Molecular nano-lenses: Directed energy migration and back-transfer in dendrimeric antenna supermolecules

Experimental and theoretical evidence is presented for the process of directed, multistep energy transport in a unique class of fractal-like dendrimeric supermolecules. Due to the meta-position branching arrangement of these Cayley trees, tight excitation localization is observed at the branching nodes. Particular forms of these dendrimers have been synthesized with localized states of decreasing energy toward the molecular locus, creating a rapid and efficient exciton funnel. Spectroscopic data is presented illustrating nearly unit transfer efficiency from the dendrimer periphery to a specialized trap at the molecular center. In addition, the energetics and spatial arrangement of these molecules allow for the destruction of multiphoton excitations at the trap, providing protection from permanent photochemical bleaching.