Photoinduced electron and energy transfer in molecular pentads

Journal Article · Tue Nov 30 23:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00077a011· OSTI ID:5207856

Gust, D; Moore, T A; Moore, A L; Macpherson, A N; Lopez, A; DeGraziano, J M; Gouni, I; Bittersmann, E; Seely, G R; Gao, F; Nieman, R A; Ma, X C; Demanche, L J; Hung, S C; Luttrull, D K; Lee, S J; Kerrigan, P K ^[1]

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

A series of molecular pentads, each consisting of a porphyrin dyad (P-P) covalently linked to a carotenoid polyene (C) and a diquinone moiety (Q[sub A]-Q[sub B]), have been prepared, and the photochemical properties of these molecules have been studied using steady-state and transient absorption and emission spectroscopies. Each of the pentads undergoes photoinduced electron transfer from the C-P-[sup 1]P-Q[sub A]-Q[sub B] singlet state to yield the charge-separated state C-P-P[sup [sm bullet]+]-Q[sub A][sup [sm bullet][minus]]-Q[sub B]. Competing with charge recombination of this species are additional electron-transfer reactions operating in series and in parallel which converge on a final C[sup [sm bullet]+]-P-P-Q[sub A]-Q[sub B][sup [sm bullet][minus]] state. The electron-transfer rate constants and the quantum yields of the various charge-separated species are sensitive functions of the state energies and the electronic coupling between the porphyrin and diquinone moieties. One of the pentads undergoes photoinduced electron transfer to produce the final C[sup [sm bullet]+]-P-P-Q[sub A]-Q[sub B][sup [sm bullet][minus]] state with a quantum yield of 0.83 and a lifetime of 55 [mu]s. This example of an artificial photosynthetic reaction center preserves about half of the initial excited singlet state energy as chemical potential. Other pentads have charge-separation lifetimes of several hundred microseconds. 28 refs., 10 figs., 1 tab.

• DOE Contract Number: FG02-87ER13791; FG02-88ER13969
• OSTI ID: 5207856
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:24; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400500 -- Photochemistry
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COMPLEXES
COMPUTERIZED SIMULATION
ELECTRON TRANSFER
ENERGY TRANSFER
FLUORESCENCE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LUMINESCENCE
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PORPHYRINS
RADICALS
RESONANCE
SIMULATION
SPECTROSCOPY
SYNTHESIS
ZINC COMPLEXES