Intramolecular directional energy transfer processes in dendrimers containing perylene and terrylene chromophores

The time-resolved fluorescence kinetics of a first and a second generation dendrimer with peryleneimide chromophores at the rim and a terrylenediimide chromophore in the core were investigated using femtosecond fluorescence upconversion and single photon timing techniques. By global analysis of an extentensive data set with lambda(em) ranging from 540 to 780 nm, combining both techniques and comparing the kinetic results obtained previously for peryleneimide and terrylenediimide reference compounds, two independent energy transfer processes could be identified. The time constants were 4 and 25 ps for the first generation dendrimer and 22 and 68 ps for the second generation, respectively. They scale as expected for Forster energy transfer processes between chromophores at the distances present in the dendrimers. Each of these processes can possibly be related to different isomers present in the samples. Analysis of the in-the-bay area substituted terrylenediimide model compound reveals subsets of molecules showing different relaxation pathways of the terrylene core.