Dual electron transfer pathways from the excited C-60 radical anion: enhanced reactivities due to the photoexcitation of reaction intermediates

作者：Fujitsuka Mamoru^*; Ohsaka Tatsuya; Majima Tetsuro

来源：Physical Chemistry Chemical Physics, 2015, 17(46): 31030-31038.

DOI：10.1039/c5cp05254h

In the present study, electron transfer (ET) processes from excited radical anions have been investigated using dyad molecules including C-60. The deactivation process of excited C-60(center dot-), including the internal conversion from the D-1 to the D-0 state and the cooling process of the vibrationally hot ground state (D-0(hot)), was observed spectroscopically for the first time. These processes could be unambiguously distinguished by the observation of the stimulated emission from the D-1 state. The intramolecular ET processes from the excited C-60(center dot) were confirmed by the transient absorption spectra. Clearly, both D-1 and D-0(hot) states acted as precursors for the ET, i.e., dual ET pathways were confirmed. The driving force dependence of the ET rates was well characterized by the Marcus theory, which revealed that the forward ET processes are located at the top region of the Marcus parabola. In addition, the ET from the excited imide radical anion to C-60 and that from the ground state C-60(center dot-) to imide were examined. The ET rate from the excited imide radical anion and that from ground state C-60(center dot-) did not follow the Marcus parabola estimated for the ET from the excited C-60(center dot-). The observed difference can be attributed to the difference in the energy required to form the reduced spacer (Delta) in the superexchange mechanism. Because the Delta value tends to become smaller for ET processes from excited radical ions, fast and efficient ET processes are expected from these states as demonstrated in the present study.

• 出版日期2015