Solvent dependence of the charge-transfer properties of a quaterthiophene-anthraquinone dyad

Wan, J., Ferreira, A., Wei, X., Chow, C.H., Takechi, K., Kamat, P.V., Jones, II, G., and Vullev, V.I.

J. Photochem. Photobiol. A 197(2-3), 364-374 (2008)

NDRL 4744

An electron donor-acceptor dyad (quaterthiophene-anthraquinone) mediates ultrafast intramolecular photoinduced charge separation and consequent charge recombination when in polar or moderately polar solvents. Alternatively, non-polar media completely impedes the initial photoinduced electron transfer by causing enough destabilization of the charge-transfer state and shifting its energy above the energy of the lowest locally excited singlet state. Furthermore, femtosecond transient-absorption spectroscopy reveals that for the solvents mediating the initial photoinduced electron-transfer process, the charge recombination rates were slower than the rates of charge separation. This behavior of donor-acceptor systems is essential for solar-energy-conversion applications. For the donor-acceptor dyad described in this study, the electron-transfer driving force and reorganization energy place the charge-recombination processes in the Marcus inverted region.

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