Energy transfer and conformational dynamics in Zn-porphyrin dendrimers

The energy transfer within a series of Zn-porphyrin appended dendrimers was studied by means of time-resolved fluorescence anisotropy. We show that the energy transfer process between the Zn-porphyrin units in the dendrimers is limited to a maximum of four porphyrin units. At 200 K, the energy transfer process takes place on a 100-ps time scale, and can be modeled by Förster theory. Our results at room temperature further show that the porphyrin units are very mobile within the dendrimer, exhibiting rotational dynamics similar to that of a monomeric building block.