Photophysical study of electron-transfer and energy-hopping processes in first-generation mono- and multichromophoric triphenylamine core dendrimers

The combination of transient absorption and fluorescence experiments performed on a femtosecond to nanosecond time scale was used to characterize the electron-transfer process in mono- (N1P1) and multichromophoric (N1P3) triphenylamine core dendrimers carrying one and three peryleneimide electron acceptor chromophores, respectively. Comparison of the monochromophoric N1P1 to the multichromophoric N1P3 allowed us to investigate the influence of the number of chromophores upon the electron transfer kinetics. The solvent effect on the electron transfer process was investigated by comparing the results obtained in the highly polar solvent benzonitrile with those in the less polar solvents as diethyl ether, 2-methyltetrahydrofuran, tetrahydrofuran, and toluene. By means of fluorescence anisotropy and transient absorption anisotropy experiments, the occurrence of energy hopping in the multichromophoric N1P3 has been demonstrated. Furthermore singlet-singlet annihilation, observed earlier in a model compound without an electron donor moiety, was confirmed in the multichromophoric N1P3.