Time-Resolved Fluorescence Investigation of Energy Transfer in Compact Phenylacetylene Dendrimers

Excitation energy transfer dynamics in light-harvesting dendritic macromolecules has generated a great deal of interest due to the fact that such systems can be used in photovoltaic and light-emitting devices. Studies on phenylacetylene-based dendrimers played a key role in stimulating this interest and extensive theoretical as well as experimental investigations have been carried out to get a better insight into the phenomena behind the excitation energy transfer dynamics of these dendrimers. In this manuscript, time-resolved femtosecond fluorescence and fluorescence anisotropy dynamics as well as temperature dependent steady state spectral studies of a second generation homogeneous (compact) phenylacetylene dendrimer are reported. The low-temperature fluorescence spectrum of the dendrimer showed two distinctive emission peaks that can be related to the existence of two closely spaced electronic states of the chromophore. Time-resolved fluorescence results suggest delocalization of the excitation energy in the excited state. The ultrafast fluorescence anisotropy decay dynamics further supports the existence of a delocalized state.