Journal of Physical Chemistry A, Vol.106, No.10, 2083-2090, 2002
Generation-dependent energy dissipation in rigid dendrimers studied by femtosecond to nanosecond time-resolved fluorescence spectroscopy
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.