Long-lived photoinitiated charge separation in carotene-diporphyrin triad molecules

Gust, Devens; Moore, Thomas A.; Moore, Ana L.; Gao, Feng; Luttrull, David K.; DeGraziano, Janice M.; Chi, Xiaochun; Makings, Lewis R.; Lee, Seung Joo; Trier, Todd T.; Bittersmann, Edith; Seely, G. R.; Woodward, Susanne; Bensasson, René V.; Rougée, Michel; Schryver, F. C. De; Auweraer, Mark Van der

doi:10.1021/ja00010a002

Cited by 99 publications

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“…This interpretation is consistent with the strong solvent dependence of the time constant and the spectroscopic and electrochemical results discussed above. Photoinduced electron transfer between porphyrins joined by similar linkages has been reported (23,24). The fact that the shortest decay component in benzonitrile has a time constant that is essentially identical to the corresponding component in cyclohexane is consistent with an absence of significant photoinduced electron transfer from 1 PF 10 -TCNP in both solvents.…”

Section: Resultssupporting

confidence: 74%

“…In related triads of the carotenoid-porphyrin-porphyrin (C-P-P) type, where the carotenoid is the secondary electron-donor and no proton transfer is involved in the charge-separation or recombination processes, the final charge-separated states C •þ -P-P •− typically live only hundreds of nanoseconds at room temperature (23,24). The systems are not strictly comparable to 1, as the thermodynamic driving forces and solvents differ in the various systems.…”

Section: Resultsmentioning

confidence: 99%

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Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Megiatto

Antoniuk-Pablant

Sherman

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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111

112

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In the photosynthetic photosystem II, electrons are transferred from the manganese-containing oxygen evolving complex (OEC) to the oxidized primary electron-donor chlorophyll P680 •+ by a proton-coupled electron transfer process involving a tyrosine-histidine pair. Proton transfer from the tyrosine phenolic group to a histidine nitrogen positions the redox potential of the tyrosine between those of P680 •+ and the OEC. We report the synthesis and time-resolved spectroscopic study of a molecular triad that models this electron transfer. The triad consists of a high-potential porphyrin bearing two pentafluorophenyl groups (PF 10 ), a tetracyanoporphyrin electron acceptor (TCNP), and a benzimidazole-phenol secondary electron-donor (Bi-PhOH). Excitation of PF 10 in benzonitrile is followed by singlet energy transfer to TCNP ( τ = 41 ps), whose excited state decays by photoinduced electron transfer ( τ = 830 ps) to yield . A second electron transfer reaction follows ( τ < 12 ps), giving a final state postulated as BiH + -PhO • -PF 10 -TCNP •- , in which the phenolic proton now resides on benzimidazole. This final state decays with a time constant of 3.8 μs. The triad thus functionally mimics the electron transfers involving the tyrosine-histidine pair in PSII. The final charge-separated state is thermodynamically capable of water oxidation, and its long lifetime suggests the possibility of coupling systems such as this system to water oxidation catalysts for use in artificial photosynthetic fuel production.

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Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Megiatto

Antoniuk-Pablant

Sherman

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

111

112

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“…T o construct nanoscale devices or molecular wires that efficiently convert photon energies to chemical potentials, extensive studies have produced photoinduced, long-distance charge separation (CS) states by using donor (D)-acceptor (A)-linked multiarray systems that mimic natural photosynthesis (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In each intramolecular, sequential electron transfer (ET) step, an electron or a hole tunnels between D and A over substantial distances (Ͼ10 Å) as in the natural photosynthetic reaction centers (12).…”

