Time–frequency two-dimensional mapping of rapid energy transfer in light-harvesting star-shaped dendrimers

Rapid energy transfer dynamics in light-harvesting small dendrimers (star-shaped stilbenoid phthalocyanine: SSS1-Pc) having oligo (p-phenylenevinylene) peripheries was studied by real-time pump-probe imaging spectroscopy implemented on a single-shot basis. Using this method, we could successfully map the time–frequency two-dimensional (2D) image of the transient absorption of SSS1-Pc with a very short accumulation time. Under the selective excitation of the peripheries, the 2D image obtained clearly shows the transient absorption as well as the ground-state bleaching due to the energy transfer to the core with a fast rise time of ∼0.3 ps. This fast rise implies that the rapid energy transfer from the peripheries to the core takes place through the short-range interactions due to the overlap of wave functions between the excited states of the peripheries and the core.