부산대학교 도서관

Photoinduced charge transfer in a double-linked zincporphyrin–fullerenedyad is studied. When the dyad is excited at the absorption band ofthe charge-transfer complex (780 nm), an intramolecular exciplex isformed, followed by the complete charge separated (CCS) state. Byanalyzing the results obtained from time-resolved transient absorptionand emission decay measurements in a range of solvents with differentpolarities, we derived a dependence between the observable lifetimesand internal parameters controlling the reaction rate constants basedon the semiquantum Marcus electron-transfer theory. The critical valueof the solvent polarity was found to be εr≈6.5: in solvents with higher dielectric constants, the energy of theCCS state is lower than that of the exciplex and the relaxation takesplace via the CCS state predominantly, whereas in solvents with lowerpolarities the energy of the CCS state is higher and the exciplexrelaxes directly to the ground state. In solvents with moderate polaritiesthe exciplex and the CCS state are in equilibrium and cannot be separatedspectroscopically. The degree of the charge shift in the exciplexrelative to that in the CCS state was estimated to be 0.55 ±0.02. The electronic coupling matrix elements for the charge recombinationprocess and for the direct relaxation of the exciplex to the groundstate were found to be 0.012 ± 0.001 and 0.245 ± 0.022 eV,respectively. [ABSTRACT FROM AUTHOR]