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Abstract:
Intramolecular kinetic processes in a series of second- generation polyphenyl dendrimers with multiple peryleneimide chromophores attached to the para position of the outer phenyl ring were investigated by steady-state and femtosecond to nanosecond time-resolved fluorescence spectroscopy. The results obtained were compared to the ones of the corresponding first- generation dendrimer series. The energy-hopping rate constant, k(hopp), observed from anisotropy decay times was found to be 5 times smaller than that of the first-generation series and scales well with the difference in average distance between the chromophores. In addition to the processes observed in first- generation dendrimers in the ultrafast time domain by fluorescence up-conversion, a second. annihilation process is found in the second-generation multichromophoric dendrimer. The observation of two singlet-singlet annihilation processes in this compound can be explained by the presence of a mixture of constitutional isomers leading to a broader distribution of distances between neighboring chromophores compared to first- generation multichromophoric dendrimers.
