Probing Forster type energy pathways in a first generation rigid dendrimer bearing two perylene imide chromophores

Ensemble and single molecule spectroscopic measurements on a bichromophoric dendrimer system were performed. Although Forster type energy processes such as energy hopping and singlet-singlet annihilation can be observed at the ensemble and single molecule level, only single molecule measurements can visualize the presence of singlet-triplet annihilation. The flux dependent population of the triplet state suggests facilitated formation of the triplet through a higher singlet excited state. The presence of synthesis inherent structural isomers, not to be distinguished at the ensemble level, could be demonstrated by analyzing modulated fluorescence intensity trajectories. These data show the complementarity of both the ensemble and single molecule approaches in the study of detailed photophysics of a multichromophoric system.