Effect of coordinated ligands on interporphyrin photoinduced-electron-transfer rates

Gust, Devens; Moore, Thomas A.; Moore, Ana L.; Kang, Hyoungku; DeGraziano, Janice M.; Liddell, Paul A.; Seely, G. R.

doi:10.1021/j100153a035

Cited by 50 publications

(45 citation statements)

References 8 publications

(8 reference statements)

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“…In addition, zinc porphyrins can bind fifth ligands, such as amines. This binding affects optical and electron transfer (48,49) properties, and could form the basis of sensor applications. Studies of the zinc analogs of triads 1 and 2 in 2-methyltetrahydrofuran and a variety of other solvents showed that formation of a C •ϩ -P Zn -C 60…”

Section: Zinc-containing Triadsmentioning

confidence: 99%

Driving Force and Electronic Coupling Effects on Photoinduced Electron Transfer in a Fullerene-based Molecular Triad¶

Bahr

Kuciauskas

Liddell

et al. 2007

Photochemistry and Photobiology

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Tuning thermodynamic driving force and electronic coupling through structural modifications of a carotene (C) porphyrin (P) fullerene (C60) molecular triad has permitted control of five electron and energy transfer rate constants and two excited state lifetimes in order to prepare a high‐energy charge‐separated state by photoinduced electron transfer with a quantum yield of essentially unity (≥96%). Excitation of the porphyrin moiety of C–P–C60 is followed by a combination of photoinduced electron transfer to give C–P·+–C60·− and singlet–singlet energy transfer to yield C–P–1C60. The fullerene excited state accepts an electron from the porphyrin to also generate C–P·+–C60·−. Overall, this initial state is formed with a quantum yield of 0.97. Charge shift from the carotenoid to yield C·+–P–C60·− is at least 60 times faster than recombination of C–P·+–C60·−, leading to the overall quantum yield near unity for the final state. Formation of a similar charge‐separated species from the zinc analog of the triad with a yield of 40% is also observed. Charge recombination of C·+–P–C60·− in 2‐methyltetrahydrofuran yields the carotenoid triplet state, rather than the ground state. Comparison of the results for this triad with those for related triads with different structural features provides information concerning the effects of driving force and electronic coupling on each of the electron transfer steps.

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Section: Zinc-containing Triadsmentioning

confidence: 99%

Driving Force and Electronic Coupling Effects on Photoinduced Electron Transfer in a Fullerene-based Molecular Triad¶

Bahr

Kuciauskas

Liddell

et al. 2007

Photochemistry and Photobiology

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“…The Hammett analysis provides a negative slope value, ρ = -1.3, indicating that photoinduced ET is favoured by electron-rich pyridine ligands. A similar approach has been previously reported in light-activated porphyrin dyads [49], but until now, the evidence that photoinduced ET is favoured by electron-rich pyridine ligands is unprecedented for photosynthetic assemblies involving multimetal cores. The crucial role of the ligands on the Co 4 O 4 core confirmed its direct participation in photocatalytic activity for water oxidation.…”

Section: Photo-induced Water Oxidation By Using Cobalt Cubane As Catamentioning

confidence: 62%

Artificial photosynthesis: a molecular approach to photo-induced water oxidation

Ganga

Puntoriero

2015

Pure and Applied Chemistry

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By the use of a molecular approach we performed photo-induced water oxidation by combining different photosensitizers and catalysts in order to obtain an efficient system that pave the way to the construction of an artificial photosynthetic system. Different types of molecular catalysts, such as ruthenium and vanadium polyoxometalates or cobalt core stabilized by different organic ligands were combined with ruthenium (II) polypyridine complexes of different nuclearity, mononuclear species like [Ru(bpy) 3 ] 2+ or a tetranuclear dendrimer.

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“…The electrochemistry of 2 in CH 2 Cl 2 shows a first oxidation at +0.94 V versus SCE. Considering that axial coordination of the pyridyl groups is expected to lower the first oxidation potential of the Zn–porphyrin units by 0.11 V,17 a value of +0.83 V vs SCE seems to be appropriate for the molecular box. On the other hand, 3 undergoes a first reduction in CH 2 Cl 2 at −1.15 V versus SCE, and this value is expected to be scarcely affected by peripheral Zn coordination 18.…”

Section: Resultsmentioning

confidence: 99%

“…In fact, when its approximate spectrum is calculated as the difference between the overall spectrum and the free‐base spectrum (i.e. between the spectra obtained with excitation at 560 and at 640 nm, both normalized at 715 nm), the emission (Figure 5, ••••) is seen to be red‐shifted21 with respect to that of isolated porphyrin metallacycle 2 , as expected for Zn–porphyrin chromophores bearing axially coordinated pyridyl ligands 17. The strong quenching of the Zn–porphyrin fluorescence and the sensitization of the free‐base emission indicates the occurrence of singlet ET from the Zn–porphyrin metallacycles to the free‐base bridging chromophores.…”

Section: Resultsmentioning

confidence: 99%

Electronic Energy Transfer in a Multiporphyrin‐Based Molecular Box

et al. 2006

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The molecular box 1 comprises of two zinc-porphyrin metallacycles connected by two free-base 4'-trans-dipyridylporphyrins, axially coordinated to the zinc centers. The photophysics of 1 were studied in chloroform by emission and ultrafast absorption spectroscopy. In the molecular box, fast singlet energy transfer (main component, tau=32 ps) is observed to occur from the zinc-porphyrin metallacycles to the free-base chromophores. From wavelength-dependent spectrofluorimetric data, the efficiency of the energy-transfer (ET) process is estimated as 0.5. The lower-than-unity value is tentatively attributed to the possibility of a competing electron-transfer quenching pathway. Molecular box 1 can be considered to be a simple, self-assembling, six-chromophore antenna system. It has an inner cavity, 11.4 Angstrom wide, that could be used, in principle, to host a variety of guest molecules and obtain higher-order assemblies.

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Effect of coordinated ligands on interporphyrin photoinduced-electron-transfer rates

Cited by 50 publications

References 8 publications

Driving Force and Electronic Coupling Effects on Photoinduced Electron Transfer in a Fullerene-based Molecular Triad¶

Driving Force and Electronic Coupling Effects on Photoinduced Electron Transfer in a Fullerene-based Molecular Triad¶

Artificial photosynthesis: a molecular approach to photo-induced water oxidation

Electronic Energy Transfer in a Multiporphyrin‐Based Molecular Box

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