mentioning

confidence: 99%

Primary charge-recombination in an artificial photosynthetic reaction center

Kobori

Yamauchi

Akiyama

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

101

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Photoinduced primary charge-separation and charge-recombination are characterized by a combination of time-resolved optical and EPR measurements of a fullerene-porphyrin-linked triad that undergoes fast, stepwise charge-separation processes. The electronic coupling for the energy-wasting charge recombination is evaluated from the singlet-triplet electronic energy gap in the short-lived, primary charge-separated state. The electronic coupling is found to be smaller by Ϸ40% than that for the primary charge-separation. This inhibition of the electronic interaction for the charge-recombination to excited triplet state largely results from a symmetry-broken electronic structure modulated by configuration interaction between 3 (b1u,b3g) and 3 (au, b3g) electronic states of the free-base porphyrin.electronic coupling ͉ long-range electron transfer ͉ molecular orbital symmetry T o construct nanoscale devices or molecular wires that efficiently convert photon energies to chemical potentials, extensive studies have produced photoinduced, long-distance charge separation (CS) states by using donor (D)-acceptor (A)-linked multiarray systems that mimic natural photosynthesis (1-11). In each intramolecular, sequential electron transfer (ET) step, an electron or a hole tunnels between D and A over substantial distances (Ͼ10 Å) as in the natural photosynthetic reaction centers (12). From Marcus theory (13)(14)(15)(16)(17)(18)(19)(20), the ET rate constant (k ET ) is described (in the weak coupling regime) aswhere -h is Planck's constant divided by 2 and V, the electronic coupling matrix element, represents the electronic tunneling interaction between D and A. FCWDS denotes Franck-Condon weighted density of states parameterized by the reorganization energy ( ) and the driving force (Ϫ⌬G) for the ET reaction. The FCWDS term is given by (4where k B is the Boltzmann constant and T is the temperature. Although for several long-range ET systems, V has been interpreted in terms of a superexchange coupling model (21) that bridges the redox sites (22-28), much remains to be resolved regarding the tunneling mechanism (29-34). In addition, characterizations of V will be useful for designing molecular electronic devices (35). Key to efficient photoinduced CS is prevention of the energywasting charge recombination (CR) characterized in part by V. Although V and have been investigated for various ET steps by experimentally measuring k ET s in systems such as D 2 -D 1 -A triad (7, 9, 36) and protein complexes (24,25,34), primary CR,-A has escaped elucidation, especially in the efficient stepwise CS systems because the CR kinetics is hidden by subsequent CS processes,In the photosynthetic reaction center protein of Rhodobacter sphaeroides, which contains as cofactors a special pair (P), two bacteriopheopheophytins (H A and H B ), and two quinones (Q A and Q B ), the CR kinetics of the primary CS state of P ؉• H A Ϫ• Q A cannot easily be observed, because H A Ϫ• 3 Q A forward ET (Ϸ200 ps) is much faster than the primary CR (10-20 ns, which has b...

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“…The first was an amide because it possesses a double bond. The amide group was produced through the coupling of either a homo substituent on each complex diamine (1-6) and dicarboxy (7)(8)(9)(10)(11)(12) or hetero substituents on the amino and carboxy groups on the same complex .…”

Section: Linkersmentioning

confidence: 99%

Optimization of Virtual Light-Harvesting Antennas Part I: Poly-Nuclear Complexes of Bis-(4′-substituted-2, 2′; 6′, 2′′-terpyridino) Group III and Group IV Elements

Alkazzaz

Y.Yousif

Hassan³

2011

Arab J Sci Eng

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Semiempirical calculations were performed on complexes of 4-substituted-2,2 ;6 ,2 -terpyridino group III and group IV elements. The energy values obtained for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were subjected to conditional sequence optimization (LUMO DONOR < LUMO ACCEPTOR and HOMO DONOR < HOMO ACCEPTOR ). The virtual libraries of candidate antennas obtained were subjected to screening to find the structures with the highest drop potential and obtain the lead antennas. Hence, this study demonstrates the application of combinatorial principles in the field of optoelectronics.

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Long-lived photoinitiated charge separation in carotene-diporphyrin triad molecules

Cited by 99 publications

References 0 publications

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

Primary charge-recombination in an artificial photosynthetic reaction center

Optimization of Virtual Light-Harvesting Antennas Part I: Poly-Nuclear Complexes of Bis-(4′-substituted-2, 2′; 6′, 2′′-terpyridino) Group III and Group IV Elements

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