COM M UNlCATlONS
oxidation of the R u 2 + center is much more positive than that of the other complexes, but the peak reduction potentials remain remarkably constant. However, what is clear is that the electrochemical processes are chemically irreversible, showing almost no perceptible return upon scan reversals. There is only a hint of a return cathodic wave for Ru3+/Ru2+ at + 0.532 V, but none could be detected upon anodic reversal after reduction of the terpyridines.
The reason for the observed chemically irreversible voltammetric responses is currently not well understood. It is possible to speculate that, due to the increased steric hindrance for 9< Ru > 12, either reduction or oxidation leads to sufficient destabilization. These redox processes occur in the vicinity of the metal center and could result in decomposition of the complex. Such a redox-driven "unlocking" of a complex could form the basis for a reversible formation-decomposition mechanism.
This possibility, as well as the full characterization of the redox products, are currently under intense investigation.
In summary, this construction concept allows the synthesis of specific polymacrocascade networks. as well as the incorporation of metal receptor units on or at a precise depth inside the macromolecule, to be controlled. We confirmed earlier that it is possible to encapsulate relevant molecules[211 randomly within a lipophilic region or to bind them covalently at a specific locus in the interior of cascades.'222' We now demonstrate the application of directed complex formation to generate the first stages in the construction of dendritic networks through metal-centered connectivity.