The presentation will focus on the synthesis and characterization of molecular assemblies, based on transition metal complexes and electronically conducting polymers, of deliberate design, for application in molecular devices. We have prepared and characterized single-molecule devices incorporating transition metal complexes designed so that electron transport occurs through well-defined charge states of a single molecule. We have also employed more complex molecular architectures as well as electronically conducting polymers. Preliminary results with novel optical techniques will also be discussed.