TY - JOUR
T1 - Ultrafast Photoinduced Electron Transfer in Rigid Porphyrin—Quinone Dyads
AU - Macpherson, Alisdair N.
AU - Liddell, Paul A.
AU - Lin, Su
AU - Noss, Lori
AU - Seely, Gilbert R.
AU - DeGraziano, Janice M.
AU - Moore, Ana
AU - Moore, Thomas
AU - Gust, Devens
PY - 1995
Y1 - 1995
N2 - Three dyad molecules, each consisting of a porphyrin (P) linked to a quinone (Q) through a rigid bicyclic bridge, have been prepared, and their photochemistry has been investigated using time-resolved fluorescence and absorption techniques. In all three molecules, photoinduced electron transfer from the porphyrin first excited singlet state to the quinone occurs with rate constants of ~1012 s_1 in solvents ranging in dielectric constant from ~2.0 to 25.6 and at temperatures from 77 to 295 K. The transfer rate is also relatively insensitive to thermodynamic driving force changes up to 0.4 eV. This behavior is phenomenologically similar to photosynthetic electron transfer. The rapid rate of photoinduced electron transfer and its lack of dependence on environmental factors suggests that transfer is governed by intramolecular vibrations. Charge recombination of P.+—Q._, on the other hand, is substantially slower than charge separation and sensitive to both driving force and environmental conditions. Thus, by changing conditions, charge recombination rates can be varied over a wide range while photoinduced electron transfer rates are relatively unaffected. This suggests that rigid dyads of this general type may be useful building blocks for more complex molecular devices.
AB - Three dyad molecules, each consisting of a porphyrin (P) linked to a quinone (Q) through a rigid bicyclic bridge, have been prepared, and their photochemistry has been investigated using time-resolved fluorescence and absorption techniques. In all three molecules, photoinduced electron transfer from the porphyrin first excited singlet state to the quinone occurs with rate constants of ~1012 s_1 in solvents ranging in dielectric constant from ~2.0 to 25.6 and at temperatures from 77 to 295 K. The transfer rate is also relatively insensitive to thermodynamic driving force changes up to 0.4 eV. This behavior is phenomenologically similar to photosynthetic electron transfer. The rapid rate of photoinduced electron transfer and its lack of dependence on environmental factors suggests that transfer is governed by intramolecular vibrations. Charge recombination of P.+—Q._, on the other hand, is substantially slower than charge separation and sensitive to both driving force and environmental conditions. Thus, by changing conditions, charge recombination rates can be varied over a wide range while photoinduced electron transfer rates are relatively unaffected. This suggests that rigid dyads of this general type may be useful building blocks for more complex molecular devices.
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U2 - 10.1021/ja00132a021
DO - 10.1021/ja00132a021
M3 - Article
AN - SCOPUS:0029344990
SN - 0002-7863
VL - 117
SP - 7202
EP - 7212
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 27
ER -