ELECTRONIC COUPLING IN STARBURST DENDRIMERS - CONNECTIVITY, DISORDER, AND FINITE-SIZE EFFECTS IN MACROMOLECULAR BETHE LATTICES

We describe the mechanism of electronic coupling in starburst dendrimers, where each repeating unit is linked to three or more nearest neighbors. The connectivity in these molecules, which is that of a Bethe lattice or Cayley tree, leads to localization of the electronic states even within the ''bands'' of the material. This localization gives rise to electronic coupling properties that are distinct from those of the corresponding linear polymers. These differences are evident in the predicted electron-transport properties of the materials. When disorder is introduced to the structure, however, the branched connectivity of the dendrimer can enhance the probability of finding some strongly coupled pathways between the core and surface sites of the dendrimer. The unusual electron mediation properties of these molecules make them particularly intriguing frameworks for investigating the molecular control of electron transport and, especially, the role that disorder can play in establishing pathways for electronic communication in macromolecules.