Ultrafast photoinduced electron transfer in rigid porphyrin-quinone dyads

Journal Article · Wed Jul 12 04:00:00 EDT 1995 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja00132a021· OSTI ID:91276

Macpherson, A N; Liddell, P A; Lin, S; Noss, L; Seely, G R; DeGraziano, J M; Moore, A L; Moore, T A; Gust, D ^[1]

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1. Arizona State Univ., Tempe, AZ (United States)

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 approximately 10{sup 12} s{sup -1} in solvents ranging in dielectric constant from approximately 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{sup {center_dot}+} {sup -}Q{center_dot}, 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. 76 refs., 9 figs., 1 tab.

• Sponsoring Organization: USDOE
• DOE Contract Number: FG03-93ER14404
• OSTI ID: 91276
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 27 Vol. 117; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
ABSORPTION SPECTRA
CHARGE TRANSPORT
ELECTRON TRANSFER
EMISSION SPECTRA
EXCITED STATES
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC REACTION CENTERS
PORPHYRINS
QUINONES