NH3)62+. Furthermore,these polycationic bipyridinium films capture electrostatically Fe(CN)64- tetraanions, which can also beexploited to transport electrons across the interfacial assembly. In fact, electrons can travel through thebipyridnium2+/1+ couples to redox probes in solution and then back to the electrode through the Fe(CN)64/3-couples. Thus, our original approach to self-assembling multilayers can produce stable electroactive filmswith unique electron transport properties, which can be regulated with a careful choice of the anioniccomponents.
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